title: Comparative study of fracture resistance of porcelain in metal ceramic restorations by using different metal coping designs- an in vitro study.
abstract: OBJECTIVE
  The aim of this study was to compare effect of different metal coping designs on fracture resistance of porcelain in metal ceramic restorations.
  
  
  METHODS
  Fracture resistance of porcelain was assessed in porcelain fused to metal crowns with three different coping designs i.e. metal coping extension on labial surface upto gingivoaxial line angle, metal coping extension 1mm short of the gingivoaxial line angle and metal coping with 0.4mm wide labial metal collar. For crowns without labial metal collar margin; shoulder porcelain was used to build the labial cervical margin of the crowns.
  
  
  RESULTS
  RESULTS were assessed with statistical analysis using the student unpaired't' test. Visual examination of the fractured specimens of group A, B and C showed remarkably similar failure modes with nearly all specimens failing through a shear fracture of porcelain from load point to facial margin of the crown.
  
  
  CONCLUSIONS
  Within the scope of this study, it was observed that the mean facture strength of the samples with shoulder porcelain labial margins having metal coping design extending upto gingivoaxial line angle of the finish line was highest as compared to samples with shoulder porcelain labial margins having metal coping design 1mm short of gingivoaxial line angle & samples having porcelain fused to metal coping design with 0.4mm wide metal collar.
authors.affiliation: Associate Professor, Department of Prosthodontics, Dr. D. Y. Patil Dental College, Dr. D. Y. Patil Vidyapeeth , Pimpri, Pune, Maharashtra, India .
authors.forename: Nilesh
authors.initials: N
authors.lastname: Bulbule
authors.affiliation: Professor and Head, Department of Prosthodontics, Chhattisgarh Dental College and Research Institute , Sundra, Rajnandgaon, Chhattisgarh, India .
authors.forename: B K
authors.initials: BK
authors.lastname: Motwani
keywords: Collarless metal ceramic crowns; Fracture resistance; Shoulder porcelain