Evaluation Of The Marginal Fit And Fracture Strength Of Cobalt-chromium Metal Ceramic Crowns Fabricated By Selective Laser Melting, CAD/CAM, And Casting

Statement of problems. The marginal and internal fit and fracture strength of metal ceramic crowns fabricated by selective laser melting is lack of research.Purpose. This study aimed to evaluate the marginal and internal fit and fracture strength of cobalt-chromium metal ceramic crowns fabricated by selective laser melting(SLM),computer-aided design/computer-aided manufacturing(CAD/CAM), and traditional casting method(CAST).Material and Methods. Thirty molar and thirty incisor metal ceramic crowns were fabricated and divided into three groups: SLM, CAM, and CAST. Before luting the crowns,the marginal gaps were measured by an optical microscope, and marginal gap and internal fitness were measured on silicone replicas in four areas: marginal gap, lateral wall, axio angle, and incisal point or occlusal surface. The measurement data were analyzed with a1-way analysis of variance(ANOVA). After thermocycling(5000 cycles, 5–55?) and pre-loading(30–300 N, 10,000 cycles), the crowns were loaded until fracture. The load(N)and fracture mode were recorded.Results. The marginal gap measurement significantly differed(p < 0.05) between the SLM,CAM with CAST groups for both the observational and silicone methods. The fracture resistance of the crowns of 3 groups for both sets did not significantly differ(P>.05) but exceeded the normal occlusal forces.Conclusions. The results of the fracture strength tests of SLM, CAM and CAST co-cr metal ceramic crowns were similar. However, SLM and CAM exhibited higher marginal and internal fitness accuracy than the CAST method.