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International Journal of Paediatric Dentistry 2003; 13: 28

2 2003 BSPD and IAPD

Blackwell Science, Ltd

Conventional versus resin-modified glass-ionomer cement

for Class II restorations in primary molars. A 3-yearclinical study

S. HBEL1 & I. MEJRE

1,2

1

Department of Paediatric Dentistry, Eastman Dental Institute, Stockholm and

2

Faculty of Odontology, Centre for Oral Sciences, Malm University, Malm, Sweden

Summary. Objective. To compare the clinical performance of two glass-ionomer cements

(GICs)for Class II restorations in primary molars: a conventional cement (Fuji II) and

a resin-modified cement (Vitremer).

Design. Split mouth and random assignment to the two materials were used for the

majority of the molars.

Sample and methods. Forty consecutive 47-year-old children were included. One

operator made 115 restorations: 53 with Vitremer and 62 with Fuji II. The restorationswere evaluated clinically, radiographically and from colour photographs.

Results. The cumulative success rate of the Vitremer restorations was 94% and that of the

Fuji II restorations 81%. The difference is statistically significant. The risk of a failed

restoration was more than five times higher with Fuji II than with Vitremer as therestorative material. Of the 13 unsuccessful restorations, seven had lost their retention,

four had secondary caries, and two were fractured.

Conclusions. The resin-modified GIC offered advantages over the conventional GIC for

restoring approximal caries in primary molars.

Introduction

For many decades, amalgam has been the standardrestorative material in paediatric dentistry. However,the detrimental environmental effects of mercuryand debates on possible health effects of amalgamhave resulted in a considerable reduction of itsuse in dentistry in the Nordic countries. Since 1995,the Swedish government has recommended restricted

use of amalgam as a restorative material, particularlyin children.

The most frequently used alternative to amalgamfor restoring primary teeth has been glass-ionomercements (GICs) [1]. The conventional GICs havemany attractive features, such as adhesion to toothstructure enabling minimal removal of sound tooth

substance, a slow release of fluoride which mayproduce a cariostatic action, good biocompatibility,and a shade similar to that of the tooth. The disadvan-tages are the slow rate of setting, susceptibility tomoisture contamination or dehydration during theearly stages of setting. Furthermore, GIC have lowfracture toughness and poor resistance to wear [2,3].

Resin-modified GICs (RMGICs) have been devel-oped to improve the mechanical properties. These

materials have a better wear resistance, highermoisture resistance, higher fracture toughness anda longer working-time. The resin ratio of RMGICsranges from 45 to 6% [4]. Unlike GICs, which setthrough slow acidbase reaction, RMGICs initiallyset through resin polymerization from exposure tovisible light, followed by additional hardening throughan acidbase reaction.

There are relatively few long-term studies onthe clinical performance and longevity of GIC andRMGIC restorations in primary teeth. The clinical

Correspondence: S. Hbel, Eastman Dental Institute, Dalagatan11, S-113 24 Stockholm, Sweden. Tel.: 087298936; Fax: 08310488; E-mail: [email protected]


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Glass-ionomer restorations in primary molars

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2003 BSPD and IAPD, International Journal of Paediatric Dentistry

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results of GIC restorations are rather disappointing.Thus, after 3 years, Chem-Fil II had a failure rateof 32% with a modified Black preparation and 25%with a saucer-shaped preparation [5], which issimilar to the failure rate reported by Wendt et al

. [6].stlund et al

. [7] reported an even higher GICfailure rate of 60% after 3 years and in a 5-year trial,Welbury et al

. [8] reported a lower survival timefor GIC compared with amalgam restorations (33 vs.41 months). Qvist et al

. [1], reporting a failure rateof 37% after 3 years, concluded that GIC is not anappropriate restorative material for Class II restora-tions in primary molars.

In contrast, promising clinical results have beenreported with RMGICs. After more than 5 yearsexperience of RMGICs, Nicholson and Croll [9]

reported the positive characteristics of Vitremerand stated that RMGICs will become a mainstayrestorative material for paediatric dentistry. Espelid

et al

. [10] compared a silver reinforced glass-ionomer material (Ketac-Silver) with an RMGIC(Vitremer) in minimal Class II preparations inprimary teeth and found that the RMGIC had thebetter performance.

Although clinical experience with RMGICs forClass II restorations in primary molars has beenencouraging, there is still a need for long-termresults on the materials clinical behaviour. The aim

of this study was to compare the clinical perform-ance of two cements: a conventional cement (Fuji II,GC Europe N.V. Leuven, Belgium) and a resin-modified cement (Vitremer, 3M Co, St Paul, MN,USA) for Class II restorations in primary molars.

Methods

Subjects

Forty consecutive children, 24 boys and 16 girls,aged 47 years (mean = 62; SD = 088) were treated

from 1995 to 98. Thirty-three of these children hadat least two approximal dentin caries lesions in theirprimary molars; the rest had one dentin caries lesioneach. All the children were regular patients at thePedodontic Department of the Eastman DentalInstitute in Stockholm. The parents gave informedconsent and the Review Board of the Public DentalHealth Service of Stockholm County Council gaveethical approval. The mean number of decayed,extracted and filled surfaces (defs) (0305d), at thetime of treatment was 47 (SD = 290).

In a majority of the cases, a split-mouth technique wasused, in which each restorative material was randomlyallocated to either side of the mouth by tossing a

coin. In all, 115 restorations were performed: 53with Vitremer and 62 with Fuji II. Radiographically,17% of the lesions reached the enamel dentin border,63% were in the outer half of the dentin and 20%in the inner half of the dentin. The number anddistribution of first (

n

= 81) and second (

n

= 34)molars are shown in Fig. 1.

Restorative technique

One operator placed all the restorations underlocal anaesthesia. Rubber dam was not used. Using

high-speed equipment and ample water-cooling, asaucer-shaped cavity was prepared, if necessarysupplemented with a dovetail. Soft carious tissue wasremoved using low-speed equipment and roundburs. The cavity preparation was finished with sharpexcavators. Deep cavities were lined with Dycal(De Trey/Dentsply, Konstanz, Germany). A thin steelmatrix band was secured around the tooth with amatrix holder, Fig. 2. All the cavities were cleanedwith 10% polyacrylic acid (Dentin Conditioner, GC,Europe N.V. Leuven, Belgium), and then irrigatedand dried carefully to avoid desiccation.

Both the Fuji II and the Vitremer materials weremanually mixed according to the manufacturersrecommendations, and then squeezed into the cavitywith a Hawe syringe (Centrix, Hawe Neos, Gentilino,Switzerland). After overfilling, the excess wasburnished against the cavity margins and the occlusalsurface was roughly modelled. Care was taken toprevent heavy occlusal contacts.

Fuji II

After placement of the filling, the surfacewas protected with an unfilled light-cured resin to

Fig. 1. Distribution of restorations according to type of toothsurface. Fuji II: n = 62, Vitremer: n = 53.


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prevent dehydration and moisture contamination.The restoration was allowed to set for 5 min (fromthe time of mixing) prior to removal of the matrixband. The filling was contoured with a petroleum- jelly coated round bur and slow speed equipment.A second coat of resin was then applied andcured.

Vitremer

To wet the internal surfaces of the cavity,a primer was applied according to the manufacturersinstructions. After insertion, the material was light-cured for at least 40 s. The matrix was then removedand necessary occlusal adjustments were made witha diamond bur and slow speed equipment withwater-cooling.

Assessment of restorations

The restorations were assessed clinically, radio-graphically and from colour photographs at 6, 12,24, 30 and 36 months after placement. (Fig. 3) Duringthe course of the study, the assessors (one of which wasthe operator) were calibrated by evaluating the clin-ical and radiographic findings simultaneously. Thisprocedure continued until agreement was obtained.At the end (after 36 months), the photos and theradiographs of the restorations were re-assessedindependently by the examiners. The level of con-

cordance of acceptable/not acceptable restorationswas 96%. In five cases of questionable results, a joint decision was made.

A modification of the United States Public HealthService criteria was used [11]. Marginal and approx-imal adaptation, anatomic form and signs of carieswere judged according to a four-grade scale: 1 and2 were considered acceptable (successful), 3 and 4not acceptable (unsuccessful):

Marginal adaptation

1

Restoration adapts closely to the tooth along margins

2

Clinically insignificant gap between restorationand cavity margins3 Poor marginal adaptation with obvious gap withor without caries. Restoration needs replacement

4

Loss of restoration

Anatomic form

1

Good anatomic form with optimal approximalcontact

2

Clinically acceptable shape with acceptable approximalcontact

3

Insufficient approximal contact resulting in foodimpaction

4

No approximal contact

Secondary caries

1

Not observed (acceptable)

2

Present clinically and/or radiographically (notacceptable)

Data analysis

The data were analysed with two methods: thelife table to assess the cumulative success rates and

the failure incidence (number of new failures/100restored tooth-years). The method for calculatingincidence has been described in detail elsewhere[12]. To illustrate how the ratio number of newfailures divided by time-at-risk can be interpreted,take, for example, a failure incidence of six newfailures/100 restored tooth-years. This means that ifwe follow 100 restorations for 1 year, we wouldexpect six new failures. Similarly, six new failureswould be expected if we follow 10 restorations for10 years. The failures are assumed to have an equaldistribution over time. The relative risk of a failure

of the two types of restoration was also calculated.Bivariate analysis was carried out with theChi-square test and logistic regression was used fortesting differences between the materials when adjust-ing for the background variables age, type of toothand defs value, and radiographic score at the timeof restoration. A P

-value of < 005 was consideredstatistically significant. The data were processed inSPSS for Windows, version 110 (Chicago, IL,USA).

Results

The median follow-up time was 36 months (SD = 69).Overall, 96% (51/53) of the Vitremer and 82% (51/62) of the Fuji II restorations were judged successfulafter 36 months or until exfoliation (including twoteeth lost to follow-up after 12 and 24 months), Fig. 3.The difference in success rate between the two materialswas statistically significant and it remained afteradjusting for the background variables. Whentested separately against the success rates of the twomaterials, none of the background variables age,


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type of tooth, defs value and radiographic score atthe time of restoration gave any statistically significantdifference.

The cumulative success rates of the two materialsafter 12, 24 and 36 months with the life table

method are given in Table 1. The success rate of theVitremer restorations declined from 98 to 94% from24 to 36 months of observation, while the successrate of the Fuji II restorations was 81% at bothtimes.

The failure incidence of the Vitremer restorationswas 13 new failures/100 restored tooth years andthe corresponding value for Fuji II restorations was62 (Table 2). Thus, the risk of a failed restorationfor Fuji II was 52 (62/13) times higher than forVitremer.

Twelve molars exfoliated during the study. Theyhad been judged as successful at the precedingexamination. The distribution of exfoliated teethaccording to time after restoration is shown inTable 1. One tooth was lost to follow-up after

24 months and another was re-restored by mistakeat the 12-month examination. Thirteen restorationsfailed and the most common type of failure wasloss of retention (Table 3). Pulpal complications asa consequence of restoring the tooth were notrecorded.

Discussion

The split-mouth design was chosen so that the tworestorative materials would be exposed to a nearly

Table 1. Cumulative success rates of Fuji II and Vitremer Class II restorations in primary molars.

Start time(months)

Number atstart of study

Withdrawnduring study (n)

Failures(n)

Cumulative proportionof success at end (SE)

Vitremer:

0 53 0 0 1 (00)12 53 0 0 1 (00)24 53 5a 1 098 (002)36 47 46 1 094 (002)

Fuji II:

0 62 0 1 098 (002)12 61 1b 3 094 (002)24 57 8c 7 081 (005)36 42 42 0 081 (005)

aexfoliated.blost to follow-up.cseven exfoliated and one lost to follow-up.

Table 2. Failure incidences (number of new failures/100 restored tooth-years) of Fuji II and Vitremer restorations followed up to

42 months and the relative risk of a failed restoration.

MaterialNumber ofrestorations

Number offailures

Risk time(months)

Failureincidence

Relativerisk

CI95%

Fuji II 62 11 2012 656 517 1341991Vitremer 53 2 1888 127

Table 3. Number of failed restorations according to type of failure and time after placement.

Type of failure

Time (months) after placement

< 12Fuji II Vitremer

1223Fuji II Vitremer

2435Fuji II Vitremer

> 35Fuji II Vitremer Total

Secondary cariesa 1 1 2 4Fracture 1 1 2Loss of retentionb 1 5 1 7Total 1 3 7 1 1 13

a judged clinically and/or radiographically.brestoration mobile or lost.


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identical oral environment. In most cases, the require-ment for inclusion was the presence of at least twoproximal dentin lesions in need of restorative treat-ment, and because of this, in general the patientsrepresented a group with a relatively high cariesactivity (reflected by a high caries experience). Thechildren were also relatively young at the time ofrestoration 47 years. It might be expected thatthis would have an effect on the success rates.However, neither the age nor the caries experienceof the child at the time of restoration significantly

influenced the success rates.Due to exfoliation of the primary teeth, follow-up times in clinical trials on the survival of resto-rations in primary molars are often short and includea number of censored teeth. For example, Andersson-Wenckert et al

. [5] and Qvist et al

. [1] reportedthat about 1/3 of the restorations were censoredbecause of exfoliation during an observation periodof 3 years. In contrast, the relatively low age of thechildren at the time of restoration in the presentstudy meant that a majority of the successful resto-rations could be followed for 3 years. Hence, the

number of censored teeth was relatively low.In the literature, different methods have been used

to assess the proportion of successful restorationsin primary teeth. Although there is no ideal way todeal with exfoliated teeth, the failure incidence hasadvantages when comparing different restorativematerials. Thus, all the restorations contribute withtheir individual follow-up time until the tooth exfo-liates, is lost to further follow-up or until the endof the study. A disadvantage with failure incidenceis the assumption that the failure rate is constant

over time, which in the present material was not thecase: the proportion of failures was higher after24 months (Table 1).

The life table method is also useful for assessingthe success rate. Notably, however, as exfoliated teethare recorded as withdrawn, they tend to lower theproportion of successful restorations in each follow-up interval. More than half of the failures occurred

after 24 months in the present study, emphasizingthe importance of follow-up beyond this time. Thiscircumstance was also pointed out by Espelid et al

.[10], who found a substantial number of failuresbeyond 2 years of observation of Ketac-Silver andVitremer restorations.

The number of restorations included in the presentstudy is small and one operator had made them all.The results may not therefore be directly compara-ble with studies involving a large number of resto-rations and several operators. Nevertheless, thestatistically significant higher success rate of

Vitremer compared with Fuji II restorations (94 vs.81%) is in agreement with previous results whereconventional GIC materials showed failure rates of2060% after 23 years [1,5,7,13,14], whereas cor-responding failure rates of RMGIC materials were220% [10,15,16].

In agreement with previous reports [10,13,16], themain reasons for failure were loss of retention andsecondary caries. It is therefore recommended thatthe prepared cavity has mechanical retention. Allfour failures due to secondary caries occurred with

Fig. 2. Matrix holder applied after cavity preparation.

Fig. 3. Clinical and radiographic appearance of successful

restorations in the same child after 3 years: (a) Vitremer and (b)Fuji II; (c) restorations in lower right molars (84d, 85 m) and(d) restorations in lower left molars (74d, 75 m).


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the Fuji II restorations. Three of them were observedradiographically as radiolucencies under the resto-rations and caries was confirmed after removal ofthe fillings. One failed restoration showed cariesalong the cavity margins. Loss of retention was lesscommon with Vitremer than with Fuji II. This mightbe explained by the dual setting mechanism ofVitremer ensuring a more complete hardening of thematerial and a higher fracture toughness comparedwith Fuji II. In a recent study by Qvist et al

. [15],longer survival times were reported for RMGICmaterials with cavity conditioning than without.Another possible explanation could therefore be thatthe use of a primer with Vitremer secures a betteradaptation to the cavity walls than the adaptationachieved with Fuji II. One of the major reasons for

failure was endodontic complication in the study byQvist et al

. [15]. In this study, however, no case ofendodontic complication was observed, possibly atleast partly due to the use of lining in deep cavitiesand perhaps also due to the relatively frequent follow-up examinations.

Conclusions

The resin-modified GICs offered advantages overthe conventional GICs for restoring approximalcaries in primary molars. The risk of a failed

restoration with Fuji II was more than five timeshigher than with Vitremer. For both types of GICs,loss of retention and secondary caries were the mainreasons for failure.

Acknowledgements

The Stockholm County Public Dental Health Servicesupported the study.

Rsum. Objectif. Comparer les performancescliniques de deux ciments verre ionompre pour

restaurations de classe II des molaires temporaires :un ciment conventionnel (Fuji II) et un ciment ren-forc en rsine (Vitremer).

Mise en place. La rpartition des deux matriaux at faite au hasard en split mouth dans la majoritdes cas

Echantillon et Mthodes. Quarante enfants gs de 4 7 ans ont t inclus. Un oprateur a ralis 115restaurations : 53 avec Vitremer et 62 avec Fuji II. Lesrestaurations ont t values cliniquement, radio-graphiquement et partir de photographies en couleur.

Rsultats. Le taux de succs des restaurations auVitremer tait de 94% et celui des restaurations auFuji II de 81%. La diffrence est statistiquementsignificative. Le risque dchec tait cinq fois plusimportant avec Fuji II quavec Vitremer. Sept destreize restaurations avec chec avaient perdu leurrtention, quatre prsentaient des caries secondaireset deux taient fractures.

Conclusions. Le ciment verre ionomre renforcen rsine a t plus efficace que le ciment verreionomre conventionnel pour la restauration descaries proximales des molaires temporaires.

Zusammenfassung. Ziel. Vergleich der klinischenEigenschaften zweier Glasionomerzemente frKlasse II-Restorationen in Milchmolaren: Ein kon-

ventionelles Material (Fuji II) und ein Material mitKunststoffbestandteilen (Vitremer).

Design. Fr die Mehrzahl der untersuchten Molarenwar eine randomisierte Halbseitenstudie durchge-fhrt worden.

Untersuchungskollektiv und Methode. Vierzig Kinderim Alter von 4-/ Jahren wurden konsekutiv einge-schlossen. Ein Behandler legte 115 Fllungen: 53mit Vitremer, 62 mit Fuji II. Die Fllungen wurdennachuntersucht durch klinische Untersuchung, Rnt-genbild und Farbphotographie.

Ergebnisse. Die berlebensrate betrug 94% fr

Vitremer-Fllungen und 81% fr Fuji II Fllungen.Dieser Unterschied war statistisch signifikant. DasRisiko einer nicht erfolgreichen Fllung war beiFuji II fnfach hher als bei Vitremer. Von den 13als nicht erfolgreich gewerteten Fllungen warensieben Retentionsverluste, vier mit Sekundrkariesund zwei waren frakturiert.

Schlufolgerung. Der Kunststoff-modifizierte Glasi-onomerzement zeigte sich als Fllungsmaterial frApproximalkaries bei Milchmolaren dem konven-tionellen Glasionomerzement berlegen.

Resumen. Objetivo. Comparar el funcionamientoclnico de dos cementos de ionmero de vidrio pararestauraciones Clase II en molares temporales: Uncemento convencional (Fuji II) y un cemento mod-ificado con resina (Vitremer).

Diseo. Se dividi la boca y se asignaron al azarlos dos materiales usados en la mayora de losmolares.

Muestra y Mtodos. Se incluyeron 40 nios entre 4y 7 aos. Un operador hizo 115 restauraciones: 53con Vitremer y 62 con Fuji II. Las restauraciones


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fueron evaluadas clnicamente, radiogrficamente yusando fotografas a color.

Resultados. El porcentaje de xito acumulado conlas restauraciones de Vitremer fue del 94% y paralas restauraciones con Fuji II un 81%. La diferenciaes estadsticamente significativa. El riesgo de queuna restauracin fallase con el Fuji II fue ms de 5veces mayor que con Vitremer como material res-taurador. De las 13 restauraciones fallidas, 7 perdi-eron su retencin, 4 tenan caries de recidiva y 2 sefracturaron.

Conclusiones. El cemento de ionmero de vidriomodificado con resina ofrece ventajas sobre el cementoconvencional de ionmero de vidrio para la restau-racin de caries proximales en molares temporales.

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12 Mejre I, Kllestl C, Stenlund H. Incidence and progressionof approximal caries from 11 to 22 years of age in Sweden:a prospective radiographic study. Caries Research 1999; 33:93100.

13 Attwood D, Reid JS, Evans D. Assessment of glass poly-alkenoate restorations in primary molar teeth. EuropeanJournal of Prosthodontics and Restorative Dentistry 1994; 2:183185.

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