PURPOSE: 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. MATERIAL AND 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).
PURPOSE: 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. MATERIAL AND 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).