## 4 Discussion  
The reconstruction of mandibular defects in children is technically and aesthetically challenging. Additional TMJ reconstruction protocols that provide long-term functionality in this group of patients are still not fully developed. In most cases of adult patients, simple total joint replacement (TMJR) is usually satisfactory because the requirements related to a growing child do not need to be met. For children the main issues are associated with the development of speech, the masticatory system, and the entire craniofacial region, which are dramatically hampered when the TMJ is lost. The best treatment should restore functionality, including adequate mouth opening, improving the airway patency, preventing the recurrence of the disease, and providing satisfactory aesthetic results [2,4]. To date, there is no proven track for mandible and TMJ grafting techniques that can assist in the postoperative growth of the jaws of pediatric patients. [PERSON] claimed that the pediatric TMJ may be reconstructed either by distraction osteogenesis, autologous reconstruction (costochondral graft, free fibula flap), or total alloplastic joint replacement [2]. However, the growth potential of the mandible in pediatric patients depends on the preservation of the mandibular epiphyseal growth plates, which are located in the proximal zone of the conical subcondylar ridge [16]. Because of this, in immature patients it is advised that the condyle be preserved at all costs when a mandibularomy is necessary. Condylar preservation has been shown to positively influence the growth potential of the mandible in the postoperative period [17]. The protocol for the reconstruction of a child's mandible is more complicated when a condyle must be removed due to malignancy, is deformed, or is absent due to deformation, as was the case in the described population of the patients operated on within this study. Figure 9: 3D CT reconstructions of representative patients. **Patient 1**: (a) tumor of the right mandible body and ramus, (b) defect after nonradical resection in another department and secondary deformation, (c) 3D virtual surgical planning (VSP) reconstruction of the mandible and custom TMJ, (d) 6 months postoperative, and (e) 24 months postoperative. **Patient 2**: (a) tumor of the left mandible body and ramus, (b) defect after nonradical resection in another department and secondary deformation, (c) reconstruction of the mandible with fibula without 3D VSP in another facility—lack of functionality, (d) reconstruction of the TMJ with stock TMJ prosthesis and maxillary advancement in order to improve function and occlusion—failure due to resorption of the previous bone grafting, and (e) 3D VSP reconstruction of the mandible body, ramus and custom TMJ. **Patient 3**: (a) tumor of the left mandible body and ramus, (b) 3D VSP reconstruction of the mandible and custom TMJ, and (c) 4 years postoperative. In the literature, costochondral grafts have been reported as the gold standard for mandible and TMJ reconstruction in children, but nonvascularized autological bone grafts have a tendency to induce osteogenesis [18]. This is the reason that they are not the treatment of choice for the ankylosis of the joints [19]. Costochondral craft fractures, hypertrophy of the bone grafts, their unpredictable growth with separation of bone from the chondral part, and resorption in the donor site have been described [20]. Resection of the lower face region without simultaneous reconstruction leads to constrictions of the native soft tissues and dislocations of other bones and, eventually, extreme malocclusion and deformation of the face. These often lead to the need for secondary reconstructions, which are always more difficult and sometimes impossible to conduct. Resection with simultaneous reconstruction of the mandible allows orthodontic treatment and dental rehabilitation for the early restoration of teeth while preventing malocclusion.