Accuracy of Mechanical Digitizing with a CAD/CAM System for Fixed Restorations

Purpose: Most research on the accuracy of dental computer-aided design/manufacturing (CAD/CAM) systems focuses on the marginal gap. A detailed analysis of the various components of CAD/CAM systems (digitizer, software, and milling machine) using this approach is nearly impossible. The purpose of this study was to determine the accuracy of the manual mechanical digitizer of the Precident-DCS system. Materials and Methods: Gauge blocks were aligned to the coordinate planes of the digitizer to determine the point and length measurement uncertainty. The values for each measuring point were compared for statistical differences concerning first versus second operator, pressure, and mode of sensing using analysis of variance. The measurement uncertainty was given by 95th percentiles. Results: The mean one-dimensional point measurement uncertainty in the Y direction was 11 µm for the first, 8 µm for the second, and 37 µm for both operators. The three-dimensional point measurement uncertainty in the Y direction was 10 µm for the first, 33 µm for the second, and 60 µm for both operators. The point measurement uncertainty was significantly influenced by the pressure during sensing and by the operator as well. There were significant differences between the first and second recordings. The length measurement uncertainty in the Y direction for a gauge block of 20 mm was 52 µm for both operators. Conclusion: The reliability of the manually guided Precident-DCS digitizer is limited because of the significant influence of the operator and the mode of sensing (one or three dimensional). Compared with an automatic digitizing system, the measurement uncertainty of the manually guided digitizer exceeds the values published in the literature.