The role of cuspal flexure in the development of abfraction lesions: a finite element study.

A tooth flexure mechanism has been proposed over the past 15 yr to explain non-carious cervical tooth loss. It is well established that cavity preparation weakens a tooth, resulting in more cuspal movement under occlusal load. The aim of this study was to investigate the effect that an occlusal restoration would have on the stress profile in the cervical region of a lower second premolar using two-dimensional finite element stress analysis. Under an eccentric 100 N occlusal load, a premolar with an occlusal amalgam restoration showed peak tensile and shear stresses in the buccal cervical region that were in excess of the known failure stress for enamel. Increases in the cavity depth of the occlusal amalgam restoration were found to increase cervical stress more than increases in cavity width. It was concluded that the weakening effect of cavity preparation may contribute to the development of non-carious cervical tooth loss.