FATIGUE OF DENTAL CERAMICS
Abstract
Objectives
Clinical
data on survival rates reveal that all-ceramic dental prostheses are
susceptible to fracture from repetitive occlusal loading. The objective
of this review is to examine the underlying mechanisms of fatigue in
current and future dental ceramics.
Data/sources.
The nature of various fatigue modes is elucidated using fracture test
data on ceramic layer specimens from the dental and biomechanics
literature.
Conclusions
Failure
modes can change over a lifetime, depending on restoration geometry,
loading conditions and material properties. Modes that operate in
single-cycle loading may be dominated by alternative modes in
multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route
to failure remains poorly understood. Whereas it is commonly held that
loss of load-bearing capacity of dental ceramics in repetitive loading
is attributable to chemically-assisted ‘slow crack growth’ in the
presence of water, we demonstrate the existence of more deleterious
fatigue mechanisms, mechanical rather than chemical in nature.
Neglecting to account for mechanical fatigue can lead to gross
overestimates in predicted survival rates. Clinical significance. Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy.
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