title: Thermally induced fracture for core-veneered dental ceramic structures.
abstract: Effective and reliable clinical uses of dental ceramics necessitate an insightful analysis of the fracture behaviour under critical conditions. To better understand failure characteristics of porcelain veneered to zirconia core ceramic structures, thermally induced cracking during the cooling phase of fabrication is studied here by using the extended finite element method (XFEM). In this study, a transient thermal analysis of cooling is conducted first to determine the temperature distributions. The time-dependent temperature field is then imported to the XFEM model for viscoelastic thermomechanical analysis, which predicts thermally induced damage and cracking at different time steps. Temperature-dependent material properties are used in both transient thermal and thermomechanical analyses. Three typical ceramic structures are considered in this paper, namely bi-layered spheres, squat cylinders and dental crowns with thickness ratios of either 1:2 or 1:1. The XFEM fracture patterns exhibit good agreement with clinical observation and the in vitro experimental results obtained from scanning electron microscopy characterization. The study reveals that fast cooling can lead to thermal fracture of these different bi-layered ceramic structures, and cooling rate (in terms of heat transfer coefficient) plays a critical role in crack initiation and propagation. By exploring different cooling rates, the heat transfer coefficient thresholds of fracture are determined for different structures, which are of clear clinical implication.
authors.affiliation: School of Aerospace, Mechanical and Mechatronic Engineering, Faculty of Engineering, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Zhongpu
authors.initials: Z
authors.lastname: Zhang
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Guazzato
authors.forename: Tanapon
authors.initials: T
authors.lastname: Sornsuwan
authors.forename: Susanne S
authors.initials: SS
authors.lastname: Scherrer
authors.forename: Chaiy
authors.initials: C
authors.lastname: Rungsiyakull
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Michael V
authors.initials: MV
authors.lastname: Swain
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D003198:Computer Simulation; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D020342:Finite Element Analysis; D006244:Hardness; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Bi-layered ceramic; Dental prosthesis; Thermal fracture; Thermomechanical; XFEM