Effects of enamel anisotropy on stress singularities in restorations of premolar class II cavities

Abstract

This paper studies the strength of inplane and antiplane stress singularities near the apex of a structure formed from the dental restoration of premolar class II cavity. In order to exclude the probability of failure, it is necessary to find the conditions such that singularity orders are kept to a minimum or inplane and antiplane stress fields are non-singular.The effects of enamel anisotropy on the stress singularities are emphasized at two critical positions in the restoration structure: (1) the apex of the enamel and restoration interface, and (2) the apex of the enamel, dentine and restoration junction. In the second case, the interface between the restoration and enamel may be bonded or debonded. The results of this paper show that the recommended cutting angles are strongly affected by the ratio R of transverse stiffness to the longitudinal stiffness. Besides, if the stiffness of the restoration material is close to the transverse stiffness of the enamel, the singularity orders will be reduced. The results of previous studies, in which the enamel is considered to be isotropic, should be modified.