Sliding contact fatigue damage in layered ceramic structures.
Porcelain-veneered restorations often chip and fracture from repeated occlusal loading, making fatigue studies relevant. Most fatigue studies are limited to uni-axial loading without sliding motion. We hypothesized that bi-axial loading (contact-load-slide-liftoff, simulating a masticatory cycle), as compared with uni-axial loading, accelerates the fatigue of layered ceramics. Monolithic glass plates were epoxy-joined to polycarbonate substrates as a transparent model for an all-ceramic crown on dentin. Uni-and bi-axial cyclic contact was applied through a hard sphere in water, by means of a mouth-motion simulator apparatus. The uni-axial (contact-load-hold-liftoff) and traditional R-ratio fatigue (indenter never leaves the specimen surface) produced similar lifespans, while bi-axial fatigue was more severe. The accelerated crack growth rate in bi-axial fatigue is attributed to enhanced tensile stresses at the trailing edges of a moving indenter. Fracture mechanics descriptions for damage evolution in brittle materials loaded repeatedly with a sliding sphere are provided. Clinical relevance is addressed.
Kim
J-W
JW
Department of Biomaterials and Biomimetics, New York University College of Dentistry, 345 E. 24th St., Room 813C, New York, NY 10010, USA.
Kim
J-H
JH
Thompson
V P
VP
Zhang
Y
Y
D019245:Compressive Strength; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D019544:Equipment Failure Analysis; D005898:Glass; D008422:Materials Testing; D013718:Tensile Strength
D003776:Dental Porcelain