title: Stress distribution in metal-ceramic crowns with a facial porcelain margin.
abstract: The use of metal-ceramic restorations with porcelain butt-joint facial margins has increased in the past several years. Although these crowns exhibit improved esthetics compared with metal-ceramic crowns which display a metal gingival collar or metal knife-edge margin, the effectiveness of this design in resisting intra-oral forces is not known. The objective of this study was to analyze the stress distribution induced by simulated intra-oral loads on crowns with variable coping configurations. The copings, with a thickness of either 0.1 or 0.3 mm, were modeled with a facial termination of metal at three locations: at the gingival floor, 0.9 mm above the gingival floor, and 4.2 mm above the gingival floor. The coping and crown dimensions were based on a prepared maxillary central incisor with a facial shoulder and a lingual chamfer. Both Ni-Cr and Au-Pd alloy copings were employed in the crown models. Finite element stress and analyses were performed on crowns which were subjected to several loading conditions. A cement film thickness of 0.030 mm was assumed. For all cases, the stresses which developed in porcelain and cement near the facial and lingual margins due to a vertical load of 200 N were predominantly compressive in nature. For the crowns with Ni-Cr copings, the tensile stress in porcelain ranged from 11.0 MPa (for crowns with a facial metal thickness of 0.3 mm) to 12.5 MPa (for a metal thickness of 0.1 mm). The corresponding stresses for crowns with Au-Pd alloy copings were 8.3 MPa and 8.6 MPa, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.forename: K J
authors.initials: KJ
authors.lastname: Anusavice
authors.forename: B
authors.initials: B
authors.lastname: Hojjatie
mesh_terms: D002858:Chromium Alloys; D003442:Crowns; D003722:Dental Alloys; D003738:Dental Cements; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003779:Denture Design; D004548:Elasticity; D006047:Gold Alloys; D007180:Incisor; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D003738:Dental Cements; D006047:Gold Alloys; D003776:Dental Porcelain