Evaluation of the fit of metal ceramic restorations fabricated with a pre-sintered soft alloy

Statement of problem. Fit is an important factor influencing the success or failure of restorations. Recently, there has been increasing use of a newly developed pre-sintered soft alloy for use in computer-aided design and computer-aided manufacturing (CAD-CAM) of cobalt-chromium alloys for the fabrication of metal ceramic restorations. However, almost no studies are available on the fit of restorations fabricated in this way. Purpose. The purpose of this in vitro study was to evaluate the fit of metal coping fabricated from a newly developed CAD-CAM soft alloy in order to investigate its clinical applicability. Material and methods. Metal coping was categorized as casting alloy (CA), fully sintered hard alloy (FHA), or pre-sintered soft alloy (PSA) depending on the material, and 10 specimens of each category were fabricated. Seven measurement locations were selected in both the mesiodistal and labiolingual directions. For measurement of the marginal and internal discrepancies, silicone molds produced using a silicone replica technique were divided into mesiodistal and labiolingual cross sections, and the width was measured. The Kruskal-Wallis and Mann-Whitney U test were performed (corrected alpha error level=.05/3). Results. The mean values of the total discrepancy were smallest in the CA group (52.53 +/- 33.40 gm) and largest in the FHA group (87.84 +/- 39.43 mu m). The CA group and the PSA group were not significantly different from each other (P>.05) but were statistically significantly different from the FHA group (P<.001). In particular, the absolute marginal discrepancy did not differ significantly between the CA (33.68 +/- 8.44 mu m) and PSA groups (37.01 +/- 8.04 mu m) (P>.05). Conclusions. The fit of the PSA restorations determined by this study was similar to that of conventional cast restorations. Both FHA and PSA restorations demonstrated clinically acceptable values (<120 mu m).