Objective: The objective of this investigation was to evaluate the degradation resin adhesive-dentin bonds resulting from enzymatic degradation in terms of the fatigue resistance.
Method: Twin bonded interface specimens were prepared using a specially designed molding procedure that includes a cube of coronal dentin obtained from caries-free third molars and a commercial resin composite (Z-250, 3M ESPE). Adhesive bonding of the twin interfaces was performed with a single bottle resin adhesive with or without (control) an experimental anticollagenolytic (AC) agent. Both groups (control and AC) of specimens were evaluated after 24 hours and 3 months of storage in water at 37°C. Specimens from each group were subjected to quasi-static (N=10) or cyclic (N=25) four-point flexure to failure within a hydration bath of HBSS. Cyclic loading was conducted using a stress ratio of 0.1 and frequency of 5 Hz.
Result: After 24 hours storage there was no significant difference (one way ANOVA; p>0.05) in the strength of the specimens bonded using the control and AC monomer evaluated by either monotonic or cyclic loading. After 3 months of storage the specimens bonded with the AC monomer exhibited significantly higher fatigue strength than the control group (Mann Whitney U test: Z=-2.03;p≤0.01). Failure of the specimens after 3 months storage initiated within the hybrid layer and appeared to result from the localized degradation of the dentin collagen.
Conclusion: The fatigue strength of resin-dentin bonds undergoes a significant decrease by collagenolytic MMPs. (This study was supported by the National Institutes of Dental and Craniofacial Research 2R01 DE015306)