Stress analysis of three marginal configuration of full posterior crowns by three-dimensional photoelasticity.

As a result of the complex configuration of a dental restoration, an analysis of internal stresses utilizing the theory of elasticity is extremely difficult to accomplish. The method of photoelasticity, however, appears to be particularly suitable for such occasions. Many investigators have used two-dimensional photoelastic dental models to study, among others, the effects of rounding axiopulpal line angles, as well as the stress distribution associated with the variations of the angle of axial walls. Fewer investigators have used the three-dimensional technique, mainly because of the complications involved in the preparation and analysis of the model and the unavailability of a photoelastic material with a wide range of values of Young's modulus at the stress freezing temperature. In 1965, Walton and Leven' presented a three-dimensional photoelastic study of an anterior jacket crown. Four models were analyzed and they concluded that the thicker the walls of the jacket, the greater was its strength. They also found that maximum mesiodistal width of the preparation was important.