Methods: ANSYS 10.0 software was used to develop an FEA mesh consisting of 23,974 to 42,491 elements and 73,037 to 128,941 nodes. The investigation tested three different tooth preparation designs: conventional veneer, partial-coverage crown restored with feldspathic porcelain, and full-coverage crown restored with porcelain-fused-to-metal. The maximum principal stress (σmax) in all models was calculated at three different loading conditions (25N, 50N, 75N). The load was applied at 135-degrees to the long axis of the tooth and at 2 mm. from the incisal edge. The relative compliance of the different occlusal conditions was evaluated in all models by relating the stress/strain values. An intact, unprepared central incisor was used as a control.
Results: The (σmax) stress in the tooth was most influenced by occlusal load, followed by preparation design. As occlusal force increased, both tensile stress values in the tooth and compressive stress values in the surrounding tissue increased. The conventional veneer preparation design demonstrated the lowest tooth flexibility. As the amount of tooth structure loss increased from partial coverage to full coverage, tooth flexibility values increased along a range from 11 percent to 400 percent as compared to the unprepared tooth. For restorative materials, both feldspathic porcelain and porcelain-fused-to-metal improved the biomechanical behavior of the prepared tooth, but not to its original, unprepared state.
Conclusions: This study indicated that an increase in stresses appeared for all situations when higher occlusal loads were applied. The amount of remaining tooth structure, primarily enamel, had an impact on the biomehcanical stress/strain behavior of anterior teeth. Understanding how this tooth behavior is related to occlusion lead to enhance restorative success.