###### Abstract  
Accuracy of implant position reproduction according to various types of scanners, implant placement depths, and tooth positions are unknown. The purpose of this study was to compare the accuracy of implant position reproduction for differences in the exposed length of the implant scan body according to scanner type and tooth position. Implants were placed at the positions of the lateral incisor, first premolar, and first molar in the study model at the bone level and submerged 1.5 mm, 3.0 mm, 4.5 mm, and 6.0 mm. The completed models were scanned with one type of tabletop scanner and three types of intraoral scanners (TRIO 3, 1500, and CS3600). A matching process was performed for all scan data to superimpose abutment library data on the scan body, and the root mean square errors were analyzed in three dimensions to evaluate the position reproducibility of the replaced abutment library. In the trueness analysis, the error increased rapidly for an implant placement depth of 4.5 mm, and was largest for a submersion of 6.0 mm. The precision analysis confirmed that the error increased for depths of at least 3.0 mm. The analysis by position identified that the accuracy was lowest for an implant placed at the position of the lateral incisor. These findings indicate that special care is required when making an impression of a deep implant with an optical scanner. digital impression; implant scan body; intraoral scanner +
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to the success of implant rehabilitation [10]. An inaccurate prosthesis will result in tensile, compressive, and bending forces between the implant and the prosthesis, and these stresses can remain even after the prosthesis has functioned for several years [11; 12; 13]. The increase in the complication rate with the occlusal load may be greater for implant restorations than for tooth-born restorations [14; 15]. The first computer-aided design (CAD)/computer-aided manufacturing technology was introduced in the early 1980s, and the use of optical scanning equipment has become very widespread in recent years. Digital impressions and restorations can be made by using an intraoral scanner to digitally acquire images of teeth and surrounding tissues directly in the oral cavity, thereby replacing existing impressions (alginic acid, polyvinyl siloxane, or polyether) and eliminating errors that may occur when using other methods [16; 17]. Consequently, fabrication of various types of implant prosthesis using a digital method has become common [18; 19; 20]. In the workflow of manufacturing an implant prosthesis, it became possible to acquire digital data and fabricate a prosthesis by capturing an implant scan body (ISB) connected to the implant fixture, surrounding teeth, and soft tissue in three dimensions using an intraoral scanner [21; 22]. The ISB is attached to the implant fixture placed in the oral cavity, and when it is scanned together with the surrounding structures, information such as the implant placement position and orientation that is not visible from the outside can be stored as a digital impression [23]. After loading the obtained digital impression into CAD software, the virtual ISB library stored in the software is matched with the previously scanned ISB to store the location. Small inaccuracies may occur during this process [24]. In particular, a low scan quality of the ISB may result in inaccuracies occurring during the registration process of the library of the ISB, producing errors in the implant fixture position of the virtual model [24; 25]. Various studies have investigated the reproducibility of the implant position in an optical scan made using an ISB. It has been reported that the accuracy of implant position reproduction is affected by the implant angle [17; 26], distance between implants [27], scan body design [28], and scan body material [29].