# Feasibility of a 3D Surgical Guide Technique for
## 4 Discussion
A previous study regarding lower third molar surgery reported that a prolonged operation time was associated with acute postoperative complications, such as severe pain and swelling [21]. Regarding the area of the window opening, the surgical guide technique did not reduce the size compared with the conventional technique. In fact, impacted ST extraction needs preparation of an access hole to the impacted ST by drilling into the underlying bone tissue. Once exposure of the impacted ST is visible, the hole should be enlarged enough to easily luxate and remove the impacted ST. Because the size of the window opening is mainly determined by the vertical and/or transverse dimensions of the impacted ST, the result may remain unaffected by the adoption of the surgical guide technique. This study also demonstrated that the surgical guide technique reduced the amount of volume loss of material than the conventional technique did. This finding indicates that adoption of the surgical guide technique can facilitate minimally invasive surgeries for impacted ST extraction. With the aid of the surgical guide, volume loss of the material was reduced, which led to minimal trauma to the adjacent permanent tooth germs. Moreover, these factors may lead to a shortened healing period and reduce the chance of postoperative complications [22]. Interestingly, there were marked differences in the standard deviation of the volume loss of the material between the surgical guide technique and the conventional technique. This finding indicates that the surgical guide technique can reduce the difficulty of the surgery for impacted STs, regardless of the surgeons' skill level or experience. This finding is in accordance with a previous study of implant placement with a surgical guide, which demonstrated that accurate implant position reproducibility was not influenced by surgeons' experience level [23]. The study concluded that the surgical guide technique provided better results by surgeons with insufficient experience. Similarly, the effect of the surgical guide did not depend on the surgeons' skill level or experience in this study. There were some limitations to this study. First, the design was that of an in vitro study under controlled conditions and the number of participants in the study was relatively small. Next, we considered only one vertical position of impacted STs, which may have affected the degree of surgical difficulty. Additionally, other factors, such as the flap elevation and the suture procedure, were not considered which may have affected the results. Because this study was performed with 3D printed models, reproduction of gingival tissues was technically difficult. Finally, even though the 3D printed model in this study mimicked the natural anatomical structures of children, natural human bone density and strength were difficult to completely reproduce. In conclusion, we developed a 3D printed simulation model and a 3D planned surgical guide for impacted ST extraction. Within the limits of this study, the 3D planned surgical guide technique was effective for impacted ST extraction. The surgical guide technique for impacted ST extraction allows for better patient acceptance and less patient discomfort. Lastly, the technique is a more preferable alternative treatment, with excellent predictability, for inexperienced oral and maxillofacial surgeons. Conceptualization, O.H.N. and H.L. ; methodology, O.H.N., H.L., and J.-W.L. ; software, H.L. ; formal analysis, Y.K.C. and S.C.; data curation, O.H.N. and M.K.J. ; writing--original draft. O.H.N. and S.C.C. ; project administration, O.H.N. ; funding acquisition, O.H.N. This research was supported by a grant from Kyung Hee University in 2019 (KHU-20191059) and the APC was funded by a grant from Kyung Hee University in 2019 (KHU-20191059). **Acknowledgments:** The authors thank [PERSON] (Dio Ortho R&D team leader) for his time and contributions to the study. **Conflicts of Interest:** The authors declare no conflicts of interest.