The Effects of Cyclic Loading on Fracture Modes in Brittle Layer Structures: Relevance to Failure of Dental Crowns
The effects of cyclic loading on contact damage in curved bi-layer systems are investigated. Dome structures consisting of glass shells, filled with epoxy resin, simulate the essential structure of monolithic all-ceramic dental crowns on natural tooth dentine. Cyclic loading, with only a vertical component, was carried out with the Multi-Functional Chewing Simulator (Willytec. Munich, Germany). The specimens were tested by indentation with hard spheres of tungsten carbide, with the load applied axially at the apex of the dome. This project reports some new results on the effect of cyclic loading on curved bi-layer systems. In addition, the effect of aqueous environments is addressed. In both air and water tests, observations taken throughout the cyclic loading course indicated that the outer cone cracks inhibited the propagation of radial cracks. Results confirm that crack initiation occurred more rapidly in wet conditions of testing, emphasizing the influences of the moist environment of the oral cavity. Furthermore, the experiments took into account the evolution of inner cone cracks observed in wet cyclic loading tests. The new results are important since nearly all-dental crowns exhibit some curvature. The implications of the results on the failure of dental crowns are discussed.
Xiaozhi Hu, Brent Fillery, Tarek Qasim and Kai Duan
S. Lam et al., "The Effects of Cyclic Loading on Fracture Modes in Brittle Layer Structures: Relevance to Failure of Dental Crowns", Advanced Materials Research, Vols. 41-42, pp. 21-26, 2008