Evaluation of trueness and precision of two 
intraoral scanners and a conventional impression: 
an in vivo clinical study

Objective: To evaluate, in vivo, trueness and precision of two intraoral scanners, CEREC Omnicam (OMNI) and CEREC Primescan (PRIM), compared to a conventional impression serving as a master model.
Method and materials: Impressions were performed for seven participants. For each participant, conventional polyvinylsiloxane impression and digital impressions using two intraoral scanners, OMNI (software 4.6; CEREC ORTHO Protocol) and PRIM (10 digital impressions per participant, per scanner), were made. Conventional impression was digitized with a laboratory scanner (INEOS X5), and used as reference model. .STL files were superimposed with software (Geomagic Control X) using the tools Initial Alignment and Best Fit Alignment, and trueness and precision were evaluated. Statistical evaluation was performed with Shapiro-Wilk and Mann-Whitney tests (P < .05).
Results: Total mean trueness for the OMNI system was 56.45 ± 7.80 µm, and 47.29 ± 5.47 µm for the PRIM system. Regarding precision, values from the OMNI system were 42.47 ± 6.91 µm and from the PRIM system 21.86 ± 4.40 µm. PRIM presented better results for both trueness (P = .000) and precision (P = .000) when compared to OMNI.
Conclusions: PRIM provided a better combination of trueness and precision than its predecessor OMNI. However, both PRIM and OMNI performed acceptably when performing indirect restorations, according to the current acceptable thresholds, considering both trueness and precision. Clinical implications: Full-arch impressions with Primescan presented more precision and trueness than Omnicam; however, compared to previous reported values of conventional impressions, they still presented lower accuracy.