Journal of Dental Research, Vol 66, 1493-1498, Copyright © 1987 by International & American Associations for Dental Research Online Journals
Stress distribution in metal-ceramic crowns with a facial porcelain margin
K. J. Anusavice and B. Hojjatie
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)
