Marginal accuracy of metal ceramic restorations with porcelain facial margins

This study compared porcelain facial margins made with the direct-lift technique using high-fusing shoulder porcelains and the platinum foil technique with conventional body porcelain. Marginal accuracy was measured directly and the marginal sharpness computed by the software program MacDraft. Both Vita high-fusing shoulder porcelain and Vita SM 90 porcelain produced restorations that had significantly smaller mean facial marginal openings than crowns created with platinum foil. However, the SM 90 porcelain recorded significantly greater cross sectional or internal marginal discrepancies than the other two techniques (p < 0.05). Externally, the shoulder porcelains followed the facial rounding of the stone die; thus porcelain marginal roundings can be manifested as either negative roundings or underextensions and positive roundings or overextensions. The lack of marginal sharpness of porcelain facial margins may be influenced more by the die material rather than by the marginal porcelain or the technique.