Abstract
This study investigated the fitting accuracy of titanium alloy fixed dental prostheses (FDP) after sequential CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) fabrication. A three-unit FDP model connecting mandibular second premolars and molars was prepared and scanned to fabricate titanium FDPs by CAD/CAM milling. A total of six FDPs were sequentially milled in one titanium alloy disk using a new set of burs every time (n = 4). The fitting accuracy of FDPs was mesiodistally evaluated by a silicone replica technique and the measurement was triplicated at four different locations: MO (marginal opening), MG (marginal gap), AG (axial gap), and OG (occlusal gap). Data were statistically analyzed using ANOVA and Tukey’s HSD test. The fitting accuracy of PMMA (polymethyl methacrylate) FDPs milled using the worn or new bur were evaluated by the same procedure (n = 6). The mean dimensions of titanium FDP for all measuring positions, except for AG, were significantly increased from the third milling. However, no difference was noted between the first FDP and the second FDP milled with the same set of burs. Severe edge chippings were observed in all milling burs. Detrimental effects of the worn burs on the fitting accuracy were demonstrated in the CAD/CAM-milled PMMA FDP. The results recommend proper changing frequency of cutting burs to achieve the quality of fit and predictable outcomes for dental CAD/CAM prostheses.
Highlights
Dental CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) systems have become mainstream in the fabrication of most dental fixed prostheses, even for metal restorations that have conventionally been fabricated by casting with the lost-wax technique [1,2,3]
The fit of metal restoration fabricated by conventional lost-wax casting is better than that of milled restoration, the marginal fit of titanium copings fabricated by the milling technique with CAD/CAM is currently comparable to that of the conventional casting technique with or without manual refinement [1,6]
Shin Dental Co., Seoul, Korea) for CAD/CAM fabrication were milled with the new set or the used set of burs for six Ti fixed dental prostheses (FDP)
Summary
Dental CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) systems have become mainstream in the fabrication of most dental fixed prostheses, even for metal restorations that have conventionally been fabricated by casting with the lost-wax technique [1,2,3]. In addition to the milling technique, metal prostheses can currently be fabricated by selective laser melting using CAD data [4] This translation was further encouraged by the following advantages of digitalized technologies: reduced production time and labor cost and less quality difference between dental laboratories [2,3,4,5]. The fit of metal restoration fabricated by conventional lost-wax casting is better than that of milled restoration, the marginal fit of titanium copings fabricated by the milling technique with CAD/CAM is currently comparable to that of the conventional casting technique with or without manual refinement [1,6]. The CAD/CAM-milling technique produced Co-Cr copings ranging from 52 to 113 μm in the marginal opening regardless of the shape of the margin, which can be considered clinically acceptable at
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