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Aims: The objective of this study was to compare the precision and trueness of full-arch impressions using either a conventional polyvinylsiloxane (PVS) material or 2 intraoral optical scanners. Methods: Full arch impressions were obtained of a reference model using addition silicone impression material (Aquasil Ultra; Dentsply Caulk, Delaware, USA) and two optical scanners (Trios, 3Shape, Copenhagen, Denmark and CEREC Omnicam, Sirona, Wals, Austria). Surface matching software (Geomagic® Control™, 3D Systems©, Rock Hill, SC, USA) was used to superimpose the scans within groups in order to determine the mean deviations (μm) between the scans. The overall mean precision and trueness for each group was calculated 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 Ltd, Portsmouth, England). Qualitative analysis was also carried out from three-dimensional maps of differences between scans. Results: Mean and standard deviations (SD) of precision for conventional, Trios and Omnicam groups were 21.7 (±5.4), 49.9 (±18.3), and 36.5 (±11.12), respectively. Mean and standard deviations (SD) for trueness were 24.3 (±5.7), 87.1 (±7.9), and 80.3 (±12.1) respectively. The conventional impression showed statistically significant 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=0.153) or trueness (P=0.757) between the digital impressions. The qualitative analysis revealed local deviations along the palatal surfaces of the molars and incisal edges of the anterior teeth in the order of <100μm. Conclusion: Conventional full-arch PVS impressions exhibited improved mean accuracy compared to 2 direct optical scanners. No significant differences were found between the two digital impression methods.

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