Abstract
The aim of this study was to compare the quality of different computer-assisted-design and computer assisted manufacturing systems (CAD-CAM) generated by only one scanner, focusing on vertical fit discrepancies and the mechanical properties. A master model was obtained from a real clinical situation: the replacement of an absent (pontic) tooth, with the construction of a fixed partial denture on natural abutments with three elements. Nine scans were performed by each tested and 36 copies were designed using a dental CAD-CAM software (Exocad). The frameworks were manufactured using three-axis and five-axis, with the same batch of the chrome-cobalt (CrCo) alloy. The frameworks were not cemented. A focus ion beam-high resolution scanning electron microscope (FIB-HRSEM) allowed us to obtain the vertical gap measurements in five points for each specimen. Roughness parameters were measured using white light interferometry (WLI). The samples were mechanically characterized by means of flexural tests. A servo-hydraulic testing machine was used with a cross-head rate of 1 mm/min. One-way ANOVA statistical analysis was performed to determine whether the vertical discrepancies and mechanical properties were significantly different between each group (significance level p < 0.05). The overall mean marginal gap values ranged: from 92.38 ± 19.24 µm to 19.46 ± 10.20 µm, for the samples produced by three-axis and five-axis machines, respectively. Roughness was lower in the five-axis machine than the three-axis one, and as a consequence, the surface quality was better when the five-axis machine was used. These results revealed a statistically significant difference (p < 0.005) in the mean marginal gap between the CAD-CAM systems studied. The flexural strength for these restorations range from 6500 to 7000 N, and does not present any statistical differences’ significance between two CAD-CAM systems studied. This contribution suggests that the number of axes improves vertical fit and surface quality due to the lower roughness. These claims show some discrepancies with other studies.
Highlights
The fabrication of dental prosthesis by using digital processes is getting more popular, thanks to the evolution of the computer-assisted-design and computer assisted manufacturing systems (CAD and CAM) workflows and to a better accuracy of the digital working files
computer-assisted-design and computer assisted manufacturing systems (CAD-CAM) systems present an important advantage, because they imply a reduced influence of the dental laboratory technician [6,7,8]. It seems that a CAD-CAM workflow favors a better standardization procedure for prosthesis manufacturing
The restorations obtained by a five-axis manufacturer machine present lower marginal gaps than the ones provided by the three-axis manufacturer
Summary
The fabrication of dental prosthesis by using digital processes is getting more popular, thanks to the evolution of the computer-assisted-design and computer assisted manufacturing systems (CAD and CAM) workflows and to a better accuracy of the digital working files. CAD-CAM systems present an important advantage, because they imply a reduced influence of the dental laboratory technician [6,7,8]. It seems that a CAD-CAM workflow favors a better standardization procedure for prosthesis manufacturing. These systems require a learning process that may take a significant time as well as an important financial investment and a different management of different materials, it seems that they represent a more viable option in the long-term
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