Comparison of Accuracy Between a Conventional and Two Digital Intraoral Impression Techniques

Purpose: To compare the accuracy (ie, precision and trueness) of full-arch impressions fabricated using either a conventional polyvinyl siloxane (PVS) material or one of two intraoral optical scanners. Materials and Methods: Full-arch impressions of a reference model were obtained using addition silicone impression material (Aquasil Ultra; Dentsply Caulk) and two optical scanners (Trios, 3Shape, and CEREC Omnicam, Sirona). Surface matching software (Geomagic Control, 3D Systems) was used to superimpose the scans within groups to determine the mean deviations in precision and trueness (mu m) between the scans, which were calculated for each group and compared statistically using one-way analysis of variance with post hoc Bonferroni (trueness) and Games-Howell (precision) tests (IBM SPSS ver 24, IBM UK). Qualitative analysis was also carried out from three-dimensional maps of differences between scans. Results: Means and standard deviations (SD) of deviations in precision for conventional, Trios, and Omnicam groups were 21.7 (+/- 5.4), 49.9 (+/- 18.3), and 36.5 (+/- 11.12) mu m, respectively. Means and SDs for deviations in trueness were 24.3 (+/- 5.7), 87.1 (+/- 7.9), and 80.3 (+/- 12.1) mu m, respectively. The conventional impression showed statistically significantly improved mean precision (P < .006) and mean trueness (P < .001) compared to both digital impression procedures. There were no statistically significant differences in precision (P = .153) or trueness (P = .757) between the digital impressions. The qualitative analysis revealed local deviations along the palatal surfaces of the molars and incisal edges of the anterior teeth of < 100 mu m. Conclusion: Conventional full-arch PVS impressions exhibited improved mean accuracy compared to two direct optical scanners. No significant differences were found between the two digital impression methods.