Influence of intraoral conditions on the accuracy of full-arch scans by Cerec Primescan AC: an in vitro and in vivo comparison

Aim: To determine the effect of intraoral conditions on the accuracy of digital full-arch scans. Materials and methods: A reference bar was used for the in vivo and in vitro parts of the present study. For the in vitro part (PAT-vitro), the bar was fixed to connect the maxillary second molars on the patient's resin model. The same reference bar was fixed in a similar position intraorally for the in vivo testing (PAT-vivo). Model and patient were digitized using an intraoral scanner (Cerec Primescan AC, N = 40, n [PAT-vitro] = 20, n [PAT-vivo] = 20). Datasets were exported and metrically analyzed (Geomagic Control 2015) to determine the 3D linear and angular distortions in all three coordinate axes of the datasets with reference to the bar. Normality of the data distribution was tested using the Kolmogorov-Smirnov and Shapiro-Wilk tests. Homogeneity of the variances was tested using the Levene test. Statistically significant differences for all measured parameters in view of trueness were determined using the two-sample t test, and in view of precision using the two-sample Kolmogorov-Smirnov test. Results: The PAT-vivo group showed significantly higher trueness for most of the measured linear and angular distortion parameters than the PAT-vitro group. Regarding precision, the PAT-vitro group showed significantly better values for most of the measured linear and angular distortion parameters than the PAT-vivo group. Conclusions: Within the limitations of the present study, Cerec Primescan AC leads to comparable accuracy parameters when applied in vivo and in vitro. The reproducibility (precision) was higher when scans were performed in vitro. Due to the high trueness, the system seems to be a valid tool to obtain digital full-arch datasets in vivo with comparable accuracy to in vitro tests.