Trueness of intraoral scanners: Its impact on the trueness and marginal and internal discrepancies of fabricated crowns (A comparative in vitro study)

Abstract

Background Digital dentistry is constantly growing, and the availability of IOSs has significantly increased in recent years. Numerous studies have investigated the accuracy of different intraoral scanners; however, limited evidence is available concerning the effects of the accuracy of IOSs on the fit of zirconia crowns. This study aimed to assess and compare the accuracy of four intraoral scanners in terms of trueness and to analyse its impact on the trueness, as well as the internal and marginal adaptations of zirconia crowns fabricated from these scanners. Methods Ten sound maxillary left first premolar teeth prepared to receive zirconia crowns were used in this research. First, the teeth were scanned with a lab scanner (inEos X5, Dentsply Sirona) as a reference. Each tooth was scanned serially with the following IOSs: PrimerScan, Medit i700 wireless, TRIOS5, and Helios 600. Five monolithic zirconia crowns were fabricated for each tooth, one crown per scanner. The trueness of the tested scanners was determined by the superposition of each IOS's scanned data with the reference scanner's scanned data by metrology software (Geomagic Control X) and presented as a colour-coded map. The accuracy of the fabricated zirconia restoration was assessed by superimposing the scanned data of the intaglio of the crown fabricated from each intraoral scanner with the intaglio of the crown fabricated from the lab scanner (reference crown). The internal and marginal gaps of the crowns were then measured via the silicone replica technique, followed by a 3D evaluation of the replica by the software. The data were analysed using one-way ANOVA and Tukey's HSD multiple comparisons test. Pearson's correlation test assessed the relationships between the trueness of the IOSs and the trueness, internal fit, and marginal fit of the fabricated crowns. Results The tested IOSs revealed significant differences in trueness (p < 0.05). Primescan, Medit i700, and their corresponding crowns showed the highest trueness among the groups, with no significant differences between them (p > 0.05), while Helios 600 and its corresponding crowns showed the lowest trueness. The lowest internal and marginal gaps were observed in the crowns fabricated from Primescan and Medit i700, whereas the highest marginal and internal gaps were observed in the crowns fabricated from Helios 600. A moderately positive correlation was found between the tested IOSs' trueness and the fabricated restorations’ marginal and internal adaptations. Conclusions There were significant differences in trueness between the IOSs, which substantially impacted the trueness and fitness of the produced crowns. Trial registration: The permission for this study was given by the research ethics committee of the College of Dentistry, University of Baghdad. Ref.number: 811/2023.