## 4 Discussions
These factors include the study design, the quality of the CBCT image and surface scanning data, the file conversion and adaptability of the radiographic data and surface scanning data, the software program, the surgical guide design and fabrication, structures that support the surgical template (mucosa/tooth/bone) or adaptability of the surgical guide on the surgical site, the surgical technique (open flap/flapless), the tolerance between mechanical components related to the fit of the cylindrical sleeve on the surgical guide, implant characteristics, and the experience of the operator [28; 29; 30; 31]. Therefore, in this study, we used various techniques to minimize the overall effect of the confounding factors as much as possible. The same guide design, drill protocol, surgeon, and type of surgical models were used to minimize the confounding factors. To reduce the drilling memorization of the surgeon, different printed guides were used at random for the implant placement. This study was conducted as an in vitro study because in vitro studies allow for more accurate measurements than clinical studies as they provide a better visual field and access for controlling the axis of the drilling instruments and a lack of patient movement as well as the absence of saliva, blood, and soft tissues [32]. According to a prior study, the accuracy of static surgical guides was affected by the stability of the surgical guide during the implant bed preparation and implant insertion processes. According to [PERSON] et al., the greatest deviation was found when the stability of the surgical guide could not be achieved [30]. In a study conducted by [PERSON], tooth-supported guides with a single-tooth edentulous space represented the most accurate result [33]. Another study evaluated whether the type and number of teeth supporting the surgical guide could affect the deviation of the static surgical guide or not. It was shown that the accuracy of the surgical guides supported by three posterior teeth was not different to that of full-arch-supported guides [34]. Thus, a single-tooth edentulous space model with a three posterior teeth-supported guide design was used in this study. Regarding the printing technique, a surgical guide manufactured by the additive technique \"3D printing\" and the subtractive technique \"milling\" showed no statistically significant difference between them. Even so, whilst producing comparable accuracy for implant-guided surgery, a surgical guide fabricated by 3D printers could be a substitution. This is due to their ease of production and the diminution of laboratory time and materials; this also increases the cost-effectiveness [35]. Therefore, a printed surgical guide was used for this study. Implant characteristics are an important factor influencing the accuracy. In this study, bone level taper (BLT) implants were used because past studies have shown that implant design characteristics affected the deviation of the implant position. This was because the different geometry of osteotomy prepared for the different implant macro-designs affected the deviation in the implant position. There are three different main types of implant characteristics (implant macro-designs): soft tissue level (TL), bone level (BL), and bone level taper (BLT). The insertion geometry of BLT implants was tapered whereas the osteotomy of TL and BL was parallel. As a result, the three-dimensional deviation values of the TL and BL implant positions were significantly less accurate than the BLT implants [36]. For the implant insertion step, the guided implant insertion technique was used in this study due to the results of previous studies that reported that a guided implant placement represented a significantly better accuracy than a freehand placement [11; 37]. In terms of the experience of the operator, an in vitro study conducted by [PERSON] et al. [27] found no significant differences in the angular and linear deviations at the entry and apical points between the experienced and inexperienced operator groups.