Evaluation of the fit of metal copings fabricated using stereolithography

Statement of problem: Rapid prototyping, including stereolithography (SLA), is a more recent technique for fabricating metal frameworks than the conventional lost-wax technique. However, investigations of the marginal discrepancies and internal spacing of cobalt-chromium (Co-Cr) metal copings fabricated using SLA are lacking. Purpose: The purpose of this in vitro study was to evaluate the clinical acceptability of the marginal discrepancies and internal spacing of Co-Cr metal copings fabricated using the SLA technique. Material and methods: A resin tooth of a maxillary right first premolar was prepared with a deep chamfer margin for a metal–ceramic crown. Titanium master dies were milled after scanning the prepared tooth (n=45). In conventional lost wax group (group LW), the conventional lost-wax technique was used to fabricate Co-Cr metal copings (n=15). In milling group (group MC), a computer-aided design (CAD) system was used to design the metal copings, which were milled from Co-Cr alloy (n=15). The CAD system was also used to design the metal copings in a 3D-printed group (group SL), and Co-Cr metal copings were cast from resin patterns fabricated using the SLA device (n=15). Marginal discrepancies and internal spaces were measured using an optical microscope at ×100 magnification at 11 reference points. The values were analyzed statistically with 1-way analysis of variance (α=.05). Results: The mean (±SD) overall space was 63.2 ±16.6 μm for group LW, 70.2 ±15.5 μm for group SL, and 130.3 ±13.8 μm for group MC. The overall spaces differed significantly between group MC and the other 2 groups (P<.05). The marginal discrepancy and internal spaces were significantly larger in group MC than in groups LW and SL. (P<.05). Occlusal spaces differed significantly among the 3 study groups (P<.05). Conclusions: Co-Cr metal copings fabricated using an SLA technique showed clinically acceptable marginal discrepancies and internal spaces. These spaces did not differ significantly from those obtained with the conventional lost-wax technique.