# A Prospective Study on Accuracy of Computer-Based Fully Guided Versus Pilot-Guided Implant Surgery
## 4 Discussion
In 1994 at the 1 st European Workshop on Periodontics, the success criteria for implants were based on [PERSON]'s study and agreed to bone loss of less than 1.5 mm for the first year after prosthesis placement proposed [20]. In addition, [PERSON] et al. [21] reported that at 5 years, the microthreaded coronal aspect implants had 0.61 \(\pm\) 0.32 mm mean crestal bone loss; the rough-surface implants without microthread, 0.99 \(\pm\) 0.38 mm; and the machined coronal aspect implants, 1.06 \(\pm\) 0.39 mm. [PERSON] et al. [22] reported that marginal bone loss at 1-year follow-up was 1.06 mm. In this study, mean 0.5 mm marginal bone loss in the first year after surgery is successful, which may be the result of the advantage of guided surgery, which allows minimally invasive, shorter time surgery. [PERSON] et al. [23] found that free hand final drilling, results in significantly less accuracy than full sequence drilling. Compared with the freehand final drilling site preparation, a reduction of maximum deviation of 0.3 and 0.6 mm was achieved with the fully guided technique for the implant shoulder and the apex reference points, respectively. Also, fully guided surgery by [PERSON] et al. [15] showed more accurate and statistically significant results were obtained compared to partially guided surgery. The contradiction between their results and the results reported in the present study might be attributed to the study design, sample size, and type of guide support. The present study investigated tissue-supported guides compared to tooth-supported guides for [PERSON] et al. The deformation that might occur with tissue-supported guides might have masked the difference between the two groups. The present study was a split mouth design for 74 implants with true allocation and blinding during measurements while [PERSON] et al. reported retrospective data for only 46 implants with no true randomization and blinding [23]. In this study, marginal bone loss was measured using CBCT images. However, the method using the CBCT causes image quality degradation due to the metallic portion of the implant. [PERSON] et al. [24] compared the accuracy of CBCT, intraoral radiographs, and histologic analysis methods, and there was no significant difference between intraoral radiographs and CBCT in assessing bone resorption of the implant. CBCT images have the advantage of being able to evaluate the bone loss on the lingual side, although post-treatment is necessary to remove the interference, and it is particularly advantageous to identify the bone perforation around the implant [25]. With regard to the detection threshold for marginal bone loss using periapical radiographs in experimental settings, radiographic assessment using the intraoral paralleling technique seems to be accurate, resulting in a mean difference of 0.18-0.2 mm between the real and the radiographic bone level measurements [26]. The limited sample size and operator's bias can be affected as a result of this study. Therefore, further clinical studies are needed to confirm this result by randomized-controlled clinical trials with a larger sample size and evaluate the efficacy of 3D printed provisional prosthesis combined with pilot guide surgery.