Purpose: To evaluate the quality of marginal and internal adaptation of Filtek Silorane composite in standardized class 1 cavities before and after thermo-mechanical loading using different application protocols of the Silorane System Adhesive (SSA).

Methods: Five groups (n = 10) of class 1 cavities were restored with Filtek Silorane using different SSA applications. Total bonding (TB): Group A (SSA), Group B (SSA without primer polymerization), Group C (enamel etching + SSA), Group D (enamel etching + SSA without primer polymerization) and Selective bonding (SB): Group E. Marginal adaptation was assessed on replicas in the SEM at x200 magnification before and after thermomechanical loading (3,000 x 5-55 degrees C, 1.2.10(6) x 49N; 1.7Hz) under simulated dentin fluid. After loading, the samples were sectioned and the internal adaptation was evaluated as well.

Results: The lowest scores of %CM (Continuous Margin) before/after thermo-mechanical loading being 80.8 (+/- 8.2) / 32.1 (+/- 8.3) were observed in the control group A. Enamel phosphoric acid etching prior to the application of the SSA resulted in significantly higher %CM before and after loading in comparison with the "non-etched" groups (P > 0.05). When enamel etching was performed before the application of the adhesive system, no statistically significant differences (P > 0.05) were observed regardless of how the SSA was applied (total vs. selective bonding). Internal adaptation was negatively influenced by omitting the SSA-primer polymerization (P > 0.05).