Parameters of MOD cavity preparations: a 3-D FEM study, Part II

Stresses induced by the influence of variations in the dimensions of three different parameters of MOD cavity preparations were studied using the finite element technique. The parameters studied were the depth, isthmus width, and the thickness of the remaining interaxial dentin. A total of eight different cavity designs, divided into three groups, were compared with the normal (unprepared) tooth and other cavity designs in the same group. Enamel and dentin experienced large regional variations in compressive stresses even in normal teeth. Teeth with prepared cavities showed even more variation, and stress combinations became critical from a tooth fracture point of view. It was seen that narrow but deep cavity preparations and wide and equally deep cavity preparations experienced a similar, damaging combination of stresses. It was deduced from the stress patterns observed in this study that the depth of the cavity preparations is the most critical factor in fracture of the tooth or cusps, whereas the width of the isthmus alone is the least critical.