Surface trueness and precision of interim restorations fabricated by digital light processing and CAD-CAM milling systems

Statement of problem. The development of digital dental technologies has enabled clinicians to use additive and subtractive manufacturing techniques to fabricate interim restorations. However, knowledge of the trueness and precision of such restorations fabricated using digital light processing (DLP) and computer-aided design and computer-aided manufacturing (CAD-CAM) methods is limited.Purpose. The purpose of this in vitro study was to assess and compare the accuracy of interim crowns fabricated using DLP and CAD-CAM methods.Material and methods. A typodont mandibular first molar was prepared for a ceramic crown, and a digital scan (Medit T500) was obtained to design interim crowns by using the CAD software program. The CAD data were designated as the reference data. A total of 20 crowns were fabricated by DLP and CAD-CAM technology. The fabricated interim crowns were further scanned using a laboratory scanner and were superimposed with the CAD data by using a 3-dimensional (3D) point cloud assessing software program (CloudCompare) for the evaluation of trueness and precision. Root mean square values (RMS) were obtained for the evaluation of discrepancies. The Student t test was used to compare data as the Shapiro-Wilk test confirmed the normal distribution.Results. RMS values for the trueness values of the external and intaglio surfaces of the 3D printed and milled interim crown displayed no statistically significant differences (P>.05). Precision for the external surface reported significance (P<.05), whereas that for the intaglio surface reported no significance (P>.05).Conclusions. The accuracy of interim crowns fabricated by using DLP was comparable with that of milled crowns. Both manufacturing systems produced a true reproduction of the CAD. As for precision, the external surface of the DLP interim crown was statistically different from that of the milled group as it relates to the CAD.