Comparison of the Overall Fit of Three-Unit Posterior Fixed Dental Prostheses Fabricated With Laser Sintering and Conventional Casting Methods

Abstract

Objectives The aim of this study was to investigate the marginal, internal, and occlusal discrepancies of three-unit posterior cobalt-chromium (Co-Cr) fixed dental prostheses (FDPs) produced using five different fabrication techniques. Materials and methods Segmental maxillary models were prepared from polyamide material using a laser sintering method. The maxillary first premolar and first molar teeth were prepared to receive posterior FDPs. Direct metal laser sintering (DMLS) and selective laser melting (SLM) were used as two metal laser Co-Cr framework production systems. FDP specimen patterns were prepared by manual wax carving (Cast), 3D-printed polymer (3DP), and CAD/CAM wax and cast using the lost-wax technique as conventional methods. In total, 100 Co-Cr metal framework specimens were prepared for posterior FDPs (n = 20). The silicone replica technique was used to measure marginal, internal, and occlusal discrepancies of all frameworks. A stereomicroscope was employed to detect discrepancies at 100x magnification. The data were analyzed using two-way ANOVA (alpha = 0.05) and post hoc Bonferroni adjustment (alpha = 0.005) for pairwise comparisons. Results There were no significant differences between the occlusal discrepancy values of premolar abutments of FDPs when compared with different fabrication methods (P > 0.05). The highest marginal discrepancy value was detected as 116.22 mu m for molar abutment when the Cast method was used (P < 0.05). The highest occlusal discrepancy values were detected as 135.60 mu m and 141.49 mu m for molar abutments of posterior FDPs when the 3DP and Cast methods were used. The lowest marginal discrepancy value was detected as 38.94 mu m for molar abutments when the DMLS method was used (P < 0.05). Conclusions The DMLS method was more successful than other fabrication methods when fit values of abutment teeth for posterior frameworks were compared. Clinical relevance The morphology of the abutment teeth and the fabrication techniques of FDPs migth affect the discrepancy values of FDPs planned. It was seen that the discrepancy values were lowest with the DMLS and SLM methods. Considering the results of this in-vitro study, DMLS and SLM techniques may be more appropriate option than the 3DP method, which starts with digital design and ends conventionally casting technique for posterior three-unit FDPs.