Evaluation of marginal fit of single implant-supported metal-ceramic crowns prepared by using presintered metal blocks

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Statement of problem.Recently, presintered metal blocks for nonprecious and precious metal implant-supported restorations have gained popularity in computer-aided design and computer-aided manufacturing (CAD-CAM) systems. However, few studies have evaluated the marginal discrepancy of implant-supported restorations made with these new alloy systems.Purpose.The purpose of this in vitro study was to compare the milling-sintering method with the lost-wax and milling methods in terms of the marginal fit of implant-supported metal-ceramic restorations.Material and methods.Thirty implant abutments screwed to implant analogs were embedded into acrylic resin to investigate marginal fit and then divided according to fabrication methods into the following 3 groups (n=10): lost-wax (LW; control group), milling (M), and milling-sintering (MS). Porcelain material was applied to all specimens after completion of the fabrication process. Subsequently, all specimens were cemented to implant abutments for the measurement of marginal discrepancies. Twelve marginal discrepancy measurements were recorded on each implant abutment by using a stereomicroscope. The arithmetic mean of these 12 measurements was considered the mean marginal discrepancy value of each abutment. Data were statistically analyzed by using 1-way ANOVA and Tukey honest significant difference tests (α=.05).Results.The lowest mean marginal discrepancy values (81 ±2 μm) were observed in the M group, which was significantly different (P<.001) from the other methods. The highest mean marginal discrepancy values (99 ±2 μm) were observed in the MS group.Conclusions.The results revealed that restorations prepared by the milling-sintering method provided clinically acceptable results (<120 μm); however, this new technique was not found to be as precise as the milling method in terms of marginal fit.

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