## 4 Discussion
Previous studies have found that the accuracy when using different intraoral scanner systems varies with factors such as the familiarity of the operator, learning curve, ergonomic design of the handheld camera, design of hardware and software, and the research method and design [31]. Therefore, future comparisons of the accuracy of scanners for digital implant impressions will require the establishment of a standardized research model [31]. The T500 device is a laboratory scanner, and unlike intraoral scanners that acquire small images using a small scanner head and stitch these images together to obtain the entire image, the overall accuracy is higher for a laboratory scanner because it obtains a whole image of the entire area and scans by rotating the model table [32]. The present study found that the accuracy of the T500 scanner was higher when the flat surface of the ISB facing the buccal direction in both the prealignment and postalignment data. The model table was scanned within the limit that allowed rotation, so the flat surface of the ISB faced the buccal direction, and the scan accessibility of the flat surface was higher, which would have contributed to increased trueness. This was an in vitro study, and real clinical scanning procedures are further influenced by patient movements (e.g., breathing), humidity, and the restricted intraoral space [33]. Therefore, future studies need to reproduce the in vivo environment of the oral cavity. Additionally, the present study analyzed the trueness by matching a reference file and the test file using a best-fit algorithm to obtain RMSE values. This method presents negative and positive deviations for each region as a color map in the scan file in three dimensions, and provides an average deviation value for the entire area as an RMSE value; however, a limitation is that it does not indicate the accuracy of the actual implant position. Future studies should, therefore, evaluate linear and angular discrepancies in the positions of implant fixtures, and also the final restorations in order to assess clinically significant differences. Moreover, the ISBs used in this study had a cylindrical shape with a flat surface and were made of polyether ether ketone. Since clinicians use various types of ISBs in clinical practice, it is necessary to conduct additional research into the effects of different materials and types of ISBs [22]. Finally, since scanning results are also affected by the individual's experience, it is also necessary to investigate outcomes for several researchers to determine the intra- and interoperator reliabilities [34]. Previous studies on the accuracy of digital implant impressions have mainly involved dedentulous cases or multiple cases [16; 17; 18; 19; 20; 21; 22; 23]. In contrast, this study focused on partial-arch models with single implants in the presence of adjacent teeth. In particular, the effect of ISB orientation and the scanning method was examined. Clinically, the operator must invest additional time and effort to completely scan all areas, including the proximal surface of the ISB. The results of this study indicate that when performing oral scanning, the operator should connect the ISB so that its flat surface faces the buccal direction, and should try to scan the full area. It was also found that it is advantageous to connect the ISBs buccally when using a tabletop scanner.