Abstract
Objectives: To evaluate a nonmetrology-grade and a metrology-grade 3D analysis software when measuring the deviations of computer-aided-design/ computer-aided-manufacturing (CAD-CAM) fabricated crowns from the virtual design file.Materials and Methods: A right first molar on a mandibular dentate model was prepared and scanned with an intraoral scanner, i500 (Medit). A complete coverage crown was designed in standard tessellation language (STL) format and 20 resin crowns were fabricated with CAD-CAM. The crowns were then digitized using the same intraoral scanner (test-scans). Root mean square (RMS) method was used to evaluate the deviations between the test-scans and the design file of the crowns on 3 surfaces (overall, external, and internal) using a metrology-grade, Geomagic Control X (3D Systems) and a nonmetrology-grade, Medit Link (Medit) software. The data were analyzed with Welch two-sample t-tests to compare two software for the non-inferiority of the nonmetrology-grade software with a 50 µm threshold and the potential superiority of the metrology-grade software (α = 0.05).Results: The Welch two-sample t-tests for the non-inferiority analysis showed that the differences between the nonmetrology-grade and the metrology-grade software were below the threshold of 50 µm for each surface tested (p <0.001). The differences between the two-tested software were nonsignificant for each surface analyzed when superiority was considered (p ≥.194).Conclusion: The nonmetrology-grade software performed similar to the metrology-grade software when analyzing the deviations of CAD-CAM crowns. Therefore, the nonmetrology-grade 3D analysis software may be considered for the deviation measurements of similar restorations.Clinical Significance: The trueness of crowns after fabrication may affect their fit, and 3D analysis of trueness prior to the delivery appointment with the tested nonmetrology-grade software after fabrication may facilitate potential clinical adjustments and delivery of the crowns.
Highlights
Given the rapid development of digital technologies, computer aided design-computer aided manufacturing (CAD-CAM) systems’ popularity increased significantly [1]
Dental restorations have free-form surfaces that require the superimposition of a test scan over the reference scan [9]
The CAD file of the test model is superimposed over the reference model through different methods [10]; best-fit alignment, which allows a fast and accurate analysis, is a commonly used superimposition method [11]. This method is based on iterative closest point algorithm that omits any operator-based decisions and calculates the mean distance between the corresponding points on the test scan and the reference scan by using the root mean square (RMS) [12]
Summary
Given the rapid development of digital technologies, computer aided design-computer aided manufacturing (CAD-CAM) systems’ popularity increased significantly [1]. Metrology-grade industrial software have been commonly used in dental studies to analyze the 3D state of digital impressions, scan bodies, and restorations [5,6,7,8]. These software enable accuracy analyses for quality controls after fabrication. Dental restorations have free-form surfaces that require the superimposition of a test scan over the reference scan [9] In this method, the CAD file of the test model is superimposed over the reference model through different methods [10]; best-fit alignment, which allows a fast and accurate analysis, is a commonly used superimposition method [11]. The clinician may use the virtual output to understand the location and magnitude of potential deviations with the fabricated restorations as well as to check the quality of the manufacturing process
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