title: In vitro failure load of metal-collar margins compared with porcelain facial margins of metal-ceramic crowns.
abstract: OBJECTIVE
  This in vitro study compared the load necessary to cause porcelain failure on traditionally fabricated metal-ceramic crowns cemented to metal tooth analogs with two different types of margins.
  
  
  METHODS
  Metal-ceramic crowns were constructed with either metal facial collars or porcelain facial margins. The metal tooth analogs were embedded in polymethyl methacrylate resin blocks, so that a load applied to the lingual surface compressed the facial margins. Increasingly greater loads were applied to specimens until failure occurred and the failure load values of all specimens were statistically evaluated.
  
  
  RESULTS
  The load required to cause porcelain fracture in the crowns with porcelain facial margins was statistically significantly greater than the load required to cause porcelain fracture for crowns with metal collars (p < 0.02).
authors.affiliation: Medical College of Georgia, Augusta, USA.
authors.forename: F M
authors.initials: FM
authors.lastname: Gardner
authors.forename: K W
authors.initials: KW
authors.lastname: Tillman-McCombs
authors.forename: M L
authors.initials: ML
authors.lastname: Gaston
authors.forename: D A
authors.initials: DA
authors.lastname: Runyan
mesh_terms: D002484:Cementation; D002858:Chromium Alloys / Q000737:chemistry; D003442:Crowns; D003481:Cuspid; D003722:Dental Alloys / Q000737:chemistry; D003734:Dental Casting Investment / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008768:Methylmethacrylates; D008953:Models, Anatomic; D013314:Stress, Mechanical; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys; D008768:Methylmethacrylates; D003776:Dental Porcelain