## 4 Discussion  
Accurate prosthetically guided implant placement is critical to achieve medium- and long-term therapeutic success. However, the procedure is poorly predictable and highly operator-dependent if performed without any appliances that guide implant insertion. A randomised controlled trial conducted by [PERSON] et al. analyzed if the surgeon's experience affected the accuracy of the dental implant procedures, concluding that an experienced surgeon tended to perform more accurate placement in the bucco-lingual direction when compared to the novice group [22]. Our study was conducted with the aim of evaluating any differences in terms of effective implant placement between the digital planning, performed in the preoperative planning, and the in vivo implant placement. To conduct the congruence analysis, three measurements on CBCT scans were selected with the aim of evaluating the implant position in the three dimensions of the alveolar process. The results of our study showed that computer-guided implant surgery in the esthetic area had an optimal precision because it allowed an implant placement with a minimal deviation of the parameters considered in this study to three dimensionally evaluate and compare the virtual and the real position of the implant. Indeed, the differences between the preoperative planning and the implant placement results were statistically significant for two parameters in both groups: the mean differences in the implant axis were 1.04\({}^{\circ}\) in group 1 and 1.18\({}^{\circ}\) in group 2, while the mean differences in the mesiodistal deviation at implant apex were 0.56 mm in group 1 and 0.53 mm in group 2. Nevertheless, despite the statistical significance, the size of these differences seems to have a very low clinical relevance. Furthermore, the measurements were also taken at the level of the implant apex, ensuring that the placement is even more representative. In addition, the different timing of implant insertion (immediate or delayed) had no influence on the consistency between preoperative digital planning and in vivo placement (group 1 vs. group 2). The only statistically significant mean difference between the groups was for mesiodistal deviation at implant head. This could be explained by the lower amount of bone available to stabilise the implant in group 1 compared to group 2. Since the implant stabilised mainly in the apical portion, there may be less primary implant stability and it is possible that the tightening of the healing screw alone may have caused this difference. The results of a randomised control trial conducted by [PERSON] et al. demonstrated that computer-guided implant placement was more accurate if compared with freehand implant placement and for these reasons this technique should be preferred by clinicians [23]. Our findings were consistent with this study, indicating that the computer-guided implant surgery is accurate and predictable. Figure 3: Comparison of mesiodistal deviation with adjacent teeth on CBCT scans performed after implant surgery to verify the congruence of implant placement. (**a**) Implant position after implant surgery in coronal projection; (**b**) mesiodistal deviation of the implant after computer-guided surgical insertion with adjacent teeth at implant axis in axial projection; (**c**) mesiodistal deviation of the implant after computer-guided surgical insertion with adjacent teeth at implant head in axial projection. Moreover, computer-guided implant surgery decreases the invasiveness and morbidity of the procedure, especially in cases of flapless technique, as well as postoperative pain [24]. An RCT study by [PERSON] et al. showed that flapless computer-guided implant placement is minimally invasive and has a more favourable impact on patients than classic open-flap surgery, as assessed by a visual analogue scale (VAS) [25]. Another advantage of performing preoperative digital planning for computer-guided surgery is the preliminary assessment of bone bioavailability at the implant insertion site.