title: Interface toughness of a zirconia-veneer system and the effect of a liner application.
abstract: BACKGROUND
  Chipping of veneering porcelain and delamination of a zirconia-veneer interface are 2 common clinical failure modes for zirconia-based restorations and may be partially due to weak interface bonding. The effect of liner on the bond strength of the interface has not been clearly identified.
  
  
  OBJECTIVE
  The purpose of the research was to evaluate the interface toughness between the zirconia core and veneering porcelain by means of a fracture mechanics test and to assess the effect of liner on the bond strength of the interface.
  
  
  METHODS
  Thirty bilayered beam-shape specimens were prepared and divided into 2 groups according to liner application. The specimens in each group were subdivided into 3 subgroups in accordance with 3 different veneer thicknesses. A fracture mechanics test was used on each specimen, and the energy release rate, G, and phase angle, ψ, were calculated according to the experimental results. A video microscope was used to monitor the crack propagation, and a scanning electron microscope was used to identify the fracture mode after testing. Two-way ANOVA and the Tukey honestly significant difference test were performed to analyze the experimental data (α=.05) .
  
  
  RESULTS
  At each phase angle, the interfaces without a liner had higher mean G values than the interfaces with a liner. Both of the interfaces showed mixed failure mode with thin layers of a veneer or a liner that remained on the zirconia surfaces.
  
  
  CONCLUSIONS
  Liner application before veneering reduced the interface toughness between zirconia and veneer.
authors.affiliation: Doctoral student, School of Mechanical Engineering, Shandong University, Key Laboratory of High Efficiency and Clean Mechanical Manufacture (Ministry of Education), Jinan, P.R. China.
authors.forename: Gaoqi
authors.initials: G
authors.lastname: Wang
authors.affiliation: Professor, School of Mechanical Engineering, Shandong University, Key Laboratory of High Efficiency and Clean Mechanical Manufacture (Ministry of Education), Jinan, P.R. China. Electronic address: zhangsong@sdu.edu.cn.
authors.forename: Song
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Chief Physician, Department of Prosthodontics, Qilu Hospital of Shandong University, Jinan, P.R. China.
authors.forename: Cuirong
authors.initials: C
authors.lastname: Bian
authors.affiliation: Resident, Department of Prosthodontics, Qilu Hospital of Shandong University, Jinan, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Kong
mesh_terms: D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018715:Microscopy, Video; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D003776:Dental Porcelain; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide