## 2 Case Presentation
Based on the correct occlusion, STL files of the maxilla and the mandible were sent to the manufacturer (Sintac S.r.L, Trento, Italy) for prostheses design. To assist the correct phase of mandible repositioning after ankylosis removal, a surgical splint was also designed. The TMJ prostheses were designed and validated by the surgical team in a collegiate web session, then the implants were received and sterilized using hydrogen peroxide (Figures 5 and 6). Figure 4: (**A**) MMO of less than 10 mm, (**B**) evidence of a recurrence of ankylosis. The TMJ was exposed by a pre-auricular approach extended to the temporal region, and a sub-mandibular one. A blunt dissection through the submandibular approach was performed until the mandible ramus was exposed. Dissection was carried out as well from the preauricular access, following the cartilage of the external auditory canal until it joined the subfascial pathway. Detachment of the zygomatic arch and evidence of the right TMJ were overturned by severe ankylosis in outcomes of previous CCG surgery (Figure 7). Figure 5: Virtual surgical planning. The mandible was isolated to define the resection plane and subsequently design specific cutting guides and the custom-made prosthesis. Figure 6: Fitting test of the custom-made prosthesis on the 3D printed model of the patient’s cranium. The custom-made surgical guide was positioned through the sub-mandibular access and then fixed to the angle and the branch of the mandible with screws. Therefore, we proceeded with a piezoelectric osteotomy [20; 21] of the mandibular branch right below the sigmoid incision and a right coronoidectomy. Simultaneously, through an intraoral vestibular incision in the molar region followed by a subperiosteal skeletonization, a left coronoidectomy was also performed. At this point, the glenoid fossa prosthesis was positioned and fixed with screws, and the condylar prosthesis was covered by fat collected from the periumbilical region to avoid a skin decompression. We proceeded by checking the intraoperatory MMO, resulting a satisfying 35 mm (Figure 8). After the TMJ replacement procedure was completed, the TMJ accesses were preliminarily sutured and draped to isolate them from the operative field. Then, the mouth was opened and the occlusion was evaluated. In addition, an intraoperative occlusal scan was performed to immediately produce an accurate assessment of the occlusion and a map of precontacts. Broad spectrum antibiotics and pain meds were administered for 1 week. The patient was placed on a soft diet for 5 days and encouraged to resume a normal diet as soon possible. Physiotherapy was started on the first day post operation, and the patient was encouraged to follow the exercise program at the quickest pace possible. This required following for at least 1 year, perhaps more, availing also of the regular use of _Therabite jaw motion rehab system_, which may contribute to the maintenance of a proper postoperative MMO. A CT scan was performed about 1 week postoperatively, in order to check the position and the alignment of the prosthetic devices to the bony stumps, as well as the relation between the fixation screws and the inferior alveolar nerve. Six months after surgery, at the clinical examination, the patient presented a 25 mm MMO, augmentable up to 30 mm if forced (Figure 9). An annual radiographic check was carried out, useful to intercept any possible complications which may deserve further investigation, but this was not the case. A teleconsultation was performed 14 months after surgery, due to the COVID-19 outbreak [22; 23; 24; 25], and the patient showed no significant clinical changes. Figure 8: The custom-made prosthesis was then positioned and the MMO was checked. Figure 7: The ankylotic block was identified and excised using the surgical guide and a piezo-surgev device.