Degradation of thermo-mechanically loaded adhesive Class V restorations after 18 months of water storage

Purpose: To assess in vitro the hydrolytic stability of adhesive systems in Class V composite restorations bonded to enamel and dentin. Methods: 16 groups of Class V cavities restored with different adhesive systems and challenged with thermal and mechanical loading under the simulation of dentin fluid were evaluated after an 18-month period of water storage at 37°C. The marginal adaptation of these restorations was quantified by evaluation of gold-coated epoxy replicas with scanning electron microscopy at ×200 magnification. Results: The percentages of "continuous margin" after 18 months of water storage with respect to the total marginal length ranged from 62.9 (5.4)% to 18.5 (3.2)% with significant differences observed among the groups (Bonferroni test P< 0.05). The range in enamel was from 71.8 (14.2)% to 8.9 (6.4)% and in dentin from 94.3 (5.1)% to 0.0 (0.0)%. Marginal adaptation of all the materials tested was affected by water storage, either in enamel, in dentin, or both. None of the restorative systems tested exhibited hydrolytically stable marginal adaptation.