title: The in-vitro clinical failure of all-ceramic crowns and the connector area of fixed partial dentures: the influence of interfacial surface roughness.
abstract: OBJECTIVE
  To assess the effect of interfacial surface roughness on the flexure strength and fracture mode and origin utilizing an in-vitro assessment of the clinical failure conditions expected for all-ceramic crowns and the connector area of fixed partial dentures (FPDs) using bilayered ceramic specimens tested in bi-axial flexure.
  
  
  METHODS
  Sets of 20 bilayered composite discs, with core:dentine thickness ratio of 2:1 and interfacial surface roughnesses determined by alumina abrasion with different alumina particle sizes, were tested in bi-axial flexure with both the reinforcing core and veneering dentine loaded in tension. Mean flexure strengths, standard deviations and associated Weibull Moduli (m) were determined. Optical microscopy was employed for identification of the fracture mode and origin for the failure all-ceramic crowns and the connector area of FPDs.
  
  
  RESULTS
  The interfacial surface roughness influenced the bi-axial flexure strength and reliability of the flexure strength data when both the reinforcing core and veneering dentine porcelain were tested in tension. The number of fracture fragments, frequency of occurrence of specimen delaminations, Hertzian cone formations and sub-critical radial cracking in the bilayered dental ceramic composite disc-shaped specimens was also dependent on the interfacial surface roughness and the surface loaded in tension.
  
  
  CONCLUSIONS
  The fracture resistance, failure mode and failure origin in bilayered ceramics tested to represent the clinical failure mode of all-ceramic crowns and FPDs are dependent upon the interfacial surface roughness and the modulus of the material in tension.
authors.affiliation: Biomaterials Unit, School of Dentistry, University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, UK. g.j.fleming@bham.ac.uk
authors.forename: Garry J P
authors.initials: GJ
authors.lastname: Fleming
authors.forename: Lawrence
authors.initials: L
authors.lastname: Nolan
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Harris
mesh_terms: D000704:Analysis of Variance; D019245:Compressive Strength; D003442:Crowns; D003775:Dental Polishing; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D003830:Denture, Partial, Fixed; D004548:Elasticity; D008422:Materials Testing; D018583:Pliability; D018709:Statistics, Nonparametric; D013499:Surface Properties; D016019:Survival Analysis; D013718:Tensile Strength
chemical_list: D003776:Dental Porcelain