Mechanical fatigue of a feldspathic dental procelain.

Ceramics are known to undergo chemical static fatigue in the presence of moisture at ambient temperatures. However, until recently, it has been assumed that ceramic materials do not undergo mechanical fatigue. This study, using an indentation technique, demonstrated the existence of mechanically induced cyclic fatigue in a feldspathic dental porcelain under ambient conditions. Growth rates (dc/dN) were consistent with the Paris Law, which is a power law function of the applied stress intensity range (delta K) governing mechanical fatigue phenomena. A Paris exponent m of the order of 4, and a constant C of the order of 2 x 10(-6) were calculated. The susceptibilities of a range of dental ceramics to mechanical fatigue, and the possible interaction between mechanical and chemical static fatigue must be investigated so that materials and techniques giving ceramic prostheses the longest possible lifetimes can be identified.