Journal of Dental Research, Vol 65, 993-997, Copyright © 1986 by International & American Associations for Dental Research Online Journals
Fatigue of dental ceramics in a simulated oral environment
R. Morena, G. M. Beaudreau, P. E. Lockwood, A. L. Evans and C. W. Fairhurst
Fatigue in ceramics refers to the subcritical growth of cracks, aided by
the combined influence of water and stress. The dynamic fatigue (constant
stressing rate) method was used to obtain subcritical crack growth
parameters for three dental ceramics: a feldspathic porcelain, an aluminous
porcelain, and a fine-grain, polycrystalline core material. The constant
stressing rate experiments were carried out at 37 degrees C for all three
ceramics in distilled water, and, for the feldspathic porcelain, in
artificial saliva as well. Considerable differences were found in the value
of the crack growth exponent (n) among the three ceramics. The feldspathic
porcelain was lowest in n-value, while the fine-grain ceramic had the
highest n-value. No differences were found for the feldspathic porcelain
with respect to n measured in water and in the artificial saliva. Lifetime
prediction curves in 37 degrees C water, constructed from the n-values and
inert strengths, showed that fatigue failure within five years is a good
possibility for feldspathic porcelain specimens at stress levels which can
reasonably be anticipated to occur in the oral environment. Little
likelihood of failure was perceived for the fine-grain ceramic. The
aluminous porcelain was intermediate between these two materials with
respect to failure probability.
