title: Effect of contact stress on the cycle-dependent wear behavior of ceramic restoration.
abstract: Ceramic restoration experiences the non-linear wear process during the chewing simulation, which contains running-in, steady and severe wear stages. However since various levels of contact stress may be applied on the occlusal surface during chewing, the cycle-dependent wear behaviors of ceramic crowns may differ. The aim of this study was to investigate the effect of contact stress on the development of wear behavior, as tested in a chewing simulator.
  
  
  
  Thirty-six anatomical metal-ceramic crowns using Ceramco III as the veneering porcelain were randomly assigned to two groups based on the contact stress applied in the wear testing. Stainless steel balls served as antagonists. The specimens were dynamically loaded in a chewing simulator up to 2.4×106loading cycles, with additional thermal cycling between 5 and 55℃. For each group, several checkpoints were employed to measure the substance loss of the crowns' occlusal surfaces and to evaluate the microstructure of the worn areas.
  
  
  
  After 2.4×106cycles, the ceramic restorations with lower contact stress demonstrated a long steady wear stage following the running-in, but without the severe wear stage. And a slowly microstructural degradation was observed that the subsurface defect could not be seen until final. With higher contact stress, however, the ceramic restorations experienced a faster transition from running-in to severe wear stage that the steady wear stage nearly disappeared. And an early formation of subsurface defects and the deterioration of microstructure were observed.
  
  
  
  Contact stress is a key factor affecting the wear development of ceramic restoration. The higher contact stress promotes the veneering porcelain to evolve into severe wear stage. In contrast, lower contact stress is prone to keep the veneering porcelain operating in steady wear stage, which delays the arrival of severe wear region.
authors.affiliation: Department of Stomatology, Lanzhou General Hospital, Lanzhou Command of PLA, Lanzhou, Gansu, China.
authors.forename: Jiawen
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Ding
authors.initials: D
authors.lastname: Li
authors.affiliation: Oral Biosciences, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Sai Ying Pun, Hong Kong.
authors.forename: Haijing
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Stomatology, Lanzhou General Hospital, Lanzhou Command of PLA, Lanzhou, Gansu, China.
authors.forename: Yanwei
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Stomatology, Lanzhou General Hospital, Lanzhou Command of PLA, Lanzhou, Gansu, China.
authors.forename: Liying
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Stomatology, Lanzhou General Hospital, Lanzhou Command of PLA, Lanzhou, Gansu, China.
authors.forename: Delin
authors.initials: D
authors.lastname: Guan
authors.affiliation: Department of Stomatology, Lanzhou General Hospital, Lanzhou Command of PLA, Lanzhou, Gansu, China.
authors.forename: Yinong
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China. Electronic address: helin@mail.xjtu.edu.cn.
authors.forename: Lin
authors.initials: L
authors.lastname: He
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China. Electronic address: sfzhang1963.fmmu@gmail.com.
authors.forename: Shaofeng
authors.initials: S
authors.lastname: Zhang
mesh_terms: D002516:Ceramics; D003442:Crowns; D003776:Dental Porcelain; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D003801:Dental Veneers; D008409:Mastication; D008422:Materials Testing; D013499:Surface Properties
chemical_list: D003776:Dental Porcelain
keywords: Chewing simulation; Contact stress; Metal ceramic crowns; Porcelain; Temporal development; Wear