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New Zealand Endodontic Journal Vol 33 December 2005

EndodonticJournalVol 33 DECEMBER 2005 ISSN 0114-7722

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Contents

4 New Methods for the Detection and Removal of Dental Caries Mike Gordon

16 Medical Considerations in Endodontics Todd Gracia

28 Should the Core for a Root-Filled Posterior Tooth that requires a crown be made of Amalgam, Composite or Gold? Radu Goga

36 ANNuAl REPORT 2005

New Zealand Societyof Endodontics (Inc)

PresidentPeter CathroPO Box 12025Maori HillDunedin

SecretaryMike Jameson2 Granville TerraceBelleknowesDunedin

TreasurerSarah JardinePO Box 7788Wellesley StreetAuckland

Journal EditorPeter CathroPO Box 12025Maori HillDunedin

Front Cover: KaVO DIAGNOdent®


Editorial NoticEs

The New Zealand Endodontic Journal is published twice yearly and sent free to members of the New Zealand Society of Endodontics (Inc). The subscription rates for membership of the Society are $35 per annum in New Zealand or $45 plus postage for overseas members. Graduates of the university of Otago School of Dentistry enjoy complimentary membership for the first year after graduation. Subscription inquiries should be sent to the Honorary Secretary, Dr Mike Jameson, 2 Granville Terrace, Dunedin. Contributions for inclusion in the Journal should be sent to the Editor, Dr Robert love, PO Box 12025, Dunedin. Deadline for inclusion in the May or November issue is the first day of the preceding month. All expressions of opinion and statements of fact are published on the authority of the writer under whose name they appear and are not necessarily those of the New Zealand Society of Endodontics, the Editor or any of the Scientific Advisers.

iNformatioN for authorsThe Editor welcomes original articles, review articles, case reports, views and comments, correspondence, announcements and news items. The Editor reserves the right to edit contributions to ensure conciseness, clarity and consistency to the style of the Journal. Contributions will normally be subjected to peer review. It is the wish of the Editor to encourage practitioners and others to submit material for publication. Assistance with word processing and photographic and graphic art production will be available to authors.

arraNgEmENtArticles should be typewritten on one side of A4 paper with double spacing and 3cm margins. The author’s name should appear under the title and name and postal address at the end of the article. If possible, the manu-script should also be submitted on computer disc, either Macintosh or PC compatible.

rEfErENcEsReferences cited in the text should be placed in parenthesis stating the authors’ names and date, eg (Sundqvist & Reuterving 1980). At the end of the article references should be listed alphabetically giving surnames and initials of all authors, the year, the full title of the article, name of periodical, volume number and page numbers.

The form of reference to a journal article is:Sundqvist G, Reuterving C-O (1980) Isolation of

Actinomyces israelii from periapical lesion. Journal of Endodontics 6, 602-6.

The form of reference to a book is:Trowbridge HO, Emling RC (1993) Inflammation,

4th edn, pp 51-7. Chicago, uSA: Quintessence Publishing Company Inc.

IllustratIonsIllustrations should be submitted as clear drawings, black & white or colour photographs and be preferably of column width. Radiographs are acceptable. However a black & white photograph is preferred. Illustrations must be numbered to match the text and bear the author’s name and an indication of the top edge on the back. legends are required for all illustrations and should be typewritten on a separate page.


I apologise that this issue arrived to you later than expected. Due to computer problems at Otago University Print, this could not be avoided, but I am grateful for their ongoing efforts and support.

Once again I am most grateful to the authors of the articles presented in this journal. Without the pool of post-graduate endodontic students (past and present) to draw upon, we simply wouldn’t have a journal. As becomes the catch-cry of every editor I know, please feel free to contribute to the journal – it is after all ‘your/our’ journal. The New Zealand Society of Endodontics is in a healthy financial position and the audited accounts are included in this edition of the journal. Negotiations are underway for the Society to be involved in a pre-NZDA Conference course in 2006. These courses have been of great value in the past, providing continuing education to the members from a number of our local endodontists.

Lastly, I would like to congratulate Nick Chandler, who has recently been promoted to Associate Professor – well done!

Peter Cathro

EdItorIal / PrEsIdEnt’s rEPort


Host

Diet

Micro-flora

Time

NOCaries

NOCaries

NOCaries

NOCaries

Caries

nEw MEthods for thE dEtEctIon and rEMoval

of dEntal carIEs

MIkE Gordon

dEfInItIon of carIEs

Dental caries is an infectious transmissible disease (Axelsson 2000). It is a complex and dynamic interplay of host and microbial factors resulting in demineralization of the mineral portion of the tooth followed by disintegration of the organic material ultimately leading to bacterial invasion and death of the pulp, pain and infection of the periapical tissues. Generally the development of dental caries is as a result of:

a. the microflora – acidogenic bacteria (mutans streptococci) that colonise the tooth surface;

b. the host – quality of the tooth, quantity and quality of the saliva, oral microbiota, availability of fluoride;

c. diet – specifically the intake of fermentable carbohydrates particularly sucrose but also starch; and

d. time – the total exposure time to inorganic acids produced by the bacteria of dental plaque (Figure 1).

Carious lesions can be classified in a number of ways:

a. type: primary or secondary; b. location: root, crown, proximal or occlusal

surfaces;

Figure 1: Development of dental caries (after Axelsson 2000).

c. tissue involvement: enamel, dentine or root cementum; and

d. shape: cavitated, noncavitated smooth, rough or soft surface (Kidd & Joyston-Bechal 1997a).

Free smooth surface caries can occur on enamel and appear as white or brown spot lesions, or on root surfaces which appear yellowish or light brown. Colour is not a good indicator of lesion activity and is due mainly to exogenous staining in porous enamel. Pits and fissures have a varied morphology ranging from a V shape to a “coke bottle” or tear shape in cross-section and can be occluded by an organic plug. The early diagnosis of pit and fissure caries is difficult as the neck or occlusal surface of the pit can remain sound while caries progresses below undisturbed (Milicich 2000). The progression and demineralization of dentine occurs at the dentinoenamel junction and corresponds to the width of the outer surface of the enamel lesion and progresses in the same direction as the dentinal tubules. Advanced demineralization of the dentine can occur without cavitation and bacterial invasion. There is potential for these lesions to be arrested without invasive treatment (Axelsson 2000).

To evaluate the need for intervention it is important to determine if a carious lesion is active or inactive, noncavitated or cavitated. Once operative intervention has begun the decision to stop caries excavation is a difficult one, as, in dentine, tissue colour is not indicative of bacterial infection. Dentine hardness does correlate significantly to bacterial infection but both of these variables are highly subjective and prone to operator error (Kidd et al. 1996). To aid in the initial diagnosis and identification of caries a number of new developments have appeared in the last few years.

dIaGnosIs of carIEs

Diagnosis of caries in its early stages is essential to allow for conservative and preventative treatment which can arrest and reverse the disease process (Kidd & Joyston-Bechal 1997a). Pitts (1997)


contact points can be opened for assessment by orthodontic separators and elastomeric impression material can be injected and examined to confirm cavitation (Kidd & Joyston-Bechal 1997a).

Magnification using loupes or an operating microscope significantly improves the accuracy of caries diagnosis (Forgie et al. 2002) however the use of a surgical microscope does not improve the validity of proximal caries detection if the operators are unfamiliar with its use (Haak et al. 2002). Indirect magnification using an intra-oral video camera (IOVC) was tested to detect occlusal caries (Forgie et al. 2003). Compared to unaided vision the IOVC significantly increased the number of occlusal lesions detected but also increased false positives.

radIoGraPhIc

The bitewing radiograph is an important tool in the diagnosis of caries, particularly proximal lesions. To be diagnostic, radiographs must be of a high standard, processed correctly and viewed under optimal conditions. Radiographs usually disclose 50% more small proximal lesions than does clinical examination alone (Mejare et al. 1999). Bitewings are not sensitive for early enamel lesions particularly in occlusal surfaces. Ketley & Holt (1993) validated non-cavitated dentine caries with histology and found visual inspection to have a sensitivity of 31% and specificity of 98%. Radiography alone had values of 67% and 92% but when combined with visual inspection the specificity was 75% and the sensitivity 90% (Table 1). The problem with the use of radiographs in caries diagnosis is the relatively large observer variation (low precision) (Hintze & Wenzel 1994). The recent introduction of F - speed film (Kodak Insight; Eastman Kodak, Rochester, N.Y., USA) has allowed the reduction of ionising radiation by 20% that required for E - speed film. Nair & Nair (2001) compared E- and F-speed film to a Schick CCD sensor and found none of the imaging modalities evaluated differed in their diagnostic capabilities with respect to proximal decay detection. Ludlow et al. (2001) found that F-speed film was not significantly different from E or D speed for caries detection and that the reduction in ionising radiation with F-speed film maintained diagnostic quality.

The introduction of digital radiography was in response to reduce ionising radiation exposure.

New Methods for the Detection and Removal of Dental Caries

described the ideal tool for caries diagnosis to be non-invasive and provide simple, reliable, valid, sensitive, specific and robust measurements of lesion size and activity. It should take into account the biologic processes directly related to the carious process and be affordable and acceptable to dentists and patients in a private practice setting. Emerging technologies however by definition are methodologies that are being developed and are not yet established through appropriate validation studies. To this end the literature on emerging technologies is mainly in-vitro and there is little clinical data to validate them (Stookey & Gonzalez-Cabezas 2001). Sensitivity and specificity are used as criteria to compare clinical studies although Receiver Operator Characteristic (ROC) curve analysis may add more insight to diagnosis and decision making (Kay & Knill-Jones 1992). The sensitivity of a test is defined by the probability of that test giving a positive finding when disease is present and specificity is the probability of a negative finding when disease is absent. A false positive therefore means unnecessary treatment may be provided and a false negative implies a carious lesion went undetected (Dodds 1993).

vIsual dIaGnosIs

For comparison purposes a brief synopsis of the current standard of care in caries diagnosis is required. Any new technology must have advantages in sensitivity and specificity over these methods to warrant its use. Sensitivity describes the ability to indicate an early carious lesion as a true positive response and specificity describes identification of caries and not plaque, stain or anatomical variation thereby giving a false positive response. Careful visual inspection by experienced clinicians after cleaning and drying of teeth has been shown to be very accurate following histological validation (Ekstrand et al. 1997, Ekstrand et al. 1998). Good lighting is essential and transillumination by overhead lights or by an additional fibre optic source can increase diagnostic accuracy (Schneiderman et al. 1997). Although the specificity for visual examination is high the sensitivity remains low for enamel and dentine lesions. The use of a sharp probe to “stick” into a cavitated lesion is no longer considered appropriate as it may cause cavitation and inoculate the lesion with cariogenic microorganisms (Stookey et al. 1999). When there is doubt in diagnosis of caries or cavitation other techniques are utilised. The


Digital radiography allows manipulation of the image to change contrast and density. Potential errors associated with processing can be avoided and there is a substantial time saving in image acquisition (Wenzel 1998). There are two types of digital radiography image systems, charge coupled devices (CCD) and storage phosphor based (PSP). In a review of currently available systems Wenzel (2000) concluded that digital radiography is at least as accurate as modern conventional dental films for the detection of occlusal and proximal caries. Similarly Syriopoulos et al. (2000) concluded that the diagnostic accuracy of digital systems is comparable to that of conventional films. They compared two films, two CCD and two PSP systems. Most digital radiography systems have image enhancement software, which can improve contrast to aid in diagnosis. Wenzel et al. (1991) showed that contrast-enhanced digitised films and CCD images tended to perform better than unenhanced images within the same system. Abreu et al. (2001) found no difference for proximal caries detection comparing high and low resolution modes with the Trophy RVGui sensor and Kodak Ektaspeed Plus film. Tyndall et al. (1998) found that observer enhanced Sidexis images exhibited a lower diagnostic accuracy than the unenhanced digital and film images.

A potential problem affecting image quality in digital radiography is the type of compression algorithm that is applied to the image for storage. This is usually applied by the imaging software. Pabla et al. (2003) described a number of compression options using the PSP system DentOptix (Gendex DentOptix Imaging system) and concluded that the JIFF 50% which reduced the image size by 1:16 could be used without significant deterioration in


Table 1:Radiographic in-vitro sensitivity and specificity values for detection of occlusal caries in dentine. (Adapted from Bader et al. 2001).

X = sensitivity O = specificity

the diagnostic accuracy for proximal caries.

Subtraction radiography uses computer software to display a digital image representing the difference between two images of the same object. In an in vitro caries study, subtraction radiography was shown to be useful for visualisation of remineralization (Maggio et al. 1990).

A more recent area of development in conjunction with digital radiography is computer aided diagnosis. Early software was shown to be more sensitive than human observers but had low specificity (Wenzel 1998). An automated caries detection program, Logicon Caries Detector (LCD; Logicon, Los Angeles, CA, USA), is being marketed together with digital images using a CCD sensor from Trophy (Trophy Radiologie, Paris, France). The program provides an estimate of the probability of caries based on comparison with a database of images confirmed by histology. Although this is promising technology the program is not very consistent and provided different opinions on the caries status in a surface (Wenzel 2001). Wenzel et al. (2002) also concluded that the LCD program had lower sensitivity than human observers and that it was less accurate than human observers in detecting proximal carious lesions. The concept of objective analysis is needed if reliable caries diagnosis is to be obtained but the accuracy of any program or device must be shown to be much greater than can be achieved by a trained observer.

A number of advanced radiographic techniques may offer more accurate and sensitive caries diagnosis. Tuned aperture tomography (TACT) has demonstrated usefulness as a diagnostic tool


for recurrent caries (Nair et al. 1998). Abreu et al. (2002) demonstrated that increasing the number of basis projections to 8 or more aids in caries diagnosis. Other methods of computer tomography have been described and show some promise in diagnostic accuracy over conventional bitewing radiographs but are not yet practical for a clinical setting (van Daatselaar et al. 2003).

dIGItal fIbrEoPtIc transIlluMInatIon

Digital fibreoptic transillumination (DIFOTI) is a relatively new method to overcome some of the shortcomings with traditional fibre optic transillumination (FOTI) (Schneiderman et al. 1997). DIFOTI uses a digital camera to capture images which are subsequently computer analysed using dedicated algorithms. An in vitro comparison of DIFOTI and conventional radiographs showed DIFOTI to be twice as sensitive in the detection of proximal lesions and three times as sensitive in the detection of occlusal lesions with similar specificity (Schneiderman et al. 1997).

ElEctrIcal conductancE

(fIxEd frEquEncy MEthod)

Electrical conductance works on the principle that conductivity will increase as enamel demineralizes.


When pores created by carious demineralizations are filled with water and soluble electrolytes, the high electrical resistance of sound dental tissue decreases and is able to be measured. A number of instruments were designed and tested, the Vanguard Electronic Caries detector (Massachusetts Manufacturing Corp., InterLeuven Iaan, Cambridge, MA) and the Caries Meter L (G-C International Corp, Leuven, Belgium) both performed well but low specificity and sensitivity were common findings in early trials (Huysmans et al. 1998a). The Electronic Caries Monitor (ECM IV), (Lode Diagnostic, Groningen, The Netherlands) is a recent version currently available. Researchers have demonstrated a significant improvement in sensitivity (93%) but specificity still remains similar to that of bitewings (77%) (Lussi et al. 1995) (Table 2).

Although used mainly in epidemiological studies to monitor progression of enamel lesions, the use of more recent models has potential in the clinical setting. Ashley (2000) compared the ECM to visual diagnosis in primary teeth and concluded that the ECM did not provide increased accuracy over visual diagnosis when detecting occlusal caries. In contrast Ricketts et al. (1997a) found excellent sensitivity and specificity when airflow over the tooth was increased to prevent gingival conductance.

Table 2: Electrical conductance sensitivity and specificity for detection of occlusal caries in dentine. (Adapted from Bader et al. 2001).

X = sensitivity O = specificity


and a detector which is a bundle of 9 photo diode fibres that surround the optical fibre light source. It detects fluorescence in the infrared spectrum (Hibst & Paulus 1999). The digital display shows the detected fluorescence intensity relative to a calibrated standard, which is a ceramic disc (Lussi et al. 1999) (Figure 2).


altErnatInG currEnt IMPEdancE sPEctroscoPy (acIst)

ACIST characterises the electrical properties of a tooth and lesion to monitor and quantify change (Huysmans et al. 1996). It does this by measuring impedance over a number of frequencies, the value of which is reflected by ionic pores in the dental hard tissues. As the pores (and demineralization) increases so to does the reading (Murdoch-Kinch 1999). Limited evaluation has revealed excellent sensitivity (100%) and specificity (100%) (Longbottom et al. 1996). This method is expensive and time consuming so might not be valid for clinical settings.

quantItatIvE lasEr (lIGht) fluorEscEncE (qlf)

QLF takes advantage of the natural luminescence of tooth tissue exposed to light at a wavelength of 488 μm produced by an argon laser. When viewed through a high-pass filter dark regions characteristic of demineralization can be registered visually or by a camera. In the quantitative method, the fluorescent light is detected by the handpiece that delivers the light and its intensity is quantified by computer (Murdoch-Kinch 1999). Studies validated QLF to demonstrate mineral loss by comparing the technique with longitudinal microradiography (Hafstrom-Bjorkman et al. 1992). It is used mainly for the detection and monitoring of early enamel lesions. A chairside unit has been described (QLF-clin, Inspektor Research Systems, Amsterdam, The Netherlands). The argon laser was replaced by an arc lamp and in-vivo studies showed early occlusal caries sensitivities between 0.29 and 0.75 and specificity between 0.58 and 0.85 (Ferreira Zandona et al. 1998, Lagerweij et al. 1999)). Interproximal lesions can also be detected but the accuracy of detection was dependent on camera angle (Buchalla et al. 2002). As QLF can only detect enamel lesions its main use would be in early prevention and remineralization treatments.

InfrarEd lasEr fluorEscEncE

The DIAGNOdent® (KaVo, Biberach, Germany) is an instrument for detecting caries that shows the most promise to be adapted to a clinical setting. It contains a laser diode (655 nm modulated, 1mW peak power) as an excitation light source

Figure 2: KaVO DIAGNOdent®

Carious teeth display a large difference in fluorescence to the enamel of a sound tooth. This phenomena was thought to because of mineral loss and light scattering from bacteria. Intensity of demineralization was also thought to be responsible for this difference however white spot lesions formed in-vitro without bacterial involvement and early white spot lesions in-vivo do not result in an increase in fluorescence when compared to the sound enamel surface (Lussi, 2001). The assumption is that bacterial metabolites are responsible for the increased fluorescence. Porphyrins are produced by oral bacteria in the synthesis of haeme and are known to show some fluorescence when excited by red light (Hibst & Paulus 1999).

There have been a number of mainly in-vitro studies testing the DIAGNOdent compared to visual inspection, radiography, histology and quantitative light-induced fluorescence. Table 3 details the specificity and sensitivity the unit achieved with an overall average specificity for dentine caries of 86% and sensitivity of 76%. A number of these studies also compared intra-examiner reproducibility on occlusal surfaces both in-vivo (Lussi et al. 2001, Pinelli et al. 2002) and in-vitro (Attrill & Ashley 2001, Lussi & Francescut 2003). They also showed good reproducibility of results with Kappa values ranging from 0.72 to 0.93.

There remains some confusion as to what readings of the DIAGNOdent indicate and when operative intervention is required. The unit can give false-


positive readings in the presence of calculus, plaque, hypomineralization, composite filling materials, remnants of polishing pastes, plaque disclosing dyes and stains. All of these may produce fluorescence (Lussi et al. 2001, Sheehy et al. 2001). Also the published values obtained from in-vitro studies cannot be extrapolated to the in-vivo situation due to the change in the fluorophores with different storage media for extracted teeth (Lussi & Francescut 2003). Histological examination is capable of detecting even small changes in dentine which may not be indicative of active disease (Bamzahim et al. 2002). In-vivo studies urge caution when defining a level at which to intervene. Anttonen et al. (2003) found that by using the value of 30 the proportion of false-negatives


Table 3: DIAGNOdent sensitivity and specificity studies

E = Enamel D = Dentine

(100% sensitivity) was 8% and false positives was 31% when using visual inspection for validation. They recommended that false positives should be reduced by other diagnostic means such as visual or radiographic inspection. Of 100 occlusal surfaces that had dentinal caries Lussi et al. (2001) found 29 of the 100 by visual inspection. This number increased to 71 correctly detected with bitewings as a second opinion and 92 were discovered using laser fluorescence as the second opinion.

The DIAGNOdent has been advocated as a tool to aid in the decision to cease excavation of a carious lesion during cavity preparation (Reich et al. 1999). The device proved to be efficient in the detection of caries in dentine however high and unusual readings


visual and laser fluorescence methods and could result in over- treatment of sound teeth.

ultrasound

An ultrasound caries detecting device (the Ultrasound Caries Detector, Novadent Ltd, Savyon, Israel) using pulse echo technology has recently been developed to diagnose proximal carious lesions. It works on the concept of the change in ultrasonic echoes for a particular tissue that changes sonic conductivity with demineralization (Ng et al. 1988). Matalon et al. (2003) compared the Ultrasound Caries Detector with bitewing radiographs to detect interproximal carious lesions and found it to be more sensitive and specific. As it is a new device and the study was in-vitro they recommended further research in clinical conditions.

rEMoval of dEntal carIEs

The demineralization and remineralization of dental tissues is now recognised as a dynamic process in carious lesions. This may result in progression, regression or stabilisation of the lesion and influences the type of therapy to be provided, either operative or preventive (Stookey et al. 1999). Operative treatment is required to remove infected dentine, protect the pulp and avoid pain, to remove a source of cariogenic bacteria, to facilitate plaque control and to restore appearance and function (Kidd & Joyston-Bechal 1997b).

tradItIonal MEthods of

carIEs rEMoval

The removal of caries is by its nature invasive and is accomplished with a combination of rotary instruments and sharp spoon like excavators when approaching the pulp to avoid traumatic exposure. Emerging technologies in caries removal tend to focus on early detection and minimal tissue loss and also reversal of the demineralization process.

A new polymer bur, the Smartprep system (SS White Burs Inc., Lakewood, NJ, USA) is designed to only remove carious dentine. The concept used is that if the Knoop hardness of the bur is less than that of sound dentine but greater than carious dentine then it will be unable to remove the sound dentine. Another advantage is the reduced requirement for


were encountered when the lesion became near to the pulp (Lennon et al. 2002). Possible explanations for this were cited as autofluorescence of the pulp inflating the response and discolouration of the dentine close to the pulp giving a false-positive reading (Reich et al. 1999). When using the DIAGNOdent for this purpose every measurement should be preceded by a baseline calibration on a sound surface of the tooth. This value should then be subtracted from the fluorescence value obtained at the chosen site.

More recently the DIAGNOdent has been advocated as a diagnostic tool to determine remineralization after ozone treatment (Abu-Naba’a, 2002). It should be appreciated that remineralizing tissue will often be discoloured by extrinsic staining which will lead to false positive DIAGNOdent readings.

vIsIblE fluorEscEncE

Lennon et al. (2002) described a method to detect residual caries using violet-blue light viewed through a 530-nm high pass filter. Residual caries fluoresced orange-red. Using this method there was only one false positive and four false negatives. They concluded that with more research this could be a valuable tool to aid in caries removal.

carIEs dEtEctIon dyE

Caries detector dyes were developed in the 1970’s as an aid during caries excavation to identify infected and demineralized dentine (Sato & Fusayama 1976). The dye constituents are red fuchsin in propylene glycol. The dye is not specific for caries and will stain the organic matrix of less mineralized dentine which includes the normal circumpulpal dentine and the sound dentine at the enamel dentine junction (Boston & Graver 1989). The low specificity will result in overexcavation and the removal of sound tissue (Kidd et al. 1993, McComb 2000). As a tool for diagnosis of occlusal caries, al-Sehaibany et al. (1996) recorded 100% sensitivity for occlusal caries using caries detection dye confirmed histologically. However the sample was small (n=30) and results may have been influenced by the dyes affinity for the dentine at the enamel dentine junction. Tonioli et al. (2002) compared CDD with 5 other diagnostic measures and concluded that CDD would rank lower than



local anaesthesia as few intact dentinal tubules are contacted. No current literature or histological comparisons are available for his system.

chEMoMEchanIcal

Carisolv (Meidteam Dental AB, Gothenburg, Sweden) was introduced in 1997 as a means to chemomechanically remove carious dentine without the use of rotary instruments and local anaesthetic and therefore reduce patient anxiety (Ericson et al. 1999). The Carisolv gel is an aqueous mixture of sodium hypochlorite, sodium chloride, and sodium hydroxide, three amino acids (glutamic acid, leucin and lysine), a colouring agent (erythrocin) and a thickener (methylcellulose). The mode of action is primarily the proteolytic effect of sodium hypochlorite and the amino acids are said to reduce healthy hard tissue involvement. Kakaboura et al. (2003) reported excellent patient acceptance of the Carisolv technique. It efficiently removed caries the majority of the time without local anaesthetic but took more than twice the time than traditional drilling techniques. The use of Carisolv does not adversely effect the bond strength of modern adhesive materials compared with conventional bur or air abrasion preparation (Cehreli et al. 2003). The chemical structure and topography of the remaining dentine is not significantly different to caries excavation with burs (Arvidsson et al. 2002). Carisolv works equally well on primary teeth and it’s use seems to be directed to more anxious patients and those with needle phobias (Ansari et al. 2003).

The chemomechanical caries removal system is simple, cheap, effective and well accepted by patients. It does not completely remove the need for rotary instruments needed for access and in some circumstances local anaesthetic is still required. The increased time required for the procedure may make it more expensive than more traditional methods.

aIr abrasIon

Air abrasion involves the kinetic energy of a sharply focussed well-defined stream of tiny aluminum oxide particles propelled by high velocity air pressure. It is not new technology as the concept was investigated in the 1950s (Black 1955) but new delivery systems and early diagnosis has seen it gain popularity once more. Air abraded dentine

has a significant smear layer that can adversely affect bond strengths of modern composite systems (Yazici et al. 2002) but the increase in surface roughness after air abrasion may help to increase bond strength (Laurell & Hess 1995).

sonIc abrasIon

The Sonicys micro (KaVo, Biberach, Germany) and the Piezo Cavity System (EMS, Nyon, Switzerland) are described in the literature as been safe to adjacent teeth when preparing Class II cavities and are as efficient in caries removal as rotary preparation with burs (Wicht et al. 2002). An advantage of these systems is that they leave little smear layer and so are ideal for use in adhesive techniques (Yazici et al. 2002).

lasErs

Lasers have been commercially available for operative dentistry since the early 1990’s, however a number of innovations have seen this technology gain more interest for routine caries removal. Lasers rely on water based absorption for cutting enamel and dentine. The Er:YAG, Er:YSSG and Er,Cr:YSSG lasers operate in the middle infrared region of the electromagnetic spectrum and are the types of lasers most commonly used for caries removal (Walsh 2003). Lasers can now effectively remove hard tissue without collateral thermal damage to the supporting structures (Walsh et al. 1989). The use of an air water spray during treatment was demonstrated in-vitro to keep pulpal temperature increases below the critical threshold of 5.5ºC for pulp vitality when using the Er: YAG laser for caries removal (Oelgiesser et al. 2003).

The Er,Cr:YSSG system is currently marketed as a laser that energises water and cuts hard tissue by “hydrokinetic” forces (Hadley et al. 2000). Recent research has revealed that “hydrokinetic” cutting does not occur but explosive subsurface expansion of interstitially trapped water, which occurs in other laser systems, is the mechanism of cutting (Walsh 2003). Hossain et al. (2002) compared the structural changes of dentine after removal of caries by bur and Er,Cr:YSSG laser and confirmed that laser irradiation caused minimal thermal damage to surrounding tissues and dental hard tissue composition. Kinoshita et al. (2003) compared the morphological changes of dentine with removal of carious dentine by air turbine,



Carisolv and Er,Cr:YSSG laser. The scanning electron microscope observations revealed the Carisolv group had a rough surface and thick smear layer, the turbine group was smooth but with substantial debris and the laser group had smooth undulations with little smear layer. The conclusion was that Er,Cr:YSSG laser treated surfaces do not need further finishing before restoration.

A laser abrasion system has been described that utilises Er:YAG laser energy to accelerate sapphire particles to cut hard tissues similar to air abrasion technology. The system can remove enamel more quickly than a high speed turbine and with low volumes of abrasive particles (Altshuler et al. 2001). Research in dispensing systems to bring this to the clinical setting are in progress.

Lasers offer an alternative to traditional methods of caries removal and are appealing due to their “high tech “ appearance, patient and dentist acceptance, lack of vibration and reduced need for local anaesthetic to complete treatment. Some research indicates that acid etching may not be required to place composite restorations (Lin et al. 1999). The removal of tissue is still non-selective and clinical judgement or use of alternative diagnostic methods are required to confirm caries removal. Most of the published research is in-vitro and there is little evidence of long term pulp vitality and restorative success after laser treatment.

ozonE

Recently a new instrument has been released that does not remove caries but uses ozone to kill the cariogenic microorganisms and encourage remineralization of carious dentine (Baysan et al. 2000). The HealOzone (KaVo GmbH Germany) is a portable ozone generator designed for dental use. The concept of ozone in dentistry is not new and was described in the literature in the 1950’s (Schwan & Bamfaste 1951, Sandhaus 1965). A recent report on the use of ozone to arrest root caries described 100% of lesions arrested after ozone treatment compared with less than 1% of the control group (Holmes 2003). The protocol for ozone treatment uses a remineralizing solution which contains xylitol, fluoride, calcium, phosphate and zinc applied to the lesion immediately after treatment. Home care required use of a remineralizing toothpaste, mouthwash and spray. The results of the ozone group were excellent, but with just the remineralizing kit and no ozone it was

surprising that so few of the control lesions arrested. Promising results have also been reported with the treatment of pit and fissure caries (Abu-Naba’a et al. 2002a, Abu-Naba’a et al. 2002b). More in-vivo research is required to assess the histological effect of ozone and the depth to which that the ozone treatment is effective (Abu-Naba’a 2003).

conclusIon

The dental profession is moving to a more conservative and preventive approach to dental caries. This is only possible if new technology and diagnostic methods are sensitive and specific enough to allow early intervention of the demineralization process. The use of good visual examination with magnification, standardised radiographs with new generation fast films or digital technology supported by laser fluorescence or DIAGNOdent would ensure early and accurate diagnosis of most carious lesions. Early diagnosis would allow either remineralization procedures using ozone or minimal intervention operative techniques using air abrasion or a laser system.

rEfErEncEsAbreu M, Jr., Mol A, ludlow JB (2001) Performance of RVGui

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MEdIcal consIdEratIons In EndodontIcs

todd GracIa

IntroductIon

Medical considerations in general endodontic textbooks are often passed over lightly, with little other than conditions impacted upon by vasoconstrictor use or risk of bacterial endocarditis. As an aging population of people that are retaining teeth well into their fit elderly years and beyond, it can be expected that a proportion of patients will have complicated medical histories and significant medical problems that may influence endodontic treatment. However, there are few systemic conditions that are an absolute contraindication to conventional endodontic treatment. In a medically compromised patient, extraction may adversely affect health, and endodontic treatment can be preferable. In terms of surgical endodontic treatment, medical considerations do not absolutely contraindicate surgery when extraction is an alternative. Endodontic conditions such as acute periapical infection can have systemic consequences. However, whether disturbance of the periapical tissues, through chronic disease or treatment itself, may contribute to systemic disease is as yet unknown. A recent review concluded that, other than potential for bacteremias in patients at risk of bacterial endocarditis, there have been no publications to suggest that root canal treatment has any adverse systemic effects (Murray and Saunders, 2000). The diagnosis and management of pain has been reported to be a significant reason for referral to an Endodontist (24.1% of patients). Providers of endodontic treatment need to be competent in the differential diagnosis of dental and other related pathologies (Abbott, 1994).Four groups of pharmacological agents are commonly used in endodontic treatment. These include local anaesthetic, vasoconstrictor, analgesic/anti-inflammatory and antibiotics. Patients can have conditions and medications that have interactions with pharmacological agents used in endodontic treatment. Only the medical considerations of vasoconstrictor use, and appropriate systemic

antibiotic use will be discussed in depth.Cross infection control is as important a medical consideration as it is in all areas of clinical dentistry. Universal precautions and aseptic techniques are required for safe and predictable endodontic treatment. Whilst medical emergencies are rare, an emergency plan should be in place. A current first aid certificate should be held by practitioners, with appropriate resuscitation equipment and medications available.

In accEssInG trEatMEnt/abIlIty to tolEratE trEatMEnt

Endodontic treatment can involve prolonged appointments in a supine position with the mouth open. Patients with chronic back pain, osteo- or rheumatoid arthritis, and cervical spine problems may not tolerate long appointments. Endodontic treatment may need to be scheduled over several shorter appointments (Gutmann and Harrison, 1991). Other alternatives include the use of small neck supporting pillows, and for surgical procedures, positioning the patient on their side in the chair for the treatment of posterior teeth is often more comfortable (Kim et al., 2001).

Patients with chronic obstructive airways disease, emphysema, or hiatus hernia can find being fully supine uncomfortable, and treatment may need to be performed in a more upright position. Neurological conditions such as Parkinson’s disease and uncontrolled epilepsy can make it difficult for patients to remain still during long appointments. These problems can often be overcome, for example with sedation techniques, but they generally make treatment more difficult (Gutmann and Harrison, 1991).

Temporomandibular joint disorders and other limitations to opening wide (facial scarring, or fatigue for example) are more local considerations than medical. However, if severe, limitation of opening can be a contraindication to endodontic


Medical Considerations in Endodontics

treatment. Judicious use of a mouth prop is needed in patients with a history of temporomandibular joint disorders, to help support the mandible in an open position.

In dIaGnosIs

Diagnosis in endodontics includes the differential diagnosis of pain and periapical lesions of non-odontogenic origin. Pain is a symptom, and whilst most orofacial pain is of odontogenic origin (Lipton et al., 1993), non-odontogenic sources of pain need to be considered when diagnosing pain associated with the dentition. Periapical lesions can be a result of non-odontogenic pathology, and should be considered when assessing teeth with periapical lesions.

non-odontoGEnIc PaInA recent review article described features of pain of odontogenic and non-odontogenic origin (Bender, 2000). These features are not pathognomic for non-odontogenic pain, but are indicators of the potential for pain being of non-odontogenic origin.

Odontogenic pain features• Etiological factors for odontogenic pain

present (caries, leaking restorations, trauma, fractures)

• Chief complaint reproducible during exam-ination

• Pain reduced with local anaesthetic admin-istration

• Unilateral pain• Quality of pain can be dull, aching, throbbing• Pain localised• Sensitivity to temperature, percussion or pal-

pation

Non-odontogenic pain features• No apparent etiological factors for odontogenic

pain present• No consistent relief of pain with local anaesthetic

injection• Bilateral or multiple painful teeth• Chronic pain that persists after dental treat-

ment• Quality of pain can be burning, shooting,

stabbing, dull ache• Increased pain with palpation of trigger points

or muscles• Increased pain during emotional stress, physi-

cal exertion, changes in head position

There are a number of sources of non-odontogenic pain that often have features listed above.

Musculoskeletal pain • Myofacial pain• Temporomandibular dysfunction

Neurogenic pain• Trigeminal neuralgia• Glossopharyngeal neuralgia• Atypical facial pain

Neurovascular pain• Migraine• Cluster headaches

Non-odontogenic inflammatory pain• Maxillary sinusitis

Pain from systemic disease• Referred cardiac pain. • Neoplastic disease. Mandibular pain not related

to dental pathology has been reported as a symptom of metastatic neoplasia (Kant, 1989)

• Sickle cell anemia and thalassemia • Multiple sclerosis• Fibromyalgia

Psychogenic origin• Somatoform pain disorder

The differential diagnosis of orofacial pain is an extensive subject, and a good overview is covered in the source of this list (Seltzer and Hargreaves, 2002).

non-odontoGEnIc PErIaPIcal lEsIonsThe differential diagnosis of periapical lesions needs to include the possibility that it may be the result of systemic disease. Endodontic practitioners need to have a comprehensive working knowledge of systemic conditions that can cause periapical radiolucencies. A very wide variety of malignant and benign neoplasm’s mimicking periapical lesions have been reported, and a partial list includes carcinoma, adenocarcinoma, sarcoma, ameloblastoma, multiple myeloma ( Wood and Goaz, 1980; Hutchison et al., 1990) and Burkitt’s lymphoma (Ardekian et al., 1996).

Atypical features which should alert to the possibility of metastatic disease include:



• Vital tooth with minimal caries• Root resorption and an irregular radiolucent

outline• Tooth mobility in the absence of generalised

periodontal disease• Regional nerve anaesthesia• Failure to respond to adequate endodontic

treatment• Pain not related to dental pathology

Periapical pathology should be reviewed after endodontic treatment, and surgery considered in cases where a lesion is unchanged or is increasing. All surgical material removed should be examined histologically (Hutchison et al., 1990). Systemic conditions that can produce periapical radiolucencies include; giant cell granuloma, Gaucher disease, Langerhans cell disease, leukemia, and giant cell lesion of hyperparathyroidism (Wood and Goaz, 1980). Other lesions that can mimic apical periodontitis and need to be included in the differential diagnosis include ameloblastoma, hemangioma, traumatic bone cyst and odontogenic keratocyst. Whilst not the usual appearance for these lesions, they can all mimic apical periodontitis, especially in the early stages (Wood and Goaz, 1980).

Periapical lesions can also be a result of lesions of cementum. Dysplastic conditions of cementum can mimic periapical radiolucencies, especially in the early osteolytic stages of lesion progression. Involved teeth are responsive to sensibility testing, are usually asymptomatic, and the lesions have well defined regular borders. Other than cementoblastoma, treatment involves monitoring of the lesions (Wood and Goaz, 1980; Hutchison et al., 1990). Cementoblastoma is a benign neoplasm seen most commonly in males less than 25 years of age, commonly in the posterior region of the mandible. It presents as a slowly enlarging swelling that may be associated with pain. Of the lesions of cementum, it is the only one requiring active treatment (Soames and Southam, 1990). Periapical cemental dysplasia is a condition that presents primarily in females, and most specifically women in their forties of African descent. A familial tendency has been reported (Thakkar et al., 1993), and the mandibular anterior teeth are the most commonly affected. Aetiology in these cases and where no familial tendency is evident is unknown (Soames and Southam, 1990).

MEdIcal condItIons contrIbutInG to EndodontIc PatholoGyA consideration in endodontic diagnosis is the possibility of systemic disease causing, or contributing to, endodontic pathology. A number of systemic conditions can directly impact on the dental pulp, and can produce symptoms and disease in otherwise intact teeth. Diabetes can result in pulpal arteritis and/or necrosis. The results of one study of pulpal histology in long term diabetics suggest that late stage diabetics can develop both vascular changes and calcifications in the pulp (Russell, 1967). A clinical and radiographic survey comparing long term diabetics, short term diabetics and patients without diabetes showed a greater prevalence of periapical lesions in Type I diabetics. This was particularly so in long term diabetics (Falk et al., 1989). A significant correlation between the development of periapical lesions around non-vital teeth and patients with a history of systemic allergy has been shown (Brummer and Van Wyk, 1987). In these patients with high levels of IgE, there is depressed neutrophil chemotaxis, modified T-cell reactions, and continued production of cytokines that can perpetuate the inflammatory process and encourage osteoclastic activity. In this patient group, successful root canal treatment may be less likely and treatment should be performed to a high level (Callis, 1992). Systemic infection can result in pulpitis and pulpal necrosis in otherwise intact teeth. Cases of activation of herpes zoster (shingles) in the trigeminal nerve, with pulpitis and necrosis of the dental pulp as a result, have been reported (Sigurdsson and Jacoway, 1995). Leprous pulpitis can develop from hematogenous infection of intact teeth in leprosy patients, leading to necrosis and periapical granuloma (Tani-Ishi, 1996). In that the scope of endodontics includes the development of teeth, infectious diseases such as rubella, congenital syphilis, measles and chicken pox can have a cytopathic effect on the ameloblasts of developing teeth. This can result in enamel defects and lines on the teeth (Bender and Hargreaves, 2002).

Radiotherapy to the tooth bearing areas can result in pulpal arteritis and necrosis in some patients (Seto et al., 1985).



Other systemic diseases of endodontic diagnostic importance are those that can influence deposition or resorption of dental hard tissues. Paget disease of bone is often associated with hypercementosis, but can also manifest as areas of bony radiolucency, root resorption, or loss of lamina dura (Bender and Hargreaves, 2002). One study showed that 93% of patients with Paget disease who have bone changes in the maxilla or mandible also have dental problems associated with the disease, whereas only 10% of those with bone changes not involving the maxilla or mandible have dental problems (Wheeler et al., 1995).

GEnEtIc and dEvEloPMEntal dIsordErs contrIbutInG to EndodontIc PatholoGyThere are several genetic and developmental disorders that can impact on the teeth.

Hypophosphatemic rickets (hereditary vitamin D-resistant rickets) can be characterised by large pulps with pulp horns that extend to the enamel-dentinal junction, enamel hypoplasia, periapical radiolucencies, absent lamina dura and sinus tracts (Bender and Hargreaves, 2002). Hereditary hemoglobinopathies such as sickle cell anemia and thalassemia are associated with odontalgia in the absence of evident dental disease. In one study, 67% of patients with sickle cell anemia reported odontalgia in the prior year (May, 1991). Pulpal necrosis can be a consequence of sickle call anemia (Andrews et al., 1983). Thalassemia is also associated with odontalgia and pulpal necrosis (Duggal et al., 1996).

Periapical replacement resorption is seen in patients with Gaucher disease, a genetic recessive disorder characterised by an accumulation of glucocerebrosides in the reticuloendothelial cells. Radiographically evident bone lesions in the mandible are common, and with disease progression the myeloid packing of glucocerebroside containing cells can produce an osteoporotic appearance to the mandible and apical resorption of the apices of teeth. If present, the affected teeth are vital, are most commonly the mandibular premolars and molars, and it is bilateral (Weigler et al., 1967).

Developmental disturbances include disorders of morphodifferentiation, such as taurodontism, dens invaginatus/evaginatus, gemination, fusion,

concrescence and dilacerations. Whilst not being pathological, these can complicate any endodontic treatment that may be necessary due to complex internal anatomy (Bender and Hargreaves, 2002). Amelogenesis imperfecta is a group of developmental disorders that results in impaired enamel formation. Endodontic treatment considerations for this and dentinogenesis imperfecta relate to the long term restorability of these teeth (Pettiette et al., 1998).

In trEatMEnt PlannInG

In some medical conditions extraction may adversely affect health, and endodontic treatment may be the preferred option. For example, extraction is contraindicated in acute leukemia and agranulocytosis (Howe, 1985). Systemic conditions that affect healing can be a contraindication for extraction. There can be complications with healing following extractions in poorly controlled diabetics, those on long term steroid treatment, and in patients with chronic renal disease. Conventional endodontic treatment may be a better option in these patients. Patients with elevated blood pressure, hepatic or renal disease, or on anticoagulant therapy can potentially bleed excessively after extraction, as opposed to conventional endodontic treatment (Gutmann and Harrison, 1991). In patients where the tooth bearing alveolar bone has received therapeutic irradiation, the blood supply of the bone will be compromised by endarteritis obliterans, and the healing potential of the bone will be reduced. Osteoradionecrosis has a high incidence after radiotherapy of the dental alveolar tissues if extraction is performed (Murray et al., 1980). In a study of the outcome of 35 post-radiation endodontically treated teeth, no osteoradionecroses were observed (Seto et al., 1985). Rarely, patients who have had radiotherapy develop pulpal arteritis with concomitant pain and eventual pulpal necrosis, which needs to be considered when diagnosing orofacial pain in these patients. Endodontic therapy is the treatment of choice if irreversible pulpitis or pulpal necrosis occurs in these patients (Seto et al., 1985).

Timing of treatment can be a consideration. In chronic diseases of a cyclic nature, such as leukemia, appointments can be scheduled around periods of immuno-suppression. In patients who are severely medically compromised, treatment may need to be deferred until conditions are under


control (Gutmann and Harrison, 1991).In patients where the systemic prognosis is extremely poor there is little benefit in extensive and involved treatment. In such patients, treatment should be directed primarily at relief of symptoms (Howe, 1985). However, endodontic treatment can be less traumatic physically and emotionally than extraction, whilst offering relief from pain (Gutmann and Harrison, 1991)

Stress management is another treatment planning factor with medical considerations. A patients’ ability to cope with treatment should be assessed, and consideration given to appropriate preoperative, intraoperative, and postoperative anxiety and pain control. If necessary, oral or intravenous sedation techniques can be employed, but will not be discussed as part of this assignment.

In bactErIal EndocardItIs

An assessment of risk from bacteremia during endodontic treatment needs to be made from the medical history, and antibiotic prophylaxis provided if necessary.

In endodontic treatment, the number of blood vessels and capillaries that are opened to bacterial entry is much less than for extraction. An animal study that looked at conventional endodontic treatment found that bacteremias were produced only when the apical tissues are traumatised (Kennedy et al., 1957). In a human study, in only one case in a series of 30 patients (where instrumentation was performed beyond the apex in the single case), was bacteremia detected (Baumgartner et al., 1976). Positive blood cultures have been reported in 93.4% of patients following the extraction of teeth (Bender and Seltzer, 1963), which is significantly higher than for endodontic procedures. Bacteremias have not been detected subsequent to direct pulp capping and pulpotomy procedures (Seltzer, 1988). Surgical endodontic procedures resulted in a bacteremia in 83.3% of cases where a flap was retracted (Baumgartner et al., 1977). In cases of severe risk of bacterial endocarditis, conventional endodontic treatment may have advantages over extraction. Although the risk of developing bacterial endocarditis subsequent to conventional endodontic therapy is low, cases have been reported in the literature and the recommendation is that at risk patients undergoing endodontic therapy (including rubber dam clamp placement and matrix band application


where the gingiva may be traumatised) have antibiotic prophylaxis (McGowan, 1982). Cardiac conditions were patients are at risk of developing bacterial endocarditis can be divided into high- and moderate-risk categories, based primarily on the potential outcome should endocarditis develop. Patients with prosthetic heart valves, a previous history of endocarditis, complex congenital heart disease or surgically constructed pulmonary shunts are most at risk of a fatal outcome should bacterial endocarditis develop (Pallasch and Slots, 1996).

High risk • Prior episode of infective endocarditis• Cardiac valve replacement• Patent ductus arteriosis• Transposition of the great vessels

Moderate risk• History of rheumatic fever with valvular

disease• Coarctation of the aorta• Mitral valve prolapse with regurgitation• Atrial-septal defect repaired with a patch• Marfan’s syndrome • Ventricular-septal defect• Hypertrophic cardiomyopathy• Arterio-venous and neurological shunts

Not at risk (antibiotic cover not required)• Previous coronary artery bypass graft surgery• Cardiac pacemakers• Isolated secundum atrial septal defect• Surgical repair of atrial-septal defect, ventriculo-

septal defect, or patent ductus arteriosis• Mitral valve prolapse without valvular regur-

gitation• Physiologic, functional or innocent heart

murmurs• Previous rheumatic fever without valvular

dysfunction

Where the medical history indicates, antibiotic prophylaxis regimes should be prescribed according to the National Heart Foundation guidelines for antibiotic prophylaxis for dental procedures (appendix 1). In the University of Otago School of Dentistry the second dose is eliminated. Antibiotic prophylaxis is not routine for dental patients who have had total joint replacement surgery, except in a very small proportion of immuno-compromised patients who may be at potentially increased risk of hematogenous prosthetic joint infection (Fitzgerald et al., 1997).



In vasoconstrIctor usE

Vasoconstrictors have a number of important roles in endodontic treatment. These include the enhancement of depth and duration of the local anaesthesia, a reduction in the peak plasma concentrations of anaesthetic agent, and hemostasis during surgery. Adrenaline is the most commonly employed vasoconstrictor. Alternatives such as felypressin often will not provide a level of pulpal anaesthesia to allow endodontic treatment of vital teeth, or sufficient bony anaesthesia and hemostasis for comfortable endodontic surgery (Gutmann, 1993). In a healthy 70kg adult, adrenaline is secreted from the adrenal medulla at a basal rate of 0.17-0.54 μg/min. This can increase up to 20-40 times during periods of pain or stress (Dimsdale and Moss, 1980). In 20ml of local anaesthetic solution containing 1:100 000 adrenaline, there is only 0.2μg of adrenaline. Patients at risk from adverse effects of adrenaline are at a higher risk from their own endogenous catecholamines if pain or anxiety management is poorly controlled (Perusse et al., 1992a). There are a number of medical conditions that can be absolute or relative contraindications to the use of vasoconstrictors commonly found in dental local anaesthetic solutions. These absolute contraindications can preclude any treatment being able to be performed in a private practice setting without medical support.

Absolute contraindications to local anaesthetic containing adrenalineUse of local anaesthetics with small quantities of adrenaline are advocated for use in the vast majority of cardiac patients (Perusse et al., 1992a), but the use of intraligamentary and intra-bony injection techniques is contraindicated. Similar hemodynamic changes in blood pressure and heart rate were observed after intravenous, intraligamentary and intrabony injections of small amounts of local anaesthetic containing 1:100 000 adrenaline (Smith and Pashley, 1983). Cardiac conditions that are absolute contraindications to the use of adrenaline, and indeed elective dental treatment, include unstable angina, <3-6 months since a myocardial infarct or coronary artery bypass surgery, refractory arrhythmias and uncontrolled congestive heart failure. Patients with blood pressure greater than 180/100 mm Hg are similarly contraindicated (Perusse et al., 1992a).

The effects of thyroid hormone on the heart are similar to that of catecholamines. In uncon-

trolled hyperthyroidism, use of adrenaline is contraindicated as there is potential to contribute to a thyrotoxic crisis, a life threatening condition. Pheochromocytoma is a rare disorder which is characterised by catecholamine-producing tumours. These patients are at risk of lethal cardiac and cerebrovascular complications and adrenaline is contraindicated (Perusse et al., 1992b).

Relative contraindications to local anaesthetic containing adrenalineRelative contraindications include uncontrolled diabetes, and potential drug interactions with several medications. Adrenaline has the potential to precipitate hyperglycaemia in diabetics, and it is recommended to limit amounts used to the minimum required for profound anaesthesia (Perusse et al., 1992b). Concomitant administration of adrenergic drugs in patients on tricyclic antidepressants (TCA) has the potential to provoke cardiac arrhythmias. This is usually associated with high plasma concentrations of the TCA and/or preexisting cardiac disease. Phenothyazines are psychotropic drugs usually used in the treatment of serious psychiatric disorders. Accidental intravascular injection of local anaesthetic containing adrenaline has the potential to worsen the hypotension frequently associated with taking these drugs. It is recommended minimum amounts of local anaesthetic containing adrenaline be used in these patients taking these types of drugs, ensuring negative aspiration before injection (Goulet et al., 1992). β-Blocking agents are commonly encountered cardiac medications. β-Blockers are either cardioselective (inhibit β1 cardiac adrenoceptors) or non-selective (inhibit β1-cardiac adrenoceptors and β

2-peripheral adrenoceptors). There is a

very wide variety of these agents used, and checking of a specific medication is necessary. There is no evidence to contraindicate the use of adrenaline in a patient taking a cardioselective β-blocker. However, potential complications can occur in patients taking non-selective β-blockers. Concurrent administration of adrenaline has the potential to seriously raise blood pressure due to the unopposed α−adrenoceptor stimulation with the blocking of the β

2-peripheral adrenoceptors

in large blood vessels. There are no reports of complications after dental local anaesthesia, but cases have been reported in the medical literature of complications following administration of adrenaline (Foster and Aston, 1983). Insufficient



data exists to assess the risk associated with the use of local anaesthetics containing adrenaline for dental procedures in these patients, and caution is recommended. Management suggestions in the use of local anaesthetics containing adrenaline in otolaryngology include changing the medication to a cardioselective β-blocker, or cessation of the medication for at least three days prior to local anaesthetic administration (obviously in consultation with the patients’ physician) (Brummet, 1984). That said, there have been no case reports in the dental literature of complications following the use of local anaesthetic containing adrenaline in these patients. The use of minimum amounts of adrenaline and ensuring negative aspiration before injection is recommended.

Finally, there is potential for a fatal interaction between the adrenaline in local anaesthetic and cocaine, if used in a patient subsequent to their abuse of cocaine or its derivatives. There are a number of adverse cardiovascular effects related to cocaine abuse, which can be compounded by concomitant administration of adrenaline. The use of adrenaline containing local anaesthetic is contraindicated in these patients (Goulet et al., 1992).

Contraindications to adrenaline as a vasoconstrictor are summarised below; Absolute contraindications to the use of adrenaline• Unstable angina• <3-6 months since a myocardial infarct or

coronary artery bypass surgery• Refractory arrhythmia• Uncontrolled congestive heart failure• Blood pressure greater than 180/100mm Hg• Uncontrolled hyperthyroidism• Pheochromocytoma

Relative contraindications to the use of adrenaline • Uncontrolled diabetes Potential drug interactions• Tricyclic antidepressants• Phenothyazines• Non-selective β-blockers• Cocaine and its derivatives

In systEMIc antIbIotIc usE

The overuse of antibiotics in medicine, dentistry, veterinary practice and agricultural industries

has led to the development of resistant strains of bacteria and a growing concern regarding the continuing effectiveness of currently available antibiotics (Harrison and Svec, 1998a; Harrison and Svec, 1998b). Antibiotics can also be responsible for other adverse effects, including nausea/gastrointestinal upset, potentially fatal allergic reactions and antibiotic associated colitis (Longman et al., 2000). There is an inherent responsibility in prescribing antibiotics to limit them to situations that require them and where patients will actually benefit from their use. Most orofacial infections are sensitive to commonly available antibiotics, and resistant strains are rare. Other than determining that a patient is not sensitised to a particular antibiotic (from the medical history), medical considerations in the endodontic use of antibiotics are mainly to ensure that prescription of an antibiotic is appropriate to the situation and antibacterial spectrum required. On rare occasion, systemic complications can arise from acute odontogenic infection. Case reports of bacterial endocarditis, cavernous sinus thrombosis, orbital cellulitis, tissue space infections such as Ludwig’s angina, brain abscess, mediastinitis and osteomyelitis have been described in reviews (Abbott, 2000; Debelian et al., 1994). Should such complications be suspected, then referral for immediate and aggressive hospital based care is indicated.

Pain of endodontic origin is due to acute inflammation of either the pulp or periapical tissues, or both. This is commonly caused by bacteria in the canal of a tooth. However, presence of bacteria inside a tooth does not constitute an infection that is invading vital tissue, or that the bacteria are accessible to antibiotics. Only a small proportion of periapical lesions are infected cysts or abscesses, and these are clinically indistinguishable from granuloma unless acute apical abscess or cellulitis develops. Systemic antibiotics have been shown to be unable to achieve levels able to kill bacteria within a vital dental pulp (Akimoto et al., 1985). In a necrotic pulp, there is no blood supply so no antibiotic reaches the reservoir of bacteria within the canal (Burke and Shipman, 1970). The management of pain in pulpitis or apical periodontitis, after correct diagnosis of the problem, should be directed at the etiology. Irreversibly inflamed pulps should be extirpated and necrotic canals debrided, and the canals dressed with an intracanal medicament. Achieving drainage



where necessary, relieving of the occlusion, and support with postoperative anti-inflammatories will usually bring about resolution of pain. A relatively recent study showed that where there is localised periapical pain and/or swelling, recovery is rapid with local treatment. There was no demonstrable benefit from the routine use of systemic penicillin (Fouad et al., 1996).

There are few indications for systemic antibiotics in endodontics. Antibiotics are used as a prophylactic measure in patients at risk of infective endocarditis. In endodontic surgery, antibiotics are also used as a prophylactic measure where the risk of post-operative infection is high. This includes immuno-compromised patients, poorly controlled diabetics, and patients on long term steroid treatment. Recent research has shown that systemic tetracycline may have a role in the prevention of resorption after dental trauma as it inhibits both inflammatory and replacement resorption (Sae-Lim et al., 1998a; Sae-Lim et al., 1998b). Antibiotics used to actively treat an infection should be limited to where they are a suitable adjunct to endodontic treatment. They should not be used as a method of pain relief in the absence of local treatment. Use is really only indicated in the treatment of rapidly spreading infection, facial cellulitis or an acute apical abscess (especially if drainage cannot be achieved). However, a lower threshold for prescribing should be employed in patients with a risk of spreading infection (immuno-compromised, poorly controlled diabetic, and long term steroid patients) (Longman et al., 2000).

An additional consideration is the use of antibiotics in female patients of child bearing age who are on oral contraceptive medications. They should be advised to use an alternative form of contraception during the time they are on the antibiotics and for seven days afterwards. There is an association between the use of antibiotics and unplanned pregnancy, and this risk is greater with the broader spectrum antibiotics (Stephens et al., 1996).

In hEalInG followInG EndodontIc trEatMEnt

There is a lack of published evidence to show that the presence of systemic disease has a major influence on the healing of periapical lesions. However, a condition that affects an aspect of the repair process can be expected to have at least

some influence on healing following endodontic treatment. The aim is to tip the balance in the periapical area between the host response and the infective or irritant pathological agents, as far as possible in favour of healing. A potential area that requires further research is the role of systemic allergies and the host immune state in healing after endodontic treatment (Callis, 1992). If a systemic disease is present, resistance of the periapical tissues can be influenced, contributing to the development of pathology or interfering with its healing potential. Mild irritation may be sufficient to produce a large response in the presence of systemic disease, and periapical inflammatory responses can be acutely intensified if conventional endodontic treatment includes instrumenting beyond the apex and dispersing bacteria and irrigant into the periapical tissues. Efforts should be made towards keeping all instrumentation and irrigation within the canal, and to achieving a high standard of treatment in order to provide the greatest chance of healing (Seltzer, 1988).

There are a number of systemic factors that could affect repair. Age and nutritional deficiencies will influence healing. Chronic diseases such as diabetes, renal and liver diseases all influence aspects of repair. For example, vascular changes in diabetics may result in slower postoperative healing after surgery. Healing is impaired in hemophilia and anemia, and in patients on long term steroid medications. Hormonal disturbances in conditions such as osteoporosis, Cushing’s syndrome, hypothyroidism, and hypoparathyroidism can all result in a lowered potential for healing (Seltzer, 1988).

Some diseases of bone can affect healing following endodontic surgery, and may contraindicate surgery. Osteopetrosis (marble bone disease) is typified by sclerotic bone that is difficult to cut and heals poorly, often resulting in chronic osteomyelitis. Affected bone in Paget disease of bone is easily cut, but tends to bleed and also heal poorly, and sequestration with chronic osteomyelitis may result following relatively simple surgery (Howe, 1985).

In human immunodeficiency virus (HIV), the reduced immune response in patients with low CD4 cell counts does not appear to be associated with an increase in endodontic complications following treatment (Glick et al., 1994).


In convEntIonal EndodontIc trEatMEnt

Contraindications to conventional endodontic treatment are relative, and are mainly related to a patients’ ability to tolerate dental care and the administration of local anaesthetic solutions containing vasoconstrictors. Hemophiliac patients and those on anti-coagulant therapies are at risk of spacial bleeds from local anaesthetic needles. Hemophiliac patients are usually managed in specialist centres in consultation with a Hematologist. Infiltration local anaesthesia and conventional endodontic treatment are considered a low-risk procedure in anti-coagulated patients, and no changes in the therapeutic level of an International Normalised Ratio (INR) of 2.0 - 4.5 are required. Regional anaesthesia (and endodontic surgery) are moderate-risk procedures, and medication should be adjusted in consultation with the patients’ physician to an INR of 2.0 – 3.0 (Weibert, 1992).

Relatively few systemic conditions have an impact on the actual conventional endodontic treatment being performed. Dentinal deposition resulting in the narrowing of root canals in patients receiving high dose, long term steroid treatment has been reported (Gold, 1989). Patients with end stage diabetes (Russell, 1967), Paget disease of bone (Wood and Goaz, 1980) and (although unlikely to be encountered) progeria (Album and Hope, 1958) can have calcific metamorphosis of the pulp. Accurate estimation of working length can be made more difficult by hypercementosis (for example, Paget disease of bone), or root resorption (for example, Gaucher disease). Confining instrumentation to within the canal is preferable (in Paget disease of bone periapical irritation may lead to osteomyelitis), and an electronic apex locator may be helpful in determining working lengths (Bender and Hargreaves, 2002).

In surGIcal EndodontIc trEatMEnt

Medical considerations in endodontic surgery are of a similar nature to all oral surgical procedures. Where surgical management may impact on an underlying systemic disorder, consultation with the patients’ physician is recommended. Patients with


underlying cardiac or pulmonary disease require assessment of the medical history prior to surgery, and consultation with the patients’ physician if there is doubt as to the patients’ suitability for endodontic surgery.

Conditions with an increased risk of post operative infection should have antibiotics prophylactically prescribed post operatively. This includes insulin dependant diabetics, patients on long term steroids and those with liver disease (Gutmann and Harrison, 1991). Patients on long term steroids may also require additional steroid medication pre- and post operatively in order to overcome the stress of the procedure. Recommendations can vary, but commonly 100mg hydrocortisone is given intramuscularly one hour pre-operatively and then similar amounts orally for several days post-operatively. Alterations to oral dosages are also frequently used, on recommendation of the patients’ physician (Howe, 1985).

Patients with significant liver damage can have bleeding tendencies (from a deficiency in synthesis of coagulation factors II, VII, IX, and X), reduced metabolism of analgesics and local anaesthetic, and impaired healing following surgery. Consultation should be sought with the patients’ physician if there is doubt as to health status and whether surgery could be contraindicated (Gutmann and Harrison, 1991). In immuno-compromised patients (patients on immuno-suppressant medications, with HIV, or genetic immuno-pathology) consultation on suitability for surgery and post-operative antibiotics should be sought from the patients’ physician.

Chronic renal failure is another group of conditions that may impact on surgical management. As renal failure progresses, most other organ systems are affected. Consideration needs to be given in regard to suitability for surgical treatment in these patients. Bleeding disorders, drug metabolism problems, postsurgical infection and impaired healing can be complications, and consultation should be sought (Gutmann and Harrison, 1991).

In anti-coagulated patients, endodontic surgery is considered a moderate-risk procedure with a relatively high risk of bleeding. Consultation should be sought from the patients’ physician regarding adjusting the INR to between 2.0 and 3.0; in some cases, it may be preferable to discontinue warfarin for 48 hours prior to surgery and to reinstitute the warfarin the night of the day



of surgery. (Weibert, 1992). A 4.8% tranexamic acid mouthwash can be helpful in anti-coagulated patients (Ramstrom et al., 1993), but prescription from a specialist physician is required in New Zealand. Administration of vitamin K to reverse the warfarin in cases of prolonged bleeding needs to be viewed in light of why the patient is anti-coagulated, and again consultation should be sought before use. Hemophiliac patients are best assessed in consultation with their Hematologist, and surgical procedures may be better carried out with specialist support available (Gutmann and Harrison, 1991). Anemia can be accompanied by a tendency for postoperative bleeding, and delayed healing. Surgical treatment should be delayed until the condition is under control (Howe, 1985).

General recommendations for endodontic surgery during pregnancy are to avoid where possible, but if it is necessary to avoid in the first and third trimesters of the pregnancy. It is in the first trimester that the fetus is most susceptible to insult, and often the patient is undergoing normal physiological responses to major endocrine changes. In the third trimester, fatigue and discomfort with lying supine (supine hypotensive syndrome from compression of the vena cava) may make treatment difficult. In a healthy patient with an uncomplicated pregnancy, endodontic surgery can be considered as a treatment option in the second trimester (Gutmann and Harrison, 1991).

In endodontic surgery, regional anaesthesia using 2% lignocaine with 1:100 000 adrenaline will produce a profound level of local anaesthesia of a surgical site, but this level of vasoconstrictor is insufficient for adequate intraoperative hemostasis (Gutmann, 1993). In periodontal surgery, the use of 1:50 000 concentration has been shown to have advantages of increased visualisation, reduced surgical time and improved postsurgical hemostasis (Buckley et al., 1984). α−Adrenoceptor stimulation in the blood vessels of the submucosa produces the vascular constriction that results in hemostasis. However, in skeletal muscle a β2-adrenoceptor response may occur, and a vasodilatory response may predominate (Milam and Giovannitti, 1984). Care should be taken to inject only into the submucosa adjacent to the surgical area, and not deeper into the facial muscles (Gutmann, 1993). A study in dogs, whilst inconclusive, failed to demonstrate any hemodynamic changes whilst using a 1:50 000 concentration of adrenaline infiltrated into the submucosa (Gutmann et al., 1996).

conclusIon

It is mandatory that an accurate and up to date medical history is taken for a patient. A patient with significant systemic disease has less potential for repair, but modern endodontic treatment directed at the pathogenesis of periapical disease is still a very predictable form of treatment in these patients, and may be preferable to extraction.

Accurate differential diagnosis of pathology or cause of pain is a vital factor in endodontic practice. Histological examination of surgically removed pathology should be routine.

Finally, whilst conventional endodontics is suitable for the vast majority of patients form a medical viewpoint, surgical endodontics requires a less carte blanche approach. Careful assessment of suitability for surgery is required before it is undertaken, after consultation with the patients’ physician if required. Appropriate emergency and resuscitation equipment should be available at all times.

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IntroductIon

Numerous restorations and root canal treatment in posterior teeth often results in loss of coronal tissue to the extent that some form of structural augmentation is necessary in order to support the final crown. Several means of retaining the core exist, as well as varying types of core materials. Core retention will be mentioned, however the primary focus of the assignment is the make-up of the actual core. The answer to the question will seek to be given on the premise that all other factors (type and amount of retention, remaining tooth structure etc.) are equal.

ProPErtIEs of thE thrEE MatErIals and corE rEtEntIon

Amalgam has traditionally been the direct restorative material of choice for core build-ups. High-copper amalgams have compressive strengths of approximately 400-500 MPa after 7 days and tensile strengths of approximately 35-60 MPa, although both those ranges in values decrease with time (Combe et al. 1999; Saygili & Mahmali 2002; Marshall et al. 2003). Clinically it has been a highly successful material as well as being very cost effective. Its chief disadvantage has been its mismatch with tooth colour, although it can also be subject to corrosion, galvanic action and may demonstrate a level of marginal breakdown. It is superior to composite because it has reduced marginal leakage, has less polymerisation contraction, has better dimensional stability, its marginal corrosion may act as a barrier to microleakage and has better compressive and tensile strength than composite (Abou-Rass 1992).

Composites were first developed around 1960 after silicates and acrylic resins, and in comparison to their predecessors have higher mechanical properties, lower coefficient of thermal expansion,

lower dimensional change on setting, and higher resistance to wear, thereby improving clinical performance. Polymerisation shrinkage however still occurs, which can result in cuspal movement and stresses (McCullock & Smith 1986). Modern posterior composites have compressive strengths ranging between 210-300 MPa and tensile strengths ranging between 25-60 MPa, although the compressive strengths do tend to decrease after 24 hours (Cho et al. 1999; Combe et al. 1999; Saygili & Mahmali 2002; Rawls & Esquivel-Upshaw 2003). Despite such advances, a recent critical review of clinical data over 10 years found that the overall survival rate for composites as permanent restorations was 67.4% after 7 years compared with 94.5% for amalgam (Chadwick et al. 2001). While the placement time for composites is significantly higher relative to amalgams, in a core situation this will be compensated by the fact that they can be shaped immediately for the crown impression. Care needs to be taken to place a well-fitting temporary crown since an added problem associated with composites is their water absorption and associated expansion (Chutinan et al. 2004). This expansion is dependant upon the mass of water absorbed by the composite. Composite core preparations exposed to moisture can begin to change within one hour, affecting the marginal seating of crowns (Oliva & Lowe 1986). Both the mass of absorbed water and linear expansion are reduced for resins with higher filler content (Hirasawa et al. 1986). Furthermore, a recent study that looked at polymerisation of dual-cure resin composite concluded that photo-initiation was necessary for optimum bonding to root canal dentine. Bond strength decreased when polymerisation of the dual-cure composite was only chemically initiated (Foxton et al. 2003).

The biocompatibility of both amalgam and composite have been questioned; amalgam due to its release of mercury, and composite due to its release of bisphenol A (BPA) and bisphenol A dimethacrylate (BPA-DM) molecules. Both BPA and BPA-DM have affinity for estrogen receptors

should thE corE for a root-fIllEd

PostErIor tooth that rEquIrEs a crown bE MadE of

aMalGaM, coMPosItE or Gold?radu GoGa


Amalgam, Composite or Gold?

and can disrupt endocrine pathways (Rawls & Esquivel-Upshaw 2003). High gold (high noble) casting alloys have a hardened yield strength (0.2%) of between 400 to 600 MPa. They have favourable biocompatible and mechanical properties. Although their use has stood the test of time, the increasing price of gold and palladium during the past 20 years has led to the introduction of less noble casting alloys (Anusavice & Cascone 2003).

Microleakage associated with various core materials is an important consideration in the restoration of the endodontically treated tooth. Larson and Jensen (1980) examined the microleakage of composite resin core, amalgam core and regular crown preparations under complete cast gold crowns. Their results showed that with thermal cycling (100 cycles between a 60° C fluorescein dye bath and a 4° C fluorescein dye bath) the regular crown preparations displayed significantly less microleakage at the tooth-crown interface than either the composite resin core or the amalgam core preparations. There was no significant difference between the amalgam and composite cores. Tjan and Chiu (1989) examined the microleakage patterns of complete cast gold crowns cemented using three different cements (zinc phosphate, glass ionomer, acrylic resin) onto teeth with pin-retained cores made from cast gold, amalgam and silver-reinforced glass ionomer. The teeth were thermocycled between 50° C and 4° C in water baths. With the same type of luting cement, no significant difference was found between the four core materials.

Recent work, utilising a 2-dimensional finite element model, investigated thermal stress distribution under a metal-ceramic crown using four combinations of post and core materials for an anterior tooth (Yang et al. 2001). The four combinations were gold/gold, stainless steel/resin composite, stainless steel/amalgam and carbon fibre-reinforced composite/resin composite. A 0° C cold irritant was placed on the surface of the metal-ceramic crown for 7 seconds. Results showed that the metal posts and cores generated lower thermal stresses in the restorations, cement layer and dentine than the other combinations. This is because the high thermal conductivity of the metallic cores and posts reduced the temperature gradient in the post and core, cement layer and tooth.

While it is tempting to draw clinical implications from such studies, in vitro testing conditions will differ greatly to conditions in the mouth. Given the lack of conclusive results greater importance needs to be given to results from fatigue testing and in vivo studies. These will be discussed later.

The general principles of core retention such as boxes, grooves and undercuts apply in the same way as for vital teeth (Ibbetson 2004). Pins are often used to gain retention, although amalgam slots have also been shown to provide good retention (Plasmans et al. 1987). Kao et al. (1989) found that the fracture resistance of both amalgam and composite was reduced by pin placement. In root filled (RF) teeth the use of self-threading pins is often contraindicated. Self-threading pins create stresses in both tooth structure and core (Standlee et al. 1971; Dhuru et al. 1979) and the access cavity will usually have minimised or even undermined dentine at the line angles of the teeth. Conversely, the pulp chamber and root canals are areas where retention and resistance for cores can be generated with relative ease. Posts have clearly been shown not to strengthen roots (Lovdahl & Nicholls 1977; Guzy & Nicholls 1979; Sorensen & Martinoff 1984; Trope et al. 1985; Plasmans et al. 1986) and their placement should be avoided unless adequate retention cannot be gained in a fashion more conservative of tooth structure.

varIous Post and/or corE systEMs

Nayyar et al. (1980) introduced the concept of an amalgam coronal-radicular core in a report that described the technique and claimed that over 4 years 400 posterior teeth restored with the technique suffered no failures (presumably meaning no fractures of the restoration, although this is not defined). Most of the teeth were permanently restored with cast crowns. It is important that a minimum of one cusp with a good dentine base remains and will still be present following crown preparation, otherwise the amalgam core could fracture at the level of the pulp chamber (Ibbetson 2004). It should be noted that Nayyar recommended pin placement where there is insufficient depth in the remaining pulp chamber to provide retention or the wall thickness is inadequate. Pin placement was very popular at the time, but no numbers were given as to how many such cases were restored with this technique. Michelich et al. (1980) compared the



mechanical properties of RF molars that had been restored with three amalgam build-up techniques. In the first group, teeth were restored with a cement base and an occlusal amalgam. In the second and third groups the crowns of the teeth were reduced flat to 4 mm occlusal to the pulp floor. The second group of teeth had the pulp chamber filled with cement base and 4 threaded pins were inserted to support a 4 mm high amalgam build-up. The third group of teeth had 3 mm of gutta percha (GP) removed from each canal and a coronal-radicular build-up was completed. Teeth were subjected to a load of 0.1 in/minute applied at 45° to the long axis of the tooth until catastrophic failure occurred. The first group of teeth had a statistically higher mean failure load than the other two groups, showing that conservation of tooth structure is the ideal restorative method. No significant difference was found between the other two groups, although the coronal-radicular build-up technique had the higher mean failure load. Further work by Michelich et al. (1981) compared RF premolars that had been cut flat 1 mm occlusal to the CEJ and restored with a cemented cast post and core, 4 mm pin-retained amalgam or a coronal-radicular build-up extending 3 mm into the root canals. The coronal-radicular technique displayed a significantly higher mean failure load than the other two groups. Mertz et al. (1987) studied RF mandibular first molars with the crown removed to a level 2 mm coronal to the CEJ. The teeth were restored with either a 4-pin amalgam, a coronal-radicular amalgam that included the coronal 3 mm of each canal or an amalgam retained by a cemented #5 (1.25 mm diameter) Parapost (Whaledent International, New York, N.Y.) placed 8 mm into the distal canal. The buccal surface of the lingual cusps was impacted at a 45° angle to the long axis of the tooth at a cross-head speed of 0.2 in/minute. There was no significant difference among the test groups. These results were confirmed by Plasmans et al. (1986) who studied failure resistance in lower molars cut flat to 2 mm coronal to the CEJ. They found that an additional cemented post with coronal-radicular amalgam restorations did not increase the fracture resistance. Of interest however, was that a silver alloy cast post and core was significantly more resistant to fracture. Kane et al. (1990) examined the effect of pulp chamber depth and amalgam extension into the root canal space for coronal-radicular amalgam restorations. Pulp chamber depths studied were

2, 4 or 6 mm. Amalgam was condensed from the floor of the pulp chamber or 3 mm into the canals. Failure testing showed that amalgam extension into the root canal space contributed minimally with 4 mm or more of chamber wall height. However, if less than 4 mm of chamber wall height remained then the fracture load was substantially increased. They recommended that amalgam extension into the root canal space should be confined to teeth with limited remaining pulp chambers.

Pioneering work in the area of composite resin restoration of RF teeth was done by Trope et al. (1985). Their results showed that preparation of a post space in anterior teeth significantly weakened the teeth, while filling the post space and access cavity with composite resin following acid etching almost restored the fracture resistance to levels where a post space had not been prepared. Most work on posterior teeth following this study has focused on comparing composite cores with other materials, usually retained by preformed posts.

Millstein et al. (1991) compared the retention of prefabricated Parapost #7 (1.8 mm diameter) posts with glass ionomer, composite or amalgam cores. Glass ionomer cores were weak in tension and not fracture resistant but composite and amalgam cores were 6-7 times stronger. There was no statistically significant difference between amalgam and composite. Cohen et al. (1994) compared the fracture strength of titanium composite (Ti-Core, Essential Dental Systems, South Hackensack, N.J.), Tytin amalgam (Kerr, Romulus, Mich.) and Ketac-Silver glass ionomer (ESPE-Premier, Norristown, Pa.) with three different post systems. Specimens were placed on a jig with a 45° angle to the long axis of the tooth and loaded until failure. Results showed that the Ti-Core had the greatest fracture load in all instances, with Ketac-Silver the least. The Flexi-Post (Essential Dental Systems) and the microthread, Vlock (Brasseler USA, Savannah, Ga.) had the greatest fracture load values, with the Parapost the least. There was no statistically significant difference between the composite and amalgam cores when retained by Flexi-Posts or Paraposts.

Further work by Cohen et al. (1996) compared the fractural load of four core materials supported by five post designs. Three of the four core materials were the same as in their 1994 study, with the



last core material being G-C Miracle Mix (G-C Dental Industrial Corp., Tokyo, Japan), another silver-reinforced glass ionomer. The five posts were: Flexi-Post, Flexi-Flange (Essential Dental Systems), ParaPost, AccessPost (Essential Dental Systems) and C-Post (Bisco Inc., Itasca, Ill.). The greatest mean fractural load was shown by ParaPost with Tytin amalgam, followed very closely by Flexi-Post with Ti-Core composite and Flexi-Flange with Ti-Core. There was no statistically significant difference between these modalities.

Reagan et al. (1999) compared the resistance of various post and core systems to fatigue testing using alternating buccal and lingual forces. Mandibular second premolars were decoronated 15 mm from their apex and treated with five different post and core systems. Amalgam (Dispersalloy, Caulk/Dentsply, Milford, De.) and composite (Ti-Core) cores were built up with either Paraposts or Tri-R (Moyco Technologies Inc., Montgomeryville, Pa.) prefabricated posts (all 1.25 mm diameter) for retention, while the final modality involved a gold-palladium cast post and core. While groups using the resin composite core material exhibited a higher number of cycles prior to failure, there was no statistically significant difference between the systems.

Sirimai et al. (1999) investigated the fracture resistance of conventional post and core systems with Ribbond (Ribbond, Inc, Seattle, Washington) polyethylene woven fibre posts and cores in maxillary central incisors. The teeth were severed at the most coronal portion of the CEJ, perpendicular to the long axis of the tooth. After post and core cementation, teeth were loaded till failure at 130° to the long axis of the root. Mean failure loads were significantly higher for cast post and cores (silver-palladium alloy) and 1.6 mm parallel-sided, serrated titanium posts with composite cores. There was no significant difference between these two treatment modalities.

Bonilla et al. (2000) compared the fracture toughsness of several core materials using 3-point flexure beams and concluded that composites and amalgam are significantly tougher than glass-ionomers, even if resin-modified, and are most likely to withstand the stresses generated during mastication. Interestingly however, hybrid composites used as core materials demonstrated higher torque resistance values when compared to microfilled composites (Akisli et al. 2002).

Recent work by Möllersten et al. (2002) examined the strength of Composipost (RTD, Meylan Cedex, France) carbon fibre post with resin cores and cast gold post and core systems on premolars. Teeth were loaded perpendicular to their long axis until failure. There was no significant difference between the two systems.

Overall it would appear that there is little difference between amalgam, composite and cast gold as a core material using in vitro testing. It is important however to also look at the situation where a crown is constructed over the core, both in vitro and in vivo.

varIous Post and/or corE systEMs wIth crowns

Once a crown is placed on a tooth, the stress distribution upon it changes relative to a non-crowned tooth, with the position of the axial margins important as this is a site of stress concentration (Craig & Farah 1977; Assif et al. 1989). In this regard the ferrule effect has been shown to be important as it helps to transfer the stresses received by the crown to the root (Sorensen & Engelman 1990), thus minimising the loads on the core.

Nayyar et al. (1982) compared pin retained amalgam build-ups and amalgam coronal-radicular build-ups with cast post-cores under full veneer crowns. The anatomical crowns were cut flat 1 mm coronal to the CEJ prior to build-up and the crowns terminated on tooth structure with a 2 mm ferrule. Failure testing was done according to a previous protocol (Michelich et al. 1980). The results showed no statistically significant differences among the groups although the amalgam coronal-radicular build-ups and cast post-cores showed substantially higher failure values. Hoag and Dwyer (1982) tested first and second mandibular molars using different post and core systems, without and with cast full gold crowns. The post and core systems were interlocking stock and cast-gold post and core, stainless steel post and composite resin core and amalgam post and core. The systems were loaded till failure at a 45° angle to the long axis of the tooth; without the presence of crowns the interlocking stock and cast-gold post and core system was significantly stronger than the other 2 systems, which were all



approximately 2H times weaker. However, when crowns were placed on the teeth (with a 1 to 2 mm ferrule on tooth structure), there was no significant difference between the 3 systems. The authors concluded that if the final restoration has adequate core retention, with margins 1 to 2 mm below the core, the selection of post and core technique may be a matter of operator preference.

Chan and Bryant (1982) compared amalgam and composite cores retained with #6 Paraposts (1.5 mm diameter) with cast gold post and cores on single-rooted mandibular premolar teeth. Full veneer metal alloy crowns were placed over the cores and the specimens were loaded until failure at an angle of 115° to the long axis of the tooth. From the diagram and photographs in the study it did not appear that a ferrule was established by the crowns, apical to the cores. Results showed that cast gold specimens required less force to fail than amalgam or composite, which were equivalent. All of the cast post and core foundations were displaced from the original cemented position, with most teeth showing root fracture. Amalgam and composite core specimens often had core fracture but less evidence of post and core dislodgment or root fracture.

Kern et al. (1984) studied the shear strength of amalgam cores with cemented posts versus coronal-radicular amalgam cores. Teeth were loaded till failure at 60° to the long axis of the tooth, with and without cast gold crowns. The build up with cemented posts had significantly greater shear strength, with or without crown coverage. Cast gold crowns increased the shear strengths of the specimens, but not significantly. It should be noted that initial testing at a 45° to the long axis of the tooth required forces of 200kg or more to initiate fractures, and these often resulted in failure of the dental stone investment. Consequently the authors changed to the 60° angulation.

Gelfand et al. (1984) studied the effect of complete veneer crowns on the compressive strength of endodontically treated posterior teeth. There were 156 maxillary and mandibular molars in the study, divided into several post and core systems: Paraposts in two canals and amalgam core, Paraposts in two canals and composite core, amalgam posts in three canals and amalgam core, composite posts in three canals and composite core, and cast post (in one canal) and core. Half of the teeth were restored with cast crowns of non-precious alloy with a 1 mm ferrule on tooth structure. Teeth were loaded

till failure at a 45° angle to the buccal surface. Without crowns, the cast posts and cores were stronger than the composite and amalgam cores with Paraposts, stronger than the amalgam with amalgam posts, and stronger than the composite cores with composite posts. With crowns however, there was no difference among any of the groups. These results indicate that the type of post and core in posterior teeth contributes minimally to the compressive strength of the tooth once it has been crowned. Assif et al. (1989) employed photoelastic analysis of stress transfer by RF teeth to the supporting structure using different restorative techniques. Of note is that when a post and composite core was covered by a complete crown with a 2 mm ferrule on to sound tooth structure and subjected to loading, there was no difference between the cylindrical and tapered post designs employed in the study. The placement of the crown intensified the CEJ stress concentration and overall changed the distribution of forces to the root, post and core complex. Thus the authors speculated that a crown may be “the great equalizer”, with the post and core characteristics becoming insignificant. This was confirmed by later work (Assif et al. 1993), where the shape of the cast post (tapered, cylindrical and cylindrical tapered-end) was shown to have no effect upon the fracture resistance of RF premolars with cast post and cores and complete cast crowns with a 2 mm ferrule. Conversely, Kovarik et al. (1992) used extracted canines to compare amalgam (Tytin), composite (Adaptic II, Johnson & Johnson, East Windsor, N.J.) and glass ionomer (Ketac Silver) cores using prefabricated posts (Flexi-post #2 and ParaPost #6) for retention and full cast crowns over the core build-up, extending 0.5-1.0 mm onto sound tooth structure. Cyclical loading of teeth with vertical and alternating bucco-lingual horizontal forces was employed for one million cycles or until failure occurred. Crowns with amalgam cores had by far the lowest failure rate (33%), followed by composite resin cores (83%). All crowns with glass ionomer cores failed. The rather unique cyclical loading system that was employed may be primarily responsible for the difference in results compared to other studies.

Fan et al. (1995) compared five modalities for rebuilding broken down premolars; buccal Parapost/amalgam core, palatal Parapost/amalgam



core, two Paraposts/amalgam core, two Minim (Coltene/Whaledent, Mahwah, N.J.) pins/amalgam core and palatal cast gold post and core. The modalities were subjected to a 5.2 kg load applied at 72 cycles per minute. Each tooth had a gold crown constructed with a 1.0 mm ferrule. The subset with the highest number of load cycles to failure contained the palatal Parapost/amalgam core, two Paraposts/amalgam core and the palatal cast post and core. Gateau et al. (1999) fatigue tested artificial teeth with titanium posts and core build-ups with either amalgam, composite or glass ionomer. Full cast crowns were cemented with GIC and the teeth cyclically loaded with a 400 N force for 1.5 million cycles. Amalgam was significantly superior to composite, which was significantly superior to glass ionomer. Glass ionomer was considered to be inadequate for posterior tooth reconstruction.

A recent study (Azer et al. 2001) looked at the influence of the core buildup material on the fatigue strength of an Optimal Pressable Ceramic (OPC) all-ceramic crown (Jeneric/Petron Inc, Wallingford, Conn.). Sixty third molar teeth were used; amalgam (Tytin; Kerr Manufacturing Co, Romulus, Mich.) and composite (XRV Herculite; Kerr) build-ups were compared with sound teeth. Teeth in the two test groups were reduced to 2 mm above the CEJ and had the pulp chamber cleaned out prior to placement of the test material. Crown preparation had a 1.0 mm ferrule in dentine. No significant difference was found among the three groups with regard to static or cyclic compressive strengths. Pilo et al. (2002) used 40 extracted human mandibular premolars equally divided into four groups: 1) cast post and core, cast crown (all base metal alloy); 2) preformed metal post (0.9 mm diameter stainless steel post), composite core (Prosthodent; Lee Pharmaceuticals, Los Angeles, Calif.), cast crown; 3) preformed metal post, amalgam core (Spherodon M; Silmet, Or Yehuda, Israel), cast crown; 4) preformed metal post, no core, cast crown. In groups 1-3 the teeth had been root filled and their anatomical crowns cut 2 mm above the CEJ, perpendicular to their long axes. In group 4 the natural crowns were not removed from the teeth. Crown margins were placed at the CEJ. A continuous load was applied to the buccal cusp at a 30° angle to the long axis until failure. No significant difference in failure load values was found among the four groups.

While amalgam has a long clinical history of success (Nayyar et al. 1980; Chadwick et al. 2001), few clinical studies have looked at the use of composites as core material. Linde (1984) followed up 49 patients who were provided with gold crowns (separate crowns or as part of bridges) and composite cores over a period of 10 years. Most (around 55%) of the teeth were anteriors. In the majority of cases, a prerequisite for treatment was that the prognosis for conventional gold restoration was considered to be too uncertain. For 75% of the cases the condition of the roots before treatment was classified as being “doubtful” or “obviously bad”. Follow-up was accomplished for 42 patients and 51 teeth, with the average observation period being 5 years and 8 months. Of the 51 teeth, 43 were found to be functioning satisfactorily at the follow-up. Of note was that only in one failed instance did the gold crown debond from its core. In the remaining 7 cases the crowns and cores were intact and the teeth had been lost over time because of root fracture, secondary caries and/or inadequate post retention. Linde makes an interesting note at the end of the article regarding a personal letter from D.J. Baraban who states that since 1971 “I have made approximately 2000 posts and cores in this manner (as in Linde’s study). I have not had any failure that can be attributed to the use of the composite resin itself.” Clearly this is a very low level of evidence but is worth noting. Mentink et al. (1993) reported on 112 post and composite core build-ups inserted during 1974-1986 in 74 patients. There were 23 screw-in Dentatus (AB Dentatus, Stockholm, Sweden) posts, 44 Unimetric (Maillefer SA, Baillaigues, Switzerland) posts and 45 Radix (Maillefer SA) posts. While unclear from the report, teeth appeared to have full veneer crowns radiographically. After a mean follow-up period of 7.9 years it was determined that failures caused by the failure of the build-up amounted to 8 cases (7.5%). It was also noted that the Dentatus posts seemed to increase the risk of failure, accounting for 4 of the 8 failed cases.

Mannocci et al. (2002) reported on a three-year clinical comparison of survival of RF premolars restored with only direct composite (Z100; 3M, St. Paul, Minn.) restorations or with composite cores and cast crowns (gold platinum-palladium alloy). Only premolars with Class II carious lesions and preserved cusp structure were included. Sixty teeth were included in the first group and 57 in the



second. All restorations were performed by one operator. Causes of failure were categorized as root fracture, post fracture, post decementation, clinical and/or radiographic evidence of marginal gap between tooth and restoration, and clinical and/or radiographic evidence of secondary caries contiguous with restoration margins. Subjects were examined for the listed clinical and radiographic causes of failure by 2 calibrated examiners at intervals of 1, 2, and 3 years. At the 1-year recall, no failures were reported. The only failure modes observed at 2 and 3 years were decementation of posts and clinical and/or radiographic evidence of marginal gap between tooth and restoration. There was no difference in the failure frequencies of the 2 groups.

thE fErrulE EffEct

A recent review concluded that the ferrule effect, which is used routinely in core material studies, is desirable but should not be provided at the expense of the remaining tooth structure (Stankiewicz & Wilson 2002). When the ferrule cannot be achieved without further compromising the tooth structure, what material should be used for the core? The literature on this is limited, but a trend towards composite use does emerge (Chan & Bryant 1982; Linde 1984; Trope et al. 1985; Mentink et al. 1993).

Furthermore, Saupe et al. (1996) examined structurally compromised roots (remaining wall thickness 0.50 to 0.75 mm at the CEJ) restored with either a cast post and core or bonded resin reinforcement followed by castings constructed from light-cured patterns. Within these groupings, half the specimens were ferruled. All castings were cemented with resin cement. Teeth were loaded at 60° to their long axis until failure.

The results showed that a ferrule made no difference to the strength of the teeth but that bonded resin reinforcement provided significantly greater resistance to fracture than a morphologic post and core, even with resin cement. More recent work has also confirmed that with prefabricated Paraposts cemented with resin cement and a composite core, the ferrule preparation has no benefit in terms of resistance to fracture (al-Hazaimeh & Gutteridge 2001). Thus, in cases where the remaining tooth structure is severely compromised, the use of composite as a core material should be encouraged.

conclusIon

For a RF posterior tooth that is going to be crowned, the evidence (primarily in vitro) points in the direction that the core material can be amalgam, composite or gold, depending on the operator’s inclination and operative skill. Nevertheless, techniques that are both conservative of remaining tooth structure and less expensive should be preferred. In cases that are severely compromised structurally, composite appears to be the material of choice.

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New Zealand Society of Endodontics Annual Report

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