Effects of Measurement Distance on Accuracy in Optical Impression with Intraoral Scanners

Recently, several reports have described that the accuracy of intraoral scanners is equal to or greater than that of conventional methods using silicone rubber impressions. However, it is unclear whether intraoral scanners are applicable to patients with more than three missing teeth or edentulous jaws. A computer numerical control coordinate-measuring machine was employed to measure the reference models as a control. Subsequently, two types of intraoral scanners, TRIOS3 (TR3) and PrimeScan (PS), were examined to estimate the trueness and precision of the distance using image analysis software. In this study, the accuracy of the new high-end model of the intraoral scanner and the popular model were examined to verify their range of application to oral implant treatment. Regarding the error in trueness, no significant differences were observed between the scanners when short distances were measured, whereas the error in TR3 was significantly larger when a long distance was measured. No significant difference in precision error was observed between the two scanners, even when long-distance scanning was performed. When measured using TR3, the errors in both trueness and precision were significantly larger when long distances were scanned. In contrast, when using PS, the error in trueness was significantly larger when long distances were scanned; however, there was no significant difference in the error in precision between long- and short-distance scanning. The results of our study suggest that the errors tend to increase with an increase in the scanned distance. In addition, these results suggest that the accuracy was equivalent between the PS and TR, when the scanning distance was short. Optical impressions obtained using an intraoral scanner could be clinically applicable to implant treatment in the case of a small number of missing teeth. A newly provided high-performance scanner might be applicable to cases with a larger number of missing teeth.