## 3 Discussion
Recently, direct reconstruction of maxillofacial defects has been performed using patient-specific 3D-printed implants using medical data and 3D printing techniques [19]. These methods also report satisfactory results and have the advantages of not having to consider additional surgery and donor site morbidities such as the use of free flaps and gait disturbance. This method may be useful for reconstruction of the jaw bone, but the reconstruction of hard and soft tissues requires additional surgery because of the soft tissue coverage. In addition, its use for the restoration of teeth for chewing,which is the main function of the jaw, has limitations. Even if the teeth are restored, infection of the titanium implant by the implant teeth may lead to infection of the entire implant. This is a big problem and may require the entire implant to be removed. On the other hand, reconstruction of jaw defects using hard and soft tissue free flaps and of the donor site using a 3D-printed implant has the following advantages over direct reconstruction. First, as in this case, it can be used in complex defect cases, including soft tissue defects. Reconstruction of complex defects, such as in this case, requires hard and additional soft tissue at the same time during the operation. Second, postoperative complications can be prevented. In the case of oral defects, various masticatory muscles and facial expression muscles exist and move for various roles such as emotion expression, mastication, and pronunciation. The oral cavity also contains a variety of microbes due to saliva and external foods, and is more susceptible to infection than other body parts [20]. For this reason, when defects in the oral cavity are directly reconstructed with 3D-printed titanium implants and teeth, various complications may occur, such as exposure of the implant site due to frequent contact, infection, and loosening of the screw fixing the implant to the surrounding bone tissue due to frequent movement. On the other hand, the iliac bone is relatively stable in position and movement due to direct ossification with the remaining bone. Third, it is easy to recover masticatory function. In the direct reconstruction method, chewing function can be restored through a predesigned titanium implant. However, as discussed above, there is a disadvantage in that it is more vulnerable to infection and it is difficult to change the prosthesis after surgery. This can present a major disadvantage as the oral environment inevitably changes, such as changes in major chewing teeth over time and changes in vertical height. Reconstruction using a free vascularized hard and soft tissue flap allows for prosthetic reconstruction using implant placement like normal oral tissue in a naturally changing environment with the surrounding bone tissue. Removal of the implant, bone graft, and replanting are also possible and safe. Donor site reconstruction using a 3D-printed patient-specific implant can thus be considered a useful method to reduce donor site morbidity in DICA-based iliac crest flap reconstruction of jaw defects. Conceptualization, S.Y.M. ; methodology, S.Y.M. ; software, S.Y.M., H.J.K. ; validation, S.Y.M., H.J.K. ; formal analysis, S.Y.M., H.J.K. ; investigation S.Y.M., H.J.K. ; resources, S.Y.M. ; data curation, S.Y.M., H.J.K. ; writing--original draft preparation, H.J.K. ; writing--review and editing, S.Y.M. ; visualization, S.Y.M. ; supervision, S.Y.M. ; project administration, S.Y.M. ; funding acquisition, S.Y.M. All authors have read and agreed to the published version of the manuscript. This research was funded by Chosun University Dental Hospital, 2018. The authors declare no conflict of interest.