Interface degradation between the ceramic material and remaining tooth may play an important role in the failure initiation process and clinical longevity of all-ceramic restorations. Objective: This study investigates the effect of cyclic loading and environmental aging on the indentation strength of ceramics bonded to human dentin. Methods: Ceramic disks (n=44) having 1.5mm diameter were bonded to human dentin using a dual cured resin cement (Nexus 2, Kerr) and following manufacturers directions. Specimens were divided into three groups: C Control (n=16), DF dynamic fatigue (n=14), and SF static fatigue (n=14). Group DF specimens were subjected to a vertical cyclic load (200N max) for 20 million cycles in water (25ºC). Group SF specimens were stored in water (37°C) for 6 months. The residual strength of the specimens was determined by indentation loading until interface fractures occurred. Failure initiation loads (N) were determined by examination with transillumination and optical magnification. Results: Characteristic Weibull failure loads were not significantly different (p>0.05) between groups but the Weibull modulii of SF and DF groups were significantly lower than that of group C. Conclusions: Dynamic and static fatigue conditions may alter the failure characteristics of bonded ceramic restorations in service.

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