Effect of Plasma-arc Bleaching on Microleakage of Cervical Composite Restorations Stored in Water for different storage times

Introduction: The aim of this invitro study was to evaluate the effect of light - activated bleachingon new and aged class V composite - resin restorations.Methods and Materials: 72 freshly extracted premolars were prepared with class V cavities (4 ×2.5 × 1.5 mm) with extension to 1 mm apical to CEJ. Cavities were restored using Single bond andZ100 composite resin. The specimens randomly divided into 6 groups. The samples in groups 2-5were bleached using in-office bleaching gel and plasma-arc bleaching unit immediately, 7, 30 and90 days after restoration respectively. Groups 1 and 6 were control groups and did not receivedbleaching treatment, stored for 1 and 90 days in waters, then evaluated. At the end of each storageperiod, the samples sealed with nail varnish and immersed in 2% basic fushin, and microleakagewas evaluated using 0-3 score scale. Data were analyzed using Kruskal-Wallis and Mann-Whitneytests at 0.95 level of significant.Restults: No statistically significant differences between study groups were observed in enamelmargins (p value = 0.244). Microleakage was increased significantly in dentinal margin of group 2(p value = 0.034).Conclusion: Performing plasma-arc bleaching immediately after restoration could increasemicroleakage of composite- resin restorations in dentinal margins. Immediate light-activatedbleaching of the composite-resin restorations might jeopardize marginal integrity of dentinalmargins.Keywords: Microleakage, bleaching, composite- resin, water storage.