Abstract
Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe’s test, and Pearson’s correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05). The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.
Highlights
Cobalt-chromium (Co-Cr) alloys have been widely used in dentistry for removable partial dentures, metal frames, and porcelain-fused-to-metal crowns, mainly because alloys are strong, resistant to corrosion, and relatively inexpensive, when compared to gold alloys and some all-ceramic materials [1,2,3,4,5]
Laser sintered technology has been introduced in clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices
Laser sintering technology has an advantage relating to the minimization of human error during the manufacturing procedures, maintaining a consistent quality of restorations
Summary
Cobalt-chromium (Co-Cr) alloys have been widely used in dentistry for removable partial dentures, metal frames, and porcelain-fused-to-metal crowns, mainly because alloys are strong, resistant to corrosion, and relatively inexpensive, when compared to gold alloys and some all-ceramic materials [1,2,3,4,5]. Base metal alloys may be preferable over noble alloys for implant-retained structures [1,6], due to their higher fracture strength, elastic modulus, hardness, and low cost [7]. The fabrication process for alloys is usually difficult because of their high melting point (1349–1449 ◦ C), hardness, and limited ductility [8]. Co-Cr alloy implant superstructures are often associated with marginal and fitting discrepancies. These faults can be attributed to the expansion and contraction of the impression materials, gypsum, wax, investment, and alloy in the lost-wax technique [9]. Lost-wax casting has been the most commonly used method for fabricating dental prosthesis for many decades [1], but errors accumulated in the series of laboratory steps are inevitable
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