In order to investigate the nature of fatigue of dental porcelain, bending tests and fatigue bending tests were carried out using test pieces of glass, dental porcelain (enamel, dentin, core porcelain), laminated dental porcelain. These tests were performed in the air (the relative humidity was 50%) and in the water.
As the results of bending tests and fatigue bending tests, the evaluated values in the water were inferior to those in the air.
The strength of core porcelain was superior to that of any other porcelain but inferior to that of glass in bending tests. In addition, core porcelain was stronger than any other porcelain and glass from the viewpoint of fatigue.
The strength of laminated porcelain was inferior to that of core porcelain and superior to those of enamel, dentin porcelain in bending tests. Moreover laminated porcelain was more influenced by fatigue than any other porcelain: the lower the applied load became, the less the difference between laminated and enamel porcelain in number of cycles became.
The test pieces which were strong in bending tests were not necessarily strong in fatigue bending tests. This result suggests that the investigation of fatigue of dental porcelain is important.
