title: Investigation of the time-dependent wear behavior of veneering ceramic in porcelain fused to metal crowns during chewing simulations.
abstract: The excessive abrasion of occlusal surfaces in ceramic crowns limits the service life of restorations and their clinical results. However, little is known about the time-dependent wear behavior of ceramic restorations during the chewing process. The aim of this in vitro study was to investigate the dynamic evolution of the wear behavior of veneering porcelain in PFM crowns as wear progressed, as tested in a chewing simulator. Twenty anatomical metal-ceramic crowns were prepared using Ceramco III as the veneering porcelain. Stainless steel balls served as antagonists. The specimens were dynamically loaded in a chewing simulator with 350N up to 2.4×10(6) loading cycles, with additional thermal cycling between 5 and 55°C. During the testing, several checkpoints were applied to measure the substance loss of the crowns' occlusal surfaces and to evaluate the microstructure of the worn areas. After 2.4×10(6) cycles, the entire wear process of the veneering porcelain in the PFM crowns revealed three wear stages (running-in, steady and severe wear stages). The occlusal surfaces showed traces of intensive wear on the worn areas during the running-in wear stage, and they exhibited the propagation of cracks in the subsurface during steady wear stage. When the severe wear stage was reached, the cracks penetrated the ceramic layer, causing the separation of porcelain pieces. It also exhibited a good correlation among the microstructure, the wear loss and the wear rate of worn ceramic restorations. The results suggest that under the conditions of simulated masticatory movement, the wear performance of the veneering porcelain in PFM crowns indicates the apparent similarity of the tribological characteristics of the traditional mechanical system. Additionally, the evaluation of the wear behavior of ceramic restorations should be based on these three wear stages.
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Changle Xi Road 145, Xi'an 710032, China.
authors.forename: Jiawen
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Changle Xi Road 145, Xi'an 710032, China.
authors.forename: Beimin
authors.initials: B
authors.lastname: Tian
authors.affiliation: State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Changle Xi Road 145, Xi'an 710032, China.
authors.forename: Weiguo
authors.initials: W
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, Changle Xi Road 145, Xi'an 710032, China.
authors.forename: Hongyun
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Changle Xi Road 145, Xi'an 710032, China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wu
authors.affiliation: State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, 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, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Changle Xi Road 145, Xi'an 710032, China. Electronic address: sfzhang1963.fmmu@gmail.com.
authors.forename: Shaofeng
authors.initials: S
authors.lastname: Zhang
mesh_terms: D032701:Biomimetics / Q000379:methods*; D003442:Crowns; D003776:Dental Porcelain; D003801:Dental Veneers; D008409:Mastication; D008422:Materials Testing; D055595:Mechanical Phenomena; D008670:Metals; D013997:Time Factors
chemical_list: D008670:Metals; D003776:Dental Porcelain
keywords: Chewing simulator; Dynamic process; Metal ceramic crowns; Porcelain; Wear