Accuracy of trial restorations from virtual planning: A comparison of two fabrication techniques.

STATEMENT OF PROBLEM: Different technologies have been used to fabricate trial restorations. However, studies investigating the accuracy of trial restorations fabricated with different techniques in comparison with the initial 3-dimensional virtual design are lacking. PURPOSE: The purpose of this clinical study was to evaluate completely digital workflows for managing the esthetic outcome through the production of trial restorations with 2 different technologies: stereolithography apparatus (SLA 3D) and computer-aided design and computer-aided manufacturing (CAD-CAM). The aim was to determine which of them provided trial restorations more similar to those of the 3D virtual design. MATERIAL AND METHODS: Thirty participants who did not meet ideal esthetic proportions for the anterior maxillary teeth were enrolled. For each, 2 intraoral and extraoral frontal photographs and intraoral digital scans were made. The digital images were processed by using the Digital Smile System (DSS) software program to have a smile preview after the treatment. Virtual designs were matched with the surface tessellation language (STL) files from the intraoral scans and edited by exocad DentalCAD to create custom trial restorations using SLA 3D and CAD-CAM technologies. Two independent examiners measured the virtual restorations by using virtual calipers in the software program and then the trial restorations by using digital calipers. The measurements were carried out from the incisal edge to the gingival margin, mesial-distal widths of the central incisors, and the distance from the distal margins of maxillary right and left canines. The trial restorations were evaluated intraorally for fit. The participants approved the definitive treatment outcome after the evaluation. The normality of data was verified with the Shapiro-Wilk test, and the Friedman test for matched groups with the Bonferroni and Dunn tests for multiple comparisons were used (α=.05). RESULTS: Comparing the 3D designs with the printed trial restorations, a significant increase was only found in the mesial-distal width of central incisors (P<.05), while the milled trial restorations showed a significant increase (P<.05) of all measurements except for the maxillary right and left canines. Comparing printed trial restorations with the milled ones, the only significant difference was found in height measures of maxillary right central incisor, with the milled trial restorations exhibiting higher values than the printed ones (P<.05). The printed trial restorations showed good clinical fit, and the milled restorations had poor clinical adaptation. CONCLUSIONS: The accuracy of printed trial restorations was higher than that of milled trial restorations, except for the canine to canine width of maxillary anterior teeth. However, this difference did not compromise the fit of the printed trial restorations. The milled trial restorations had increased dimensions in comparison with the measurements made in 3D designs, and consequently, their clinical fit was compromised. SLA 3D- printing technology provided the best fit.

The step further smile virtual planning: milled versus prototyped mock-ups for the evaluation of the designed smile characteristics.

BACKGROUND: Mock-up based approach allows the preview of the aesthetic rehabilitation, however, it is crucial that the mock-up does not differ from the expected aesthetic outcomes. With CAD-CAM technologies, it is possible to directly create mock-ups from virtual planned smile project, with greater accuracy and efficiency compared to the conventional moulded mock-ups. In this study, we investigated the trueness of mock-ups obtained with milling and 3D printing technology and a full digital work-flow system. METHODS: Ten adults subjects were included and digital smile design/digital wax-up were performed to enhance the aesthetic of maxillary anterior region. Ten milled mock-ups and 10 prototyped mock-ups were obtained from the original .stl file and a digital analysis of trueness was carried out by superimposing the scanned-milled mock-ups and the scanned-prototyped mock-ups to the digital wax-up, according to the surface-to-surface matching technique. Specific linear measurements were performed to investigate and compare the dimensional characteristics of the physical manufactures, the 3D project and the scanned mock-ups. All data were statistically analyzed. A clinical test was also performed to assess the fitting of the final manufacture. RESULTS: The prototyped mock-ups showed a significant increment of the transversal measurements (p < 0.001) while the milled mock-ups showed a significant increment of all vertical and transversal measurements (p < 0.001). The prototyped mock-ups showed good fitting after clinical tests while none of the milled mock-ups showed good adaptation (no fitting or significant clinical compensation required). Deviation analysis from the original 3D project reported a greater matching percentage for the scanned-milled mock-ups (80,31% ± 2.50) compared to the scanned-prototyped mock-ups (69,17% ± 2.64) (p < 0.001). This was in contrast with the findings from linear measurements as well as from the clinical test and may have been affected by a reductive algorithmic computation after digitization of physical mock-ups. CONCLUSION: Both prototype and milled mock-ups showed a slight dimensional increment comparing to the original 3D project, with milled-mock-ups showing less fitting after clinical tests. Caution must be taken when assessing the trueness of scanned manufacture since an intrinsic error in the system can underestimate the dimensions of the real object.