Effects of Class II Cavity Design and Restorative Materials on Biomechanical Behavior of Posterior Tooth

Restoration failure is a common problem in dental daily practice. The obvious failure types were restoration fracture, dislodgement, or tooth fracture. A well-designed cavity and proper restoration material are important factors to the prognosis of therestoration. With new adhesive restorations and good adhesive techniques, preparation guidelines for the restorations seems to be less strict. Instead, the properties of the restoration and the cavity design are become more significant. The purpose of this study was to evaluate the biomechanical effects of different cavity designs and restorative materials in human upper premolar model. Furthermore, to improve the stress distribution of the cavity and reduce the possibility of tooth fracture and adhesive failure by cavity design and restorative material selection. In this study, finite element methods and compressive test of tooth model were used. Restorative materials were one dental ceramic material and two composite resins with different elastic modulus. The cavities were designed with coves or without coves. By comparing the displacement and stress distribution of the model, in order to analyze the effects of cavities and the restorative materials. The results showed that a greater stress concentration over palatal cervical area. Tooth with ceramic restoration had lower stress distribution within the cavity margin. Application of two coves to the gingival margin of the cavity could reduce the stress distribution of the cavity margin. For the ceramic restorations, the effect was more obvious than composite restorations. The depth and the width of the coves need to be investigated further. Based on the result of this study, using restoration with high elastic modulus combined cavity designed with coves could reduce the stress distribution over cavity margin when restore class II cavities of posterior teeth. The efficacy of the cove cavity design was affected by the elastic modulus of the restoration.