An 8-year-old male rhesus macaque weighing 7.7 kg was imported from China and was intended to be a recipient of a heterotopic porcine heart transplantation. The animal experiments were approved by the Institutional Animal Care and Use Committee (IACUC) of the Biomedical Research Institute at the Seoul National University Hospital, an AAALAC-accredited facility (IACUC number: 14–0034-C2A0). The monkeys were maintained in single-housed cages and had daily access to a certified primate biscuit diet (2050C, Harlan, Indianapolis, IN, USA) and unlimited access to water. Their room was maintained at 24 ± 4 °C and a relative humidity of 50 ± 10%, with a 12-h artificial light-dark cycle (7:00 am onset) and with 13–18 air changes per hour. After quarantine, lockjaw was identified. A supplementary video is available at. The animal was sedated for physical examination, canine tooth crown reduction, computed tomography (CT), and euthanasia using intravenous medetomidine (0.2 mg/kg, Sedastart, Yuhan, Seoul, Korea) and ketamine (5 mg/kg, Yuhan Ketamine 50 Inj, Yuhan, Seoul, Korea). A physical examination of the head and neck was conducted to identify the etiology of lockjaw in this monkey. We monitored how the rhesus monkey moved food into the oral cavity. Moderate to severe attrition was identified in the middle labial portion of the left maxillary canine, which was caused by the locked portion of the left mandibular canine. No tenderness around the jaw was detected in the physical examination. The monkey used its incisor tooth to nibble the food (supplementary video 2). We performed CBC, blood chemistry, radiographic and computed tomographic examinations. For comparison with normal TMJ appearance, we conducted CT examination with the other monkey with a normal TMJ. CT was performed using a multislice scanner (Brivo 380, GE Medical System, Seoul, Korea) under the following conditions: 100 kVp, 10 mAs, 0.625 to 2.5-mm slice thickness, and helical scan type with the animal under general anesthesia with isoflurane. To exclude rheumatoid arthritis, the rheumatoid factor level (by turbidity immunoassay) was analyzed. The WBC count, CRP level, rheumatoid factor level, and other parameters were normal. More severe irregularity in the joint surface was observed in the left TMJ compared with the right TMJ in the radiographic and computed tomographic examinations, and the diagnosis based on these examinations was DJD of both TMJs with fibrous ankylosis. It was determined that the removal of the locked portion of the left canine would alleviate the case of lockjaw and allow intubation with an endotracheal tube. Canine tooth crown reduction was performed for both canine teeth. Briefly, the canine tooth is cut to the level of the incisor teeth using a disc bur. A 1.5-mm-diameter bur removes the pulp and dentin with saline irrigation to prevent thermal injury, and the removed pulp cavity has a larger diameter at the base than at the cutting surface. A cotton pellet soaked with a hemostatic agent (dental formocresol; AGSA JAPAN CO., Osaka, Japan) is used to control the bleeding induced by pulpotomy. A phosphoric acid etchant (CharmEtch 35 HV; DentKist Inc., Gunpo, Gyeonggi-do, Korea) is applied for 20 s for strong adhesion to the filling material. The cavity is washed with a 5.25% sodium hypochlorite solution with antimicrobial effects and then dried gently with air. The cavity is filled with calcium hydroxide/iodoform paste (Vitapex, Neo Dental Clinical Co., Tokyo, Japan) and with glass-ionomer restorative cement (Fuji IX GP; GC Corporation, Tokyo, Japan) according to the manufacturers’ protocols. An antibiotic (cefazolin 20 mg/kg, bid, cefazoline injection 1 g, Chong Kun Dang, Seoul, Korea) and an analgesic (meloxicam 0.1 mg/kg, sid, Metacam 5 mg/ml, Boehringer Ingelheim, Seoul, Korea) are injected intramuscularly for 3 days after canine tooth reduction. The distance of mouth opening was evaluated. The mouth opening distance slightly increased, and the maximum distance of mouth opening was approximately 20 mm after the locked portion of the left canine teeth was removed. We concluded that the attrition of canine teeth was not the reason for the lockjaw and ankyloses originating from TMJ disease. After the heterotopic porcine heart transplantation experiment was finished, euthanasia was performed by exsanguination under deep anesthesia with thiopental sodium (50 mg/kg, Pentothal sodium injection 0.5 g, JW Joongwae Pham, Seoul, Korea) after sedation. We conducted necropsy and histological examination (H&E and Masson’s trichrome stain) on the TMJ joint. The masseter muscle appeared normal, and fibrotic synovial tissue and joint surface irregularity were observed by necropsy. The presence of fibrocartilage in most areas of the TMJ was confirmed by histology. The diagnosis was fibrous ankylosis of the TMJ associated with DJD.