Influence of the CAD-CAM Systems on the Marginal Accuracy and Mechanical Properties of Dental Restorations

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.

The Internal and Marginal Adaptation of Zirconia Based Fixed Dental Prostheses in the Posterior Region

“…1 It has been reported that 50-200 µm marginal gap width is clinically acceptable. 2,3,[5][6][7][8][9] When the total internal fit was examined in our study, an average of 139.16 ±49.01 µm was found, which was within the clinically acceptable range.…”

“…2,3 The success of all restoration types used in dentistry is highly related to the marginal fit of the restorations, and it has been reported that a 50-200 µm marginal gap is clinically acceptable. [2][3][4][5][6][7][8][9] The factors affecting the internal and marginal adaptations indicate that fit of the selected restoration with the tooth struc-ture and wear resistance is effective. 10 Another factor is the location of the teeth, which determines the tooth preparation.…”

Fracture Resistance of Endodontically Treated Premolars Reconstructed by Traditional Casting and CAD-CAM Milling Post and Cores

“…The higher fracture load of CAD/CAM milling posts may be attributed to the more homogenous structure of metal and greater accuracy in the manufacturing process [ 21 , 32 , 33 ], whereas casting posts probably have more porosity in their structure. Furthermore, the alloy composition may influence the resistance to fracture.…”

“…In this way, the frameworks made from the Co-Cr alloy are reduced by CAD-CAM milling (Table 1). e use of CAD-CAM system for post-manufacturing is associated with multiple benefits such as reducing the construction cost and material usage, saving time required for the design and construction of the posts, eliminating the manufacturing and human errors, and enhancing the accuracy of fitting [19][20][21][22][23].…”

Production time, effectiveness and costs of additive and subtractive computer‐aided manufacturing (CAM) of implant prostheses: A systematic review

“…The waste of material, which includes also unused remnants of the blocks, may reach up to 90% (Strub et al., 2006 ). Fabrication accuracy applying s‐CAM is influenced by the type of milling device (Bosch et al., 2014 ; Padros et al., 2020 ; Zeltner et al., 2017 ). Moreover, number, size and geometry of milling burs used for s‐CAM seem to influence the surface resolution and represent a limitation that cannot be overcome (Atzeni & Salmi, 2012 ; Koch et al., 2016 ; Yara et al., 2005 ).…”