The mandible, as the largest bone in the orofacial region with a prominent position, mainly constitutes the framework of the lower 1/3 of the face and forms an occlusal relationship with the maxilla; its median union, chin foramen area, mandibular angle and condylar neck are the weak links, and when subjected to external forces, they can often occur individually or in a combination of several parts of the fracture [13]. Mandible fractures can give rise to occlusal disorders, facial deformities, and functional damage; therefore, accurate and timely reduction is necessary for the restoration of occlusal relationships and facial aesthetics.

The treatment of severely comminuted mandibular fractures still remains a challenge for surgeons. One of the major intraoperative difficulties is how to restore the contour of fractured sites, considering many cases of complex comminuted mandibular fractures present severe bone displacement and bone loss that make anatomic reduction almost impossible [9]. When the fracture fragments are not reduced correctly, the risk of short-term and long-term postoperative complications will increase. In addition, the restoration of the occlusal relationship is also difficult due to the fact that complex comminuted mandibular fractures are often accompanied by dentition disorders as well as dentition defect [19], [20]. In cases of severely comminuted mandibular fractures, the outcome of traditional surgical treatment depends almost entirely on the surgeon's clinical experience. Currently, there is no personalized reduction guides to achieve accurate reconstruction of severely comminuted mandibular fracture fragments.

Vast advances in virtual surgical planning (VSP) and 3D printing technique have greatly improved surgical accuracy and efficiency [4], [16], [12]. An increasing number of surgeons have been using digital surgery and 3D printing technology to plan and perform maxillofacial surgery recently. This technology provides a platform for osteotomy, cutting, and positioning guidelines to optimize preoperative planning and intraoperative execution [2], [4]. This study attempted to achieve accurate reduction of severely comminuted mandibular fracture fragments using short-segment drilling guides (SSDGs) and horseshoe-shaped reduction guide (HSRG) through VSP and 3D printing technology by a prospective analysis of consecutive cases. We evaluated the postoperative mandibular contour aesthetics and occlusal relationship of the patients, and then compared mandibular 3D parameters between the preoperative VSP and postoperative data.