title: Fractographic analysis of anterior bilayered ceramic crowns that failed by veneer chipping.
abstract: OBJECTIVE
  To fractographically analyze the reasons for the chipping of veneering porcelain in clinically failed anterior lithium disilicate glass-ceramic (LDG) and glass-infi ltrated alumina (GIA) crowns.
  
  
  METHODS
  Five anterior bilayered ceramic crowns with clinical veneer chipping failure were retrieved, of which three were LDG crowns and two were GIA crowns. The fractured surfaces of the failed restorations were examined using stereomicroscopy and scanning electron microscopy (SEM). The principles of fractography were used to identify the location and dimensions of the critical crack and to estimate the stress at failure.
  
  
  RESULTS
  All five anterior crowns failed by cohesive failure within the veneer on the labial surface. Fractography showed that the critical crack initiated at the incisal contact area and propagated gingivally. The estimated stresses at failure for veneer chipping were lower than the characteristic strength of the veneer materials.
  
  
  CONCLUSIONS
  Within the limitations of this in-vivo study, the contact damage, fatigue, and processing fl aws within the veneer are important reasons leading to chipping of veneering porcelain in anterior LDG and GIA crowns.
authors.forename: Qian
authors.initials: Q
authors.lastname: Du
authors.forename: Michael V
authors.initials: MV
authors.lastname: Swain
authors.forename: Ke
authors.initials: K
authors.lastname: Zhao
mesh_terms: D002516:Ceramics; D003442:Crowns; D003764:Dental Materials; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning
chemical_list: D003764:Dental Materials