The Role of Cuspal Flexure And the Weakening Effect of occlusal Amalgam Restoration in the Development of Abfraction Lesions – A Finite Element Study

The pathogenesis of ‘abfraction’ has been considered to be multifactorial with contributions from occlusal loading becoming increasingly prominent in recent years. The objective of this study was to find out whether the presence of an extensive occlusal amalgam restoration and eccentric parafunctional loads would cause increased cuspal movement and therefore, increase in cervical stress exceeding the failure stress of enamel, capable of initiating tooth substance loss. Materials and Method: Two-dimensional finite element models (FEM) of maxillary premolar having variations in the size of an occlusal amalgam restoration were generated and the cervical stress profile under eccentric occlusal loads ranging from 10-100N were analysed using the ANSYS finite element stress analysis software package. Results: The mean cervical shear stress value for an intact premolar did not exceed the failure stress of enamel under the normal functional occlusal load of 10-70 N, but, with deep and wide occlusal amalgam restorations,the values exceeded the failure shear stress of enamel even at the normal functional occlusal load. Conclusion: The present investigation shows that in patients having excessive occlusal loads like bruxism and malocclusion and with increased dimensions of the occlusal cavity for amalgam restorations, the chances of developing abfraction lesions are more.