Effect of thermal cycling and filling technique on leakage of composite resin restorations

Silvia Kenshima,Rosa Helena Miranda Grande,Julio Da Motta Singer,Rafael Yagüe Ballester

doi:10.1590/s1678-77572004000400010

Silvia Kenshima, Rosa Helena Miranda Grande + Show 2 more

Open Access

https://doi.org/10.1590/s1678-77572004000400010

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Abstract

The objective of this study was to evaluate in vitro the effect on leakage of two incremental filling techniques and two composite resins with different elastic modulus and similar polymerization shrinkage. Eighty Class V cavities (4x4x2mm) were prepared in bovine incisors and were randomly restored with Z-250 (Z) or Durafill VS (D) + Single Bond in axial (a) or oblique (o) increments. The restorations were divided into two groups: Not Aged - N (4-hour-storage in water at 37ºC) and Aged - A (1-week storage in water at 37ºC + 1000 x - 5º-55ºC / 1-min dwell time). The specimens were covered with 2 coats of nail varnish so that only the restoration margins were exposed to silver nitrate 50% (2h) and developed under fluorescent light (8h). After they were sectioned twice in buccal-lingual direction, the four exposed surfaces were digitized (Vidcap) and the silver nitrate penetration was measured (ImageLab) at the incisal and gingival walls. Data were analyzed by a 3-way ANOVA (Resin, Filling Technique and Aging) separately for incisal and gingival walls (alpha=0.05). Resin and Aging were statistically significant either for the incisal and the gingival walls. The microfill composite resin infiltrated more than the hybrid composite. The thermal cycling caused an overall increase in silver nitrate penetration. The filling technique affected leakage depending on the composite resin and aging regimen.

Highlights

Composite resin restorations are subjected to polymerization shrinkage stress that may cause premature failure at the interface[3]
The comparatively weaker bond to dentin has been reported to result in more severe leakage at the gingival than at the incisal wall of the restorations[5,9,14]
The present study supports these previous observations, as the mean incisal values of silver nitrate penetration were approximately one third of those found at the gingival wall

Summary

Introduction

Composite resin restorations are subjected to polymerization shrinkage stress that may cause premature failure at the interface[3]. As aging tends to aggravate the restoration’s original deficient seal[11], minimizing polymerization shrinkage stress is the first step for a reliable long-term performance of composite resin restorations. A stress relief mechanism by the resin’s flow was reported and considered as the key factor in reducing the adhesive interface breakdown[6]. Based on these findings, the incremental filling technique has been suggested to contribute to the C-factor reduction[1]. Some authors, using finite element models, have contested this stress reduction capacity and have suggested different stress patterns according to the filling technique applied[21,26]

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