Abstract
The dynamic fatigue method was used to obtain subcritical crack growth parameters n and A for a commercial feldspathic dental porcelain and for a lanthanum‐glass‐infiltrated alumina glass ceramic. Five stress rates __d__σ/dt ranging from 50 to 0.01 MPa s^−1^ were applied. The inert strength values were calculated with the use of Weibull statistics and maximum‐likelihood approaches for the Weibull parameter m. Strength–probability–time (SPT) diagrams were derived for both materials. The alumina glass composite showed a high fracture strength σ~0~ (442 MPa) at a failure probability of P~F~ = 63.2% and a high resistance against subcritical crack growth (n = 36.5). The development of strength under fatigue conditions was calculated for exemplary 1 year. The strength of the alumina glass material dropped to 228 MPa within this period. This fact is due to a low content of infiltrated lanthanum glass phase in the composite material (25 wt%). In contrast, for the high‐silica‐glass‐containing porcelain a distinct decrease of strength σ~0~ from initial 133 to 47 MPa after 1 year was predicted. This, mainly because of a low crack growth resistance (n = 16.8) of the feldspathic porcelain. Much lower strength values were calculated, assuming a failure probability of P~F~ = 5%. The decrease is mainly caused by the sensitivity of high–glass‐containing ceramics against water corrosion. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 780–785, 2002