Abstract
Deformations of crowns on model teeth were measured with strain gages for the cases of experimental crowns which had uniform thickness at their axial surfaces, and the effect of axial metal thickness on the rigidity of the crown and the cement fracture strength was examined. Cemented crowns exhibited smaller strains than those not cemented, showing that cementing integrated the crown structures with the abutment teeth. Among the structures of cemented crowns and abutment teeth, that of the axial metal thickness of 0.3 mm had cement failure at the smallest loads. As the metal thickness was increased, the crown deformation decreased and cement failure loads increased. For a thickness greater than 0.7 mm, however, the increase in failure loads was not obvious. Accordingly, the rigidity of dental prostheses should be one of the most important design factors in preventing failure under occlusal load, and it is recommended that the axial surface of prostheses should have a thickness of at least 0.7 mm.
