The Impact of Scan Spans on the Accuracy of Three Intraoral Scanners: A Comparative Study

Objectives: The aim of this study was to evaluate and compare the accuracy, encompassing both trueness and precision, of intraoral scanners (IOSs) across different scan spans. It aims to determine whether the length of the scan span impacts the accuracy of both intraoral and desktop scanners, and whether there exist notable variations in accuracy and reliability among three IOSs. Methods: Three Plaster models representing different spans (full arch, half arch, and three teeth) were obtained from silicone impressions of a mandibular typodont. An industrial scanner (Ceramill 600 plus) captured reference digital models of these plaster models. Subsequently, the same plaster models were scanned using three IOS (Trios 3, Helios 600, Heron 3Disc) to obtain 90 test digital models. Professional reverse engineering software Geomagic control x was employed for processing and analysis. Differences between the reference and test models were evaluated using the root mean square value. Statistical analysis was conducted using two-way analysis of variance (ANOVA) and Shapiro-Wilk tests. Results: The precision and accuracy of IOSs can be assessed in terms of trueness and precision. Trueness measures how closely the digital model matches the actual scanned object, while precision gauges the consistency of digital models derived from multiple scans of the same object. To evaluate trueness, the root mean square (RMS) value was computed for each set of models in comparison to a reference model. Statistical analyses, including two-way analysis of variance (ANOVA) and subsequent post-hoc tests, were conducted to detect significant differences among scan types and durations. Precision assessment involved analyzing RMS values, with Levene's test assessing variance consistency across groups. The significance level was set at 5%. Both trueness and precision showed significant differences across scan spans (p < 0.001) and scanner types (p < 0.001), highlighting the impact of scanner choice and scan duration on accuracy. Conclusions: The study explored the impact of scan span and scanner type on the accuracy of intraoral scanners in dental applications. It found significant differences in accuracy across various scan spans and among different scanners, highlighting the influence of both factors. Additionally, smaller scan spans tended to produce more precise outcomes, and Trios demonstrated superior precision compared to other scanner types. These findings emphasize the importance of considering both scan span and scanner type for optimizing scanning accuracy in dental practice. KEYWORDS: CADCAM; Dental Arch/diagnostic imaging; Dental Impression Technique; Imaging/Three-Dimensional; Models/Dental