title: Contact fatigue of human enamel: Experiments, mechanisms and modeling.
abstract: Cyclic contact between natural tooth structure and engineered ceramics is increasingly common. Fatigue of the enamel due to cyclic contact is rarely considered. The objectives of this investigation were to evaluate the fatigue behavior of human enamel by cyclic contact, and to assess the extent of damage over clinically relevant conditions. Cyclic contact experiments were conducted using the crowns of caries-free molars obtained from young donors. The cuspal locations were polished flat and subjected to cyclic contact with a spherical indenter of alumina at 2Hz. The progression of damage was monitored through the evolution in contact displacement, changes in the contact hysteresis and characteristics of the fracture pattern. The contact fatigue life diagram exhibited a decrease in cycles to failure with increasing cyclic load magnitude. Two distinct trends were identified, which corresponded to the development and propagation of a combination of cylindrical and radial cracks. Under contact loads of less than 400N, enamel rod decussation resisted the growth of subsurface cracks. However, at greater loads the damage progressed rapidly and accelerated fatigue failure. Overall, cyclic contact between ceramic appliances and natural tooth structure causes fatigue of the enamel. The extent of damage is dependent on the magnitude of cyclic stress and the ability of the decussation to arrest the fatigue damage.
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China. Electronic address: gaoss@scu.edu.cn.
authors.forename: S S
authors.initials: SS
authors.lastname: Gao
authors.affiliation: Department of Physics, Shanghai University, Shanghai, PR China; Department of Mechanics, Shanghai University, Shanghai, PR China.
authors.forename: B B
authors.initials: BB
authors.lastname: An
authors.affiliation: Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
authors.forename: M
authors.initials: M
authors.lastname: Yahyazadehfar
authors.affiliation: Department of Mechanics, Shanghai University, Shanghai, PR China.
authors.forename: D
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA; Department of Restorative Dentistry, Dental School, University of Washington, Seattle, WA, USA. Electronic address: darola@uw.edu.
authors.forename: D D
authors.initials: DD
authors.lastname: Arola
mesh_terms: D000537:Aluminum Oxide; D002516:Ceramics; D003743:Dental Enamel; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D008963:Molar
chemical_list: D000537:Aluminum Oxide
keywords: Ceramic crowns; Contact; Crack; Enamel; Fatigue; Fracture