university of siena
TRANSCRIPT
UNIVERSITY OF SIENA SCHOOL OF DENTAL MEDICINE
PHD PROGRAM:
“DENTAL MATERIALS AND THEIR CLINICAL APPLICATIONS”
PhD THESIS OF: Michele Vano TITLE A study into the mechanical properties and clinical aspects of fiber posts
Academic Year 2007/08 12 April 2008 Siena, Italy Committee: Promoter Prof. Marco Ferrari
Co-Promoter Dr. Cecilia Goracci
Prof. Piero Balleri
Prof. Lorenzo Breschi
Prof. Carel Davidson
Prof. Raquel Osorio Ruiz
Prof. Manuel Toledano Perez
Dr. Grandini Simone
TITLE A study into the mechanical properties and clinical aspects of fiber posts CANDIDATE Michele Vano
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CONTENTS Chapter 1 1.1 General Introduction 6 1.2 Fiber post in dentistry: background information 9 1.3 Principles for post placement 11
References
1.4 Superficial treatments: a way to improve bond strength to fiber posts 20
References
1.5 The adhesion between fiber posts and composite resin cores: the evaluation of
microtensile bond strength following various post-surface chemical treatments to
posts 25
References
Chapter 2
2.1 Timing of post space preparation and cementation 49
References
2.2 The effect of immediate versus delayed cementation on the retention of
different types of fiber post in canals obturated using a eugenol sealer 53
References
2.3 Retention of fiber posts cemented at different time intervals in canals obturated
using an epoxy resin sealer 65
3
References
2.4 Endodontic sealer: eugenol versus non-eugenol sealers 84
References
Chapter 3
3.1 Water detrimental effect on fiber-reinforced composite and dental resins 86
References
3.2 Flexural strength of fiber post: the influence of storage condition
and duration 89
References
3.3 The effect of different storage conditions and duration on the fracture strength
of three types of translucent fiber posts 92
References
3.4 The influence of storage condition and duration on the resistance to fracture of
different fiber posts systems 114
References
Chapter 4
4.1 Effects of wear on fiber post morphology 134
References
4.2 Effects of oral environment and occlusal wear on FRC-posts integrity in
clinical service for 5 years 137
4
References
Chapter 5 5.1 Summary 153 5.2 Conclusions 155 5.3 Riassunto e conclusioni 156 5.4 Resumen, conclusiones 160 5.5 Resumé, conclusions 165 5.6 Zusammenfassung, schlussfolgerungen 168 5.7 Sumário, conclusões 171 References Complete list of references 177 Curriculum Vitae 199 Acknowledgements 207
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Chapter 1
1.1. General Introduction Patients and dentists have been making increasing demands on the aesthetics of
dental restorations used in recent years. Industry has reacted by introducing several
innovative post-and-core systems for restoring nonvital teeth. Endodontically
treated teeth with insufficient coronal tooth structure generally require radicular
posts to assist in restoring the tooth to function (Goodacre and Spolnik, 1994). First
introduced in 1990 (Duret et al., 1990), fiber posts were rapidly accepted by
clinicians (Ferrari et al., 2000 a, b), and provided a viable alternative to cast metal
posts for the restoration of root filled teeth. The major advantage of fiber posts is
their similar elastic modulus to dentine, producing a stress field similar to that of
natural teeth, whereas metal posts exhibit high stress concentrations at the post
dentine interface (Stankiewicz and Wilson, 2002). Clinical studies have
demonstrated high success rates without the occurrence of root fractures (Ferrari et
al., 2000 a,b). Moreover fiber posts are ready to use whereas the construction of a
cast post and core is more time consuming and demands extra clinic and laboratory
time (DeSort,1983).
In order to improve the fracture resistance of endodontically treated teeth restored
with a post-and-core system, research has focused on post materials (Ferrari et al.,
2000), (Sorensen and Engelman, 1990), post designs and luting agents (Ferrari et
al., 2006), (Grandini et al., 2004), (Ferrari et al., 2001). However recently it has
been shown that other factors such as storage condition (Mannocci et al., 2001) and
duration (Chai et al., 2004) may influence the fracture resistance of fiber posts.
Aging in water or aqueous fluids is known to decrease the fracture resistance of
fiber reinforced composites (FRC) materials as a result of water absorption by the
resin matrix and hydrolisis of filler matrix interfaces (Ferracane et al., 2006),
6
(Santos et al., 2002), (Lassila et al., 2002), (Miettinen et al., 1999). In vitro tests
reported that water storage negatively affects the flexural properties of fiber posts
when directly immersed in water (Lassila et al., 2004). The inflow predominantly
occurs in the resinous matrix and depends on the nature of the resin and the amount
of this phase within the material (Fan et al., 1985). This process is generally time
dependent and increases with time until the material is saturated and hydrolytically
stable (Takahashi et al., 2006).
In clinical conditions endodontic posts are cemented into the root canal and their
coronal part is immersed into the composite resin core, therefore fiber posts are
protected from the oral environment and from any water or saliva uptake.
However a recent study reported the presence of water into root canals after
endodontic and prosthodontic procedures (Chersoni et al., 2005). Chersoni et al.,
showed blistering formation on the surface of simplified adhesives when applied on
intra-radicular dentin. The authors speculated that droplets formation occurred due
to residual dentin water that was osmotically soaked by the etching and adhesives
and then retrieved on the adhesive surface due the intrinsic permeability of the
polymerized bonded surface. More recently Ferrari et al., (Ferrrari et al., 2007),
repeated a similar in vivo protocol, the results showed that after etching of the
intra-radicular dentin no water droplets formation occurred on the dentin surface.
The authors concluded that the adhesives themselves are responsible for the
droplets formation, probably due to residual un-evaporated solvent (Van Landuyt et
al., 2005). Therefore once fiber posts are cemented into the root canal of
endodontically treated teeth and their coronal part is immersed into the composite
resin core, no water uptake or outflow is expected from radicular dentin.
However observation of exposed post on a direct restoration is a common finding
(Fredriksson et al., 1998). It is not clear yet whether post exposition to the oral
environment may influence its morphological and mechanical properties.
7
This thesis contains a study into different aspects related to fiber posts, with the
purpose of identifying factors affecting the bond strength between the post, the
resin cement, and radicular dentin as well as selecting the procedures for enhancing
post retention.
In addition this thesis aimed to evaluate in vitro the effects of water aging on the
resistance to fracture of different fiber posts systems and to assess in vivo whether
the exposure to the oral environment and occlusal wear during function affects the
morphological integrity of luted endocanalar fiber posts retaining a direct
composite restoration.
Microtensile bond strength test and push-out test were used to perform mechanical
trials. Stereo and scanning electron microscopy (SEM) were essential to understand
and to show the results obtained. An overview of the literature was provided in
order to present the background information existing on fiber posts.
The first study aimed at evaluating the influence of post-surface treatments on the
microtensile bond strength between fiber posts and different composite resins for
core build-up.
The second study evaluated the effect of immediate versus delayed post
cementation on the retention of different types of fiber post systems in canals
obturated with a eugenol sealer or with an epoxy resin sealer.
In the final part of this thesis two investigations assesed the flexural strength of
different types of fiber posts stored under different conditions including water
aging. Finally an in vivo study provived interesting results on the clinical behaviour
of fiber posts exposed to the oral environment and occlusal function.
8
1.2. Fiber post in dentistry: background information Fiber posts were first introduced by Duret at the beginning of the 90s (Duret et al.,
1990). Fiber posts can be considered as composite reinforced materials in which
the fibers are embedded in a matrix of epoxy-resin or methacrylate-resin, and an
interfacial agent such as silane is used to optimize the link between the two
components. The post is fabricated through a semi-automated industrial process
called pultrusion (Grandini, 2004). The diameter and density of the fibers as well as
the adhesion between them and the matrix, strictly influence the quality of the post
and its mechanical properties. The resinous matrix (epoxy or methacrylate) is
injected into the pre-tensioned fiber bundle to completely fill the spaces between
fibers. As alternative, fibers are simply immersed in a resin bath. Differences in
manufacturing are strictly related to the quality, mechanical and clinical behaviour
of posts (Grandini et al., 2005).
Fiber posts main advantage is the variability of their modulus of elasticity
depending on loading direction: in particular, when considering a transversal
loading, the modulus of elasticity has a value close to sound dentin (Ferrari and
Scotti, 2002). This property reduces stress transmission to root canal walls and thus
the risk of vertical fractures (Asmussen et al., 1999). On the contrary the highly
rigid metal post would transfer lateral forces without distortion to the less rigid
dentin and lead to a higher chance of root fracture (Bateman et al., 2003). In the
event of failure when restored with fiber reinforced posts, teeth are more likely to
be restorable (Cormier et al., 2001, Akkayan et al., 2002).
The failure rate for metal post and fiber posts is different. Studies demonstrated that
metal posts reported a higher failure rate when compared to fiber posts (Ferrari et
al., 2000). The most common failure that can occur with a fiber post, is a
“debonding” of the post, especially at the time of removing the temporary
restoration, but this failure can easily be dealt with by repeating the adhesive
procedures. In the presence of a fiber post, if a root fracture occurs, is usually
located more coronally and is more easily retreatable (Reagan et al., 1999, Ukon et
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al., 2000, Cormier et al., 2001). On the contary, metallic posts tend to produce an
irreversible root fracture. This type of failure may be due to the wider amount of
tooth structure that must be sacrificed when a metallic post is placed (Stankiewicz
et al., 2002). This concept is valid even if a crown is made, when a failure occurs,
favorable fractures are seen in teeth restored with fiber posts and resin cores,
whereas unfavorable fractures or failures are usually encountered with the use of a
metal post (Heydecke et al., 2002).
Many commercially available prefabricated posts exist. For example, the axial form
is either tapered or parallel, and the surface can be smooth, serrated with or without
vents, or threaded using taps or self-threading. Caputo and Standlee 1987,
categorize these different design features into three basic combinations: 1) tapered,
serrated or smoothsided, cemented into a post space prepared with a matched-size
post drill; 2) parallel-sided, serrated or smooth-sided, cemented into matched
cylindrical channels prepared by a postdrill; 3) parallel-sided, threaded and inserted
into pretapped channels.
Stainless steel, titanium and titanium alloys, goldplated brass, ceramic and fiber
reinforced polymers have been used as materials for prefabricated posts. However
the carbon fibers were first used for manufacturing posts, representing the first true
alternative to cast metal posts and cores. The ideal post and core material should
have physical properties such as modulus of elasticity, flexural strength and
coefficient of thermal expansion that are similar to those of dentin.
The increased demand for newer products influenced research on posts with the
purpose of saving tooth structure modifying their shape and improving aesthetics.
Translucent quartz and glass fiber post systems recently were introduced as an
alternative to achieve optimal esthetics. These types of posts allow the light to pass
through the post and they can be light-polymerized during cementation (Vichi et
al., 2000) (Ferrari et al., 2001).
10
1.3. Principles for post placement
The restoration of endodontically treated teeth frequently poses a challenge for the
clinician. Apart from substantial tissue loss which can be considered as one of the
major obstacles, endodontically treated teeth are assumed to be more prone to
fracture because of desiccation or premature loss of moisture supplied by a vital
pulp (Carter et al., 1983). In cases of severe hard tissue loss, posts are frequently
used as reinforcing elements in the prosthodontic restoration of endodontically
treated teeth. Previously posts were believed to reinforce tooth structure and
strengthen weakened endodontically treated teeth against intraoral forces by
distributing torquing forces within the radicular dentin to supporting tissue along
their roots. Currently, posts are not believed to function as a reinforcing component
of prosthodontic treatment but rather as an element supporting a core foundation
(Lloyd et al., 1993), (Sorensen et al., 1990), (Morgano et al., 1996), (Abou-Rass,
1992). Due to substantial loss of coronal tooth structure, corono-radicular
stabilization is often required, especially in anterior teeth to provide retention and
resistance form for the restoration. Ideal posts should impart minimal stress to the
tooth, provide adequate retention to the core, and be easily removed to permit
endodontic retreatment. Preservation of sound tooth structure is regarded as one of
the the most important aspect in increasing the survival rate of endodontically
treated teeth (Assif et al., 1994), (Guttman, 1992), (Cohen et al., 1996). Resistance
to fracture of the non-vital tooth is related with the thickness of remaining root
dentin, especially in the bucco-lingual direction (Guzy et al., 1979), (Mattison,
1982), (Tjan and Whang, 1985). Many factors affect the fracture resistance and the
failure modes of post-core restorations (Morgano et al.,1999). Among these the
type of tooth and its position in the dental arch. In retrospective clinical reports,
(Tamse A et al., 1999) premolars were found to be the most frequently fractured
teeth.
Many authors have offered guidelines for determining the desired post length. The
longer the post in the canal, the more retentive it is. However, increased post length
11
also increases risk of fracture and perforation of the remaining root (Leary et al.,
1987). It is generally accepted that the apical 3 to 6 mm of guttapercha must be
preserved to maintain the apical seal (Zillich et al., 1984).
The post diameter makes little difference in the retention of the post. An increase in
the post’s width, on the other hand, will increase the risk of root fracture (Caputo
and Standlee, 1987).
In general, the post width should not exceed one-third of the root width at its
narrowest dimension. A minimum of 1 mm of sound dentin should be maintained
circumferentially, especially in the apical area where the root surface usually
becomes narrower and functional stresses are concentrated.
Anterior teeth with a minimal loss of tooth structure can be restored conservatively
(Sorensen and Martinoff, 1984), but if the tooth is planned to receive a crown, a
post is often required. Single-rooted teeth are loaded non-axially and in most cases
the remaining tooth structure is not able to provide adequate resistance and
retention for a crown without a post (Peters et al., 1983). Molars should receive a
cuspal coverage after endodontic treatment but sometimes cast post is not
necessary if the pulp chamber may provide an adequate retention for a core build-
up (Kane and Burgess, 1991). Premolars require post more often than molars:
functional demands and the amount of remaining tooth structure are, once again,
key factors for treatment planning. These aspects were recently confirmed by a 5
years follow-up prospective clinical study, in which the survival rate of cast versus
direct post and core restoration was evaluated revealing that the amount of
remaining dentin height after preparation influenced the longevity of the restoration
(Creugers et al., 2005).
Several investigations reported that fixed prosthodontics continues to be performed
in significant quantities as the final restoration of structurally compromised
endodontically treated teeth. However the possibility of using fiber posts in
12
conjunction with direct composite restorations (without additional crown coverage)
is becoming a reliable alternative, ensuring long-term service (Grandini, 2004).
References 1.1, 1.2, 1.3
Abou-Rass M. Post and core restoration of endodontically treated teeth. Curr Opin
Dent1992;2:99-107.
Akkayan B, Gulmetz T. Resistance to fracture of endodontically treated teeth
restored with different post systems. J Prosthet Dent 2002;87:431-7.
Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit and strength of
newer types of endodontics posts. J Dent 1999;27:275-78.
Assif D, Gorfil C. Biomechanical considerations in restoring endodontically treated
teeth. J Prosthet Dent 1994;71:565-7.
Bateman G, Ricketts DN, Saunders WP. Fibre-based post systems: a review. Brit
Dent J 2003;195:43-8.
Caputo AA, Standlee JP. Restoration of endodontically involved teeth. In:
Biomechanics in clinical dentistry. Chicago: Quintessence;1987:185-203.
Carter JM, Sorensen SE, Johnson RR, Tietelbaum RL, Levine MS. Punch shear
testing of extracted
vital and endodontically treated teeth. J Biomech 1983;16(10):841-848.
13
Chai J, Takahashi Y, Hisama K, Shimizu H. Water sorption and dimensional
stability of three glass fiber-reinforced-composites. Int J Prosthodont 2004;17:195-
9.
Chersoni S, Acquaviva GL, Prati C, Ferrari M, Pashley DH, Tay FR. In vivo fluid
movement through dentin adhesives in endodontically treated teeth. J Dent Res
2005;84:223-7.
Cohen BI, Pagnillo MK, Condos S, Deutsch AS. Four materials measured for
fracture strength in combination with five designs of endodontic posts. J Prosthet
Dent1996;76:487-95.
Cormier CJ, Burns DR, Moon P. In vitro comparison of the fracture resistances and
failure mode of fiber, ceramic and conventional post systems at various stages of
restoration. J Prosthod 2001;10:26-36.
Creugers NH, Mentink AG, Fokkinga WA, Kreulen CM. 5-year follow-up of a
prospective clinical study on various types of core restorations. Int J Prosthod
2005;18:34-9.
Duret B, Reynaud M, Duret F. Un noveau concept de reconstitution
coronoradiculaire : le Composipost 1º. Le Chir Dent de France 1990a ;540:131-41.
Fan PL, Edahl A, Leung RL, Stanford JW. Alternative interpretations of water
sorption values of composite resins. J Dent Res 1985;64:78–80.
Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks. Dent
Mater 2006;22:211-222.
14
Ferrari M, Coniglio I, Magni E, Cagidiaco MC, Gallina G, Prati C, Breschi L. How
can droplets formation occur in endodontically treated teeth during bonding
procedures? J Adhes Dent, In press.
Ferrari M, Goracci C, Sadek FT, Monticelli F, Tay FR. An investigation of the
interfacial strengths of methacrylate resin-based glass fiber post-core buildups. J
Adhes Dent 2006;8:239-45.
Ferrari M, Scotti R. Fiber post: Characteristics and clinical applications. Masson
Ed, Milano, 2002.
Ferrari M, Vichi A, Garcia-Godoy F. Clinical evaluation of fiber reinforced epoxy
resin posts and cast post and cores. Am J Dent 2000;13:8B-15B.
Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques on
bonding to root canal walls: an SEM investigation. Dent Mater 2001;17:422-9.
Ferrari M, Vichi A, Grandini S, Goracci C. Efficacy of a self-curing adhesive-resin
cement system on luting glass-fiber posts into root canals: an SEM investigation.
Int J Prosthodont 2001;14:543-9.
Fredriksson M, Astback J, Pamenius M. A retrospective study on 236 patients with
teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent
1998;80:151-7.
Grandini S. Basic and clinical aspects of selection and application of fiber posts.
PhD Thesis 2004: pp 16-8.
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Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and
structural integrity of fiber posts: three-bending test and SEM evaluation. Dent
Mater 2005;21(2):75-82.
Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. A one step procedure for
luting glass fibre posts: an SEM evaluation. Int Endod J 2004;37:679-86.
Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically
treated teeth: a literature review. Part I. Success and failure data, treatment
concepts. J Prosthod 1994;3:243-50.
Gutmann JL. The dentin-root complex: anatomic and biologic considerations in
restoring endodontically treated teeth. J Prosthet Dent 1992;67:458-67.
Guzy GE, Nicholls JI. In vitro comparison of intact endodontically treated teeth
with and without endo-post reinforcement. J Prosthet Dent 1979;42:39-44.
Heydecke G, Peters MC. The restoration of endodontically treated, single-rooted
teeth with cast or direct posts and cores: A systematic review. J Prosthet Dent
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Kane JJ, Burgess JO. Modification of the resistance form of amalgam coronal-
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on the flexural properties of unidirectional glass fiber-reinforced composites.
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Leary JM, Aquilino SA, Svare CW. An evaluation of post length within the elastic
limits of dentin. J Prosthet Dent 1987;57:277-81.
Lloyd PM, Palik JF. The philosophies of dowel diameter preparation: a literature
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Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J
Endod 2001;27:758-61.
Mattison GD. Photoelastic stress analysis of cast-gold endodontic posts. J Prosthet
Dent 1982;48:407-11.
Miettinen VM, Narva KK, Vallittu PK. Water sorption, solubility and effect of
post-curing of glass fibre reinforced polymers. Biomaterials 1999;20:1187–1194.
Morgano SM. Restoration of pulpless teeth: application of traditional principles in
present and future contexts. J Prosthet Dent 1996;75:375-80.
Morgano SM, Brackett SE. Foundation restorations in fixed prosthodontics: current
knowledge and future needs. J Prosthet Dent 1999;82: 643-57.
Peters MC, Poort HV, Farah JW, Craig RG. Stress analysis of a tooth restored with
a post and core. J Dent Res 1983;62:760-3.
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Pilo R, Tamse A. Residual dentin thickness in mandibular premolars prepared with
gates glidden and ParaPost drills. J Prosthet Dent 2000; 8: 617-23.
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Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption
characteristics of dental composites incorporating hydroxyapatite filler.
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endodontically treated teeth. J Prosthet Dent 1990;64:419-24.
Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a
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18
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19
1.4. Superficial treatments: a way to improve bond strength to fiber posts
The quality of the bond between the post and the dentin both at the coronal and
radicular level is of uttermost importance for post retention (Ferrari et al., 2001)
(Ngoh et al., 2001) (Ari et al., 2003). Since the introduction of fiber posts, a
continuous effort has been made to improve bonding inside the root canal, however
radicular dentin still offers less favourable conditions for bonding than coronal
dentin (Ferrari et al., 2002) (O’Keefe and Powers, 2001).
The most frequent cause of adhesive failure is debonding of post restoration at the
resin cement/dentin interface (Ferrari et al., 2000a) (Ferrari et al., 2000b). The
weakest point of the restoration, is represented by the adhesion into the root canal.
Nonetheless also the post/composite adhesion has to be considered, in fact, the
restoration has to resist to the stresses transmitted during core trimming to adapt the
provisional crown (Goracci et al., 2005).
At the post-core interfacial level, only the chemical interaction between the fiber
post surface and the resin composite may ensure the bond of the core material
around the post.
Surface treatments are common methods to improve the general adhesion
properties of a material, by facilitating chemical and micromechanical retention
between different constituents. Surface conditioning techniques are used for natural
substrates (i.e. dentine) (Nakabayashi, 1982) (Nakabayashi et al., 1991) and
restorative materials (i.e. ceramics) (Horn, 1983). In fact the use of acids to
condition the surfaces or to partially dissolve the substrate generate a rough surface
that enhance adhesion (Hayakawa et al., 1992).
With respect to post/core restorations, most studies were designed to improve the
performances of these restorations acting on the mechanical properties of the
composite core build-up materials (Combe et al., 1999) (Chutian et al., 2004). In
20
other scientific fields many chemical treatment techniques have been introduced to
improve the adhesion between the components of fiber reinforced resin composites
(Cheng et al., 1993) (Crasa et al., 1999) (Roizard et al., 2002). A similar approach
may be applied in dentistry for surface pre-treatment of fiber posts to increase their
post-core bond strength. Hydrofluoric acid in combination with a silane coupling
agent is often employed to enhance the bond strength between composite resins
and feldspathic ceramics (Aida et al., 1995), (Chen et al., 1998), (Ozcan and
Vallitu, 2003). Silanes are also used for coupling the glass filler particles or the
glass fibers with the embedding matrix in composite and fibre-reinforced resins
respectively (Ishida, 1985), (Iglesias et al., 2002). Silane coupling agents are able
to chemically bridge resins and OH-covered inorganic substrates (Plueddemann,
1991). Although the clear benefit of silane coating in enhancing post-core bond
strength, it still remains a weak bond. Treating the post surface with a silane
coupling agent is advisable for enhancing adhesion (Aksornmuang et al., 2004)
(Goracci et al., 2005).
Post surface pre-treatment with hydrogen peroxide has been shown to significantly
increase the bond strength between fiber posts and flowable materials used for core
build-up (Monticelli et al., 2005). Recently other investigations showed that
retentive post bond strengths were significantly enhanced with hydrofluoric acid or
hydrogen peroxide post surface pretreatments (D’acangelo et al., 2006) (Yenisey
and Kulunk, 2008).
The following study aimed at evaluating the influence of post surface treatment
with hydrofluoric acid or hydrogen peroxide on the microtensile bond strength
between glass fiber posts containing methacrylate resin and different composite
resins for core build-up.
21
References 1.4.
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Chen JH, Matsumura H, Atsuta M (Effect of etchant, etching period and silane
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Cheng TH, Jones FR, Wang D. Effect of fibre conditioning on the interfacial shear
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Chutian S, Platt JA, Cochran MA, More BK. Volumetric dimensional changes of
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Crasa JJ, Rowe-Tattib CA, Nivensb DA, Ligler FS. Comparison of chemical
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8.
22
D'Arcangelo C, D'Amario M, Prosperi GD, Cinelli M, Giannoni M, Caputi S.
Effect of surface treatments on tensile bond strength and on morphology of quartz-
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Ferrari M, Grandini S, Simonetti M, Monticelli F, Goracci C. Influence of a
microbrush on bonding fiber posts into root canals under clinical conditions. Oral
Surg, Oral Med, Oral Path, Oral Rad and Endod 2002;94:627-31.
Ferrari M, Mannocci F, Vichi A, Cagidiaco MC, Mjör IA. Bonding to root canal:
structural characteristics of the substrate. Am J Dent 2000;13:255-60.
Ferrari M, Vichi A, Garcia-Godoy F. A retrospective study of fiber-reinforced
epoxy resin posts vs. cast posts and cores: a four year recall. Am J Dent 2000a; 13:
9B-13B.
Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques on
bonding to root canal walls: an SEM investigation. Dent Mater 2001;17:422-9.
Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of clinical
behaviour of several types of fiber posts. Am J Dent 2000b; 13:14B-19B.
Goracci C, Raffaelli O, Monticelli F, Balleri P, Bertelli E, Ferrari M. The Adhesion
between fiber posts and composite resin cores: microtensile bond strength with and
without post silanization. Dent Mater 2005;12:437-44.
Hayakawa T, Horie K, Aida M, Kanaya H, Kobayashi T, Murata Y. The influence
of surface conditions and silane agents on the bond of resin to dental porcelain.
Dent Mater 1992;8:238-40.
23
Horn HR. Porcelain laminate veneers bonded to etched enamel. In; Phillips RW,
editor. Symposium on Dental Materials. Dent Clin of North Amer 1983;27:671-84.
Monticelli F, Toledano M, Tay FR, Cury AH, Goracci C, Ferrari M.
Post surface conditioning improves interfacial adhesion in post/core restorations.
Dent Mater 2006;22(7):602-9.
Nakabayashi N. Resin reinforced dentin due to infiltration of monomers into
dentine at the adhesive interface. Jpn J Dent Mater 1982;1:78-81.
Ngoh EC, Pashley DH, Loushine RJ, Weller N, Kimbrough F. Effect of eugenol on
resin bond strengths to root canal dentin. J Endod 2001;27:411-4.
O’Keefe KL, Powers JM. Adhesion of resin composite core materials to dentin. Int
J Prosthod 2001; 14:451-6.
Ozcan M, Vallitu PK Effect of surface conditioning methods on the bond strength
of luting cement to ceramics. Dent Mater 2003;19:725-31.
Roizard X, Wery M, Kirmann J. Effects of alkaline etching on the surface
roughness of a fibre-reinforced epoxy composite. Comp Struct 2002;56:223-8.
Plueddemann EP. Silane coupling agents. New York: Plenum Press; 1991.
Yenisey M, Kulunk S. Effects of chemical surface treatments of quartz and glass
fiber posts on the retention of a composite resin. J Prosthet Dent 2008;99(1):38-45.
24
1.5. The adhesion between fibre posts and composite resin cores: the
evaluation of microtensile bond strength following various post-surface
chemical treatments to posts
Michele Vano, Cecilia Goracci, Francesca Monticelli, Francesco Tognini, Mario
Gabriele, Franklin R. Tay, Marco Ferrari. International Endodontic Journal
2006;39(1):31-9.
Introduction
The restoration of root filled teeth often requires the placement of a post to ensure
adequate retention of the core (Gutmann 1992). First introduced in 1990 (Duret et
al. 1990), fibre posts were rapidly accepted by clinicians (Ferrari et al. 2000), and
provided a viable alternative to cast metal posts for the restoration of root filled
teeth. The major advantage of fibre posts is their similar elastic modulus to dentin,
producing a stress field similar to that of natural teeth, whereas metal posts exhibit
high stress concentrations at the post-dentin interface (Pegoretti et al. 2002).
Clinical studies have demonstrated high success rates without the occurence of root
fractures (Ferrari et al. 2000). Moreover fibre posts are ready to use whereas the
construction of a post core casting is more time consuming and demands extra
clinic and laboratory time (DeSort 1983).
In vivo data have shown that the establishment of reliable bonds at the root-post-
core interfaces are critical for the clinical success of a post-retained restoration
(Monticelli et al. 2003). It has also been demonstrated that parameters such as post
length, shape, and post surface characteristics influence post retention (Schwartz &
Robbins 2004).
25
In order to improve the bond strength between the post and the resin cement, many
surface pre-treatment procedures for posts have been investigated that involve the
use of mechanical (Kern & Thompson 1994, Sahafi et al. 2003) or chemical agents
(Kern & Wegner 1998, Yangida et al. 2001). Chemical treatment is aimed at
roughening the post surface, thus enhancing the mechanical interlocking between
post and resin cement (Wolf et al. 1993). In a recent in vitro study, post surface
pre-treatment with hydrogen peroxide has been shown to significantly increase the
bond strength between fibre posts and flowable materials used for core build-up
(Monticelli et al. 2005).
Hydrofluoric acid in combination with a silane coupling agent is often employed to
enhance the bond strength between composite resins and feldspathic ceramics
(Hayakawa et al. 1992, Aida et al. 1995, Chen et al. 1998, Ozcan & Vallitu 2003).
Silanes are also used for coupling the glass filler particles or the glass fibres with
the embedding matrix in composite and fibre-reinforced resins respectively (Ishida
1985, Iglesias et al. 2002). Silane coupling agents are able to chemically bridge
resins and OH-covered inorganic substrates. At the fibre post-composite core
interface, chemical coupling is only possible between the resin of the core material
and the exposed glass fibres of the post (Ferrari & Scotti 2002, Aksornmuang et al.
2004, Goracci et al. 2005). Due to the difference in chemistry, no bonding is
expected to occur between the methacrylate based resin of the core and the epoxy
resin of the fibre post matrix (Monticelli et al. 2005).
Several materials have been used for core build-ups that differ in their mechanical
properties, viscosities and setting reactions (Combe et al. 1999). In a recent
microscopic study (Monticelli et al. 2005), flowable composites achieved structural
homogeneity and continuity with the post surface that were superior to hybrid
composites. However, the latter materials are expected to provide higher
mechanical properties than the lightly filled flowable composites. Also, several
composite resins specifically formulated for abutment build-up are currently
available in the market.
26
Previous studies (Goracci et al. 2005, Monticelli et al. 2005) have shown that
hydrogen peroxide is able to dissolve the epoxy resin matrix, breaking epoxy resin
bonds and exposing the fibres surface to silanisation. This method of pre-treatment
was found to be effective for enhancing the retention between epoxy resin-based,
conventional fibre post systems and core materials (Monticelli et al. 2005).
However, little is known of the physical and chemical effects of hydrogen peroxide
on methacrylate-based resin fibre post systems.
The present study was aimed at evaluating the influence of post surface treatment
with hydrofluoric acid or hydrogen peroxide on the microtensile bond strength
between glass fibre posts containing methacrylate resin and different composite
resins for core build-up. The changes in post surface characteristics following the
different pre-treatments were also observed using scanning electron microscopy
(SEM). The tested null hypotheses were: 1) the microscopic aspect of the post
surface and the post-core strength are not affected by different post surface pre-
treatments; 2) the type of resin composite used for core build-up has no influence
on the post-core interfacial strength.
Materials and methods
One hundred and ten translucent glass fibre posts (GC Corporation, Tokyo, Japan)
with a maximum diameter of 1.6 mm were used in the study. They are made of
unidirectional glass fibres (77% vol) bound in a methacrylate resin matrix (23%
vol). Posts were randomly picked from their boxes and divided into five groups of
22 each, depending on the post surface pre-treatment to be performed. These pre-
treatments include: immersion in 24% hydrogen peroxide for 10 min at room
temperature and silanisation for 60 s (Group 1); immersion in 10% hydrogen
peroxide for 20 min at room temperature and silanisation for 60 s (Group 2);
immersion in 4% hydrofluoric acid gel (Porcelain Etchant, Bisco, Schaumburg, IL,
USA) for 60 s and silanisation for 60 s (Group 3); silanisation of the post surface
for 60 s and application of the bonding agent G-Bond (GC Corp.) (Group 4);
27
silanisation of the post surface for 60 s only (Group 5, control group). After the
application of hydrogen peroxide or hydrofluoric acid, all the posts were rinsed
with water and air-dried. The silane coupling agent (Monobond-S, Ivoclar-
Vivadent, Schaan, Liechtenstein) was applied in a single layer with a brush on the
post surface, and left to air-dry for 60 s at room temperature. The chemical
composition and batch numbers of the tested materials are reported in Table 1.
SEM Analysis
Two posts were randomly selected with the flip of a coin from each group for SEM
examination of the superficial aspect of the post following surface pre-treatment. In
each group one post was observed longitudinally, while the other one was cross-
sectioned by means of a water-cooled diamond blade (Isomet 1000, Buehler, Lake
Bluff, IL, USA). All the posts were sonicated for 5 min in deionised water (CP104,
CEIA Int., Rassy CDG, France), immersed in 96% ethanol, and gently air-dried.
Each post was mounted on a metallic stub, gold-sputtered (Polaron Range SC7620,
Quorum Technology, Newhaven, UK), and observed under a JSM 6060 LV
microscope (JEOL, Tokyo, Japan) at different magnifications (200X, 1000X).
Core build-up and microtensile test procedures
The materials used for core build-up were: two flowable composites UniFil Flow
(subgroup A) and UniFil Lo Flo Plus (subgroup B), the hybrid composite Gradia
Direct (subgroup C), and the core material UniFil Core (subgroup D). These
materials were handled according to the instructions supplied by the manufacturer
(GC Corp.).
For the core build-up procedure, each post was positioned upright on a glass slab,
and secured with a drop of sticky wax. A cylindrical plastic matrix was then placed
around the post and adjusted so that the post would be exactly in the middle. The
matrix was 10 mm in diameter and the length was equal to the non-tapered portion
of the post. For an easier calculation of the bonding surface in microtensile
28
specimens, it is desirable that the post diameter be constant throughout the post
length (Goracci et al. 2005).
The light-activated composites were applied to the post in 1-2 mm thick
increments. Each increment was carefully placed onto the post surface, and light-
cured separately for 40 secs according to the manufacturer’s instructions, using a
halogen light curing unit with an output of 600 mW/cm2 (VIP, Bisco, Schaumburg,
IL, USA). The composite was always irradiated directly from the open upper side
of the matrix and through the post. Irradiation was never performed through the
plastic matrix. Once the matrix was completely filled, the composite cylinder was
detached from the glass slab. An additional 40 s irradiation was then performed
from the bottom of the cylinder prior to the removal of the matrix, to ensure
optimal polymerisation of the core material.
The sectioning and loading of the specimens began on completion of the core
build-up procedure, in order to simulate the clinical situation of immediate loading
following core build-ups. Each composite cylinder was secured on an Isomet
cutting machine for sectioning (Buehler). Two longitudinal cuts were initially made
with the water cooled diamond blade along the two opposite sides of the post at its
outermost periphery. This sectioning produced a rectangular slab of uniform
thickness, with the post in the centre and the core build-up composite on either
side. Each slab was subsequently sectioned into 1-mm thick sticks for microtensile
bond testing (Fig.1).
Each stick was secured with cyanoacrylate adhesive (Zapit, Dental Ventures of
America, CA, USA) to the two free sliding components of a jig, that was mounted
on a universal testing machine (Controls, Milan, Italy). The stick was loaded in
tension at a cross-head speed of 0.5 mm/min,
until failure occurred at either side of the post-composite interface. Bond strength
was expressed in MegaPascals (MPa), by dividing the load at failure by the
bonding surface area. As the bonded interface was curved, its area was calculated
using a mathematical formula previously applied by Bouillaguet et al. (2003).
29
Statistical analysis of the microtensile bond strength data
After analysing the bond strength data for the normality of data distribution
(Kolmogorov-Smirnov test) and homogeneity in variances (Levene’s test), a two-
way ANOVA was applied with bond strength as the dependent variable, and the
types of surface pre-treatment and core material as factors. The Tukey test was
used for post-hoc multiple comparisons of surface pre-treatments and core
materials. In all the tests, the level of significance was set at α=0.05, and
calculations were handled by the SPSS 11.0 software (SPSS Inc, Chicago, IL,
USA).
Results
Microtensile bond strength test
The means and standard deviations of the bond strengths for the five experimental
and control groups are shown in Table 2. Statistical analysis revealed that both the
post-surface treatment procedure and the type of composite resin used for core
build-up had significant influence on microtensile bond strength (p<0.05). More
precisely, the post-core strengths achieved following the two variants of hydrogen
peroxide pre-treatment (Groups 1 and 2) were comparable and significantly higher
than those of Groups 3, 4 and 5 in which the post surface had been treated with 4%
hydrofluoric acid/silane, silane/bonding agent and silane (control group)
respectively. In the control group (Group 5), the lowest post-core strength was
achieved, and the difference was statistically significant (p<0.05).
In Groups 1 and 2, the post-core bond strengths were similar regardless of the
composite resin used for the core build-up (Table 2). Conversely, core material was
a significant factor in Groups 3, 4 and 5 with UniFil Core recording the highest
bond strengths (p<0.05). In addition the difference between Gradia and UniFil
Flow was significant (p<0.05) in Groups 4 and 5 (Table 2).
30
SEM Analysis
SEM evaluation revealed that the post surface morphology was modified following
treatment with hydrogen peroxide and hydrofluoric acid. The two variants of
treatment with hydrogen peroxide produced similar changes in the ultrastructure of
the post surface. At a lower magnification (Fig. 2a, 3a), a uniform distribution of
micro-spaces was evident among the exposed fibres. As a result, a rough surface
along the whole post length was created. Exposed fibres did not appear to be
damaged by the action of hydrogen peroxide and no defects or fractures were
evident on their surfaces (Fig. 2b, 3b). The cross-sections revealed a significant
exposure of the superficial fibres due to resin matrix removal, especially following
24% hydrogen peroxide-10 min treatment (Fig. 2c, 3c). However, the resin matrix
was retained in the spaces among the inner fibres.
Treatment with 4% hydrofluoric acid had a greater impact on the post structure.
The resin matrix was removed more extensively and to a greater depth (Fig. 4a).
Some fibres appeared to be thinner (Fig. 4a, 4c), and damaged (Fig. 4b). Cross-
sections of the posts revealed that the outermost glass fibres were deprived of their
resin embedding to a greater extent (Fig. 4c).
Discussion
The bond strengths of different composite resins to translucent glass fibre posts
were affected by both the core material and by the type of post surface pre-
treatment. Moreover, SEM revealed that the post pre-treatments under investigation
had an impact on post surface characteristics. Thus, the null hypotheses tested in
this study can be rejected.
Hydrogen peroxide was found to be the most effective treatment with respect to
post-core bond strength. In fact, either concentration of hydrogen peroxide
significantly enhanced the interfacial bond strength between fibre posts and core
materials (p<0.05). These data are in agreement with the results of previous
microtensile tests by Monticelli et al. (2005). In particular, post-core bond strengths
31
in Group 1 and 2 were very similar, regardless of the material used for core build-
up (Table 2).
Interestingly, the flowable composites groups benefited the most from post surface
pre-treatment with hydrogen peroxide. It can be speculate that because of their low
viscosity, the flowable composites were able to penetrate optimally within the post
surface irregularities, taking the greatest advantage of the increase in surface area
available for bonding following post surface pre-treatment. This enabled the
flowable composites to achieve a bond with the post that was as solid as that
established by intrinsically stronger composites, such as Gradia Direct and UniFil
Core (Graph 1).
The depths of the resin removed from the matrices of the fibre posts were similar
for the two concentrations of hydrogen peroxide (Fig 2c, 3c). Post-core bond
strengths were also increased as a result of post treatment with 4% hydrofluoric
acid, though to a lesser extent than following post immersion in hydrogen peroxide.
One conceivable explanation for these results could be that hydrofluoric acid
selectively dissolves the glass component of the fibre post, producing an irregular
pattern of microspaces on the post surface (Fig. 4a, 4b). This may increase the
surface area and facilitate the penetration of the composite, especially the flowable
resins, into the microretention of the etched post surface. Hydrofluoric acid etching
has been found to improve the bond strength between resin and conventional
silicate-based ceramics (Stangel et al. 1987, Wolf et al. 1993). However, this study,
in agreement with a previous report (Dallari & Mason 2004), showed that
hydrofluoric acid alters the post structure more radically. Conversely, for hydrogen
peroxide pre-treatment, SEM analysis revealed a differential removal of the resin
matrix instead of the glass fibre component, leaving denuded, intact fibres that
appeared undamaged.
This study also evaluated the use of a single-component silane coupling agent with
and without a bonding agent. The results clearly showed that in the absence of
surface modification of the post surface, the adjunctive use of an adhesive only
32
produced limited improvement in the coupling of resin composites to even
methacrylate resin-based fibre posts. Silane coupling agents mainly exert their
function by bonding chemically to the posts and core material and improving
surface wettability (Plueddemann 1991). Following the manufacturer’s
specifications, the silane was applied in a single layer. According to the results of a
recent in vitro study, the formation of a multi-layer structure may result in a
reduction of the effectiveness of silane coupling, since the number of free
methacrylate groups is reduced, and cohesive failure within the silane coating may
occur (Debnath et al. 2003). The low bond strength values obtained for Group 4
and 5 may be due to the absence of free radicals in the pre-polymerised post that is
performed under heat and vacuum by the manufacturer. As an oxygen inhibition
layer is absent, the bonding is poor.
The method utilised for bond strength testing was the microtensile bond test that
has been reported to be suitable for the evaluation of interfacial bond strengths on
areas below 1 mm2 (Pashley et al. 1999). In particular, the non-trimming variant of
the technique was adopted to reduce the number of premature failures during
specimen preparation, in comparison with the “more aggressive” trimming variant
of the microtensile bond test (Goracci et al. 2004).
However this experimental technique has some limitations: The data of this in vitro
study does not give an exact prediction whether the in vitro performance of the
fibre posts is the same as the performance in vivo. Only one type of fibre post was
tested in this study. It would be of interest to analyse other types of posts and to
compare their performances. In this in vitro study the pre-treatment of the post was
immediately followed by the application of the resin composite for the core build-
up. Further in vitro and in vivo studies are necessary to evaluate whether the
positive effect on post-core bond strength is still retained by pre-treating the post
surface well in advance of the clinical use. Evaluation of such a strategy will enable
manufacturers to supply pretreated fibre posts in pre-sealed sachets, as well as
saving clinicians valuable chair-time.
33
Conclusions
Surface treatment of post with hydrogen peroxide and silane application or
hydrofluoric acid and silane application significantly enhances the interfacial bond
strength between fibre posts and core materials. Post pre-treatment with 24%
hydrogen peroxide for 10 min appears to be as an easy, effective and inexpensive
method that can improve the clinical performance of methacrylate resin-based glass
fibre posts.
34
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39
Table 1. List of investigated materials
Material Batch
number Composition Manufacturer
Post GC fibre post
100602061 Glass fibres (77% vol), methacrylate resin matrix (23% vol)
GC Corporation, Tokyo, Japan
Core material
UniFil Flow
0309101 Di-2-Methacryloyloxyethyl, 2,2,4-trimethylhexamethylene dicarbamate, Triethylene glycol dimethacrylate, Fluoro-alumino silicate glass (50- 60%), Silica powder 10-15%
GC Corporation, Tokyo, Japan
UniFil Lo Flo Plus
0405131 Urethane dimethacrylate, Triethylene glycol dimethacrylate, Fluoro-alumino silicate glass (30-40%), Silica powder 5-10% , Camphorquinone
GC Corporation, Tokyo, Japan
Gradia Direct
0305151 Urethane dimethacrylate, Dimethacrylate comonomers, silica, Prepolymerised filler, pigments, catalysts
GC Corporation, Tokyo, Japan
UniFil Core
0310162 Urethane dimethacrylate, Dimethacrylate, photo/chemical initiator, Fluoro-amino silicate glass
GC Corporation, Tokyo, Japan
Surface treatment
Monobond S
E26882 1% wt 3-methacryloxypropyltrimethoxysilane (3-MPS), ethanol/water-based solvent
Ivoclar-Vivadent, Schaan, Liechtenstein
Porcelain Etchant
0300012353 4% Hydrofluoric acid gel Bisco, Schaumburg, IL, USA
Hydrogen peroxide
073196 24% Hydrogen peroxide Sella, Schio, Italy
40
Material Batch number
Composition Manufacturer
24% Hydrogen peroxide 10%
12 10% Hydrogen peroxide Nova Argentia, Milano, Italy
G-Bond
0411221
4-methacryloyl-oxyethyl trimelliate Monomer, Phosphoric Acid Ester Monomer
GC Corporation, Tokyo, Japan
41
Table 2. Mean and standard deviation (in parenthesis) of post-core strength
calculated for all the experimental groups.
Post surface treatment (MPa) Core
material Silane
for 60
seconds
Silane for
60 seconds
+
G-Bond
24% H2O2
for 10
minutes
+ Silane
for 60
seconds
10% H2O2
for 20
minutes
+ Silane
for 60
seconds
4%
Hydrofluoric
acid gel for 60
seconds +
Silane for 60
seconds
UniFil
Flow
5.02
(0.95)
6.04
(2.06)
13.75
(3.20)
13.44
(2.26)
8.55
(3.26)
UniFil Lo
Flo Plus
5.88
(1.13)
6.37
(2.01)
14.93
(3.03)
13.82
(3.32)
9.66
(2.94)
Gradia Direct
7.07 (1.2)
7.48 (2.41)
14.54 (3.36)
13.62 (3.38)
10.96 (3.21)
UniFil Core
8.29 (1.79)
8.53 (2.95)
15.35 (3.37)
14.49 (3.22)
12.78 (2.63)
42
Legends to Figures.
Fig 1. A schematic of the sectioning procedure. One mm thick sticks were serially
cut from the slab (C=core, P=post).
Fig 2. SEM images of the post surface after treatment with 24% hydrogen peroxide
for 10 min (Fig. 2a) (200X bar = 100 µm), (Fig. 2b) (1000X, bar = 10 µm). Cross
section of the post (Fig. 2c) (1000X, bar = 10 µm).
43
44
Fig 3. Representative SEM micrographs of the post surface treated with 10%
hydrogen peroxide for 20 min: (Fig. 3a) (200X, bar =100 µm), (Fig. 3b) (1000X,
bar = 10 µm). Cross-section of the post (Fig. 3c) (1000X, bar = 10 µm).
45
46
Fig 4. SEM images of the post surface after treatment with 4% hydrofluoric acid
gel for 60 s: (Fig. 4a) (200X bar = 100 µm), (Fig. 4b) (1000X, bar = 10 µm). Cross
section of the post (Fig. 4c) (1000X, bar = 10 µm).
47
48
Chapter 2
2.1. Timing of post space preparation and cementation
Many factors can possibly interfere with the development of high bond strength
values between an endodontic post and root canal dentin. Among these the timing
of post preparation and cementation plays an important role (Ewart and Saunders,
1990). There is no consensus on the time interval between the endodontic treatment
and the post preparation. Posts can be placed immediately after completion of the
endodontic treatment or at a later stage after full setting of the sealer. Immediate
post space preparation and cementation is less time consuming (Galen and Mueller,
1998) (Saunders et al.,1991). In addition dye leakage studies reported less apical
leakage when immediate post space preparation was performed (Solano et al.,
2005).
To properly cement a fiber post, is necessary to remove the sealer impregnated
dentin from the canal walls during post space preparation. Then paper points are
required for drying the canal and a microbrush (Ferrari et al., 2001) is required for
placing the primer and the adhesive in the post space. However, both the paper
points and the microbrush can be contaminated by the unset sealer when
performing an immediate post space preparation. This may jeopardize the
cementation procedure as the unset sealer may be transported from the apical to the
coronal portion of the canal before post insertion. Contamination of the post space
with the sealer may impede the set of the luting resin cement during post
cementation (Rosenstiel et al., 1998).
An ideal endodontic sealer should, in part, adhere firmly both to dentin and to
gutta-percha. Differences in the adhesive properties of endodontic sealers may be
expected, because their interaction with either dentin or gutta-percha may vary with
49
their chemical composition. No specific interaction either with dentin or
guttapercha is expected from the setting reaction of the epoxy-based sealers. In
contrast, the zinc oxide-eugenol sealer should firmly bond to dentin and
guttapercha. The setting reaction of the zinc oxide-eugenol mixtures is a chelation
reaction occurring with the zinc ion of the zinc oxide (Lee et al. 2002). In addition,
eugenol is a solvent of gutta-percha that may soften it during the setting reaction
and increase bonding of sealer to gutta-percha.
The effect of eugenol and noneugenol sealers on the retention of resin-cemented
posts has been studied with conflicting results. There have been several
investigations into the effects of endodontic sealers or their constituents on post
retention. Tjan and Nemetz 1992, reported substantial loss of retention of resin
retained posts when they contaminated canals with eugenol before cementation.
Other authors (Wu et al., 1994), (Rohde et al., 1996), (De Almeida et al., 2000),
(Miletic et al., 2002) found lower leakage with the use of epoxy resin sealants
compared with zinc oxide-eugenol sealers. On the other hands other investigations
(Schwartz et al., 1998), (Karapanou et al., 1996) reported that zinc oxide-eugenol
and epoxy resin sealers had similar behaviours.
In the following studies an evaluation of the effect of immediate versus delayed
post cementation on the retention of different types of fiber posts in canals
obturated with a eugenol sealer or with an epoxy resin sealer was conducted.
50
References 2.1.
De Almeida WA, Leonardo MR, Tanomaru Filho M, Silva LA. Evaluation of
apical sealing of three endodontic sealers. Int Endod J 2000;33(1):25-7.
Ewart A, Saunders WP. Investigation into the apical leakage of root-filled teeth
prepared for a post crown. Int Endod J 1990;23(5):239-44.
Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on
efficacy of bonding to root canal walls: an SEM investigation. Dent Mater
2001;17:422-9.
Galen WW, Mueller KI. Restoration of the endodontically treated tooth. In: Cohen
S, Burns RS, editors. Pathways of the pulp. 7th ed. St. Louis: Mosby; 1998. p.691-
717.
Karapanou V, Vera J, Cabrera P, White RR, Goldman M. Effect of immediate and
delayed post preparation on apical dye leakage using two different sealers. J Endod
1996;22(11):583-5.
Lee KW, Williams MC, Camps JJ, Pashley DH. Adhesion of endodontic sealers to
dentin and gutta-percha. J Endod 2002;28(10):684-8.
Miletic I, Ribaric SP, Karlovic Z, Jukic S, Bosnjak A, Anic I. Apical leakage of
five root canal sealers after one year of storage. J Endod 2002;28(6):431-2.
Rosenstiel SF, Gegauff AG. Effect of provisional cementing agents on provisional
resins. J Prosthet Dent 1988;59:29-33.
51
Rohde TR, Bramwell JD, Hutter JW, Roahen JO. An in vitro evaluation of
microleakage of a new root canal sealer. J Endod 1996;22(7):365-8.
Saunders EM, Saunders WP, Rashid MY. The effect of post preparation on the
apical seal of root fillings using chemically adhesive materials. Int Endod J
1991;24:51-7.
Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol
endodontic sealer cements on post retention. J Endod 1998; 24:564-7.
Solano F, Hartwell G, Appelstein C. Comparison of Apical Leakage Between
Immediate Versus Delayed Post Space Preparation Using AH Plus Sealer. J Endod
2005; 31:752-4.
Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention of
prefabricated posts luted with an adhesive composite resin cement. Quintessence
Int 1992;22:839-44.
Wu MK, De Gee AJ, Wesselink PR. Leakage of four root canal sealers at different
thickness. Int Endod J 1994;27(6):304-8.
52
2.2. The effect of immediate versus delayed cementation on the retention of
different types of fiber post in canals obturated using a eugenol sealer
Michele Vano , Alvaro Cury, Cecilia Goracci , Nicoletta Chieffi, Mario Gabriele,
Franklin R Tay, Marco Ferrari. Journal of Endodontics. 2006;32(9):882-5.
Introduction
When restoring endodontically treated teeth with posts and cores, meticulous
attention to details during post cementation is crucial for post retention (1). Posts
may be placed immediately after completion of the endodontic treatment or at a
later stage after full setting of the sealer. Although cementation of a post
immediately after a root filling has been considered safe and less time consuming
(2), there are significant disadvantages. Post space preparation is performed when
the remaining apical 4-5 mm of sealer and gutta-percha are not fully set. Thus,
paper points and microbrushes that are used to apply the dentin adhesives and
luting composites may be contaminated with the unset sealer, jeopardizing their
polymerization and stability. Immediate post space preparation may also disrupt the
apical seal (3). Eugenol-containing root canal sealers represent the gold standard of
sealers in endodontics (4,5). The effect of eugenol and non eugenol sealers on the
retention of resin-cemented posts has been studied with conflicting results. The
presence of eugenol on the canal walls appeared to have an adverse effect on post
retention (6,7). However, others reported no difference between the use of a
eugenol and a noneugenol sealer on post retention (8). Clinically, the ideal time
needed for the sealers to set should be neither too fast nor too slow (9). Depending
on the type of sealer and the experimental technique, a wide range of setting times
has been recorded (10,11). A variable setting time ranging from a few minutes to
one day has been reported for Pulp Canal Sealer (Sybron-Kerr Romulus, MI) (12).
Controversial results exist on the manifestation of leakage after post placement.
53
While some authors demonstrated there was no difference in leakage between
immediate and delayed post space preparation (13-15), others reported that
immediate removal of gutta-percha resulted in less leakage when compared to
delayed removal (16-18). Recently, the effects of the sequence of post space
preparations and cementation using eugenol and resin-based sealers have been
examined (19). Post spaces prepared prior to obturation exhibited lower post
retention strength than preparation after root canal obturation.
The aim of this study was to evaluate the effect of immediate versus delayed post
cementation on the retention of different types of fiber posts in canals obturated
with a eugenol sealer. The null hypothesis tested was that there are no differences
in the interfcaial strengths derived from posts cemented immediately, 24 h or 1
week after completion of the root canal fillings.
Material and Methods
Sixty caries-free, recently extracted single-root human teeth with straight root
canals were used in this study. They were stored in 0.5% chloramines T until use.
All root canals were prepared by one trained operator with nickel titanium rotary
instruments M-two (Sweden & Martina, Due Carrare, Padova, Italy) and Profiles
(Dentsply Maillefer, Ballaigues, Switzerland) that were mounted in a 16:1 gear
reduction handpiece and driven by an electric motor (Endo IT professional,
Aseptico Inc., Woodinville, WA).
Specimen Preparation
Each tooth was decoronated below the cementoenamel junction and
perpendicularly to the longitudinal axis with a diamond blade under copious water
cooling. The working length was obtained at 1 mm above the radiographic apex.
The roots canals were endodontically instrumented using stainless steel instruments
K-files (#08-10-15; Dentsply Maillefer) and rotary Ni-Ti instruments M-two (#10-
54
15-20-25) and Profiles .06 taper (#30-35-40). Instrumentation was performed under
an operating microscope (OPMI pico, Carl Zeiss Surgical, Inc., Thornwood, NY)
at 12.5X magnification. The root canal was irrigated in between instrumentation
with 3 mL of 5.25% sodium hypochlorite using a long 27 gauge needle. Deionized
water was employed as the final rinse and patency of the canals was maintained
with a #10 K-file. The canals were dried with multiple paper points.
Warm Vertical Compaction of Gutta-Percha
A nonstandardized gutta-percha master cone (Hygienic, Coltène/Whaledent,
Mahwah, NJ) was fitted with tug-back to the working length of each root canal.
Pulp Canal Sealer was placed in the canal and spread with a #45 K-file with a
counterclockwise motion. The master gutta-percha cone was coated with the sealer
and seated in the canal 1 mm short of the working length. The gutta-percha was
compacted using the continuous wave technique up to 4 to 5 mm from the apex
with a System B heat source (Analytic Technology, Redwood). Backfilling of
gutta-percha was performed using thermoplastic gutta-percha and an Obtura II unit
(Obtura Corp., Fenton, MO) at 185°C. The filled teeth were divided into four
experimental groups (N=15) according to the different times of post space
preparation and cementation:
Group 1: The post space was prepared immediately after obturation, with part of
the filling material was removed with burs. The canal walls of each specimen were
enlarged with low-speed post drills provided by the manufacturer. To preserve the
apical seal, at least 5 mm of the root filling was retained at the apical level (20).
Prior to post cementation, each specimen was examined with the operating
microscope to observe any irregularities in the post space preparation.
Group 2: The teeth were stored in saline at 37°C for 24 h after obturation and the
post spaces were prepared in the same manner as in Group 1.
Group 3: The teeth were stored in saline at 37°C for 1 week after obturation and
the post spaces were prepared in the same manner as in Group 1.
55
Group 4: The roots were cleaned and shaped as in the other groups but no filling
was performed (positive control). Post spaces were then created in the same
manner as in Group 1.
After post space preparation, the access cavities of the teeth from all groups were
restored with a non-eugenol temporary filling material (Coltosol,
Coltène/Whaledent). The teeth were kept moist in deionized water prior to the
luting procedures.
Each group was further divided into three subgroups of 5 teeth each, according to
the type of post and the materials used for luting the posts (Table 1). Prior to
cementation, each post was cleaned with 95% ethanol. A microbrush was used to
introduce the primer and the adhesive into each canal (21). A gentle stream of air
was directed over the canal orifice for 2 s. The cement was then placed on the post
and into the canal space. The post was inserted as close to the center of the post
space as possible to mantain a circumferential layer of sealer between the post and
the intraradicular dentin. The materials were used according to the manufacturers’
instructions (Table 1).
Push-out Test
A push-out test was performed to evaluate the post-intraradicular dentin interfacial
strength (22-24). The portion of each root that contained the fiber post was
sectioned into five to six 1 mm thick slices with a water-cooled diamond blade
(Labcut 1010, Extec Corp., Enfield, CT). A compressive load was applied to the
apical aspect of the slice via a cylindrical plunger of 0.65 mm diameter that was
mounted on a universal testing machine (Controls S.P.A., Milano. Italy). A plunger
tip size was selected and positioned to contact only the post, without stressing the
surrounding root canal walls (22). The load was applied to the apical aspect of the
root slice and in an apical-coronal direction, so as to push the post toward the larger
part of the root slice, thus avoiding any limitation to the post movement. Care was
also taken to ensure that the contact between the punch tip and the post section
56
occurred over the most extended area, to avoid notching of the punch tip into the
post surface. Loading was performed at a crosshead speed of 0.5 mm/min until
bond failure occurred. Bond failure was manifested by the extrusion of the post
from the root section. Interfacial strength (in megaPascal) was calculated by
dividing the load at debonding (Newtons) by the area (mm2). The area (SL) was
estimated by using the formula for calculating the lateral surface area of a truncated
cone: SL = π(R+r)[(h2 + (R-r)2]0.5, where R represents the coronal post radius, r
the apical post radius, and h the thickness of the slice.
Statistical Analysis
As bond strength data were normally distributed (Kolmogorov-Smirnov test) and
homogeneous in variances (Levene’s test), a two-way ANOVA was performed to
examine the effect of the type of post and timing of post space preparation on
interfacial strength. Post-hoc multiple comparisons were performed using the
Tukey test, with the significance level set at α=0.05.
Results
Statistical analysis revealed that both the type of post used and the timing of post
space preparation significant affected the interfacial strength between the post and
intraradicular dentin (p<0.05). The interaction between these two factors was not
significant (p>0.05). For the factor "post type', interfacial strength of the FRC
Postec post (Ivoclar Vivadent, Liechtenstein, Germany) was significantly higher
than the ENA posts (GDF, Rosbach, Germany) (p<0.05). Interfacial strengths of
the DT Light Post (Dentsply DeTrey, Konstanz, Germany) were higher than the
ENA Post but lower than the FRC Postec post; however the differences were not
statistically significant (Table 2).
For the factor "timing of post space preparation", interfacial strength achieved with
immediate post preparation (Group 1) was significantly lower than those achieved
when post preparations were performed after 24 h (Group 2) and at 1 week (Group
57
3) (p<0.05). There was no difference in interfacial strengths measured at 24 h and 1
week (p>0.05). Regardless of the post type, the control group (Group 4) showed
the highest interfacial strengths. These values were significantly higher that those
in Group 1 (p<0.05), but were similar to those in Groups 2 and 3 (p>0.05). A
summary of interfacial strength data is depicted in Table 2.
Discussion
The results of this study indicated that irrespective of post type, immediate post
space preparation and post cementation resulted in inferior post retention, as
manifested by the lower interfacial strengths between the bonded post and
intraradicular dentin. Conversely, better post retention was achieved, as manifested
by the higher interfacial strengths, when the post space preparation and post
cementation were performed 24 h or one week after the canals with filled with
gutta-percha and a eugenol sealer. Thus, the null hypothesis that there are no
differences in the interfacial strengths derived from posts cemented immediately,
24 h or 1 week after completion of the root canal fillings has to be rejected.
Mechanical removal of the sealer-impregnated dentin from the canal walls during
post space preparation is considered to be critical to achieve ideal post retention
using adhesive techniques (19). A disadvantage of the immediate technique is that
post space preparation and cementation are perfomed when the sealer in the apical
part of the canal is not fully set yet. To properly cement a fiber post, paper points
are required for drying the canal and a microbrush (21) is required for placing the
primer and the adhesive in the post space. However, both the paper points and the
microbrush may be contaminated by the unset sealer. This may jeopardize the
cementation procedure as the unset sealer may be transported from the apical to the
coronal portion of the canal before post insertion. Contamination of the post spaces
with the eugenol-containing sealer may impede the set of the luting resin cement
during post cementation (25). Interestingly, bond strengths in the 24 h and 7-day
groups (i.e. Groups 2 and 3) were similar (Table 2). A possible explanation is that
58
contamination of the post spaces is minimized when the sealer is allowed to set
completely before post space preparation. Indeed, the highest interfacial strength
values were recorded from the control group that was only clean and shaped but
without being filled. Clearly the adhesive procedure benefited the most from a
perfect clean root surface which was not contaminated with the eugenol-containing
sealer. Apart from the timing of post space preparation, interfacial strength was
also significantly affected by the type of post employed. In particular the FRC
Postec posts achieved the highest interfacial strengths in all the tested groups than
the DT Light Posts and the ENA posts. Presumably, the methacrylate resin matrix
of the FRC Postec posts allows better bonding with the methacrylate-based
adhesives and resin cements (26, 27). Conversely, apart from silanization of the
glass fibers, there is no chemical interaction between the epoxy resin matrices of
the DT Light Posts and ENA posts with the methacrylate-based adhesives and resin
cements. Within the limits of this study, it may be concluded that clinicians should
be cautious about performing post space preparation and cementation of fiber posts
immediately after filling of the root canals with a zinc oxide eugenol root canal
sealer, as delayed preparation and cementation shows higher interfacial strengths
irrespective of the type of fiber post employed.
59
References
1. Standlee JP, Caputo AA, Hanson EC. Retention of endodontic dowels: effect of
cement, dowel length, diameter, and design. J Prosthet Dent 1978; 39:401-5.
2. Galen WW, Mueller KI. Restoration of the endodontically treated tooth. In:
Cohen S, Burns RS, eds. Pathways of the pulp. 7th ed. St. Louis: Mosby, 1998;
691-717.
3. Saunders EM, Saunders WP, Rashid MY. The effect of post preparation on the
apical seal of root fillings using chemically adhesive materials. Int Endod J 1991;
24:51-7.
4. Hagge MS, Wong RD, Lindemuth JS. Retention of posts luted with phosphate
monomer-based composite cement in canals obturated using a eugenol sealer. Am J
Dent 2002; 15:378-82.
5. Mickel AK, Wright ER. Growth inhibition of Strreptococcus anginosus (milleri)
by three calcium hydroxide sealers and one zinc oxide-eugenol sealer. J Endod
1999; 25:34-7.
6. Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention
of prefabricatedposts luted with an adhesive composite resin cement. Quintessence
Int 1992; 22:839-44.
7. Ngoh EC, Pashley DH, Loushine RJ, Weller RN, Kimbrough WF. Effects of
eugenol on resin bond strengths to root canal dentin. J Endod 2001; 27:411-4.
8. Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol
endodontic sealer cements on post retention. J Endod 1998; 24:564-7.
9. Allan NA, Walton RC, Schaeffer MA. Setting times for endodontic sealers under
clinical usage and in vitro conditions. J Endod 2001; 27:421-3.
10. McComb D, Smith D. Comparison of physical properties of polycarboxylate-
based and conventional root canal sealers. J Endod 1976; 2:228–34.
11. Ørstavik D, Nordahl I, Tibballs J. E. Dimensional change following setting of
root canal sealer materials. Dent Mater 2001; 17:512-19.
60
12. Caicedo R, von Fraunhofer J. The properties of endodontic sealer cements. J
Endod 1988; 14: 527–33.
13. Bourgeois RS, Lemon RR. Dowel space preparation and apical leakage. J
Endod 1981;7:66–9.
14. Madison S, Zakariasen KL. Linear and volumetric analysis of apical leakage in
teeth prepared for posts. J Endod 1984;10:422–7.
15. Abramovitz I, Tagger M, Tamse A, Metzger Z. The effect of immediate vs.
delayed post space preparation on the apical seal of a root canal filling: a study in
an increased-sensitivity pressuredriven system. J Endod 2000; 26:435–9.
16. Kwan EH, Harrington GW. The effect of immediate post preparation on apical
seal. J Endod 1981; 7:325–9.
17. Fan B, Wu MK, Wesselink PR. Coronal leakage along apical root fillings after
immediate and delayed post space preparation. Endod Dent Traumatol 1999;
15:124–6.
18. Solano F, Hartwell G, Appelstein C. Comparison of Apical Leakage Between
Immediate Versus Delayed Post Space Preparation Using AH Plus Sealer. J Endod
2005; 31:752-4.
19. Boone KJ, Murchison DF, Schindler WG, Walker WA. Post retention: the
effect of sequence of post-space preparation, cementation time and different
sealers. J Endod 2001; 27:768-71.
20. Abramovitz L, Lev R, Fuss Z, Metzger Z. The unpredictability of seal after post
space preparation: a fluid transport study. J Endod 2001; 27:292–5.
21. Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on
efficacy of bonding to root canal walls: an SEM investigation. Dent Mater
2001;17:422 9.
22. Goracci C, Tavares AU, Fabianelli A, Monticelli F, Raffaelli O, Cardoso PC,
Tay F, Ferrari M The adhesion between fiber posts and root canal walls:
comparison between microtensile and pushout bond strength measurements. Eur J
Oral Sci 2004;112:353-61.
61
23. Goracci C, Fabianelli A, Sadek FT, Papacchini F, Tay FR, Ferrari M. The
contribution of friction to the dislocation resistance of bonded fiber posts. J Endod
2005; 31:608-12.
24. Gesi A, Raffaelli O, Goracci C, Pashley DH, Tay FR, Ferrari M. Interfacial
strength of Resilon and gutta-percha to intraradicular dentin. J Endod 2005;
31:909-13.
25. Rosenstiel SF, Gegauff AG. Effect of provisional cementing agents on
provisional resins. J Prosthet Dent 1988;59(1):29-33.
26. Monticelli F, Osorio R, Albaladejo A, Aguilera FS, Ferrari M, Tay FR,
Toledano M. Effects of adhesive systems and luting agents on bonding of fiber post
to root canal dentin. J Biomed Mater Res B Appl Biomater 2005; 21:[Epub ahead
of print].
27. Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M.
The adhesion between fibre post and composite resin cores: the evaluation of
microtensile bond strength following various post surface chemical treatments to
posts. Int Endod J 2006;39(1):31-9.
62
TABLE 1. Summary of the “step-by-step” procedures employed for fiber post cementation, according to the manufacturer’s instructions
Dentsply DeTrey Konstanz, Germany (Post type: DT Light Post)
Ivoclar-Vivadent Schaan, Liechtenstein (Post type:
FRC Postec)
GDF Gesellschaft für Dental Forschung und
Innovationen, Rosbach, Germany (Post type: ENA
Post) Acid-etch post space with Conditioner
Acid-etch post space with Total Etch
Acid-etch post space with ENA-Etch
36 Gel for 15 s for 15 s for 60 s
Water/Rinse without desiccation Water/Rinse without desiccation
Water/Rinse without desiccation
Mix Prime&Bond NT + Dual Cure Mix Primer A � B (1:1) for5sand
Mix ENA Bond � Catalyst (1:1) for
catalyst for 2 s and apply for 20 s in
apply to the root canal for 15 s 5 s and apply to the root canal
the root canal and on the DT Light for 20 sec and on the ENA post
Post (0,90/1,50)* surface (0,95/1,45)* surface
Gently air dry for 5 s Gently air dry for 5 s Gently air dry for 5 s
Apply Monobond S (silane) to the
FRC Postec post (0,85/1,45)* surface for 60 s and gently air
dry
for5s Apply Calibra Esthetic Resin Cement
Apply MultiLink resin cement on Apply ENA Cem cement on the
on the post and place the post the post and place the post inside
post and place the post inside
inside the root canal the root canal the root canal
Light-cure with minimum output Light-cure with minimum output Light-cure with minimum output
intensity of 600 mw/cm2 for 40 s intensity of 600 mw/cm2 for 40 s
intensity of 600 mw/cm2 for 40 s
*Minimum/maximum cross-section post diameter in mm.
63
Table 2. Effect of immediate versus delayed post space preparation on post retention
Post type Group 1 Immediate
Group 2 24 hours
Group 3 7 days
Group 4 Control
DT Light Post 6.0 ± 3.60 (49)a 6.6 ± 3.6 (47)b 7.1 ± 3.1 (47)b 7.5 ± 3.5 (48)b
Ena Post 5.2 ± 2.0 (47)a 6.4 ± 3.3 (47)b 5.8 ± 3.2 (48)b 6.1 ± 2.7 (57)b
FRC Postec 5.8 ± 5.8 (59)a 7.6 ± 3.1 (51)b 7.7 ± 3.2 (54)b 8.1 ± 4.4 (58)b
Values are mean ± standard deviation in MPa. The number in parenthesis represents the number of specimens tested. Symbols represent significant differences with regard to the factor “time of post insertion” (P < 0.05). Lower case letters represent significant differences among the post systems (P<0.05).
64
2.3. Retention of fiber posts cemented at different time intervals in canals
obturated using an epoxy resin sealer
Michele Vano, Alvaro H. Cury, Cecilia Goracci, Nicoletta Chieffi , Mario
Gabriele, Franklin. R. Tay, Marco Ferrari. Journal of Dentistry, Submitted
Introduction
Many factors can possibly interfere with the development of high bond strength
values between an endodontic post and root canal dentin. Among these the timing
of post space preparation and cementation plays an important role.1 There is no
consensus on the time interval between the endodontic treatment and the post space
preparation.2 Posts can be placed immediately after completion of the endodontic
treatment or at a later stage after full setting of the sealer. Dye leakage studies
reported less apical leakage when immediate post space preparation was
performed.3 In addition immediate post space preparation and cementation is less
time consuming.4,5 However concerns on the immediate procedure were arousen
because of the possible negative effect of the unset sealer on post retention. The
removal of the sealer impregnated dentin from the canal walls during post space
preparation represents an important factor for post retention.6 To properly cement a
fiber post, paper points are required for drying the canal and a microbrush is
required for placing the primer and the adhesive in the post space.7 However, both
the paper points and the microbrush can be contaminated by the unset sealer. This
may jeopardize the cementation procedure as the unset sealer may be transported
from the apical to the coronal portion of the canal before post insertion.
Contamination of the post space with the sealer may impede the set of the luting
resin cement during post cementation.8 A recent study recorded low bond strength
values between the post and root dentin when immediate post space preparation
and cementation with an eugenol sealer were performed.9
65
The effect of eugenol sealers on the retention of resin-cemented posts has been
studied with conflicting results.10,11 The presence of eugenol on the canal walls
appeared to have an adverse effect on post retention.12 To avoid this problem epoxy
resin root canal sealers have been recomended.13 AH Plus (Dentsply, De Trey,
Konstanz, Germany) is an epoxy-amine resin sealer that has gained recent
popularity among clinicians.
The aim of this study was to evaluate the effect of immediate versus delayed post
space preparation and cementation on the retention of different types of fiber post
systems in canals obturated with an epoxy resin sealer. Post space characteristics
following immediate versus delayed post cementation were also observed using
scanning electron microscopy (SEM)
The null hypothesis tested was that there are no differences in the retentive
strengths derived from post systems cemented immediately, 24 hours or 1 week
after completion of the root canal fillings.
Material and Methods
Sixty-eight caries-free, recently extracted single-root human teeth with straight root
canals were used in this study. They were stored in 0.5% chloramines T until use.
Each tooth was decoronated below the cementoenamel junction and
perpendicularly to the longitudinal axis with a diamond blade under copious water
cooling.
All root canals were prepared by one trained operator. The roots canals were
endodontically instrumented using stainless steel instruments K-files (#08-10-15;
Dentsply Maillefer Ballaigues, Switzerland) and rotary Ni-Ti instruments M-two
(#10-15-20-25; Sweden & Martina, Due Carrare, Padova, Italy) and Profiles .06
taper (#30-35-40; Dentsply Maillefer) that were mounted in a 16:1 gear reduction
handpiece, driven by an electric motor (Endo IT professional, Aseptico Inc.,
Woodinville, WA). The working length was obtained at 1 mm above the
66
radiographic apex. Instrumentation was performed under an operating microscope
(OPMI pico, Carl Zeiss Surgical, Inc., Thornwood, NY) at 12.5X magnification.
The root canal was irrigated in between instrumentation with 3 mL of 5.25%
sodium hypochlorite using a long 27 gauge needle. Deionized water was employed
as the final rinse and patency of the canals was maintained with a #10 K-file. The
canals were dried with multiple paper points. A nonstandardized gutta-percha
master cone (Hygienic, Coltène/Whaledent, Mahwah, NJ) was fitted with tug-back
to the working length of each root canal. AH Plus sealer (Dentsply, De Trey,
Konstanz, Germany) was placed in the canal and spread with a #45 K-file with a
counterclockwise motion. The gutta-percha was compacted using the continuous
wave technique up to 4 to 5 mm from the apex with a System B heat source
(Analytic Technology, Redwood). Backfilling of gutta-percha was performed using
thermoplastic gutta-percha and an Obtura II unit (Obtura Corp., Fenton, MO) at
185°C. After the root filling, the access cavities of the teeth from all groups were
restored with a non-eugenol temporary filling material (Coltosol,
Coltène/Whaledent). The teeth were kept moist in saline solution at 37° before the
luting procedures. The filled teeth were divided into three experimental groups
according to the different times of post space preparation and cementation. A
control group was included.
Group 1: The post space was prepared immediately after obturation and part of the
filling material was removed with an heated instrument (System B Spreader)
(Analytic Technology, Redwood) inserted into the canal to the desired length. The
canal walls of each specimen were enlarged with low-speed post drills provided by
the manufacturer. To preserve the apical seal, at least 5 mm of the root filling was
retained at the apical level.14 Before post cementation, each specimen was
examined with the operating microscope to observe any irregularities in the post
space preparation.
67
Group 2: The teeth were stored for 24 h after obturation. Then the post spaces
were prepared in the same manner as in group 1.
Group 3: The teeth were stored for 1 week after obturation. Then the post spaces
were prepared in the same manner as in group 1.
Group 4: The roots were cleaned and shaped as in the other groups but no filling
was performed (control group). Post spaces were then prepared in the same manner
as in group 1.
Each group was furtherly divided into three subgroups of five teeth each (n=5),
according to the type of post and the materials used for luting the posts (Table 1).
Before cementation, each post was cleaned with 95% ethanol. A microbrush was
used to introduce the primer and the adhesive into each canal.7 A gentle stream of
air was directed over the canal orifice for 2 s. The cement was then placed on the
post and into the canal space. The materials were used according to the
manufacturers’ instructions (Table 1).
SEM analysis
Two teeth were randomly selected from each group for SEM examination of the
post space. In order to assess qualitatively the cleanliness of the post space just
before post insertion the luting procedure were performed without cementing the
post in the canal. The specimen was then sectioned longitudinally. Each specimen
was mounted on a metallic stub, gold-sputtered (Polaron Range SC7620, Quorum
Technology, Newhaven, UK), and observed under a JSM 6060LV microscope
(JEOL, Tokyo, Japan) at different magnifications.
Push-out Test
A push-out test was performed to evaluate the post-intraradicular dentin interfacial
strength.15,16 The portion of each root that contained the fiber post was sectioned
into five to six 1 mm-thick slices with a water-cooled diamond blade (Labcut 1010,
68
Extec Corp., Enfield, CT). A compressive load was applied to the apical aspect of
the slice via a cylindrical plunger of 0.65 mm-diameter that was mounted on a
universal testing machine (Controls S.P.A., Milano. Italy). A plunger tip size was
selected and positioned to contact only the post, without stressing the surrounding
root canal walls.15 The load was applied to the apical aspect of the root slice and in
an apical-coronal direction, so as to push the post toward the larger part of the root
slice, thus avoiding any limitation to the post movement. Care was also taken to
ensure that the contact between the punch tip and the post section occurred over the
most extended area, to avoid notching of the punch tip into the post surface.
Loading was performed at a crosshead speed of 0.5 mm/min until bond failure
occurred. Bond failure was manifested by the extrusion of the post from the root
section. Interfacial strength (in megaPascal) was calculated by dividing the load at
debonding (Newtons) by the area (mm2). The area (SL) was estimated by using the
formula for calculating the lateral surface area of a truncated cone: SL = π(R+r)[(h2
+ (R-r)2]0.5, where R represents the coronal post radius, r the apical post radius, and
h the thickness of the slice.
Statistical Analysis
After having checked that bond strength data were normally distributed
(Kolmogorov-Smirnov test), that group variances were homogeneous (Levene’s
test), and that the root of origin of the slices was not a significant factor for bond
strength (Regression analysis), root slices were considered as statistical units and a
two-way ANOVA was performed to examine the effect of the type of post and
timing of post space preparation on interfacial strength. Post-hoc multiple
comparisons were performed using the Tukey test, with the significance level set at
α=0.05.
69
Results
Statistical analysis revealed that both the type of post system used and the timing of
post space preparation and cementation significantly affected the interfacial
strength between the post and intraradicular dentin (p<0.05). The interaction
between these two factors was not significant (p>0.05). For the factor post type,
interfacial strength values of the FRC Postec posts (Ivoclar Vivadent,
Liechtenstein, Germany) and DT Light Post posts (Dentsply DeTrey, Konstanz,
Germany) were significantly higher than those achieved with ENA Post posts
(GDF, Rosbach, Germany) (p<0.05). (Table 2).
For the factor timing of post space preparation, interfacial strength values achieved
with immediate post preparation (group 1) were significantly lower (p<0.05) than
those achieved when post preparation and cementation were performed 24 h (group
2) and/or 1 week (group 3) after the root canal filling. There was no difference in
interfacial strength values measured at 24 h and 1 week (p>0.05) after root canal
fillings. Regardless of the post type, the control group (group 4) showed the highest
interfacial strength values. These values were significantly higher than those in
group 1 (p<0.05), but comparable to those in groups 2 and 3 (p>0.05). A summary
of interfacial strength data is depicted in Table 2.
SEM investigation
SEM examination revealed a higher presence of sealer remnants along the post
space walls of the specimens in group 1 (immediate post space preparation and
cementation) when compared to those in group 2 (post space preparation and
cementation performed 24 h after the root canal filling) and 3 (post space
preparation and cementation performed 1 week after the root canal filling)
independently of the type of luting materials used (Fig.1A-B). The aumont of
sealer remnants along the post space walls observed in group 2 (Fig. 2A-B), and 3
(Fig. 3A-B) was similar.
70
Discussion
There was a significant increase in retention when the post space preparation and
post cementation were performed 24 h and/or one week after the canals were filled
with gutta-percha and AH Plus sealer (Dentsply DeTrey, Konstanz, Germany).
Conversely, immediate post space preparation and cementation resulted in low
interfacial strength values between the bonded post and radicular dentin (Table 2).
Thus, the null hypothesis that there are no differences in the interfacial strengths
derived from posts cemented immediately, 24 h or 1 week after completion of the
root canal filling has to be rejected.
SEM micrographs revealed that specimens in group 1 showed more remnants of
sealer and gutta-percha than specimens in group 2 and 3 (Fig. 1A-B, 2A-B, 3A-B).
These findings lead the authors to speculate that there could be a correlation
between post retention and the cleanliness of the post space walls. The data of the
present study are in accordance with those obtained in a recent report 9 in which the
canals were obturated with an eugenol sealer (Pulp Canal Sealer) (Sybron-Kerr
Romulus, MI,USA).
Both AH Plus (Dentsply, De Trey, Konstanz, Germany) and Pulp Canal Sealer
have a similar setting time (6-8 h) therefore when immediate post space preparation
and cementation are perfomed the sealer in the apical part of the canal is not fully
set yet.17,18 As a consequence both the paper points and the microbrush used in the
luting procedure contaminate the post space with the unset sealer just before post
insertion. On the contrary a delayed post space preparation and cementation allows
the sealer to set properly thus the contamination of the post space is avoided.
Apart from the timing of post space preparation, the interfacial strength was also
significantly affected by the type of post employed. In particular the FRC Postec
achieved the highest interfacial strengths when compared to DT Light Post and the
ENA Post. Presumably, the methacrylate resin matrix of the FRC Postec allows
better bonding with the methacrylate-based adhesives and resin cements.19,20
Conversely, apart from silanization of the glass fibers, there is no chemical
71
interaction between the epoxy resin matrices of the DT Light Post and ENA Post
with the methacrylate-based adhesives and resin cements.
Conclusions
Within the limits of this study, it may be concluded that clinicians should be
cautious about performing post space preparation and cementation of fiber posts
immediately after filling of the root canals, as delayed preparation and cementation
shows higher interfacial strengths irrespectively of the type of fiber post employed.
72
References
1. Ewart A, Saunders WP. Investigation into the apical leakage of root-filled teeth
prepared for a post crown. International Endodontic Journal 1990;23:239-44.
2. Karapanou V, Vera J, Cabrera P, White RR, Goldman M. Effect of immediate
and delayed post preparation on apical dye leakage using two different sealers.
Journal of Endodontics 1996;22:583-5.
3. Solano F, Hartwell G, Appelstein C. Comparison of Apical Leakage Between
Immediate Versus Delayed Post Space Preparation Using AH Plus Sealer. Journal
of Endodontics 2005; 31:752-4.
4. Galen WW, Mueller KI. Restoration of the endodontically treated tooth. In:
Cohen S, Burns RS, editors. Pathways of the pulp. 7th ed. St. Louis: Mosby; 1998.
p.691-717.
5. Saunders EM, Saunders WP, Rashid MY. The effect of post preparation on the
apical seal of root fillings using chemically adhesive materials. International
Endodontic Journal 1991;24:51-7.
6. Boone KJ, Murchison DF, Schindler WG, Walker WA. Post retention: the effect
of sequence of post-space preparation, cementation time and different sealers.
Journal of Endodontics 2001;27:768-71.
7. Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on
efficacy of bonding to root canal walls: an SEM investigation. Dental Materials
2001;17:422 9.
73
8. Rosenstiel SF, Gegauff AG. Effect of provisional cementing agents on
provisional resins. Journal of Prosthetic Dentistry 1988;59:29-33.
9. Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M. The
effect of immediate versus delayed cementation on the retention of different types
of fibre post in canals obturated using a eugenol sealer. Journal of Endodontics
2006;3:882-5.
10. Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention
of prefabricated posts luted with an adhesive composite resin cement. Quintessence
International 1992;22:839-44.
11. Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol
endodontic sealer cements on post retention. Journal of Endodontics 1998; 24:564-
7.
12. Ngoh EC, Pashley DH, Loushine RJ, Weller RN, Kimbrough WF. Effects of
eugenol on resin bond strengths to root canal dentin. Journal of Endodontics
2001;27:411-4.
13. Cohen BI, Volovich Y, Musikant BL, Deutsch AS. The effects of eugenol and
epoxy-resin on the strength of a hybrid composite resin. Journal of Endodontics
2002;28:79-82.
14. Abramovitz I, Tagger M, Tamse A, Metzger Z. The effect of immediate vs.
delayed post space preparation on the apical seal of a root canal filling: a study in
an increased-sensitivity pressure-driven system. Journal of Endodontics
2000;26:435–9.
74
15. Goracci C, Tavares AU, Fabianelli A, Monticelli F, Raffaelli O, Cardoso PC,
Tay F, Ferrari M. The adhesion between fiber posts and root canal walls:
comparison between microtensile and push-out bond strength measurements.
European Journal of Oral Science 2004;112:353-61.
16. Goracci C, Fabianelli A, Sadek FT, Papacchini F, Tay FR, Ferrari M. The
contribution of friction to the dislocation resistance of bonded fiber posts. Journal
of Endodontics 2005;31:608-12.
17. Allan NA, Walton RC, Schaeffer MA. Setting times for endodontic sealers
under clinical usage and in vitro conditions. Journal of Endodontics 2001;27:421-3.
18. McMichen FRS, Pearson G, Rahbaran S, Gulabivala K. A comparative study of
selected physical properties of five root-canal sealers. International Endodontic
Journal 2003;36:629-35.
19. Monticelli F, Osorio R, Albaladejo A, Aguilera FS, Ferrari M, Tay FR,
Toledano M. Effects of adhesive systems and luting agents on bonding of fiber post
to root canal dentin. Journal of Biomedical Materials Research Part B: Applied
Biomaterials 2006;77:195-200.
20. Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M.
The adhesion between fibre post and composite resin cores: the evaluation of
microtensile bond strength following various post surface chemical treatments to
posts. International Endodontic Journal 2006;39:31-9.
75
Table 1 Summary of the “step-by-step” procedures employed for fiber post
cementation, according to the manufacturer’s instructions
Dentsply DeTrey Konstanz, Germany (Post type: DT Light
Post)
Ivoclar-Vivadent Schaan, Liechtenstein
(Post type: FRC Postec)
GDF Gesellschaft für
Dental Forschung und Innovationen,
Rosbach, Germany (Post type: ENA Post)
Acid-etch post space with Conditioner 36 Gel for 15 s
Acid-etch post space with Total Etch for 15 s
Acid-etch post space with ENA-Etch for 60 s
Water/Rinse without desiccation
Water/Rinse without desiccation
Water/Rinse without desiccation
Mix Prime&Bond NT + Dual Cure catalyst for 2 s and apply for 20 s in the root canal and on the DT Light Post (0,90/1,45)* surface
Mix Primer A+B (1:1) for 5 s and apply to the root canal for 15 s
Mix ENA Bond + Catalyst (1:1) for 5 s and apply to the root canal for 20 sec and on the ENA Post (0,95/1,45)* surface
Gently air dry for 5 s Gently air dry for 5 s Gently air dry for 5 s Apply Monobond S
(silane) to the FRC Postec post (0,90/1,45)* surface for 60 s and gently air dry for 5 s
Apply Calibra Esthetic Resin Cement on the post and place the post inside the root canal
Apply MultiLink resin cement on the post and place the post inside the root canal
Apply ENA Cem cement on the post and place the post inside the root canal
Light-cure with minimum output intensity of 600mw/cm2 for 40 s
Light-cure with minimum output intensity of 600mw/cm2 for 40 s
Light-cure with minimum output intensity of 600mw/cm2 for 40 s
* minimum / maximum cross-section post diameter in mm.
76
Table 2. Effect of immediate versus delayed post space preparation and cementation on post retention
Post type Group 1 Immediate
Group 2 24 hours
Group 3 1 week
Group 4
Control
DT Light Post* 5.9 ± 2.2 (51)a 7.3 ± 2.3 (49)b 7.0 ± 2.8 (48)b 7.5 ± 3.5 (48)b
ENA Post§ 5.0 ± 2.1 (50)a 6.5 ± 2.6(46)b 6.8 ± 2.5 (47)b 6.1 ± 2.7 (57)b
FRC Postec* 6.3 ± 2.7 (57)a 7.9 ± 2.8 (49)b 7.4 ± 2.3 (55)b 8.1 ± 4.4 (58)b
Values are mean ± standard deviation in MPa. The number in parenthesis represents the number of specimens tested Symbols represent significant differences with regard to the factor “post type” (p < 0.05) Lower case letters represent significant differences with regard to the factor “timing of post space preparation and cemenattion” (p < 0.05)
77
Figure 1A. SEM photomicrographs of the post space in Group 1. Sealer and gutta-
percha remnants are visible all along the post canal walls (original
magnification×20, bar=1 mm).
78
Figure 1B. Higher magnification of the post space (original magnification×500,
bar=50 µm).
79
Figure 2A. SEM photomicrographs of the post space in Group 2. Small areas of
sealer and guttapercha remnants are present along the post canal walls (original
magnification×20, bar=1 mm).
80
Figure 2B. Higher magnification of the post space. The surface of the post space is
clean with only few areas of sealer and gutta-percha remnants (original
magnification×500, bar=1 µm).
81
Figure 3A. SEM photomicrographs of the post space in Group 3. The surface of the
post space is clean with only few areas of sealer and gutta-percha remnants
(original magnification×22, bar=1 mm).
82
Figure 3B. Higher magnification of figure 3A (original magnification×500, bar=50
µm).
83
2.4. Endodontic sealer: eugenol versus non-eugenol sealers
Retention is of high importance for the success of intracanal posts in
endodontically treated teeth. The effect of eugenol and noneugenol sealers on the
retention of resin-cemented posts has been studied with conflicting results. There
have been several investigations into the effects of endodontic sealers or their
constituents on post retention. Tjan and Nemetz 1992, reported substantial loss of
retention of resin retained posts when they contaminated canals with eugenol
before cementation. Other authors (Wu et al., 1994), (Rohde et al., 1996), (De
Almeida et al., 2000), (Miletic et al., 2002) found lower leakage with the use of
epoxy resin sealants compared with zinc oxide-eugenol sealers. On the other hands
other investigations (Schwartz et al., 1998), (Karapanou et al., 1996) reported that
zinc oxide-eugenol and epoxy resin sealers had similar behaviours. In agreement
with these investigations, the studies described in sections 2.2. and 2.3. of this
thesis, found no differences in terms of post retention when an eugenol or an epoxy
resin based sealer were used as endodontic sealers.
84
References 2.4
De Almeida WA, Leonardo MR, Tanomaru Filho M, Silva LA. Evaluation of
apical sealing of three endodontic sealers. Int Endod J 2000;33(1):25-7.
Karapanou V, Vera J, Cabrera P, White RR, Goldman M. Effect of immediate and
delayed post preparation on apical dye leakage using two different sealers. J Endod
1996;22(11):583-5.
Miletic I, Ribaric SP, Karlovic Z, Jukic S, Bosnjak A, Anic I. Apical leakage of
five root canal sealers after one year of storage. J Endod 2002;28(6):431-2.
Rohde TR, Bramwell JD, Hutter JW, Roahen JO. An in vitro evaluation of
microleakage of a new root canal sealer. J Endod 1996;22(7):365-8.
Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol
endodontic sealer cements on post retention. J Endod 1998;24:564-7.
Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention of
prefabricated posts luted with an adhesive composite resin cement. Quintessence
Int 1992;22:839-44.
Wu MK, De Gee AJ, Wesselink PR. Leakage of four root canal sealers at different
thickness. Int Endod J 1994;27(6):304-8.
85
Chapter 3
3.1. Water detrimental effect on fiber -reinforced composite and dental resins
The exposure of polymeric restorative materials such as fiber-reinforced
composites (FRC) and restorative resins to the aqueous oral environment
immediately draws one to the attention of the potentially detrimental effect of water
sorption on these materials. There is concern that the effects of solvent uptake and
hydrolytic degradation may lead to a shortened service life of dental resins. In fact
water ingress into dental composites in the oral cavity can, with time, lead to
deterioration of the physical/mechanical properties, mainly due to a hydrolytic
breakdown of the bond between silane and filler particles, filler–matrix debonding
or even hydrolytic degradation of the fillers (Soderholm et al., 1984) (Ferracane,
2006) (Takahashi et al., 1998) (Takahashi et al., 1999). Negative effects caused by
water exposure in composite materials have been reported as a reduction in their
physical properties, like tensile strength (Söderholm et al., 1996), flexural strength,
modulus of elasticity (Öysaed et al.,1986) and wear resistance (Scarret et al., 1991)
(Miettinen et al., 1999). Water is absorbed into the FRC by diffusion. The inflow
predominantly occurs in the resinous matrix and depends on the nature of the resin
and the amount of this phase within the material (Fan et al., 1985) (Santos et al.,
2002). This process is generally time dependent and increases with time (Chai et
al., 2004) (Behr et al.,2000).
FRC materials differ for the amount of water sorption, but show a similar
dimensional stability, after water storage (Chai et al., 2004). Among the reasons
used to explain the variation were the difference in the amount of water sorption,
fiber content and voids present within the matrix and at the fiber-matrix interface
(Chai et al., 2006). The sorbed water which is molecularly dispersed into the
polymer matrix acts as plasticizer, causing the swelling of polymer. The quantity of
water uptake depends on the available equilibrium hole-free volume, the
86
physicochemical affinity of polymer groups to water, and the resistance of polymer
chains to a swelling deformation stress (Ping et al., 2001) (Patil et al., 2000).
References 3.1 Behr M, Rosentritt M, Lang R, Handel G. Flexural properties of fiber reinforced
composite using a vacuum/pressure or a manual adaptation manufacturing process.
J Dent 2000;28:509–514.
Chai J, Takahashi Y, Hisama K, Shimizu H. Water sorption and dimensional
stability of three glass fiber-reinforced-composites. Int J Prosthodont 2004;17:195-
9.
Chai J, Takahashi Y, Hisama K, Shimizu H. Effect of water storage on the flexural
properties of three glass fiberreinforced-composites. Dent Mater 2006;22(3):291-7.
Fan PL, Edahl A, Leung RL, Stanford JW. Alternative interpretations of water
sorption values of composite resins. J Dent Res 1985;64:78–80.
Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks. Dent
Mater 2006;22:211-222.
Miettinen VM, Narva KK, Vallittu PK. Water sorption, solubility and effect of
post-curing of glass fibre reinforced polymers. Biomaterials 1999;20:1187–1194.
Öysaed H, Ruyter I. Composites for use in posterior teeth: mechanical properties
tested under dry and wet conditions. J Biomed Mater Res 1986;20:261-271.
Patil RD, Mark JE,.Apostolov A, Vassileva E, Fakirov S. Crystallization of water
in some crosslinked gelatins. Eur Polym J 2000;36:1055–1061.
87
Ping ZH, Nguyen QT, Chen SM, Zhou JQ, Ding YD. States of water in different
hydrophilic polymers-DSC and FTIR studies. Polymer 2001; 42:8461–8467.
Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption
characteristics of dental composites incorporating hydroxyapatite filler.
Biomaterials 2002;23:1897–1904.
Scarret DC, Söderholm KJM, Ybatich CD. Water and abrasive effects on three-
body wear of composites. J Dent Res 1991;70:1074-1081.
Söderholm K, Mukherjee R, Longmate J. Filler leachability of composites stored in
distilled water or artificial saliva. J Dent Res 1996;75:1692–1699.
Soderholm K-JM, Zigan M, Ragan M, Fischlschweiger W, Bergman M. Hydrolytic
degradation of dental composites. J Dent Res 1984;63:1248–1254.
Takahashi Y, Chai J, Kawaguchi M. Effect of water sorption on the resistance to
plastic deformation of a denture base material relined with four different denture
reline materials. Int J Prosthodont 1998;11:49–54.
Takahashi Y, Chai J, Kawaguchi M. Equilibrium strengths of denture polymers
subjected to long-term water immersion. Int J Prosthodont 1999;12:348–352.
88
89
3.2. Flexural strength of fiber post: the influence of storage condition and
duration
Thanks to a rapid evolution, several types of fiber posts are currently available, and
their mechanical properties must be taken into account when making a clinical
decision. Evaluation of strength related properties of experimental and
commercially available posts have been investigated utilising fatigue resistance
(Grandini et al., 2005) (Sahafi et al., 2005) and flexural strength tests (Asmussen et
al., 1999) (Seefeld et al., 2007) (Plotino et al., 2007). The quality of the support of
the coronal restoration can be reflected by the stiffness of the post, being related to
loss of retention of a crown (Sahafi et al., 2004). The flexural modulus parameter
defines the flexibility of a sample and higher values indicate more stiffness, while
lower values indicate more flexibility. The flexural strength parameter determines
the resistance to fracture of a sample. Higher values indicate that a sample is more
resistant to fracture, lower values that it is less so. The flexural strength is
determined by the highest load a sample can withstand and depends on the
specimen configuration. A linear correlation between the diameter of posts and
their resistance to fracture load was shown in an investigation involving 17
different FRC-posts (Lassila et al., 2004). It is still not clear how the structural
properties of FRC-posts influence their flexural strengths. To investigate the
relationship between flexural strength and the structural characteristics of FRC-
posts the combination of scanning electron microscopy (SEM) and fracture testing
can be used. SEM observations can provide the information to assess the fiber/resin
matrix ratio and the fiber diameter and look at the interface between the fibers and
the matrix.
A previous study (Mannocci et al., 2001) showed that storage of posts in bovine
teeth immersed in water resulted in similar flexural strength values of posts that
were dry-stored. In order to reproduce a clinical situation, in the following studies
extracted human canines teeth were selected as one of the storage condition to be
tested.
89
90
References 3.2
Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of
newer types of endodontic posts. J Dent 1999;27(4):275-8.
Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and
structural characteristics of fiber posts: three-point bending test and SEM
evaluation. Dent Mater 2005;21(2):75-82.
Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of
fiber reinforced root canal posts. Dent Mater 2004;20:29–36.
Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J
Endod 2001;27:758-61.
Ferracane JL, Berge HX, Condon JR. In vitro aging of dental composites in water-
effect of degree of conversion, filler volume, and filler/matrix coupling. JBiomed
Mater Res 1998;42:465-72.
Plotino G, Grande NM, Bedini R, Pameijer CH, Somma F. Flexural properties of
endodontic posts and human root dentin. Dent Mater 2007;23(9):1129-35.
Sahafi A, Peutzfeldt A, Asmussen E, Gotfredsen K. Retention and failure
morphology of prefabricated posts. Int J Prosthodont 2004;17:307-12.
Sahafi A, Peutzfeldt A, Ravnholt G, Asmussen E, Gotfredsen K. Resistance to
cyclic loading of teeth restored with posts. Clin Oral Investig 2005;9(2):84-90.
90
91
Seefeld F, Wenz HJ, Ludwig K, Kern M. Resistance to fracture and structural
characteristics of different fiber reinforced post systems. Dent Mater
2007;23(3):265-71.
91
92
3.3. The effect of different storage conditions and duration on the fracture
strength of three types of translucent fiber posts.
Alessandro Vichi, Michele Vano, Marco Ferrari. Dental Materials 2007, In press.
Introduction
Water degradation is a phenomenon that can cause several alterations in dental
resins, from physical changes, such as plasticization and softening, to chemical
ones (i.e oxidation or hydrolysis) [1-3]. Negative effects caused by water exposure
in composite materials have been reported as a reduction in their physical
properties, like tensile strength [4], flexural strength, modulus of elasticity [5] and
wear resistance [6]. Fiber reinforced composites (FRC) materials may be affected
by the detrimental effect of water uptake [7]. Water is absorbed into the FRC by
diffusion. The inflow predominantly occurs in the resinous matrix and depends on
the nature of the resin and the amount of this phase within the material [8,9]. This
process is generally time dependent and increases with time [10,11].
It is known that water storage negatively affects the flexural properties of fiber
posts [12,13]. Methacrylate-based posts have been recently introduced as an
alternative to epoxy resin-based translucent fiber posts [14]. Both methacrylate and
epoxy dental resins exhibit a tendency to water uptake due to their hydrophilicity
[15-18].
In a previous study Mannocci et al., [13] showed that storage of posts in bovine
teeth immersed in water resulted in similar flexural strength values of posts that
were dry-stored. In order to reproduce a clinical situation, in this study extracted
human canines teeth were selected as one of the storage condition to be tested.
Moreover storage in mineral oil was selected as a control group to avoid the effects
of water storage [19].
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Endodontic posts are cemented into the root canal of endodontically treated teeth,
and their coronal part is immersed into the composite resin core. Therefore in
clinical conditions the coronal restoration prevent fiber posts to be contaminated by
the oral environment and from any water or saliva uptake [13].
Thus, the aims of the study were: a) To evaluate the effects of storage duration and
condition on the flexural strength of different translucent fiber posts; b) To
morphologically evaluate the post structure before and after different storage
conditions. The null hypotheses tested were that the storage duration and condition
had no effect on the flexural strength and surface morphology of fiber post and the
post type (methacrylate or epoxy resin-based) did not affect the flexural strength in
each storage condition.
Materials and Methods
Three types of translucent fiber posts were investigated in the study: DT Light
Post, (RTD, St. Egreve, France), GC Post (GC Corporation, Tokyo Japan) and FRC
Postec Plus (Ivoclar-Vivadent, Schaan, Liechtenstein) (Table 1). The posts were
divided in 36 groups (n=14 posts each group) according to the aging protocol
performed in terms of storage duration (1, 6, 12 months) and condition: 1. Dry
storage at 37° C. 2. Storage in saline water at 37° C. 3. Storage in mineral oil
(Rhodorsil Huile 47 V 20 bacth no. 3053002, Franceschi, Pisa, Italy) at 37° C. 4.
Storage in root canal immersed in saline water at 37° C. In groups restored
according to condition 4, human canine teeth extracted for periodontal disease were
used. The teeth were endodontically treated. All root canals were treated by one
trained operator using stainless steel instruments K-files (#08-10-15; Dentsply
Maillefer Ballaigues, Switzerland), M-two instruments (#10-15-20-25; Sweden &
Martina, Due Carrare, Padova, Italy), and Profiles .06 taper (#30-35-40; Dentsply
Maillefer) mounted in a 16:1 gear reduction handpiece, driven by an electric motor
(Endo IT professional, Aseptico Inc., Woodinville, WA). The working length was
obtained at 1 mm above the radiographic apex. Instrumentation was performed
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under an operating microscope (OPMI pico, Carl Zeiss Surgical, Inc., Thornwood,
NY) at 12.5X magnification. The root canal was irrigated in between
instrumentations with 3 mL of 5.25% sodium hypochlorite using a long 27 gauge
needle. Deionized water was employed as the final rinse, and patency of the canals
was maintained with a #10 K-file. The canals were dried with multiple paper
points. AH Plus sealer (Dentsply, De Trey, Konstanz, Germany) was placed in the
canal and spread with a #45 K-file with a counterclockwise motion. The gutta-
percha was condensed using the continuous wave technique up to 4 to 5 mm from
the apex with a System B heat source (Analytic Technology, Redwood, USA).
Backfilling of the root canal was performed using thermoplastic gutta-percha and
an Obtura II unit (Obtura Corp., Fenton, MO) at 185°C.
Then the post space was prepared with low-speed post drills provided the
manufacturer to achieve diameters corresponding to those to the posts. The depth
of each canal was adjusted in such a manner that the post could be completely
inserted inside the root. The posts were not luted into the roots. After that, the
access cavity was sealed with adhesive system (Scotchbond Multi-Purpose
Adhesive, 3M/ESPE, St. Paul, MN, USA) and composite resin (Filtek Supreme
XT, 3M/ESPE, St. Paul, MN, USA shade A3). The root surface was painted with
two consecutive coats of nail varnish. Then the tooth were stored in water at 37°
for the reported time. After storage, the composite seal was removed, and the posts
were taken out from the root.
Flexural strength measurements
Artificial root canals were drilled in acrylic resin blocks (1x1x3 cm) (Endo-
Training-Bloc, Dentsply Maillefer, Ballaigues, Switzerland). The artificial canals
were enlarged with low-speed calibrated drills provided by the same manufacturer
in order to have a correspondence with the post diameter. The depth of each canal
was adjusted leaving 4.8 mm of the post extending above the resin blocks,
according to the experimental procedure previously described by Asmussen et al.,
[20]. The posts were then cemented into the artificial canals with a dual-cured
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luting cement (Calibra, Batch no. 050811-0501102, Dentsply Caulk, Milford, DE,
USA).
After the complete setting of the luting cement, the specimens were loaded in a
universal testing machine (Triaxial Tester T400 Digital, Controls S.P.A., Milano,
Italy) with a compressive load applied on the end of the post at a 45° angle to the
long axis using a crosshead speed of 1 mm/min until specimen failure (Fig. 1). The
fracture strength (S) in Newton was converted into MPa with the following
equation: S=32/π•Fl/d3 where F is the fracture load (N), l is the length of the post
(4.8 mm), and d is the diameter of the post (mm).
SEM investigation
Two posts from each group were observed longitudinally and in cross-section
before and after the storage to qualitatively evaluate their morphology. The
specimens were fixed on metallic stubs and sputtered with gold in an ion-sputtering
device (Polaron Range SC7620, Quorum Technology, Newhaven, UK). The visual
examination of the surfaces was performed with a scanning electron microscope
(SEM JSM-6060 LV, JEOL, Tokyo, Japan) at different magnifications.
Statistical Analysis
Having checked that flexural strength data were normally distributed
(Kolmogorov-Smirnov test) and group variances were homogeneous (Levene’s
test), a three-way ANOVA and Tukey's test were used to compare the effect of the
experimental factors (storage duration, storage condition, type of fiber post) on the
fracture strength (α=.05).
Results
The mean flexural strength values and standard deviations of the tested post are
presented in Table 2.
Statistical analysis revealed that the type of post and storage condition, had a
significant effect on flexural strength (p<0,001). The interaction between the two
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factors was also significant (p<0,05). Storage duration did not affect flexural
strength (p>0,05). GC Post showed the highest flexural strength (p<0,05). Water
storage significantly decreased the mean flexural strength, regardless of the post
type and the storage duration (Table 2). Posts stored into human roots immersed in
water, showed similar strength values to those stored in dry and in mineral oil.
SEM results
SEM-micrographs revealed a higher amount of voids and discontinuities between
the fibers and the resinous matrix after water storage for each post type (Fig. 2a).
All the tested posts showed a similar amount of defects in which the detachment of
the complex fiber-resin matrix was observed as the predominant degradation
pattern (Fig. 2b). No major differences were found between the three different
types of posts. However, qualitatively, FRC Postec Plus showed at 12 months of
water immersion a more pronounced delamination of the complex fiber-resin
matrix (Fig.3a). For all the post type the delamination of the fibers from the
adjacent resin matrix could be identified only along the periphery of the fiber post
(Fig. 3b). No significant alterations were recorded when posts were stored in dry,
in oil and in root dentin regardless of the post type (Fig. 4a, 4b, 4c).
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Discussion
The results of this study indicated that storage of fiber posts in human root
immersed in water resulted in similar flexural strengths values to those obtained in
dry and oil storage. Water storage had a detrimental effect on the mechanical and
morphological properties of the tested fiber posts. Thus, the null hypothesis that
there is no effect of storage conditions on the flexural strength and on the
morphology of fiber post has to be rejected. With respect to post type GC Post
showed the highest fracture strength values. Thus, also the null hypothesis that
there is no effect of post type on the flexural strength was rejected. Storage
duration did not influence fracture strengths values. Therefore the null hypothesis
that there is no effect of storage duration on the flexural strength was accepted.
The results of this study confirm the absence of any detrimental water effect on
post inserted into root canal. Previous studies clarified that droplets formation is
evident on the surfaces of replicas of deep vital dentin in the presence of positive
pulpal pressure [21-24]. Conversely as intra-radicular dentin is characterized by
absence of pulpal pressure, minor water should spontaneously emanates from the
surface. It was also previously revealed that after proper endodontic
instrumentation no increased radicular dentin permeability is evident in the
presence of intact cementum on the root surface [25] thus suggesting that the
outward fluid coming from the intra-radicular dentin is negligible in presence of at
least 1.5 mm residual dentin [26]. This hypothesis was confirmed by the analysis of
replicas showing no spontaneous droplets formation after post space preparation
[27]. The absence of water after root canal space preparation can also be due to
residual gutta-percha fragments, endodontic cement, smear layer and smear plugs
which reduce dentin permeability. Moreover unbound water is around 11% of the
entire water amount contained into a tooth and therefore hydraulic pressure and/or
osmotic gradient can unlikely attract water toward the surface of the endodontic
post space [28,29]. It should be also considered that adhesive and luting materials
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are interposed between the root dentin and a luted post therefore, even in case of a
small residual amount of water left after etching and rinsing, no water contact is
foreseen.
These results showing a reduction in the mechanical properties of fiber posts after
acqueos storage are in agreement with several reports [12,13]. The effects of water
immersion on post structure are both physical and chemical. The resinous matrix
may undergo a process of plasticization and softening, with the result of a
reduction in hardness and in wear resistance [30]. The process of water uptake is
generally time dependent and material dependent. Thus, the amount of water
absorbed into the fiber post is expected to increase with time until the material is
saturated and hydrolytically stable [31]. However in this study the storage duration
did not influence the flxural strengths values. One possible explanation is that the
water immersion time difference between the groups is relatively short or that the
water immersion time for each duration (1, 6, 12 months) was long enough to
saturate the material.
SEM-micrographs revealed a higher amount of voids and discontinuities between
the fibers and the resinous matrix after water storage. It has been described that
these voids can negatively influence the mechanical properties of posts [32]. Under
functional loading, these defects could act as starting points for microcracks
propagation, eventually leading to post fracture (Fig. 2a). Indeed under the
experimental condition of direct water immersion, a complete hydrolyzation of the
silane coupling agent which is normally used to promote adhesion between fibers
and polymer matrix may occur. As a result, fibers may detach from the matrix that
may account for the reduction in flexural strength [33,34]. In fact all the tested
posts showed a similar amount of defects in which the detachment of the complex
fiber-resin matrix was observed as the predominant degradation pattern (Fig. 3a).
No significant alterations were recorded when posts were stored in dry, in oil and
in root dentin regardless of the post type (Fig. 4a, 4b, 4c).
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The fiber posts investigated in this study differed for the nature of the resinous
matrix and the fibers. This diversity could explain the different flexural strength
values recorded between the three post types [35]. It has been shown that water has
a detrimental effect both on epoxy and methacrylate-based resinous matrixes [36].
Methacrylate and epoxy resin matrixes exhibit a high susceptibility to water
sorption and undergo a variable extent of hydrolysis over time [37,38].
Specimens exposure to water for up to 12 months resulted in partial delamination
of the quartz fibers from the epoxy resin matrix along the periphery of the DT
Light Posts (Fig. 2a). Although quartz fibers are basically inert to water sorption,
these defects may be the consequence of hydrolysis of the silane employed in
manufacturing and/or swelling of the epoxy resin matrix after water sorption [39].
A similar delamination pattern was observed also for FRC Postec and GC Post
posts, in which the glass fibers were detached from the methacrylate matrix
especially in the peripheric portions of the post.
All post types showed a reduction of flexural strength after direct water storage.
Therefore, under clinical conditions, it is advisable that fiber posts should not be
exposed to the oral environment. On the other hand the storage in human
endodontically treated teeth (group 4) which is very similar to that of a clinical
situation, was effective in avoiding the flexural-strength reduction due to contact of
posts with water. Therefore in a clinical scenario, if the fiber post is protected from
contact with water by the root canal filling and by resin composite materials, its
flexural strength will remain intact.
Further in vivo researches should be conducted to assess the clinical effect of water
on fiber posts exposed to the oral environment.
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Conclusion
Within the limitations of the study, the following conclusions can be drawn:
1. Fiber posts placed inside human root canals immersed in water showed to be
effectively preserved from water degradation effect.
2. Fiber posts stored in direct contact with water showed significant lower flexural
strength values and morphological changes regardless the post type tested.
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Table 1. Chemical composition and diameters of the fiber posts investigated in the study Post Brand and (batch number)
Composition Post diameter (Min / Max cross-section in mm)
Manufacturer
DT Light Post (batch n. 0401A)
Quartz fibers (60 vol%) Epoxy resin matrix (40 vol %)
1/2 RTD, St. Egreve, France
Gc Post (batch n. N4409005)
Glass Fibers (77 vol %), Methacrylate resin matrix (23 vol %),
1/2
GC Corporation, Tokyo Japan
Frc Postec Plus (batch n. H31059)
Glass fibers (70 vol %), Dimethacrylate resin matrix (21 vol %) Ytterbium fluoride (9 vol%)
1/2
Ivoclar-Vivadent Schaan, Liechtenstein
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Table 2 Mean flexural strength and standard deviation of the tested posts
Post type and store conditions 1 month 6 months
12 months
DT Light Post
Dry stored at 37°
939,33 (85,48) a 963,61 (121,94) a 1012,96 (102,89) a
Stored in saline water at 37° 654,82 (45,08) b 593,9 (61,77) b 562 (97,98) b
Stored in oil 37°
904,64 (87,64) a 837,96 (86,81) a 917,52 (114,97) a
Stored in root dentin and
immersed in water at 37°
906,33 (65,31) a 901,09 (86,11) a 926,29 (88,42) a
GC Post
Dry stored at 37° 1144,5 (189,19) c 1121,38 (112,84) 1179,86 (159,61) c
Stored in saline water at 37° 829,28 (103,93) d 716,1 (101,39) d 675,55 (124,46) d
Stored in oil at 37° 1079,18 (183,9) c 1035,5 (132,86) c 1079,18 (130,4) c
Stored in root dentin and
immersed in water at 37°
1128,02 (122,65) c 1118,5(66,18) c 1166,38( 130,95) c
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FRC Postec Plus
Dry stored at 37° 870,37(72,02) a 930,82 (99,07) a 917,9 (84,98) a
Stored in saline water at 37° 596,09 (25,98) b 547,3 (57,43) b 532,9 (41,1) b
Stored in oil 37° 822,05 (100,38) a 859,63 (101,49) a 895,1 (54,36) a
Stored in root dentin and
immersed in water at 37°
908,47 (85,29) a 884,08 (86,19) a 917,14 (84,79) a
Values are mean and standard deviation in MPa. Values with the same lower case letters are not significantly different (p > 0.05)
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FIGURE LEGENDS
Fig. 1 Schematic drawing of the setup for ultimate fracture strength testing of the
post
Fig. 2 (a) Representative SEM micrograph of DT Light Post after 12 months of
water storage condition (1500x; bar=10 µm). Lack of bonding between the fibers
and the resinous matrix is evident. (b) Representative SEM micrograph of GC Post
after 12 months of storage in water (250x; bar=100 µm). The fibers appear denuded
of the resinous matrix.
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Fig. 3 (a) Representative SEM micrograph of FRC Postec Plus after 12 months of
water storage condition (1500x; bar=10 µm). The complex fiber-resin matrix
appears disrupted.
(b) Representative SEM micrograph of a cross section showing the delamination of
the glass fibers (GC Post) from the adjacent methacrylate resin matrix along the
periphery of the fiber post after 12 months of water storage (70x; bar=200 µm).
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Fig. 4 (a) Representative SEM micrograph of DT Light Post after 12 months of
storage in root immersed in water (500x; bar=50 µm) showing a compact matrix
without porosities. (b) Representative SEM micrograph of GC Post after 12 months
of storage in root canal immersed in water showing the integrity of the post
structure (500x; bar=50 µm). (c) Representative SEM micrograph of FRC Postec
Plus after 12 months of storage in root canal immersed in water showing an intact
post structure (500x; bar=50µm).
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3.4. The influence of storage condition and duration on the resistance to
fracture of different fiber posts systems
Michele Vano, Carlos Carvalho, Maurizio Sedda, Mario Gabriele, F Garcia-Godoy,
Marco Ferrari. American Journal of Dentistry; Accepted 2007.
Introduction
In order to improve the fracture resistance of endodontically treated teeth restored
with a post-and-core system, research has focused on post materials,1,2 post designs
and luting agents.3-7 However recently it has been shown that other factors such as
storage condition 8 and duration 9 may influence the fracture resistance of fiber
posts.
Aging in water or aqueous fluids is known to decrease the fracture resistance of
fiber reinforced composites (FRC) materials as a result of water absorption by the
resin matrix and hydrolisis of filler matrix interfaces.10-13 In vitro tests reported that
water storage negatively affects the flexural properties of fiber posts when directly
immersed in water. 14 The inflow predominantly occurs in the resinous matrix and
depends on the nature of the resin and the amount of this phase within the material.
15 This process is generally time dependent and increases with time until the
material is saturated and hydrolytically stable. 16
In clinical conditions endodontic posts are cemented into the root canal of
endodontically treated teeth and their coronal part is immersed into the composite
resin core, therefore fiber posts are protected from the oral environment and from
any water or saliva uptake.
However a recent study reported the presence of water into root canals after
endodontic and prosthodontic procedures.17 Chersoni et al., 17 showed blistering
formation on the surface of simplified adhesives when applied on intra-radicular
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dentin. The authors speculated that droplets formation occurred due to residual
dentin water that was osmotically soaked by the etching and adhesives and then
retrieved on the adhesive surface due the intrinsic permeability of the polymerized
bonded surface. More recently Ferrari et al., 18 repeated a similar in vivo protocol,
the results showed that after etching of the intra-radicular dentin no water droplets
formation occurred on the dentin surface. The authors concluded that the adhesives
themselves are responsible for the droplets formation, probably due to residual un-
evaporated solvent.19 In order to reproduce a similar clinical situation, in this study
extracted canines were selected as one of the storage condition to be tested.
Thus, the aims of the study were: a) To evaluate the effects of storage condition
and duration on the resistance to fracture of different translucent fiber posts; b) To
morphologically evaluate the post structure before and after different storage
conditions. The null hypotheses tested were that the post type, the storage condition
and duration had no effect on the resistance to fracture and on the surface
morphology.
Materials and Methods
Three types of translucent fiber posts of small size were investigated in the study:
DT Light Post, (RTD, St. Egreve, France), GC Post (GC Corporation, Tokyo
Japan) and FRC Postec Plus (Ivoclar-Vivadent, Schaan, Liechtenstein) (Table 1).
Four different test groups were evaluated and for each of these 3 post types and 2
storage duration were evaluated. Thus a total of 24 individual groups, each
consisting of 12 posts were evaluated, ten of them, randomly chosen, were used for
the three-point bending test and two were used for SEM evaluation without being
fractured.
The groups were divided according to the aging protocol performed in terms of
storage duration (6, 12 months) and storage condition: 1. Dry storage at 37° C. 2.
Storage soaked in saline water at 37° C. 3. Storage soaked in mineral oil (Rhodorsil
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Huile 47 V 20 bacth no. 3053002, Franceschi, Pisa, Italy) at 37° C. 4. Storage
inside the root canal immersed in saline water at 37° C. Storage in mineral oil was
selected as a control group 20. In groups restored according to condition 4, human
canine teeth extracted for periodontal disease were used. The teeth were
endodontically treated. All root canals were treated by one previously calibrated
operator using stainless steel instruments K-files (#08-10-15; Dentsply Maillefer
Ballaigues, Switzerland), M-two instruments (#10-15-20-25; Sweden & Martina,
Due Carrare, Padova, Italy), and Profiles .06 taper (#30-35-40; Dentsply Maillefer)
mounted in a 16:1 gear reduction handpiece, driven by an electric motor (Endo IT
professional, Aseptico Inc., Woodinville, WA). The working length was obtained
at 1 mm above the radiographic apex. Instrumentation was performed under an
operating microscope (OPMI pico, Carl Zeiss Surgical, Inc., Thornwood, NY) at
12.5X magnification. The dowel space was irrigated in between instrumentations
with 3 mL of 5.25% sodium hypochlorite using a syringe with and endodontic
needle. Deionized water was employed as the final rinse, and patency of the canals
was maintained with a #10 K-file. The canals were dried with multiple paper points
until moisture was not detected. AH Plus sealer (Dentsply, De Trey, Konstanz,
Germany) was placed in the canal and spread with a #45 K-file with a
counterclockwise motion. The gutta-percha was condensed using the continuous
wave technique up to 4 to 5 mm from the apex with a System B heat source
(Analytic Technology, Redwood, USA). Backfilling of the root canal was
performed using thermoplastic gutta-percha and an Obtura II unit (Obtura Corp.,
Fenton, MO) at 185°C.
Then the post space was prepared with low-speed post drills provided the
manufacturer in order to have diameters corresponding to those to the posts. The
depth of each canal was adjusted in such a manner that the post could be
completely inserted inside the root. The posts were not luted into the roots. After
that, the access cavity was sealed with adhesive system (Scotchbond Multi-Purpose
Adhesive, 3M/ESPE, St. Paul, MN, USA) and resin composite (Filtek Supreme
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XT, 3M/ESPE, St. Paul, MN, USA shade A3). The root surface was sealed with
two consecutive coats of nail varnish. Then the roots were maintained soaked in
water at 37° C for the reported storage time. After storage, the composite seal was
removed, and the posts were carefully dislocated from the root.
Three-point bending test
The three-point bending method was conducted according to the DIN-EN 843-1 in
a universal testing machine (Triaxial Tester T400 Digital, Controls S.P.A., Milano,
Italy). The load was applied to the posts with a loading angle of 90° and a
crosshead speed of 0.5 mm/min until fracture. The two supports and the central
loading anvil had a 2-mm cross-sectional diameter and the distance between the
two supports was 8 mm. In order to eliminate the influence of the conical end of
some of the posts, a short span length (8 mm) was used to get support for the post
within the cylindrical part of the post. The parallel-sided cylindrical part of the post
was considered to be the specimen. Fracture loads were recorded and the flexural
strength was calculated using the formula: 38dFl
πσ =
where F is the applied load (N) at which the sample fractured, l (mm) is the span
length, d (mm)is the diameter of the specimens.
Scanning Electron Microscopy (SEM) evaluation
Two posts randomly selected from each group were observed longitudinally and in
cross-section before and after the storage to qualitatively evaluate their
morphology. The specimens were cleaned with ethanol, fixed on metallic stubs and
sputtered with gold in an ion-sputtering device (Polaron Range SC7620, Quorum
Technology, Newhaven, UK). The visual examination of the surfaces was
performed with a scanning electron microscope (SEM JSM-6060 LV, JEOL,
Tokyo, Japan) at different magnifications.
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Statistical Analysis
Having checked that flexural strength data were normally distributed
(Kolmogorov-Smirnov test) and group variances were homogeneous distributed
(Levene’s test), a three-way ANOVA and Tukey's test were used to compare the
effect of the experimental factors (storage condition, storage duration, type of fiber
post) on the flexural strength (α=0.05).
Results
The flexural strength of tested specimens is presented in Table 2.
Statistical analysis revealed that the type of post and storage condition, had a
significant effect on flexural strength (p<0.05). The interaction between the two
factors was also significant (p<0.05). Storage duration did not affect flexural
strength (p>0.05). GC Post and DT Light Post showed the highest flexural strength
(p<0.05). Water storage significantly decreased the mean flexural strength,
regardless of the post type and the storage duration (Table 2). Posts stored inside
human roots immersed in water, showed similar flexural strength values to those
stored in dry and in mineral oil.
SEM analysis
SEM-micrographs revealed a high quantity of voids and discontinuities between
the fibers and the resinous matrix after water storage for each post type (Fig. 1
a,b,c). All the tested posts showed a similar quantity of defects in which the
detachment of the complex fiber-resin matrix was observed as the predominant
degradation pattern. No major differences were found among the three different
types of posts. However, qualitatively, FRC Postec Plus showed at 12 months
immersed inside water more pronounced delamination of the complex fiber-resin
matrix (Fig. 1c). For all the post type the delamination of the fibers from the
adjacent resin matrix could be identified only along the periphery of the fiber post
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(Fig. 1b). No significant alterations were recorded when posts were stored in dry,
in oil and inside root dentin regardless of the post type (Fig. 2 a,b,c).
Discussion
The results of this study indicated that storage of fiber posts in human roots
immersed in water resulted in similar flexural strengths values to those obtained in
dry and oil storage. On the other hand the storage of fiber posts in water, showed
the lowest fracture loading values. Moreover water storage affected the
morphological properties of the tested fiber posts. Thus, the null hypothesis that
there is no effect of storage conditions on the fracture resistance and on the
morphology of fiber post has to be rejected. Regarding the storage duration no
significant difference was observed. Thus, the null hypothesis that there is no effect
of storage duration on the fracture resistance of fiber post has to be accepted. The
highest flexural strength values were achieved by GC Post and DT Light Post.
Thus, the null hypothesis that there is no effect of post type on the flexural strength
was rejected.
The results of this study confirm the absence of any detrimental water effect on
post inserted in root canal. Indeed the statistics showed that after storage in human
teeth all posts had flexural strength values that were not significantly different from
posts that were dry-stored or oil stored. On the contrary, fiber posts immersed
directly in water showed a reduction in the flexural strength values. The effects of
water immersion on post structure are both physical and chemical. The resinous
matrix may undergo a process of plasticization and softening, with the result of a
reduction in hardness and in wear resistance.21 The process of water uptake is
generally time dependent and material dependent.9 Thus, the amount of water
absorbed into the fiber post is expected to increase with time until the material is
saturated and hydrolytically stable.22 Conversely, in this study the storage duration
did not influence the flexural strengths values. One possible explanation is that the
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water immersion time difference among the groups is relatively short or the tested
storage duration (6, 12 months) was long enough to saturate the material.
SEM-micrographs revealed a higher quantity of voids and discontinuities between
the fibers and the resinous matrix after water storage. It has been described that
these voids can negatively influence the mechanical properties of posts.23 Under
functional loading, these defects could act as starting points for microcracks
propagation, eventually leading to post fracture (Fig. 1a). Indeed under the
experimental condition of direct water immersion, a complete hydrolyzation of the
silane coupling agent which is normally used to promote adhesion between fibers
and polymer matrix may occurs. As a result, fibers may detach from the matrix that
may account for the reduction in flexural strength values.24,25 In fact, all the tested
posts showed a similar amount of defects in which the detachment of the complex
fiber-resin matrix was observed as the predominant degradation pattern (Fig. 1b).
No significant alterations were recorded when posts were stored in dry, in oil and
in root dentin regardless of the post type (Fig. 3 a,b,c).
Explanations of the difference of flexural strengths among the tested posts could
include the differences in matrix, fiber nature, the number of flaws, and porosities
at the fiber–matrix junction.26 It has been shown that water has a detrimental effect
both on epoxy and methacrylate-based resinous matrixes.27 Methacrylate and epoxy
resin matrixes exhibit a high susceptibility to water sorption and undergo a variable
extent of hydrolysis over time.28,29 Specimens exposure to water for up to 12
months resulted in partial delamination of the quartz fibers from the epoxy resin
matrix along the periphery of the DT Light Post (Fig. 1a). Although quartz fibers
are basically inert to water sorption, these defects may be the consequence of
hydrolysis of the silane employed in manufacturing and/or swelling of the epoxy
resin matrix after water sorption.30 A similar delamination pattern was observed
also for GC Post (Fig. 1b) and FRC Postec Plus (Fig. 1c), in which the glass fibers
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were detached from the methacrylate matrix especially in the peripheric portions of
the post.
All post types showed a reduction of fracture load after direct water storage.
Therefore, under clinical conditions, it is advisable that fiber posts should not be
exposed to the oral environment. On the other hand the storage in human
endodontically treated teeth which is very similar to that of a clinical situation was
effective in avoiding the fracture-load reduction due to contact of posts with water.
Within the limitations of the study, the following conclusions can be drawn:
1. Fiber posts placed inside human root canals immersed in water are not affected
by water detrimental effect.
2. Fiber posts stored in direct contact with water showed significant lower flexural
strength values and morphological changes regardless the post type.
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REFERENCES
1. Ferrari M, Vichi A, Garcia-Godoy F. Clinical evaluation of fiber reinforced
epoxy resin posts and cast post and cores. Am J Dent 2000;13:8B-15B.
2. Sorensen JA, Engelman MJ. Effect of post adaptation on fracture resistance of
endodontically treated teeth. J Prosthet Dent 1990;64:419-24.
3. Ferrari M, Goracci C, Sadek FT, Monticelli F, Tay FR. An investigation of the
interfacial strengths of methacrylate resin-based glass fiber post-core buildups. J
Adhes Dent 2006;8:239-45.
4. Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M. The
effect of immediate versus delayed cementation on the retention of different types
of fiber post in canals obturated using a eugenol sealer. J Endod 2006;32:882-5.
5. Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. A one step procedure
for luting glass fibre posts: an SEM evaluation. Int Endod J 2004;37:679-86.
6. Ferrari M, Vichi A, Grandini S, Goracci C. Efficacy of a self-curing adhesive-
resin cement system on luting glass-fiber posts into root canals: an SEM
investigation. Int J Prosthodont 2001;14:543-9.
7. Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques on
bonding to root canal walls: an SEM investigation. Dent Mater 2001;17:422-9.
8. Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J
Endod 2001;27:758-61.
9. Chai J, Takahashi Y, Hisama K, Shimizu H. Water sorption and dimensional
stability of three glass fiber-reinforced-composites. Int J Prosthodont 2004;17:195-
9.
10. Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks.
Dent Mater 2006;22:211-222.
11. Miettinen VM, Narva KK, Vallittu PK. Water sorption, solubility and effect of
post-curing of glass fibre reinforced polymers. Biomaterials 1999;20:1187–1194.
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12. Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption
characteristics of dental composites incorporating hydroxyapatite filler.
Biomaterials 2002;23:1897–1904.
13. Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water
storage on the flexural properties of unidirectional glass fiber-reinforced
composites. Biomaterials 2002;23:2221–9.
14. Lassila LVJ, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties
of fiber reinforced root canal posts. Dent Mater 2004;20:29-36.
15. Fan PL, Edahl A, Leung RL, Stanford JW. Alternative interpretations of water
sorption values of composite resins. J Dent Res 1985;64:78–80.
16. Takahashi Y, Chai J, Tan SC. Effect of water storage on the impact strength of
three glass fiber-reinforced composites. Dent Mater 2006;22:291-7.
17. Chersoni S, Acquaviva GL, Prati C, Ferrari M, Pashley DH, Tay FR. In vivo
fluid movement through dentin adhesives in endodontically treated teeth. J Dent
Res 2005;84:223-7.
18. Ferrari M, Coniglio I, Magni E, Cagidiaco MC, Gallina G, Prati C, Breschi L.
How can droplets formation occur in endodontically treated teeth during bonding
procedures? J Adhes Dent, In press.
19. Van Landuyt KL, De Munck J, Snauwaer J, Coutinho E, Poitevin A, Yoshida
Y, Inoue S, Peumans M, Suzuki K, Lambrecths P, Van Meerbeek B. Monomer-
solvent phase separation in one-step self-etc adhesives. J Dent Res 2005;84:183-8.
20. Carrilho MR, Tay FR, Pashley DH, Tjaderhane L, Carvalho RM. Mechanical
stability of resin-dentin bond components. Dent Mater 2005;21:232-41.
21. Ferracane L, Berge HX, Condon JR. In vitro aging of dental composites in
water–effect of degree of conversion, filler volume, and filler/matrix coupling. J
Biomed Mater Res 1998;42:465–47.
22. Nishiyama N, Komatsu K, Fukai K, Nemoto K. Influence of absorption
characteristics of silane on the hydrolytic stability of silane at the silica-matrix
interface. Composites 1995;26:309-313.
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23. Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and
structural characteristics of fiber posts: three-point bending test and SEM
evaluation. Dent Mater 2005;21:75–82.
24. Söderholm KJM, Roberts MJ. Influence of water exposure on the tensile
strength of composites. J Dent Res 1990;69:1812-6.
25. Meyer M, Friedman R, Del Schutte H, Latour R. Long-term durability of the
interface in FRP composites after exposure to simulated physiologic saline
environments. J Biomed Mater Res 1994;28:1221–1231.
26. Drummond JL, Mahenda SB. Static and cyclic loading of fiber-reinforced
dental resin. Dent Mater 2003;19:226–31.
27 Venz S, Dickens B. NIR-spectroscopic investigation of water sorption
characteristics of dental resins and composites. J Biomed Mater Res 1991;25:1231–
1248.
28. Miyata N, Matsuura W, Kokubo T. Mechanical behaviour of bioactive
composite cements consisting of resin and glass-ceramic powder in a simulated
body fluid: Effect of silane coupling agent. J Mater Sci 2004;15:1013-1020.
29. Harper EJ, Braden M, Bonfield W. Mechanical properties of hydroxyapatite
reinforced poly(ethylmethacrylate) bone cement after immersion in a physiological
solution: influence of silane coupling agent. J Mater Sci 2000;11:491-497.
30. Van Landingham MR, Eduljee RF, Gillespie JW. Moisture diffusion in epoxy
systems. J Applied Polymer Sci 1999;71:787-98.
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Table 1. Chemical composition and diameters of the fiber posts investigated in the study. Post Brand and Manufacturer
Composition Mean Post diameter (mm)
Post Design
DT Light Post, RTD, St. Egreve, France
Quartz fibers (60 vol%) Epoxy resin matrix (40 vol %)
1.22 Cylindrical-conical
Gc Post, GC Corporation, Tokyo Japan
Glass Fibers (77 vol %), Methacrylate resin matrix (23 vol %),
1.15
Cylindrical
Frc Postec Plus, Ivoclar-Vivadent Schaan, Liechtenstein
Glass fibers (70 vol %), Dimethacrylate resin matrix (21 vol %) Ytterbium fluoride (9 vol%)
1.35
Cylindrical-conical
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Table 2. Mean flexural strength of the tested post systems
Post type and store media 6 months
12 months
DT Light Post
Dry stored at 37°
940,22 (95,75) a 946,7 (68,62) a
Stored in saline water at 37° 553,39 (52,92) b 503,32 (122,45) b
Stored in oil 37°
896,9 (64,77) a 899,47 (55,56) a
Stored in root dentin and
immersed in water at 37°
922,55 (42,9) a 903,61 (64,34) a
GC Post
Dry stored at 37° 985,02 (91,72) a 921,14 (92,66) a
Stored in saline water at 37° 490,04 (56,54) b 458, 67(72,9) b
Stored in oil at 37° 919,4 (98,01) a 902,46 (76,92) a
Stored in root dentin and
immersed in water at 37°
935,72(103,13) a 922,67( 83,79) a
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FRC Postec Plus
Dry stored at 37° 816,56 (83,47) c 824,46 (96,42) c
Stored in saline water at 37° 473,25 (88,17) d 426,53 (45,69) d
Stored in oil 37° 809,81 (91,59) c 819,36 (77,58) c
Stored in root dentin and
immersed in water at 37°
824,11 (105,99) c 817,28 (62,57) c
Values are mean and standard deviation in Mpa.
Values with the same lower case letters are not significantly different (p >0.05)
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FIGURE LEGENDS
Fig. 1 (a) Representative SEM micrograph of DT Light Post after 12 months of
water storage condition (250x; bar=100 µm). Lack of bonding between the fibers
and the resinous matrix is evident.
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(b) Representative SEM micrograph of GC Post after 12 months of storage in water
(500x; bar=50 µm). The fibers appear denuded of the resinous matrix.
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(c) Representative SEM micrograph of FRC Postec Plus after 12 months of storage
in water (1500x; bar=10 µm). The fibers appear denuded of the resinous matrix
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Fig. 2 (a) Representative SEM micrograph of DT Light Post after 12 months of
storage in root immersed in water (1000x; bar=10 µm) showing a compact matrix
without porosities.
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(b) Representative SEM micrograph of GC Post after 12 months of storage in root
canal immersed in water showing the integrity of the post structure (500x; bar=50
µm).
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(c) Representative SEM micrograph of FRC Postec Plus after 12 months of storage
in root canal immersed in water showing an intact post structure (500x; bar=50µm)
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Chapter 4
4.1. Effects of wear on fiber post morphology
The wear resistance of dental composites is of great consideration in the case of
dental restorations, as significant loss of restored surface due to wear can
jeopardize its clinical longevity (Venhoven et al., 1996). This loss of substance in
the dental context can be due to erosive, abrasive, corrosive and other types of
wear. The wear behavior of dental materials is an important research topic and
must be investigated when developing materials for dental applications. Based on a
literature survey, there is minimal data available on the mechanical behavior and
wear characteristics of fiber posts. The fiber-reinforced radicular posts have been
produced by incorporating various fibers into the resin matrix (Fortin et al., 2000).
Wear of composites is known to depend on filler particle-related features,
particularly on the concentration and size of the filler reinforcement (Turssi et al.,
2003). While many dental composites may contain a high percentage of filler
particles (some up to 90% by weight), FRCs are limited to a much smaller filler
ratio, for proper homogenous mixing. From the available compatible fibers, glass
fibers have drawn the most attention due to their esthetic qualities and easy
manipulation (Karacaer et al., 2002).
In vitro studies showed that fiber volume fraction and the water sorption of the
polymer matrix had a significant effect on the flexural properties of FRCs (Lassila
et al., 2002, 2004). A decrease of flexural properties after water immersion was
considered to be mainly caused by plasticizing effect of water.
Endodontic posts are cemented into the root canal of endodontically treated teeth,
and their coronal part is immersed into the composite resin core. Therefore in
clinical conditions the coronal restoration prevent fiber posts to be contaminated by
the oral environment and from any water, saliva uptake or wear effect (Mannocci et
al., 2001). However observation of exposed post on a direct restoration is a
common finding (Fredriksson et al., 1998). Therefore is it of interest to evaluate
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whether the exposure to the oral environment and occlusal function affects the
morphological integrity of luted intracanalar translucent fiber posts.
References 4.1.
Fortin D, Vargas MA. The spectrum of composites: new techniques and materials.
J Am Dent Assoc 2000;131:26–30.
Fredriksson M, Astbäck J, Pamenius M, Arvidson K. A retrospective study of 236
patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet
Dent 1998;80:151-7.
Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water storage
on the flexural properties of unidirectional glass fiber-reinforced composites.
Biomaterials 2002;23:2221–9.
Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of
fiber reinforced root canal posts. Dent Mater 2004;20:29-36.
Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J
Endod 2001;27:758-61.13
Karacaer O, Dogan A, Dogan OM, Usanmaz A. Dynamic mechanical properties of
dental base material reinforced with glass fiber. J Appl Polymer Sci 2002;85:1683–
97.
Turssi CP, Purquerio BM, Serra MC. Wear of dental resin composites: insights into
underlying processes and assessment methods-a review. J Biomed Mater Res
2003;65B:280–5.
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Venhoven BA, De Gee AJ, Werner A, Davidson CL. Influence of filler parameters
on the mechanical coherence of dental restorative resin composites. Biomaterials
1996;17:735–40.
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4.2. Effects of oral environment and occlusal wear on FRC-posts integrity in
clinical service for 5 years
Michele Vano, Franklin Garcia-Godoy, Cecilia Goracci, Alessandro Vichi, Marco
Ferrari. Journal of Adhesive Dentistry, Submitted.
Introduction
Fiber posts can be used for restoring endodontically treated teeth with both direct
and indirect restorations.8 The primary purpose of a post is to connect the root with
the build-up material placed on the coronal portion and to provide retention to the
coronal restoration.10 Fiber post are made in several standardised lengths in order to
be adaptable to different roots. Each post must be tried in and then cut at the
adequate length to remain within the abutment and/or the direct restoration .11
Coronally the post surface should be completely covered by a composite resin layer
of at least 1.5 mm in thickness, in order to mask the post surface color shade,22 and
to protect the post itself from microfractures that may occur to the restoration
or/and the abutment.12 Visibility of the exposed post on a direct restoration is a
common finding,9 however it is not clear yet whether the exposure of the post to
the oral environment may lead to clinical failure of the restoration .
In vitro studies reported that the exposed post may undergo structural alterations
due to wear and water degradation that may influence its mechanical properties.13A
valid method to qualitatively evaluate the detrimental effect of water on post
morphology is scanning electron microscopy (SEM).21,23 Clinical evaluation is the
most widely accepted method to measure the wear resistance of a dental material.
2,4 Unfortunately, the complex and variable conditions in a human mouth makes
wear difficult, if not impossible to reproduce in a laboratory. Limited information
is available on the mechanical behavior and wear characteristics of dental FRCs.
Among the parameters for measuring wear, SEM analysis is commonly used as it
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allows to evaluate wear patterns and characteristics.3 Ideally, the wear of a dental
material should be similar to that of enamel. To date, however, this property may
only be found in ceramic materials and some metal alloys.1,6
Although significant improvements have been achieved, composite resins still
exhibit considerable in vivo wear in the long run.24 However, in vivo wear
measurements are generally scarce and differ from study to study, in relation to
differences in wear analyzing methods and sample selection.19 No data are
available on fiber posts wear under in vivo and in vitro conditions.
The aim of this study was to evaluate whether the exposure to the oral environment
and occlusal function affects the morphological integrity of luted intracanalar fiber
posts retaining a direct composite restoration or a composite resin crown abutment.
Material and Methods
Participants in the study were recruited from patients visiting the Department of
Fixed Prosthodontics and Dental Materials, University of Siena, Italy. The study
was approved by the Ethical Committee of the University. All patients signed an
informed consent form. Criteria for excluding patients from the study were being
under the age of 18 years or incapable of signing a contract (mentally disabled or
disordered patients, unable to give freewill statements), pregnancy or lactation,
unacceptable oral hygiene status, clenching or grinding of teeth, known allergic
reaction to the materials used (all evaluated from answers to specific questions by
the examiner). The study group consisted of 20 subjects (13 females and 7 males),
aged between 22 and 58 years, with a mean age of 40 years. All subjects had
comparable oral hygiene status. It was required that the teeth had opposing tooth
contacts. One tooth of each subject included in the study underwent a standardized
endodontic treatment. All root canals were treated by one trained operator using the
following instruments: K-files #08-10-15 (Dentsply Maillefer Ballaigues,
Switzerland), M-two instruments #10-15-20-25 (Sweden & Martina, Due Carrare,
Padova, Italy), Profiles .06 taper #30-35-40 (Dentsply Maillefer), mounted in a
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16:1 gear reduction handpiece driven by an electric motor (Endo IT professional,
Aseptico Inc., Woodinville, WA). The working length was obtained at 1 mm above
the radiographic apex. The root canal was irrigated in between instrumentation with
3 mL of 5.25% sodium hypochlorite using a long 27 gauge needle. Deionized water
was employed as the final rinse, and patency of the canals was maintained with a
#10 K-file. The canals were dried with multiple paper points. Endodontic sealer
(AH Plus, Dentsply, De Trey, Konstanz, Germany) was placed in the canal and
spread with a #45 K-file with a counterclockwise motion. The gutta-percha was
condensed using the continuous wave technique up to 4 to 5 mm from the apex
(System B heat source, Analytic Technology, Redwood, USA). Backfilling of the
root canal was performed using thermoplastic gutta-percha and an Obtura II unit
(Obtura Corp., Fenton, MO) at 185°C.
Then the post space was prepared with low-speed post drills provided by the
manufacturer (RTD, St. Egreve, France) in order to have diameters corresponding
to those to the DT Light Post posts (RTD, St. Egreve, France). Posts were luted
with Calibra Esthetic Resin Cement (Dentsply DeTrey Konstanz, Germany).
In ten teeth (Group 1) the post head remained exposed on the occlusal surface of a
direct resin composite restoration (Scotchbond Multi-Purpose Adhesive and Filtek
Supreme XT, 3M/ESPE, St. Paul, MN, USA) (Fig. 1), that was polished with
carbide burs (Diatech, Diatech Dental AC, Heerbrugg Switzerland) and extra thin
contouring and polishing discs (Sof-Lex, 3M Dental Products, St Paul, MN, USA).
In the other ten teeth (Group 2) (control group) the post head remained exposed on
the occlusal surface of a resin composite abutment (Filtek Supreme XT, 3M/ESPE,
St. Paul, MN, USA), to be covered with a porcelain fused to metal crown.
One experienced prosthodontist performed all tooth preparations in a standardized
manner with an occlusal reduction of 2.0 mm, axial reduction of 1.2–1.5 mm, a
total convergence angle of 6◦, and rounded line angles. The finish line was a 1.2
mm internally rounded circumferential shoulder.
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The crowns were finished and inspected with a microscope (OPMI pico, Carl Zeiss
Surgical, Inc., Thornwood, NY) at 12.5X magnification. All crowns were
fabricated by one dental laboratory technician. The fit of the crowns was assessed
on the respective teeth visually and tactually with a dental explorer. The fit of each
crown was repeatedly assessed, before and after the cementation procedures.
Crowns were cemented with a provisional cement (Temp Bond, Kerr, Romulus,
MI). All patients received oral hygiene instructions after cementation. For baseline
evaluation, polyether impressions (Permadyne, 3M ESPE Seefeld, Germany) were
taken of the restorations occlusal surfaces immediately after polishing in Group 1
and of the abutments before crown luting in Group 2 (Fig. 2). After a 5-year period
of clinical service, polyether impressions were taken again for the directly restored
teeth and the abutments.
SEM investigation
All the impressions were poured in epoxy resin (Buehler, Lake Bluff, IL, USA).
The specimens were fixed on metallic stubs, sputtered with gold in an ion-
sputtering device (Polaron Range SC7620, Quorum Technology, Newhaven, UK),
and observed under a scanning electron microscope (SEM JSM-6060 LV, JEOL,
Tokyo, Japan) at different magnifications, in order to assess whether the post
surface underwent structural changes due to water uptake and/or occlusal wear
during clinical function.
Results
No remarkable differences were seen between baseline (Fig. 3a) and after 5 years
(Fig. 3b) for either group. Neither group exhibited after the 5-year clinical service
microscopic signs of post surface degradation due to water uptake. In group 1
specimens, the exposed post exhibited some signs of wear, that appeared to be
more pronounced for the fiber-reinforced composite post than for the particle-filled
composite of the coronal restoration (Fig. 4).
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Discussion
No signs of degradation of post surface due to water uptake were seen for group 1
and group 2 specimens. In group 1 a limited amount of wear rate probably due to
the 5 years period of clinical service was detected. Therefore the null hypothesis
that the exposure to the oral environment has no effect on the morphological
integrity of fiber posts retaining a direct composite restoration must be accepted.
Aging in water or aqueous fluids is known to decrease the fracture resistance of
fiber reinforced composites (FRC) as a result of water absorption by the resin
matrix and hydrolisis of filler matrix interfaces 7,18. In vitro tests reported that water
storage negatively affects the flexural properties of fiber posts when directly
immersed in water 14. However in clinical conditions endodontic posts are
cemented into the root canal of endodontically treated teeth and their coronal part is
immersed into the composite resin core, therefore fiber posts are protected from the
oral environment and from any water or saliva uptake. Nonetheless observation of
exposed post on a direct restoration is a common finding.9 Therefore in the present
study the post was positioned in order to have its coronal portion exposed to the
oral environment in order to mimic those clinical situations. In addition having the
post head exposed was the only method to evaluate any morphological changes of
the post by polyether impressions.
Abutments under porcelain fused metal crowns were chosen as control group,
because represent the standard of care for indirect restorations thanks to their high
wear and occlusal loading resistance.16 Another advantage of metal ceramic crown
was that it could be removed when luted with a provisional cement. That allowed
taking several polyether impressions for SEM analysis.
The homogeneity of the bonding interface between the post and the core material
can play an important role on the longevity of the final restoration of the
endodontically treated tooth. The presence of voids/bubbles within the post surface
and the development of gaps along the interface with the resin core or abutment
may increase the risk of fracture under functional loading. 17 In the present study no
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voids or bubbles within the post and no gaps between the post and the restoration
were detected. Recent studies have showed that water storage of fiber post resulted
in a reduction of the mechanical properties.23 On the other hand when fiber posts
were placed inside human root canals immersed in water no detrimental effect was
observed.21 Specimens in group 1 are surrounded by a direct resin restoration,
which may impede any water effect. This could be a possible explanation for the
absence of any morphological alteration for tested posts.
When measuring wear, both the material of interest and the opposing material must
be considered, especially if the opposing substrate is enamel. All the samples tested
had enamel as opposing substrate, therefore a high rate of wear was expected .5 On
the contrary SEM observations both in group 1 and 2 revealed after 5 years of
clinical service respectively few and no wear signs. In particular the fibers
appeared well bonded to the matrix material with an uniform distribution pattern
(Fig.5). Interestingly in group 1 the resin matrix of the fiber post, after 5 years of
clinical service, abraded more than the resin matrix of the composite restoration
(Fig. 4). Wear of composites is known to depend on filler particle-related features,
particularly on the concentration and size of the filler reinforcement. 20 The
composition of DT Light Post posts (RTD, St. Egreve, France) differs from the
resin composite used for the direct restoration (Filtek Supreme XT, 3M/ESPE, St.
Paul, MN, USA). In fact the resin matrix of the composite restoration has a higher
filler content, that may enhance its wear resistance. 15
SEM observation of the surface of group 2 specimens after a 5 years period showed
no wear signs. This was rather expected, once the abutment is covered with a
prosthetic crown it can be assumed that the occlusal surface will remain intact.
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Conclusion
In conclusion, within the limitations of this 5-year study, the fiber post surface
exposed in direct resin restoration did not show evidence of morphological changes
related to water degradation, although it exhibited a limited loss of structure due to
occlusal wear. When the fiber post surface was exposed on the top of the abutment,
the seal provided by the crown effectively protected the fiber post against
deterioration.
Clinical relevance: Exposition of a fiber post in a direct restoration does not lead
to clinical failure. Over a 5-year period, the post surface exposed in a direct resin
restoration did not show morphological changes related to water degradation
although it exhibited a limited loss of structure due to occlusal wear.
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References
1. Anusavice KJ. Degradability of dental ceramics. Adv Dent Res 1992;6:82–9.
2. Barkmeier WW, Latta MA, Erickson RL, Lambrechts P.Comparison of
laboratory and clinical wear rates of resin composites. Quintessence Int
2004;35:269–74.
3. Callaghan DJ, Vaziri A, Hashemi HN. Effect of fiber volume fraction and length
wear characteristics of glass fiber-reinforced dental composites. Dent Mater
2006;22:84–93.
4. Condon JR, Ferracane JL. In vitro wear of composite with varied cure, filler
level, and filler treatment. J Dent Res1997;76:1405–11.
5. DeLong R. Intra-oral restorative materials wear: Rethinking the current
approaches: How to measure wear. Dent Mater 2006;22:702–711.
6. Ekfeldt A, Fransson B, Soderlund B, Oilo G. Wear resistance of some
prosthodontic materials in vivo. Acta Odontol Scand 1992;51:99–107.
7. Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks.
Dent Mater 2006;22:211-222.
8. Ferrari M, Cagidiaco MC, Grandini S, De Sanctis M, Goracci C. Post placement
affects survival of endodontically treated premolars. J Dent Res 2007;86:729-34.
9. Fredriksson M, Astbäck J, Pamenius M, Arvidson K. A retrospective study of
236 patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J
Prosthet Dent 1998;80:151-7.
10. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically
treated teeth: a literature review. Part I. Success and failure data, treatment
concepts. J Prosthodont 1994;3:243-50.
11. Grandini S, Balleri P, Ferrari M. Scanning electron microscopic investigation
of the surface of fiber posts after cutting. J Endod 2002;28:610-2.
12. Grandini S, Goracci C, Tay FR, Grandini R, Ferrari M. Clinical evaluation of
the use of fiber posts and direct resin restorations for endodontically treated teeth.
Int J Prosthodont 2005;18:399-404.
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13. Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water
storage on the flexural properties of unidirectional glass fiber-reinforced
composites. Biomaterials 2002;23:2221–9.
14. Lassila LVJ, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties
of fiber reinforced root canal posts. Dent Mater 2004;20:29-36.
15. Lim BS, Ferracane JL, Condon JR, Adey JD. Effect of filler fraction and filler
surface treatment on wear of microfilled composites. Dent Mater 2002;18:1–11.
16. Limkangwalmongkol P, Chiche GJ, Blatz MB. Precision of Fit of Two Margin
Designs for Metal-Ceramic Crowns. J Prosthodont 2007;16:233-237.
17. Monticelli F, Osorio R, Albaladejo A, Aguilera FS, Ferrari M, Tay FR,
Toledano M.
Effects of adhesive systems and luting agents on bonding of fiber posts to root
canal dentin. J Biomed Mater Res B Appl Biomater 2006;77:195-200.
18. Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption
characteristics of dental composites incorporating hydroxyapatite filler.
Biomaterials 2002;23:1897–1904.
19. Soderholm KJ, Lambrechts P, Sarrett D, Abe Y, Yang MC, Labella R. Clinical
wear performance of eight experimental dental composites over three years
determined by two measuring methods. Eur J Oral Sci 2001;109:273–81.
20. Turssi CP, Purquerio BM, Serra MC. Wear of dental resin composites: insights
into underlying processes and assessment methods—a review. J Biomed Mater Res
2003;65B:280–5.
21. Vano M, Carvalho C, Sedda M, Gabriele M, Ferrari M. The influence of
storage condition and duration on the resistance to fracture of different fiber posts
systems. Am J Dent 2007, in press.
22. Vichi A, Fraioli A, Davidson CL, Ferrari M. Influence of thickness on color in
multi-layering technique. Dent Mater 2007; Sep 6; ahead of print.
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23. Vichi A, Vano M, Ferrari M. The effect of different storage conditions and
duration on the fracture strength of three types of translucent fiber posts. Dent
Mater 2007, in press.
24. Willems G, Lambrechts P, Braem M, Vanherle G. Three-year follow-up of five
posterior composites: in vivo wear. J Dent 1993;21:74–8.
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Fig 1 Fiber post head exposed on the occlusal surface of a direct resin composite
restoration (Group 1).
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Fig 2 Polyether impressions of the abutment were taken at baseline and after 5
years of clinical service in group 2 samples.
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Fig 3a Representative SEM micrograph of DT Light Post at baseline.
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(b) Representative SEM micrograph of DT Light Post after 5 years of clinical service.
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Fig 4 Higher magnification of Fig 3b. No volume loss at the border between the
direct resin material and the fiber post was noted.
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Fig 5 SEM micrograph showing a good bonding between the fibers and the matrix
after 5 years of clinical service.
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Chapter 5
5.1. Summary Retention is one of the main aspect for the clinical success of fiber intracanal posts.
Thanks to research endodontics and adhesive dentistry improved the quality and
the longevity of the complex fiber post-dentin-core material (Akkayan and
Gulmetz, 2002) (Newman et al., 2003).
However the interfacial strength between composite core and fiber post is still
relatively weak, mainly due to chemical incompatibility among different
components (Aksornmuang et al., 2004) (Goracci et al., 2005).
In order to improve adhesion between fiber post and core build up, the first study
(Chapter 1) aimed at evaluating the influence of post surface treatment with
hydrogen peroxide or hydrofluoric acid. The results validated the effectiveness of
the surface treatment with hydrogen peroxide and silane application or hydrofluoric
acid and silane application as a method for enhancing bond strength. In addition
regarding the type of core build-up, the study demonstrated that flowable
composites exhibited the best adaptation to the post surface.
The timing of post space preparation and cementation also influences the retention
of the complex post-core (Ewart and Saunders, 1990). Posts can be placed
immediately after completion of the endodontic treatment or at a later stage after
full setting of the endodontic sealer (Galen and Mueller, 1998) (Saunders et
al.,1991).
In Chapter 2 the effect of immediate versus delayed post cementation on the
retention of different types of fiber posts in canals obturated with a eugenol sealer
or with an epoxy resin sealer was evaluated. Indipendently from the type of
endodontic sealer (eugenol or epoxy based sealer), immediate post space
preparation and post cementation resulted in lower interfacial strengths between the
bonded post and intraradicular dentin. Conversely, a significant increase in
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retention was recorded when the post space preparation and post cementation were
performed 24 hours and one week after the canals were filled with gutta-percha. In
agreement with previous investigations (Schwartz et al., 1998), (Karapanou et al.,
1996), the results of the studies in Chapter 2, showed no differences in terms of
post retention when an eugenol or an epoxy resin based sealer were used as
endodontic sealers.
It is important that the clinician considers the mechanical properties of fiber posts
when designing or using a post restoration in an endodontically treated tooth. In
fact the quality of the support of the coronal restoration can be reflected by the
stiffness of the post, being related to loss of retention of a crown (Sahafi et al.,
2004). The mechanical properties of fiber posts are negatively affected by water
exposure. In particular a reduction of flexural strength (Lassila et al., 2004)
(Mannocci et al., 2001) was reported after water storage. In Chapter 3 the water
detrimental effect on the flexural strength of different translucent fiber posts was
tested. In order to mimic a clinical situation extracted human canines teeth were
selected as one of the storage condition to be tested. The results of these studies
indicated that storage of fiber posts in human root immersed in water resulted in
similar flexural strengths values to those obtained in dry and oil storage, therefore
no detrimental effect was recorded. Conversely, a reduction in the mechanical
properties of fiber posts after water storage was observed in those groups in which
the fiber posts were soaked in water.
The results of the studies in Chapter 3 showed that once an endodontic post is
cemented into the root canal, and the coronal part is immersed into the composite
resin core, it can be considered free from any water detrimental effect. However
observation of exposed post on a direct restoration is a common finding
(Fredriksson et al., 1998). Therefore it was of interest to evaluate clinically whether
the exposure to the oral environment and occlusal function affected the
morphological integrity of luted intracanalar translucent fiber posts retaining a
direct composite restoration (Chapter 4). The results showed that after 5 years of
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clinical service no microscopic signs of post surface degradation due to water
uptake were seen. Only a limited amount of wear rate due to the 5 years period of
clinical service was detected for the exposed posts.
5.2. Conclusions
The following conclusions may be drawn from our evaluation of the factors
affecting fiber posts retention and mechanical properties:
1) Surface treatment of post with hydrogen peroxide and silane application or
hydrofluoric acid and silane application significantly enhances the interfacial bond
strength between fiber posts and core materials. Post pre-treatment with 24%
hydrogen peroxide for 10 min appears to be as an easy, effective and inexpensive
method that can improve the clinical performance of methacrylate resin-based glass
fiber posts.
2) Indipendently from the type of endodontic sealer (eugenol or epoxy based
sealer), immediate post space preparation and post cementation resulted in lower
interfacial strengths between the bonded post and intraradicular dentin. Conversely,
a significant increase in retention was recorded when the post space preparation
and post cementation were performed 24 hours and one week after the canals were
filled with gutta-percha.
3) Fiber posts placed inside human root canals immersed in water showed to be
effectively preserved from water degradation effect. Fiber posts stored in direct
contact with water showed significant lower flexural strength values and
morphological changes regardless the post type tested.
4) Exposition of a fiber post in a direct restoration does not lead to clinical failure.
Over a 5-year period, the post surface exposed in a direct resin restoration did not
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show morphological changes related to water degradation although it exhibited a
limited loss of structure due to occlusal function.
5.3. Riassunto e conclusioni
La ritenzione rappresenta un aspetto fondamentale per il successo clinico dei perni
in fibra intracanalari. La ricerca nel campo endodontico e conservativo ha permesso
di migliorare la qualità e la longevità del complesso perno endodontico-dentina-
materiale da ricostruzione (Akkayan and Gulmetz, 2002) (Newman et al., 2003).
Tuttavia la forza di adesione tra il materiale da ricostruzione e il perno in fibra è
ancora relativamente debole a causa della scarsa affinità chimica tra i componenti
(Aksornmuang et al., 2004) (Goracci et al., 2005).
Al fine di aumentare l’adesione tra il perno in fibra ed il materiale da ricostruzione,
il primo studio (capitolo 1) ha valutato l’influenza del trattamento di superficie del
perno applicando acido idrofluoridrico o perossido d’idrogeno. I risultati hanno
dimostrato l’effettiva capacità dell’acido idrofluoridrico con silano e del perossido
d’idrogeno con silano di aumentare la forza di adesione tra perno e materiale da
ricostruzione. Inoltre lo studio ha evidenziato un migliore adattamento dei
compositi di tipo flowable alla superficie del perno.
La tempistica nella preparazione del sito per il perno e la sua cementazione
influenza la ritenzione del complesso perno-materiale da ricostruzione (Ewart and
Saunders, 1990). Il perno infatti può essere posizionato subito dopo il trattamento
endodontico o in una fase successiva quando il cemento radicolare ha raggiunto la
stabilità ed è indurito (Galen and Mueller, 1998) (Saunders et al.,1991). Nel
Capitolo 2 è stata valutato l’effetto della cementazione immediata o ritardata sulla
ritenzione di differenti tipologie di perni in fibra in canali otturati con un cemento a
base di eugenolo o a base di resina epossidica. Indipendentemente dal tipo di
cemento utilizzato (eugenolo o epossidico), la preparazione immediata del sito per
il perno con susseguente cementazione ha prodotto i più bassi valori di adesione tra
perno e dentina radicolare. Al contrario un significativo aumento in termini di
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ritenzione fu riscontrato nei gruppi dove la preparazione del sito per il perno e la
cementazione erano effettuate 24 ore o una settimana dopo l’otturazione canalare
con cemento canalare e guttaperca. In accordo con altri studi (Schwartz et al.,
1998), (Karapanou et al., 1996), i risultati presentati nel capitolo 2, non
evidenziano alcuna differenza in termini di ritenzione del perno tra l’uso di un
cemento a base di eugenolo o di resina epossidica per la chiusura del canale
radicolare.
Prima di effettuare una riabilitazione di un dente trattato endodonticamente, il
clinico deve scegliere il tipo di perno in fibra tenendo conto delle sue proprietà
meccaniche. La qualità del supporto del restauro a livello coronale può essere
condizionata dalla rigidità del perno (Sahafi et al., 2004). I perni in fibra subiscono
una riduzione delle loro caratteristiche meccaniche ed in particolare della resistenza
alla flessione dopo lo ‘storage’ in acqua (Lassila et al., 2004) (Mannocci et al.,
2001). Nel terzo capitolo sono stati valutati gli effetti di alcune tipologie di
‘storage’ sulla resistenza alla flessione di differenti perni in fibra. I risultati di
questi studi indicano che lo ‘storage’ dei perni in fibra, in canali di denti umani
estratti, otturati coronalmente e immersi in acqua, non produce alcuna riduzione
delle loro proprietà meccaniche. I dati provenienti dai gruppi sopradescritti sono
comparabili con i dati ottenuti da perni in ‘storage’ in olio e a condizioni ambiente.
Al contrario i perni immersi in acqua (senza essere posizionati dentro le radici
dentarie) hanno mostrato valori di resistenza alla flessione significativamente
inferiori se paragonati agli altri gruppi.
I risultati presentati nel capitolo terzo dimostrano che il perno in fibra, dopo la
cementazione nel canale radicolare e la ricostruzione della porzione coronale con
materiale composito, non subisce alcun effetto negativo da parte dell’acqua o dei
fluidi orali. Tuttavia l’esposizione di una parte del perno nell’ambiente orale a
causa di un fallimento del restauro coronale rappresenta una situazione clinica
abbastanza comune (Fredriksson et al., 1998). Di conseguenza era di grande
interesse valutare clinicamente se l’esposizione del perno all’ambiente orale
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potesse compromettere la sua integrità morfologica (Capitolo 4). Dopo 5 anni di
servizio clinico nessun segno microscopico di degrado della superficie del perno
dovuto all’azione dell’acqua o dei fluidi orali è stato registrato. E’stato osservato
solo un lieve grado di usura delle superfici dei perni esposti in seguito ai 5 anni di
funzione masticatoria.
Conclusioni
Alla luce della valutazione dei fattori che influenzano la ritenzione dei perni e le
loro proprietà meccaniche è possibile trarre le seguenti conclusioni:
1) L’applicazione di perossido d’idrogeno e silano o l’applicazione di acido
idrofluoridrico e silano come trattamenti di superficie del perno, hanno la capacità
di aumentare la ritenzione tra perno in fibra e materiale composito. In particolare il
trattamento di superficie del perno con perossido d’idrogeno al 24% per 10 minuti
rappresenta una metodica semplice, efficace e poco costosa con la quale è possibile
migliorare la prestazione clinica dei perni in fibra di vetro a base di resina
contenente metacrilati.
2) Indipendentemente dal tipo di cemento radicolare utilizzato (a base di eugenolo
o di resine epossidiche) la preparazione del sito per il perno e la sua cementazione
subito dopo la chiusura del canale radicolare produce bassi valori di adesione tra il
perno e la dentina radicolare. E’ raccomandabile quindi ritardare la preparazione
del sito del perno e la sua cementazione di almeno 24 ore.
3) I perni in fibra immersi liberamente in acqua per lunghi periodi (6 mesi)
subiscono una riduzione delle loro proprietà meccaniche. Al contrario i perni in
fibra dentro i canali radicolari, otturati coronalmente, non subiscono alcuna
riduzione.
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4) L’esposizione di una porzione di un perno in fibra nella cavità orale non
pregiudica necessariamente la sopravvivenza clinica del restauro. Dopo 5 anni di
servizio clinico, i perni aventi la superficie coronale esposta all’ambiente orale non
mostravano alcun segno di degrado morfologico dovuto all’azione dell’acqua o dei
fluidi orali. Un lieve grado di usura è stato osservato a livello della superficie del
perno, in relazione a 5 anni di funzione occlusale.
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5.4. Resumen
La buena retención intrarradicular de un poste de fibra representa
una de las características más importantes para alcanzar un éxito
clínico. La calidad y la durabilidad de las restauraciones de los
dientes endodonciados se han mejorado por efecto del continuo
perfeccionamiento de la endodóncia y de la odontología adhesiva
(Akkayan and Gulmetz, 2002) (Newman et al., 2003).
De toda forma, la fuerza de adhesión establecida por el muňon de
resina compuesta -poste de fibra-dentina es aún relativamente
débil, principalmente debido a la incompatibilidad química entre
los distintos componentes (Aksornmuang et al, 2004) (Goracci et
al., 2005).
En la parte inicial de esta tesis doctoral (Capítulo 1) se realizó
una evaluación de diferentes metodos de grabado superficial de la
superficie de los postes por peroxido de hidrogeno y acido
hidrofluorico con el objetivo de mejorar la fuerza de adhesión con
el muňon de resina compuesta. Este enfoque validó con suceso el
grabado con peroxido de hidrogeno junto a la aplicación de silano
como agente de acoplamiento y el grabado con acido
hidrofluorico y aplicación de silano para aumentar la fuerza de
adhesión. Con respecto a la restauración en resina compuesta, el
estudio demostró que los composites de tipo fluido mostraron una
mejor adaptación a la superficie del poste.
El tiempo, que transcurre desde el fin del tratamiento endodóntico
hasta la preparación del espacio para el poste, y la cementación
del mismo en el canal radicular son dos factores que pueden
influenciar la retención final del complejo poste-muňon (Ewart
and Saunders, 1990). Tál y como sugerido en la literatura, el
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poste de fibra puede ser colocado en el conducto radicular
inmediatamente a fin del tratamiento endodóntico o bien después
del completo endurecimiento del cemento sellador (Galen and
Mueller, 1998) (Saunders et al, 1991).
En el Capitulo 2 se realizó una comparación entre dos distintas
tecnicas de cementación del poste, inmediata y postergada, y el
efecto que estas tuvieron sobre la retención intrarradicular de
varios tipos de postes de fibra cementados en canales radiculares
obturados por cemento óxido de zinc eugenol o cemento en resina
epóxida. A pesar del tipo de cemento endodóntico utilizado
(eugenol y epóxido), la preparación del espacio para el poste y su
cementación inmediata resultó en una reducida fuerza de
adhesión entre el poste cementado y la dentina intrarradicular.
Contrariamente, se lograron resultados mejores cuando la
preparación y cementación del perno de fibra fueron performadas
24 horas y 1 semana después de acabar la obturación del canal
radicular con gutapercha. De acuerdo con otras investigaciones
(Schwartz et al., 1998) (Karapanou et al., 1996), los resultados
conseguidos en el estudio (Capitulo 2) enseňaron que ní el
cemento de zinc eugenol ní aquello a base de resina epóxica
utilizados para el sellado endodontico influenciaron las
características retentivas intracanalares de los postes de fibra.
Es muy importante para el clínico considerar las propriedades
mecanicas de los postes de fibra cuando proyectan de utilizarlos
para restaurar los dientes desvitalizados. De hecho, la calidad del
soporte corónale de la restauración se vé influenciada por la
rigidez del poste, ya que está relacionada con la pérdida de
retención de la corona (Sahafi et al., 2004). Las propriedades
mecanicas de los postes de fibra se ven negativamente
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influenciadas cuando expuestos a medio acuoso. Sobretodo, una
reducción de las fuerzas flexurales (Lassila et al., 2004)
(Mannocci et al., 2001) ha sido reportada después de conservar el
especimen en agua. En el Capitulo 3 se valoró la fuerza de
flexión de diferentes tipos de postes de fibra translucidos
guardados en medio acuoso y el efecto perjudicial que resultó.
Así como para simular la verdadera situación clínica, se
seleccionaron caninos humanos extraidos representantes una de
las condiciones experimentales. La conservación de raices
endodociandas restauradas por postes de fibra en medio acuoso
mostró resultados parecidos, en termino de fuerza flexural, de
aquellos logrados por raices mantenidas en medios secos o en
aceite, aunque si no aparecieron defectos deletéreos. Sin
embargo, al mantener los postes de fibra completamente
inmergidos en agua, se asistió a una disminución de las
propriedades mecanicas.
A partir de los resultados del Capitulo 3, se deduce que, una vez
que el poste de fibra haya sido cementado en el canal radicular, y
que suya porción coronal haya sido completamente recubierta de
la resina compuesta, no hay posibilidad de que el agua pueda
perjudicar las propriedades del poste. Todavía ocasionalmente se
nota la exposición del poste através de la restauración corónal en
composite (Fredriksson et al., 1998). Además, se puso necesaria
una evalución clínica de como la exposición a los fluidos orales
hasta la función oclusal puedan afectar a la integridad
morfologíca de los postes de fibra traslucidos cementados nel
canal radicular y detenientes una restauración directa en
composite (Capitulo 4). El estudio clínico se desarrolló durante 5
aňos, al final de los cuales no se detectaron signos de degradación
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microscópica de la superficie de los postes de fibra por el efecto
de agua. Durante todos los 5 aňos se registrió solamente un
pequeňo porcentaje de infiltración de los postes expuestos.
Conclusiones
Las conclusiones siguientes se pueden deducir de las
evaluaciones de laboratorio y clínicas de los factores que pueden
influenciar la retención intracanal de los postes de fibra y sus
propriedades mecanicas:
1) Dos tratamientos de superficie de los postes llevaron a una
mejoría de la fuerza de adhesion del complejo poste-muňon:
grabado por peroxido de hidrogeno conjunto a la aplicación
de silano y tratamiento con acido hidrofluorico seguido de
silano. En particular, el utilizo de peroxido de hidrogeno 24%
por 10 minutos parece una práctica fácil, efectiva y
económica para mejorar el comportamento clínico de los
postes de fibra de vidrio a base de metacrilato.
2) A pesar del tipo de cemento sellador utilizado (eugenol o
epóxido), la preparación inmediata del espacio para poste y su
cementación revelaron una fuerza menor a nivel de la
interfase poste-dentina intrarradicular. Sin embargo, se asistió
a un aumento significativo de la retención cuando la
preparación y la cementación del poste se cumplieron 24
horas y 1 semana después de acabar la obturación canalar con
gutapercha.
3) Los postes de fibra utilizados para la restauración de dientes
endodonciados inmergidos en agua mostraron de ser lo
sufficientemente eficaz como para resistir a la acción
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degradante del agua. Mientras que los postes de fibra
completamente hundidos en medio acuoso desvelaron una
inferior fuerza flexural y modificaciones morfologicas de
superficie según el tipo de poste empleado.
4) La exposición del poste de fibra desde una restauración
directa no nos lleva necesariamente a un fracaso clínico.
Durante los 5 aňos de investigación clínica, la pieza del poste
sobresaliente a la restauración directa no demostró
alteraciones morfologicas relacionadas a la degradación
acuosa, aunque si aparecieron pérdidas de estructura causadas
por la oclusión.
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5.5. Résumé
La rétention est l’un des aspects majeurs en ce qui concerne le succès clinique des
tenons canalaires renforcés en fibres (TRF). La recherche dans les domaines de
l’endodontie et de l’adhésion dentaire a amélioré la qualité et la longévité des
complexes TRF/dentine/faux-moignon (Akkayan and Gulmetz, 2002) (Newman et
al., 2003). Toutefois, la force d’adhésion à l’interface entre les matériaux
composant le faux-moignon et les TRF demeure faible en raison principalement de
leur incompatibilité chimique (Aksornmuang et al., 2004) (Goracci et al., 2005).
Dans le but d’améliorer l’adhésion entre les TRF et les matériaux composant le
faux-moignon, l’étude rapportée au chapitre 1 avait pour but d’évaluer l’influence
du traitement de la surface des TRF par le peroxyde d’hydrogène ou par l’acide
fluorhydrique. Les résultats ont validé l’efficacité du traitement par le peroxyde
d’hydrogène ou de l’acide fluorhydrique suivi par une application de silane pour
améliorer la force d’adhésion. De plus, concernant le faux-moignon, l’étude a
montré que les composite “flowables” présentent la meilleure adaptation à la
surface des TRF.
Le timing de la préparation du logement du tenon et du scellement a également une
influence sur la rétention du complexe TRF/faux-moignon (Ewart and Saunders,
1990). Les TRF peuvent être places immédiatement à la fin du traitement
endodontique ou différés après la prise du matériau de scellement endodontique
(Galen and Mueller, 1998) (Saunders et al.,1991).
Le Chapitre 2 traite de l’effet du scellement immédiat vs. différé de différents
types de TRF dans des canaux obtures à l’aide d’un ciment endodontique eugénate
ou à base de résine époxy. Nonobstant le type de ciment endodontique (eugénate ou
résine époxy), la préparation du logement de tenon et son scellement immédiat ont
entraîné des forces d’adhésion plus faibles entre les TRF et la dentine
intracanalaire. En revanche, une augmentation significative de la rétention a été
enregistrée lorsque le logement canalaire et le scellement étaient différés de 24h ou
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d’une semaine après le traitement endodontique. En concordance avec les
précédentes études de (Schwartz et al., 1998), (Karapanou et al., 1996), les
résultats des études du Chapitre 2 n’ont pas montré de différence concernant la
rétention des TRF lorsque utilisés avec des ciments endodontiques type eugénate
ou résine époxy.
Il est important pour le clinicien de prendre en considération les propriétés
mécaniques des TRF lors du design et l’utilisation des restaurations à tenon sur les
dents traitées endodontiquement. En fait, la qualité du support de la restauration
coronaire se reflète dans la rigidité du tenon comme étant directement reliée à la
perte de rétention de la couronne (Sahafi et al., 2004). Les propriétés mécaniques
des TRF sont affectées négativement par l’exposition à l’eau. En particulier, une
réduction de la résistance à la flexion a été rapportée après stockage dans l’eau
(Lassila et al., 2004) (Mannocci et al., 2001). Le Chapitre 3 analyse l’effet délétère
de l’eau sur la résistance a la flexion de différents TRF. Afin de reproduire la
situation clinique, des canines humaines extraites ont été choisies comme étant
l’une des conditions de stockage testées. Les résultats de ces études ont montré que
le stockage des TRF dans des canines humaines immergées dans l’eau a entraîné
des résistances à la flexion similaires à celles stockées dans l’huiles ou en milieu
sec, et donc aucun effet délétère ne fut enregistré. Par ailleurs, une réduction des
propriétés mécaniques des TRF a été notée après stockage pour les échantillons ou
le TRF avait été préalablement immergé dans l’eau.
Les résultats des études du Chapitre 3 ont montré qu’une fois le TRF scellé dans le
canal, et que sa projection coronaire est noyée dans le matériau composite formant
le faux-moignon, le TRF peut être considéré comme libre de tout effet délétère dû à
l’eau. Toutefois, l’exposition d’un TRF n’est pas rare lors de l’observation de
restaurations directes (Fredriksson et al., 1998). Il était donc intéressant d’évaluer
cliniquement si l’exposition au milieu buccal et la fonction occlusale affectent
l’intégrité structurale des TRF translucides scellées soutenant une restauration
directe en résine composite (Chapitre 4). Les résultats ont montré qu’après 5
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années de service clinique, l’observation microscopique n’a révélé aucun signe de
dégradation des TRF due à l’absorption d’eau. Seul, un taux d’usure limité a été
noté pour les TRF exposés.
Conclusions
Les conclusions suivantes peuvent être tirées de notre évaluation des facteurs
affectant la rétention des TRF et leurs propriétés mécaniques:
1) Le traitement de surface traitement des tenons au peroxyde d’hydrogène ou
l’acide fluorhydrique, suivie par l’application de silane augmente de manière
significative la force d’adhésion à l’interface entre les TRF et les matériaux
composant le faux-moignon. Le pre-traitement du TRF par le peroxyde
d’hydrogène à 24% pendant 10min semble être une méthode simple, facile, et peu
onéreuse capable d’améliorer les performances des TRF à base de méthacrylate de
méthyle.
2) Indépendamment du type de ciment endodontique (eugénate ou résine époxy), la
préparation du logement de tenon et le scellement immédiats ont entraîné des
forces d’adhésion moindres à l’interface TRF/dentine que celles obtenues après un
délais de 24h et une semaine après le traitement endodontique.
3) Les TRF placés dans des racines humaines et immergés dans l’eau se sont
révélés être non affectés par la dégradation due a l’eau. Les TRF stockés en contact
direct avec l’eau ont démontré des valeurs de résistance à la flexion moindres ainsi
que des variations morphologiques indépendamment du type de TRF testé.
4) L’exposition de TRF dans une restauration directe n’entraîne pas l’échec
clinique. Sur un suivi de 5 ans, la surface du TRF exposé dans une restauration
directe en résine composite n’a pas montre de signes morphologiques de
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dégradation due l’eau bien qu’elle ait présenté une perte de substance due à la
fonction occlusale.
5.6 Zusammenfassung
Die Retention ist einer der wichtigsten Aspekte für den klinischen Erfolg von
Faserstiften. Dank der Forschung, haben die Endodontie und die adhäsive
Zahnmedizin die Qualität und die Langlebigkeit des Faserstift-Dentin-
Stumpfaufbau Komplexes verbessert (Akkayan and Gulmetz, 2002) (Newman et
al., 2003).
Dennoch ist die adhäsive Kraft zwischen Stumpfaufbaumaterial und Faserstift noch
relativ schwach, bedingt vorwiegend durch die chemische Incompatibilität
zwischen den unterschiedlischen Komponenten (Aksornmuang et al., 2004)
(Goracci et al., 2005).
Um die Adhäsion zwischen Faserstift und Stumpfaufbau zu verbessern, wurde in
der ersten Studie (Kapitel 1) der Einfluss der Behandlung der Faserstiftoberfläche
mit Wasserstoffperoxid oder mit Fluorwasserstoffsäure untersucht. Die Ergebnisse
haben bewiesen, dass die Behandlung der Faserstiftoberfläche mit
Wasserstoffperoxid und Silan bzw. mit Fluorwasserstoffsäure und Silan eine
wirksame Methode ist, um die adhäsive Kraft zu erhöhen. Außerdem hat die Studie
bewiesen, dass die Flowable-Kompositen die beste Anpassung an die
Faserstiftoberfläche haben.
Auch das Timing der Post-Space Vorbereitung und der Zementierung beeinflusst
die Retention des Faserstift- Stumpfaufbau Komplexes (Ewart and Saunders,
1990). Der Faserstift kann sofort nach der endodontischen Behandlung positioniert
werden, oder nachdem die Wurzelkanalfüllpaste total erhärtet ist (Galen and
Mueller, 1998) (Saunders et al.,1991).
Im Kapitel 2 wurde der Effekt einer sofortigen oder verschobenen Zementierung
des Faserstiftes auf die Retention unterschiedlicher Typen von Faserstiften in
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Wurzelkanälen gefüllt mit Eugenol bzw. Epoxidharz-Paste bewertet. Unabhängig
von dem Typ der Wurzelkanalfüllpaste (Eugenol oder Epoxidharz), haben die
sofortigen Post-Space Vorbereitung und Zementierung niedrige Adhäsionskräfte
zwischen dem zementierten Faserstift und dem Wurzelkanaldentin bewirkt. Im
Gegenteil wurde eine signifikante Erhöhung der Retention beobachtet, wenn die
Post-Space Vorbereitung und die Zementierung des Faserstiftes entweder 24
Stunden oder eine Woche nach der Wurzelkanalfüllung mit Guttapercha eingesetzt
wurden. Die Ergebnisse der Studien im Kapitel 2 haben keinen Unterschied in der
Retention des Faserstiftes gezeigt, wenn eine Eugenol-Wurzelkanalfüllpaste oder
eine Epoxidharz-Wurzelkanalfüllpaste verwendet wurden. Diese Ergebnisse
stimmen überein mit vorhergehenden Untersuchungen (Schwartz et al., 1998),
(Karapanou et al., 1996).
Es ist sehr wichtig, dass der Zahnarzt die mechanischen Eigenschaften der
Faserstifte in Betracht zieht, wenn eine Restauration mit einem Faserstift in einem
endodontisch behandelten Zahn verwendet werden soll. In der Tat kann die
Qualität des Gestells der koronalen Restauration von der Festigkeit des Faserstiftes
beeinflusst werden, die mit dem Verlust der Retention der Krone im
Zusammenhang gebracht wird (Sahafi et al., 2004).
Die mechanischen Eigenschaften der Faserstifte werden negativ von der
Wasserlagerung beeinflusst. Eine Herabsetzung der Biegefestigkeit wurde
besonders nach Wasserlagerung beschrieben (Lassila et al., 2004) (Mannocci et al.,
2001). Im Kapitel 3 wurde daher getestet, ob Wasser einen negativen Effekt auf die
Biegefestigkeit von unterschiedlich durchscheinenden Faserstiften hat. Um
klinische Bedingungen zu simulieren, wurden extrahierte Eckzähne als eine der
Lagerungs-Bedingungen gewählt. Die Ergebnisse dieser Studien haben gezeigt,
dass die Lagerung von Faserstiften in Zahnwurzeln im Wasser, ähnliche
Biegefestigkeitswerte hervorgebracht hat, wie eine Öl oder Trockenlagerung. Ein
negativer Effekt der Wasserlagerung konnte somit nicht festgestellt werden.
Dagegen wurde eine Herabsetzung der mechanischen Eigenschaften der Faserstifte
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nach Wasserlagerung in den Gruppen beobachtet, in denen die Faserstifte direkt im
Wasser eingetaucht wurden. Die Ergebnisse der Studien im Kapitel 3 haben gezeigt
dass, wenn ein Faserstift im Wurzelkanal zementiert wird, und der koronale Teil ist
auf dem Komposit-Stumpfaufbau angebracht, der Faserstift wird von dem
negativen Effekt des Wassers nicht beeinflusst. Trotzdem werden ungedeckten
Faserstiften in direkten Restaurationen häufig beobachtet (Fredriksson et al., 1998).
Deshalb war es interessant klinisch zu bestimmen, ob das Mundmilieu und das
Kauen die morphologische Unversehrtheit zementierter durchscheinender
Faserstifte beeinflussen, wenn die Faserstifte eine direkte Komposit-Restauration
befestigten (Kapitel 4). Die Ergebnisse haben gezeigt, dass, nach 5 Jahren
klinischen Einsatz, keine mikroskopischen Zeichen von Degradation der
Oberfläche des Faserstiftes durch Aufnahme von Wasser beobachtet wurden.
Lediglich wurde ein geringer Verschleiß der ungedeckten Faserstifte nach 5 Jahren
klinischen Einsatz festgestellt.
Schlussfolgerungen
Folgende Schlussfolgerungen können aus unserer Bestimmung der Faktoren, die
die Retention und die mechanischen Eigenschaften der Faserstifte beeinflussen,
gezogen werden:
1) Die Behandlung der Faserstiftoberfläche mit Wasserstoffperoxid und Silan bzw.
mit Fluorwasserstoffsäure und Silan erhöht signifikant die adhäsive Kraft zwischen
Faserstiften und Stumpfaufbau-Materialien. Die Behandlung des Faserstiftes mit
24% Wasserstoffperoxid für 10 Minuten scheint eine einfache, wirksame und
kostenlose Methode zu sein, um das klinische Verhalten von Methacrylat-
Faserstiften zu verbessern.
2) Unabhängig von dem Typ der Wurzelkanalfüllpaste (Eugenol- oder Epoxidharz-
Wurzelkanalfüllpaste), haben die sofortigen Post-Space Vorbereitung und
Zementierung geringere Adhäsionskräfte zwischen dem zementierten Faserstift und
dem Wurzelkanaldentin bewirkt. Im Gegenteil wurde eine signifikante Erhöhung
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der Retention beobachtet, wenn die Post-Space Vorbereitung und die Zementierung
des Faserstiftes entweder 24 Stunden oder eine Woche nach der
Wurzelkanalfüllung mit Guttapercha eingesetzt wurden.
3) Faserstifte, zementiert in Zahnwurzeln eingetaucht im Wasser, wurden von der
Wasser-Degradation effektiv geschützt. Unabhängig von dem Typ des Faserstiftes,
haben Faserstifte in direkter Wasserlagerung signifikant niedrigere
Biegefestigkeitswerte und morphologische Änderungen gezeigt.
4) Die Abdeckung des Faserstiftes in einer direkten Restauration verursachte
keinen klinischen Misserfolg. Die ungedeckte Faserstiftoberfläche in einer direkten
Restauration zeigte auch nach 5 Jahren keine bedingte morphologische
Veränderungen durch Wasser-Degradation, auch wenn ein begrenzter Verlust von
Struktur durch Kauen festgestellt wurde.
5.7 Sumário
Retenção é um dos principais aspectos para o sucesso clinico de pinos de fibra
intra-canais.
Devido às pesquisas endodônticas e as melhorias na odontologia adesiva houve um
aumento na qualidade e a longevidade do conjunto pino-dentina-restauração
(Akkayan and Gulmetz, 2002) (Newman et al., 2003).
Contudo, a força na interface do corpo da restauração e pino de fibra é
relativamente frágil, principalmente devido a incompatibilidade entre diferentes
componentes (Aksornmuang et al., 2004) (Goracci et al., 2005).
De maneira a melhorar a adesão entre pino de fibra e restauração, o primeiro estudo
(Capitulo 1) concentrou em avaliar a influencia do tratamento superficial com
peróxido de hidrogênio ou acido fluorídrico. Os resultados comprovaram a
eficiência do tratamento superficial com peróxido de hidrogênio e aplicação de
silano ou acido hidro-fluoridrico e aplicação de silano como método de melhorar a
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força adesiva. Ainda em respeito ao tipo da restauração, o estudo demonstrou que
resinas fluidas exibiram a melhor adaptação a superfície do pino.
O período de preparação do canal e a cimentação também influenciam a retenção
do conjunto pino-restauração (Ewart and Saunders, 1990). Pinos pode ser
cimentados imediatamente após finalizada o tratamento endodôntico ou num
período pós-operatório após a colocação do cimento obturador endodôntico (Galen
and Mueller, 1998) (Saunders et al.,1991).
No Capitulo 2 o efeito imediato versus mediato da cimentação na retenção de
diferentes tipos de pinos de fibra em canais obturados com cimentos contendo
eugenol ou com uma resina epóxica foram avaliados. Independente do tipo do
cimento obturador ( eugenol ou resina epóxica), a cimentação imediata logo após a
preparação do canal obturador resultou em menor força de resistência entre o pino
e a dentina intra-radicular. Diferentemente, um significante aumento na retenção
quando a preparação do canal radicular e a cimentação do pino foram feita 24 horas
e uma semana após os canais terem sido obturados com guta-percha. Resultados
semelhantes foram encontrados por diversos estudos (Schwartz et al., 1998),
(Karapanou et al., 1996), demonstrando a não diferença em retenção quando um
cimento a base de eugenol ou resina epóxica forma usados como cimentos
endodônticos.
Importante é salientar aos clínicos que as propriedades mecânicas dos pinos de
fibra quando idealizados ou usados em conjunto com a restauração em dentes
tratados endodonticamente. Na verdade a qualidade do suporte pode ser refletida
pela rigidez do pino, sendo correlacionada a perda de retenção das coras (Sahafi et
al., 2004). Em particular a redução da força flexural (Lassila et al., 2004)
(Mannocci et al., 2001) foi reportada após o armazenamento em água. No Capitulo
3 o efeito deletério da água na força flexural em diferentes tipos de pino de fibra foi
testada. De maneira a simular a situação clinica caninos extraídos foram
selecionados como uma das melhores formas de armazenamento. Os resultados
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deste estudo indicaram que o armazenamento de pinos de fibra em raízes imersos
em água foram similares aos armazenados em ambiente seco e óleo em relação à
força flexural, conseqüentemente o efeito deletério não foi identificado. Contudo, a
redução nas propriedades mecânicas dos pinos de fibra após o armazenamento em
água foi observada em grupos nos quais os pinos de fibra foram imerso em água.
Os resultados do estudo no Capitulo 3 demonstraram que uma vez o pino é
cimentado no canal radicular, e a parte coronal e imersa dentro de resina composta,
isto pode ser considerado livre de qualquer efeito deletério da água. Contudo,
encontrar pinos expostos em restaurações diretas é corriqueiro (Fredriksson et al.,
1998). Relacionado a essa afirmação foi avaliado clinicamente se a exposição ao
ambiente oral em contato oclusal afeta a integridade morfológica do pino de fibra
mantido por restaurações em compósito diretas (Capitulo 4). Os resultados
demonstraram que após 5 anos de função clinica nenhum sinal microscópico de
degradação devido a embebição de água foi notado. Somente um pequeno volume
de desgaste devido aos 5 anos de função clinica foi detectado nos pinos expostos.
Conclusões
As seguintes conclusões podem ser assumidas dos nossos estudos dos fatores que
afetam a retenção de pinos de fibra e as propriedades mecânicas:
1) O tratamento superficial do pino com peróxido de hidrogênio e aplicação de
silano ou acido fluorídrico e aplicação de silano significantemente aumenta
a força de adesão entre o pino de fibra e material restaurador. Pinos com
pré-tratamento com 24% de peróxido de hidrogênio por 10 min.
demonstram ser pratico, efetivo e baixo custo; melhorando a desempenho
clinica dos pinos de metacrilato.
2) Independente do tipo de cimento obturador (eugenol ou resina expóxica),
imediatamente a preparação do conduto radicular e cimentação do pino
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resultou em baixa força entre o pino e a dentina intra-radicular.
Diferentemente, uma significante melhora na retenção foi notada quando a
preparação do conduto e a cimentação dos pinos eram realizadas em 24
horas e uma semana após os canais terem sidos obturados com guta-percha
3) Pinos de fibra dentro de raízes de dentes humanos imersas em água
demonstraram promover um efeito de preservação do efeito deletério da
água. Pinos de fibra armazenados em contato direto com a água
demonstram uma significante redução dos valores da força flexural e
modificações a respeito dos pinos testados.
4) A exposição do pino de fibra em restaurações diretas não conduz a falha
clinica. Acima de um período de 5 anos, a superfície do pino exposto em
uma restauração direta não demonstrou modificações morfológicas
relacionadas a degradação pela água contudo demonstrou uma limitada
perda de estrutura devido a função oclusal.
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Curriculum Vitae Dr. Michele Vano Date of birth : May 23th, 1977 Place of birth: Pisa, Italy Civil status: Unmarried Citizenship: Italian Home address: Via Giusti, 18, Pisa, 56127, Italy Telephone number: +393356890180, 057133791 E-mail address: [email protected]@unisi.it February 2002: Degree in Dentistry; 110/110 cum laude; University of Pisa, Pisa, Italy Research activity 2002-2003: Master of Oral Surgery, University of Pisa, Pisa, Italy
2003-2004: Master of Science in Dental Materials and their clinical applications,
University of Siena, Italy
2004-2007: PhD Program in Dental Materials and their clinical applications,
University of Siena, Italy
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Professional positions
2002-2004: Intership at the Department of Oral Surgery at the University of Pisa,
Italy.
2004-2007: Contract Professor of Basic Research Principles at the University of
Siena, Italy
Membership in Dental societies
2002-2007 S.I.d.C.O. (Italian Sociaty of Oral Surgery)
2005-2007 - Member of SIDOC (Italian Society of Restorative Dentistry)
2006 - Member of IADR (International Association of Dental Research)
International publications
Simonetti M, Radovic I, Vano M, Chieffi N, Goracci C, Tognini F, Ferrari M. The
influence of operator variability on adhesive cementation of fiber posts. J Adhes
Dent. 2006 Dec;8(6):421-5.
Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,
Ferrari M. Effect of the seating pressure on the adhesive bonding of indirect
restorations. Am J Dent. 2006 Dec;19(6):333-6.
Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M. The
effect of immediate versus delayed cementation on the retention of different types
of fiber post in canals obturated using a eugenol sealer. J Endod. 2006
Sep;32(9):882-5.
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Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M.
Retention of fiber posts cemented at different time intervals in canals obturated
using an epoxy resin sealer. J Dent, Submitted.
Graziani F, Vano M, Cei S, Tartaro G, Gabriele M. Unusual asymptomatic giant
sialolith of the submandibular gland: a clinical report. J Craniofac Surg. 2006
May;17(3):549-52.
Hiraishi N, Loushine RJ, Vano M, Chieffi N, Weller RN, Ferrari M, Pashley DH,
Tay FR. Is an oxygen inhibited layer required for bonding of resin-coated gutta-
percha to a methacrylate-based root canal sealer? J Endod. 2006 May;32(5):429-33.
Graziani F, Vano M, Viacava P, Itro A, Tartaro G, Gabriele M. Microvessel
density and vascular endothelial growth factor (VEGF) expression in human
radicular cysts. Am J Dent. 2006 Feb;19(1):11-4.
Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,
Ferrari M. The effect of application sustained seating pressure on adhesive luting
procedure. Dent Mater. 2007 Feb;23(2):159-64.
Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M. The
adhesion between fibre posts and composite resin cores: the evaluation of
microtensile bond strength following various surface chemical treatments to posts.
Int Endod J. 2006 Jan;39(1):31-9.
Graziani F, Vano M, Tartaro G, Fanelli G, Gabriele M. The use of hydrogen
peroxide in the experimental therapy of cysts. An in vitro analysis. Minerva
Stomatol. 2003 Jul-Aug;52(7-8):373-80.
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Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,
Ferrari M. An in vitro study of the effect of the seating pressure on the adhesive
bonding of in direct restorations. Am J Dent, In press.
Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,
Ferrari M. The effect of adding an antibacterial monomer on the bond quality of a
luting cementation system. Int Dent SA, 2006;8:48-54.
Vichi A, Vano M, Ferrari M. The effect of different storage conditions and duration
on the fracture strength of three types of translucent fiber posts. Dent Mater 2007,
In press.
Vano M, Carvalho C, Sedda M, Gabriele M, Garcia-Godoy F, Marco Ferrari. The
influence of storage condition and duration on the resistance to fracture of different
fiber posts systems. Am J Dent, In press.
Porciani PF, Vano M, Radovic I, Goracci C, Grandini S, Garcia-Godoy F, Ferrari
M. Fracture resistance of fiber posts: combinations of several small posts vs.
standardized single post. J Adhes Dent, In press.
Vano M, Garcia-Godoy F, Goracci C, Vichi A, Ferrari M. Effects of oral
environment and occlusal wear on FRC-posts integrity in clinical service for 5
years. J Adhes Dent, Submitted.
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Abstracts
Vano M, Coniglio I, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M. The
effect of immediate versus delayed post cementation on retention of different types
of fibre post in canals obturated using a resin based sealer. European Federation of
Conservative Dentistry 3rd
Triannual Meeting and Italian Society of Conservative
Dentistry 10th
Annual Meeting, February 9-11, 2006, Rome, Italy. Italian Journal of
Operative Dentistry, Jan-Mar 2006; Supplement IV, 1:63-64.
Vano M, Mazzitelli C, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M.
Retention of different types of fibre post luted at different intervals in canals
obturated using a eugenol sealer. European Federation of Conservative Dentistry
3rd
Triannual Meeting and Italian Society of Conservative Dentistry 10th
Annual
Meeting, February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry,
Jan-Mar 2006; Supplement IV, 1:63-64.
Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M. The
adhesion between fibre posts and composite resin cores: the evaluation of
microtensile bond strength following various post surface chemical treatments to
posts. European Federation of Conservative Dentistry 3rd
Triannual Meeting and
Italian Society of Conservative Dentistry 10th
Annual Meeting, February 9-11,
2006, Rome, Italy. Italian Journal of Operative Dentistry, Jan-Mar 2006;
Supplement IV, 1:63-64.
Vano M, Magni E, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M. The
effect of root canal filling on retention of different types of fibre posts in canals
obturated using a resin sealer. European Federation of Conservative Dentistry 3rd
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Triannual Meeting and Italian Society of Conservative Dentistry 10th
Annual
Meeting, February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry,
Jan-Mar 2006; Supplement IV, 1:63-64.
Vano M, Raffaelli O, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M. The
effect of eugenol versus noneugenol endodontic sealer on post retention of different
types of fibre post. European Federation of Conservative Dentistry 3rd
Triannual
Meeting and Italian Society of Conservative Dentistry 10th
Annual Meeting,
February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry, Jan-Mar
2006; Supplement IV, 1:63-64.
Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,
Ferrari M. The effect of the seating pressure on self-etch adhesive/chemical cure
resin cement bond. European Federation of Conservative Dentistry 3rd
Triannual
Meeting and Italian Society of Conservative Dentistry 10th
Annual Meeting,
February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry, Jan-Mar
2006; Supplement IV, 1:63-64.
Vano M, Sedda M, Monticelli F, Gabriele M, Ferrari M. The effect of storage time
and media on fiber posts. J Dent Res 2006, 85 (sp issue): abstract 0337.
Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Magni E, Davidson CL,
Tay FR, Ferrari M. Factors affecting the adhesive cementation of indirect
restorations. J Dent Res, 85 (sp issue): abstact 00062. IADR Pan European
Federation 2006, Dublin, September 13-16.
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Graziani F, Cei S, Guerriero A, La Ferla F, Vano M, Tonetti M, Gabriele M.
Adjunctive effect of a systemic biphosphonate in non surgical periodontal therapy
of advanced generalized chronic periodontitis a randomized clinical trial.
Europerio, Madrid, Giugno 2006.
National Publications
Graziani F, Vano M, Gabriele M.
Profilassi dell’alveolite post-estrattiva. Proposte di linee guida. Dental Cadmos
2002;1:55-61.
Graziani F, Vano M, Gabriele M.
Angiogenesi ed espressione del fattore di crescita dell’endotelio vascolare nelle
cisti radicolari dei mascellari. Doctor OS 2003;1:14(1) suppl.1.
Vano M, Cei S, Graziani F.
Inusuale caso di scialolitiasi asintomatica del dotto di Wharton. Doctor Os
2005;16(4):345-347.
Vano M, Tognini F, Goracci C, Gabriele M, Bosco M, Ferrari M.
Vutazione della forza di adesione di differenti resine composite utilizzate nel
restauro di monconi su perni in fibra. Doctor Os 2005;16(1) Suppl.1:33-35.
Graziani F,Vano M, Gabriele M.
Terapia cistica sperimentale: ruolo dell’angiogenesi nelle cisti radicolari delle
ossa mascellari. Atti del 1° congresso nazionale S.l.C.O – S.I.d.C.O. Pescara,
29-30 Novembre 2002.
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Graziani F, Vano M, Gabriele M.
Marcatori immunoistochimici della vascolarizzazione nelle cisti radicolari. 10°
Congresso Nazionale “ Collegio dei docenti di odontoiatria” Roma 9-10-11-12
aprile 2003.
Vano M, Tosi E.G, Graziani F, Gabriele M.
Complicanze post-estrattive: valutazione dei parametri che influiscono sulla
guarigione alveolare. 12° Congresso Nazionale “ Collegio dei docenti di
odontoiatria”Roma 16-17-18-19 marzo 2005.
Cei S, Graziani F, Ducci F, Vano M, Gabriele S.
Valutazione della responsività di cellule mesenchimali stremali isolate da ratti di età
differente. Studio in vitro. 13° Congresso Nazionale del “Collegio dei docenti di
Odontoiatria”5-6-7-8 Aprile Roma 2006.
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Acknowledgements
This thesis is respectfully submitted to Prof. Silvano Focardi, Rector of the
University of Siena, to Prof Alberto Auteri, Dean of the Faculty of Medicine of the
University of Siena, to Prof. Egidio Bertelli, Director of the Department of Dental
Science, University of Siena and to Prof. Marco Ferrari, President of Dental
School, and Director of the PhD Program, University of Siena.
My sincere gratitude and admiration to my promoter Prof. Marco Ferrari. He
patiently and continuously reviewed my work and encoraged me to achieve this
goal.
I would like to thank my Co-promoter Dr. Cecilia Goracci for her scientifical
guidance. Her support was priceless.
I gratefully thank Dr. Simone Grandini for his clinical advice and support.
A deep thankfulness goes to Prof. Franklin Tay, for his unique and precious
scientific support.
I am also grateful to the whole Committee, for spending time on reviewing this
thesis.
I am sincerely grateful to Prof. Mario Gabriele. He has always provided me
guidance and encouragement in all these years.
My appreciation goes to Dr. Francesca Monticelli, Dr. Fernanda Sadek, Dr. Alvaro
Cury, Dr. Federica Papacchini, Dr. Maurizio Sedda, Dr. Nicoletta Chieffi, Dr.
Ivana Radovic, Dr. Filippo Graziani and all the PhD students and candidates for
their scientific support and above all their friendship.
I acknowledge my friends and colleagues for the translation of the ‘Summary and
Conclusions’ chapter: Dr. Elisa Magni (German), Dr. Carlos Augusto Ramos de
Carvalho (Portuguese), Dr. Hani Ounsi (French) and Dr. Claudia Mazzitelli
(Spanish).
I want to thank my family for their support and love.
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