Fatigue of Restorative Materials

Abstract

Failure due to fatigue manifests itself in dental prostheses and restorations as wear, fractured margins, delaminated coatings, and bulk fracture. Mechanisms responsible for fatigue-induced failure depend on material ductility: Brittle materials are susceptible to catastrophic failure, while ductile materials utilize their plasticity to reduce stress concentrations at the crack tip. Because of the expense associated with the replacement of failed restorations, there is a strong desire on the part of basic scientists and clinicians to evaluate the resistance of materials to fatigue in laboratory tests. Test variables include fatigue-loading mode and test environment, such as soaking in water. The outcome variable is typically fracture strength, and these data typically fit the Weibull distribution. Analysis of fatigue data permits predictive inferences to be made concerning the survival of structures fabricated from restorative materials under specified loading conditions. Although many dentalrestorative materials are routinely evaluated, only limited use has been made of fatigue data collected in vitro: Wear of materials and the survival of porcelain restorations has been modeled by both fracture mechanics and probabilistic approaches. A need still exists for a clinical failure database and for the development of valid test methods for the evaluation of composite materials.

Fatigue behavior of resin-modified monolithic CAD–CAM RNC crowns and endocrowns

“…The rationale behind the second phase was to intensify the testing conditions in order to provoke restoration failure under fatigue conditions, over a certain number of cycles. Under these testing conditions the first degradation of the material may occur below critical failure stresses and involve the growth of subcritical defects at subcritical loads [26,33]. However, neither the load-to-fracture values nor the number of cycles-to-fracture obtained with this second phase of the fatigue test -the stepwise test -should be used to predict clinical mechanical limits of different restorations, due to the extreme and DENTAL-2840 ( 2 0 1 6 ) xxx.e1-xxx.e13 xxx.e9 non-physiological testing conditions imposed on the materials.…”

Clinical longevity of ceramic laminate veneers bonded to teeth with and without existing composite restorations up to 40 months

“…The greatest shortcoming of ceramic materials is their low ductility that is an inherent problem yielding to crack formation [27]. Also, polymerization shrinkage of the luting composite may create stress concentrations at the adhesive interface [28] or failures may occur simply due to heavy occlusion.…”

Fracture process characterization of fiber-reinforced dental composites evaluated by optical coherence tomography, SEM and optical microscopy

“…The fatigue on dental restorations of the composite resins is also influenced by water absorption by resin matrix (2) and occlusion cyclical forces (3). Fiber-reinforcement has been introduced to increase both flexural strength and modulus of these materials (4).…”