## 4 Discussion  
Previous studies compared the accuracy of implant positions (coincidence between preoperative and postoperative positions) between dynamic navigation surgery, static guided surgery and freehand surgery. Most of them concluded that dynamic navigation surgery could enable accurate implant placement, with similar accuracy to static guided surgery and greater accuracy than freehand surgery [3; 6; 7; 8; 9; 10; 11; 12; 13]. Current systematic reviews and meta-analyses have also noted that dynamic navigation surgery achieved a clinically acceptable accuracy, although heterogeneity must be taken into account [24; 25; 26; 27]. The mean values of the deviations shown in Table 2 fell into the intermediate values of previous reports. Similarly to these previous studies, this study compared preoperative and postoperative implant positions to evaluate the accuracy and the practicality of our system. In addition, the effects of different surgical procedures (flapless and open-flap surgeries) and surgeons' experiences on the accuracy of implantation were also assessed. To define the number of subjects, we calculated the sample size based on the results of the present study; these were 71 (angular deviations), 49 (apical deviations), 67 (coronal deviations) and \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Angular Deviations (\(\lx@math@degree\))** & **Apical Deviation (mm)** & **Coronal Deviation (mm)** & **Vertical Deviation (mm)** \\ Well-experienced & 2.76 (2.38–3.22) & 0.93 (0.71–1.12) & 0.61 (0.51–0.88) & 0.71 (0.61–0.88) \\ Less-experienced & 3.29 (2.35–3.62) & 0.92 (0.76–1.05) & 1.15 (0.62–1.63) & 0.71 (0.63–0.89) \\ \(p\) value & 0.11 & 0.96 & \textless{}0.01 & 0.95 \\ Effect size (r) & 0.19 & \(-\)0.004 & 0.33 & 0.007 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistical comparisons between more experienced and less experienced surgeons (Mann–Whitney U test). \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Angular Deviations (\(\lx@math@degree\))** & **Apical Deviation (mm)** & **Coronal Deviation (mm)** & **Vertical Deviation (mm)** \\ \hline Flapless surgery & 2.92 (2.37–3.41) & 0.93 (0.72–1.11) & 0.68 (0.56–1.21) & 0.72 (0.61–0.88) \\ \hline Open-flap surgery & 3.34 (2.64–3.65) & 1.37 (0.90–1.88) & 1.27 (0.72–1.67) & 0.67 (0.51–0.90) \\ \hline \hline \(p\) value & 0.06 & 0.01 & \textless{}0.05 & 0.70 \\ \hline Effect size (r) & 0.23 & 0.36 & 0.30 & \textless{}0.04 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Statistical comparisons between flapless surgery and open-flap surgery (Mann–Whitney U test). 217 (vertical deviations). Although previous clinical studies which evaluated the accuracy of a dynamic navigation system had a sample size between 20 and 231 [6; 9; 10; 11; 12; 13; 16], which seemed to be wide-ranging, there was, unfortunately, an insufficient number of patients for formal statistical analysis in this study. Effect sizes were calculated to compensate for this insufficient sample size and to evaluate validity; medium effect sizes were confirmed in our statistical comparisons, which showed significant differences and are displayed in Tables 3 and 4. However, it was decided that this study was conducted as a pilot study, due to the insufficient sample size. Prior to the discussion of our results, it is necessary to mention the difference between previous dynamic navigation systems and the newly developed one. The dynamic navigation systems in previous studies used visible wavelength light for their optical cameras. The new system in this study uses a conventional infrared optical camera, as in some previous studies [28; 29; 30]. Dynamic navigation systems using an infrared optical camera for tracking have been known to be stable regardless of the environment, especially with respect to brightness in the surgical room, and have been widely used because of their compact and simple system. The system with an infrared optical camera went off-patent in 2018 and the development of this new system was undertaken.