With the growing demand on tooth restoration, the study of failure mechanisms of restored tooth under different conditions including impact and fatigue loadings is of great interest to the researchers. Failure at the tooth restoration interface is known as one of the most common types of fatigue failure of restored teeth. Conducting the in vitro low-stress fatigue failure tests is time-consuming and costly, and hence, numerical simulation provides appropriate means for fatigue analyses. In this study, the low-stress fatigue life of a restored tooth with Mesial-Occlusal-Distal cavity was estimated considering two cumulative fatigue theories using finite element simulation. Under the specified occlusal loading, the maximum von Mises stresses at the dentin and restoration interface were determined as the critical points, and the effect of damage cumulation on fatigue life was studied using Palmgren-Miner and Manson theories. Results indicated that the failure of the restored tooth occurs first at the restoration interface. This can cause debonding and stress elevation in the residual components. Furthermore, prior to deboning, the maximum stress at dentin was lower than the material endurance limit, and hence, the dentin has infinite life. However, debonding elevates the stress at dentin exceeding the material endurance limit, which results in a limited life. Finally, no significant difference was observed between fatigue lives estimated by two theories.

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