# Feasibility of a 3D Surgical Guide Technique for
## 4 Discussion  
3D printing refers to rapid prototyping manufacturing technology that makes products by adding materials layer by layer. Contrary to the use of inks in traditional printers, 3D printers are built with powders using the blueprints made by CAD software [13; 14]. Owing to the advances in 3D printing, the surgical guide technique, used in dentistry, has been a remarkable success. With its patient-customizable and reproducible property, it has made dental surgery easier and more predictable with reduced risk [15; 16]. The surgical guide technique is also promising for impacted ST extraction. The results of this study showed that less time was required for completing ST extraction using the surgical guide technique than the conventional technique. The guide technique simplified the whole surgery procedure, resulting in shorter operation time. This may be because the guide technique helped the surgeons understand the precise 3D localization of STs, and provided direct access which increased the surgeons' confidence in performing the surgery and positively affected the operation time. A previous clinical study of eight patients with impacted STs revealed that the average operation time of the surgical guide technique for impacted ST extraction was approximately 16 min, which was approximately 4 min shorter than that of the conventional technique [17]. In the present study, the surgical guide technique needed approximately 2 min, whereas the conventional technique needed approximately 3.5 min. This difference may be related to the study design. Because the previous study was designed based on patient data, the results were greater than those obtained in this study. This study was designed under controlled conditions without the need for some clinical procedures, such as the flap elevation procedure for impacted ST and the suture procedure after impacted ST extraction. Only patients with deeply impacted ST were included in the previous study and large amounts of osteotomy were conducted to extract impacted ST. Thus, degrees of surgical difficulty \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Mean (sec)** & **SD (sec)** & **Z** & \(p\) \\ \hline Conventional technique & 213.65 & 167.45 & & \\ Surgical guide technique & 114.76 & 42.87 & & \\ \hline \multicolumn{5}{c}{Wilcoxon signed-rank test, \({}^{1}\)\(p<0.05\).} \\ \end{tabular}
\end{table} 
Table 1: Comparison of the time required for supernumerary tooth extraction. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Mean (sec)** & **SD (sec)** & **Z** & \(p\) \\ \hline
**Area of window opening (mm\({}^{2}\))** & & & & \\ Conventional technique & 48.10 & 9.44 & & \\ Surgical guide technique & 45.90 & 8.17 & & \\
**Volume of material removed (mm\({}^{3}\))** & & & & \\ Conventional technique & 121.65 & 43.69 & & \\ Surgical guide technique & 99.12 & 17.88 & & \\ \hline \hline \multicolumn{5}{c}{Wilcoxon signed-rank test, \({}^{1}\)\(p<0.05\).} \\ \end{tabular}
\end{table} 
Table 2: Required area of the window opening and the volume of the material removed for supernumerary tooth extraction. could be responsible for the different results. Moreover, the physical strength differences between human bone tissue and our model material should not be ignored. This study demonstrated that the surgical technique allowed reduced operation times for impacted ST removal. If general anesthesia is planned for impacted ST extraction, the guide technique will reduce the incidence of perioperative complications, as prolonged anesthesia is a predisposing factor of perioperative adverse events [18]. Furthermore, the guide technique can be used for impacted ST extraction also with local anesthesia. Reduced operation time can positively affect children's behavior in the dental setting. Prolonged dental treatment is correlated with negative behaviors in children [19; 20]. In addition, reduced operation time can also decrease the chances of postoperative complications.