The effect of tooth size on the dimensional accuracy of three types of intraoral scanners

Background: Digital impressions by intraoral scanning (IOS) have become an increasingly popular alternative to conventional impressions. From previous studies, scanning systems, scanner acquisition process, and powder application do not appear to be major influencing factors on accuracy of IOS. Studies revealed multiple variables that can influence accuracy of IOS, such as span length and surface morphology. There is evidence that smooth surfaces are easier to capture by light scanners than irregular and corrugated surfaces. Another influential factor affecting scan results is tooth dimensions that previous studies have not studied. This laboratory study aimed to evaluate the accuracy of IOS based on effect of tooth size on dimensional accuracy recorded by three types of scanners. Materials and methods: Samples of this study include two gypsum and ceramic dies from canine and molar acrylic teeth. All-ceramic restoration standard guidelines have prepared samples. For gypsum dies, digital impressions were made by an Open Technology scanner, and then zirconia samples were manufactured by CAD / CAM technology. Each ceramic piece was scanned ten times by three IOSs. The reference STL file was considered CAD, and the STL files obtained from scanners were considered Mesh. Mesh was then superimposed using the "best-fit" protocol on the reference file. Shapiro-Wilk and paired t-test were used to find the data discrepancies. Results: The lowest and highest values and mean of precision and trueness in molar teeth were observed in Cerec Omnicam. The highest value and mean precision in molar teeth were observed in Open Technology. There were no significant differences within the four types of scanners in canine teeth in the mean of precision and trueness. Conclusion: Based on the findings of this study, it seems that tooth size does not affect the accuracy of these types of scanners in terms of accuracy and repeatability.