Fit analysis of implant-supported Co-Cr bars fabricated using casting, selective laser sintering, soft and dense milling techniques

Abstract

PURPOSE. This in vitro study evaluated the fit of implant-supported bars fabricated using different computer-aided manufacturing (CAM) techniques. Materials and Methods. A mandibular model with four dental implants (Nobel Replace Conical Connection, 3.5 mm × 11.5 mm) was fabricated using photoelastic resin. Sixteen Co-Cr implant-supported bars were produced using four CAM techniques: casting milled wax (CMW), selective laser sintering (SLS), dense milling (DM), and soft milling (SM) (n = 4). Fit was assessed through photoelastic stress analysis and digital scanning with a topographic digitizer (BreuckmannSmartScan). A standardized coordinate system was used for fit analysis. Data were analyzed using the Kruskal-Wallis test, with Dunn-Bonferroni for multiple comparisons (α = .05). RESULTS. Photoelastic analysis showed that bars fabricated with DM exhibited the lowest stress levels, while SM showed moderate stress. Fit was significantly influenced by Δy-z, Δdin, and Δdout (P < .01), whereas Δhex and Δx-z had no significant effect (P > .05). The highest mean Δy-z value was observed in CMW (0.68 ± 0.28°) and the lowest in SLS (0.01 ± 0.34°). CMW had the highest Δdin (-160.44 ± 61.17 µm) and DM the lowest (-5.46 ± 11.80 µm). DM showed the highest Δdout (46.23 ± 39.32 µm), while SM had the lowest (-55.04 ± 35.06 µm), with significant differences among the techniques. CONCLUSION. In conclusion, full-arch implant supported Co-Cr bars fabricated using the different CAM techniques exhibited clinically acceptable passive fit. [J Adv Prosthodont 2025;17:210-23]