Objective: In cases where an articular disk malposition such as anterior disk displacement is caused by a failure of coordinated movements of the mandibular condyle and articular disk, elucidation of the coordinating mechanism of the mandibular condyle and articular disk movements may help clarify the pathogenesis of the anterior disk displacement. The purpose of this study was not to observe static positions of the mandibular condyle and the articular disk but to clarify the coordinating mechanism between the mandibular condyle and articular disk by investigating the movements of the mandibular condyle and articular disk during masticatory movements.
Method: EMG activities of the masseter muscle were simultaneously recorded with movements of the condyle and disk as well as the incisor point during masticatory-like jaw movements induced by electrical stimulation of the cortical masticatory area of anesthetized rabbits.
Conclusion: The trajectory of the anterior point of the mandibular condyle was localized to a vertically small region and straight pathway. It has been suggested that the mandibular condyle moves across the articular disk from the articular tubercle and maintains a stable relation with the articular disk. The articular disk moved along the articular tubercle during masticatory movements but slight forward-projecting movements were seen in an early occlusal phase. The forward-projecting movements occurred simultaneously with the peak of the masseter muscle contraction force, suggesting that the articular disk received compressive force from the mandibular condyle. However, significant deformation of the articular disk was not observed.

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The purpose of this retrospective study was to evaluate the efficacy of eminectomy in patients with recurrent luxation, who suffered severe mental disorders, neurological and cerebrovascular diseases. Seven patients were studied in terms of background status, pre- and post-operative findings, and outcomes. The results showed satisfactory outcomes in all patients, although one patient had facial nerve temporal paralysis of the temporal branch. In conclusion, the present study indicated that eminectomy appears to be a safe and easily applicable technique for the surgical treatment of recurrent temporomandibular joint luxation. Further studies, however, are necessary to establish the efficacy and adequate indications for cases with systematic diseases.

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Generally, temporomandibular joint surgery has been performed with temporomandibular joint ankylosis to restore condylar movement, however, the possibility of post-operative recurrence has been highly indicated. Therefore, to reduce recurrence, a tissue grafted from a living body such as a skin flap, temporalis muscle flap, or auricular cartilage is used as an interpositional inset after the resection of an articular disc.
In this case report, a five-year follow-up study was conducted with regard to temporomandibular joint ankylosis treated by gap arthroplasty and interpositional grafting with temporalis muscle flap. A 54-year-old female patient who complained of severe restricted mouth opening was diagnosed as having left temporomandibular joint ankylosis based on clinical and radiographic findings.
The mouth-opening exercise showed no effect, so gap arthroplasty and interpositional grafting with temporalis muscle flap was performed. The maximum mouth opening distance improved to 30 mm after the surgery. Neither particular change of facial appearance nor facial nerve paralysis was detected after the surgery. CT images taken 1.5 years after the surgery showed no findings of recurrence. The postoperative course was uneventful, with a maximum mouth opening of 30 mm maintained and no esthetic or functional disturbance found for 5 years.

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Synovial chondromatosis is a benign disorder characterized by developmental nodules of cartilage within the synovial connective tissue of the articular joint. It is often reported in the larger joints of the body including the knee, hip, elbow, and ankle. We report a case of recurrent synovial osteochondromatosis of the temporomandibular joint (TMJ). The patient was a 63-year-old woman, complaining of swelling and pain of the left TMJ. Ten years earlier, she had been diagnosed as synovial chondromatosis of the left TMJ, and initially treated with arthroscopic surgery by oral and maxillofacial surgery at another hospital. Although years passed without symptoms after surgery, swelling and pain of the left TMJ appeared from April 2010. Magnetic resonance imaging revealed expansion of the TMJ cavity; this area showed low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. As the clinical diagnosis was recurrent synovial chondromatosis, we performed removal of the metaplasia and discectomy by open surgery under general anesthesia. Histopathologically, the diagnosis was synovial osteochondromatosis. The postoperative course was uneventful, and there was no evidence of recurrence or any symptoms 23 months after the operation.

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Fibromyalgia (FM) is characterized by chronic pain over the entire body resulting from an unknown cause. The patients' quality of life is often poor due to chronic fatigue and multiple tenderness. The disease is also complicated by a variety of orofacial manifestations, such as temporomandibular disorders, dry mouth and taste disorders. We herein report a 62-year-old female with trismus who was diagnosed with FM, and who improved after medical therapy. The patient had experienced domestic stress, and developed numbness of the left side of face after being beaten by husband five years earlier. Three years previously, she had noticed trismus, and lip and left eyelid movement disorders. She also suffered from dry mouth and taste disorders, and was referred to our department. She complained of fatigue and anorexia. A physical examination revealed bilateral tenderness of the temporal, digastric, sternocleidomastoid, trapezius, and medial pterygoid muscles. Trismus was also observed, and the range of maximum mouth opening was 31 mm. The patient was referred to a rheumatologist due to a suspicion of systemic disease. A clinical examination revealed chronic and wide-spread pain in combination with tenderness at 17 of the 18 specific tender points. Based on the American College of Rheumatology 1990 criteria, a diagnosis of FM was confirmed. The patient's chronic pain in the whole body decreased after the oral administration of pregabalin (Lyrica^®). The tenderness of the masticatory and neck muscles also decreased, and the maximum mouth opening increased to 42 mm. The treatment continued for one year, and her symptoms have been stable. Although this disease is often associated with manifestations in the orofacial region, its recognition by dentists is low. Therefore, dentists should pay attention to this disease, and if necessary, should promptly refer the patient to a specialist to achieve an improvement of the symptoms.

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