Application of Structural Mechanics to Dentistry

The idea and analytical method in structural mechanics have been applied to the prosthetic dentistry and are confirmed to be effective for the design and failure analysis of dental restorations. A tooth and its limbic structure are made of pulp being treated as cavity in a sense of structure mechanics, periodontal tissue with the small Young's modulus E of 1-10MPa and Poisson's ratio ν of 0.45,dentin, cement and alveolar bone of E=14-15GPa and ν = 0.2-0.3,and enamel of E= 40-60GPa and ν = 0.3. Dental restorations complicate the structural configuration severely. For example, in the crown restoration a metal crown being made by Au-Cu alloy of E=80-100GPa and ν =0.33 or an all ceramic crown being made by ceramics of E=100-130GPa and ν =0.2 is set with dental cement of E= 9-20GPa and ν = 0.35 or resin cement of E= 4GPa and ν =0.3,after abutment teeth are prepared. Therefore, the finite element method (FEM), that is, a versatile numerical one even for the analysis of complicated structures being made up of different materials is appropriate for the stress, deformation and fracture analyses of a tooth and its limbic structure. In this paper, the author presents some of the results of his study using FEM. A newly developed mechanical model to handle the three-dimensional teeth and limbic structures is mentioned first and the design parameters of fixed restorations using the model are discussed in Section II and III. A crack growth analysis along the adhesive layer of resin-bonded bridge based upon the energy release rate (G) concept is described in Section IV. The effect of the cementing materials on the strength of an all ceramic crown is presented in Section V