Effect of mechanical load cycling on the marginal integrity of adhesive Class I resin composite restorations

Objectives: The purpose of this study was to determine the effect of cycle loading on the sealing capacity of different adhesive systems in Class I restorations in vitro. Methods: (1) Clearfil Liner Bond/Clearfil Photo Posterior, (2) Scotchbond Multipurpose/Z100, (3) Syntac/Heliomolar, and (4) Gluma 2000/Pekalux were employed to restore Class I cavities in extracted human premolars and molars. For each test group, half of the specimens were subjected to mechanical loading at 125 N for 5000 cycles in a dye solution. After sectioning, dye penetration was assessed. Results: Without loading, no specimen showed leakage, while loading did affect the sealing capacity of groups 3 and 4. Groups 1 and 2 showed no significant increase in leakage after the loading procedure. Conclusion: The results indicate that mechanical cycle loading can adversely affect the interface of adhesive Class I resin composite restorations unless hybridizing adhesive systems are used.