## 2 Materials and Methods  
Criteria for study inclusion of the patients were those who have (1) inflammatory arthritis involving the TMJ that is not responsive to other treatments, (2) recurrent fibrosis and/or bony ankylosis not responsive to other modalities of treatment, (3) failed tissue grafts of bone and soft tissue, (4) failed alloplastic joint reconstruction, and/or (5) loss of vertical mandibular height, and/or (6) occlusal relationships because of trauma, pathologic bony resorption, or developmental abnormalities).  
The patients who were subjected in this study were received unilateral alloplastic TMJ reconstruction with a ready-made TMJ stock prosthesis (Biomet TMJ Replacement System; Biomet Microfixation, Jacksonville, FL, USA) [21]. All surgical procedures were performed by a single skilled surgeon ([PERSON]) at Asan Medical Center (Seoul, Korea) and all data were independently analyzed by three different doctors; and minimum three-year postsurgical follow-up. Standardized pre-surgical and post-surgical evaluation forms as approved by the institutional review board at Asan Medical Center (reference number S2020-0684-0001) were used to collect objective and subjective clinical data from patients.  
According to our protocol, all patients were evaluated periodically based on maximum mouth opening (MMO), level of pain on a visual analogue scale (VAS) and any functional and physiological sequelae in both side joint conditions and occlusion. Both side joint conditions were also evaluated radiologically. Occlusal relationship was clinically evaluated for determining condylar stability of the TMJ.  
On the alloplastic TJR side, any post-operative infection, implant displacement, and allergic response were observed. On the opposite natural joint side, any newly developed clinical symptoms, such as joint pain and noise, and condylar degenerative changes, such as absorption or erosion of condyle structures, were also monitored.  
All surgical procedures of TMJ TJR with the Biomet system were consistently conducted by one skilled surgeon (Figure 1).  
For all patients, CT scans were taken pre-operatively for manufacturing 3D printed skull models (TAEGO Science Ltd., Seoul, Korea). To reduce total operation time and improve accuracy of the surgery, pre-surgical trial of fitting the artificial fossa and standard titanium condylar stem component (small, 45 mm; medium, 50 mm; large, 55 mm) was conducted and the appropriated sized artificial fossa and condylar stem component were selected. In addition, bone grinding area for better fitting of the alloplastic TMJ components and inferior alveolar nerve location were also identified on the 3D printed patients' own skull model.  
Surgery was done with standard technique in accordance with previously published reports [21, 22, 23, 24].  
The following post-operative protocol was instructed for all of the patients. There was no requirement for maxillomandibular fixation (MMF) post-operatively and active physiotherapy was commenced 5-7 days after surgery to first allow any pain and/or swelling to subside [21]. Briefly, the physiotherapy protocol was to perform maximal mouth opening exercise using patient's own fingers, 3 times in a row every set, and about 10 sets every 2-3 h a day. Patients were told to continue physiotherapy for at least 1 year and possibly longer.  
On the next day after the operation, radiographs (panorama, cephalogram, CBCT scans) were taken to evaluate the position of the prosthesis and the natural condyle (Figure 2). For clinical evaluation, imaging was repeated at one month, six months, and three years after surgery.  
Figure 1: Surgical view for alloplastic total TMJ replacement.