ABSTRACT
Mechanical fracture is a common cause for the failure of three-unit dental bridges, particularly the all-ceramic ones. The goal of the present study was to evaluate the effects of convergent angles of the abutments on the peak and distribution of mechanical stresses within the prosthesis and at the restoration abutment interlace of a three-unit all-ceramic bridge using finite element method. The cloud points of three-D geometrical data of the second premolar and first and second molar teeth were obtained using ATOS Scanner system and utilized for the reconstruction of a surface model of the three-unit bridge in CATIA software. Data were than transferred to I-DEAS software for mesh generation and finite element analysis. Two EF models were developed with convergent angles corresponding to the up and low defined range including 171900 and 168700 tetraherdal solid four-node elements, respectively. The models were subjected to two different prosthesis materials and three different load cases. The maximum tensile stresses occured on the gingival surface of the second premolar retainer and at the tooth/restoration interface on the marginal distal surface of the second molar abutment. The peak tensile stress was relatively lower for the model with the higher convergent angle but the difference was not significant. Changing the prosthesis material from IE[2] to Dicor desreased the stresses within the prosthesis. Higher safety factor was found for IE[2] due to its higher mechanical strength. Moreover, it was proved that load condition played an important role on the mechanical stress observed