###### Abstract  
This study aimed to determine the influence of the healing abutment (HA), placed at the implant placement site, on the accuracy of intraoral scanning and buccal bite registration in quadrant maxillary and mandibular models when using three types of intraoral scanner (IOS) and elucidate the distribution of arch distortion. Six experimental groups based on whether the HA was connected and the location of missing teeth were digitized using one laboratory scanner (Identica T500) and three IOSs (Trios 3, CS600, and i500). Three-way ANOVA was used to analyze the effects of the scanner, location and number of missing teeth, and HA using Tukey investigation analyses for multiple comparisons (\(\alpha\) = 0.05). Linear distances between hemispheres from the upper and lower arches were analyzed using the Jonckheere-Terpstra trend test to investigate the tendency of distortion from anterior to posterior tooth positions (\(\alpha\) = 0.05). The accuracy of IOSs in groups with HAs was found significantly more accurate than groups without HAs. There was a significant trend in distortion from anterior to posterior tooth positions when using the Trios 3 and i500 IOSs. The scanning accuracy was affected by the presence of an HA, and the distortion along with the arch span may vary with the IOS utilized. healing abutment; intraoral scanner; jaw relation record; implant-supported prosthodomics; digital dentistry +
Footnote †: journal: Medical  
process, whereas the digital magnifications and quality-control tools of digital impression devices reveal visible areas of defects so as to allow clinicians to rescan and correct those areas immediately without needing to restart the entire process like in the conventional procedures [6]. Additionally, the performance of digital impressions on the margin or internals of fixed restorations is better than for conventional techniques [7]. However, there are still concerns about distortion in digital impressions obtained using different devices and under various intraoral conditions [8; 9]. Numerous researchers have recently made efforts to determine the accuracy of IOSs. Several studies have evaluated the trueness and precision of different IOSs and revealed that their accuracy is at least as good as for conventional impressions in short-span areas [10; 11; 12]. However, the trueness and precision of IOSs are lower for the full arch than in short-span areas [13]. Additionally, the accuracy of IOSs was found to decrease with increasing distance between the implant scan bodies [14]. Several studies have found it difficult for an IOS to capture accurate impressions for long-span restorations [15; 16]. Low accuracy results were observed in long distance scan and rather high accuracy in short distance, thus implying the scanning distance could be an impact factor to the accuracy of the scan [17]. These results revealed that the accuracy of IOS devices may be related to the length of scanning target and likely to decrease with the extension of the arch span. This may be due to the influences of the joints on errors during the stitching process when images overlap over a curved span. One of the important factors that can affect the accuracy of intraoral scanning data is the landmark structure in the region of interest. The landmark is important for accurate alignment when registering the bite during the oral scanning process. A recent study found that the trueness and precision of intraoral scanning were improved if an artificial landmark in the long dedentulous area was used [18]. Errors may occur when aligning images during scanning by an IOS if the digitized items are too simple [19], with the errors being lower when complex geometric items are added [20]. Another recent study found that the use of auxiliary geometric structures can enhance the outcomes of digital impressions of the dedentulous maxilla [21]. Implant placement and prosthesis production are performed in an edentulous area where a tooth is missing.