Objective: The aim of this study was to apply a deep learning system to the diagnosis of degenerative disease of the temporomandibular joint (TMJ) on panoramic radiographs and to clarify its diagnostic performance (precision and consistency).

Methods: Panoramic radiographs of 138 TMJs in 92 patients suspected of having degenerative disease of the TMJ and verified for presence of condylar osseous changes on computed tomography (CT) were evaluated. As controls, 138 panoramic radiographs were selected from patients who underwent CT and panoramic radiography for suspected maxillary sinusitis and were confirmed to have no condylar osseous changes. A deep learning system was constructed using AlexNet. Learning models were created with a five-fold cross-validation method and data augmentation technique, and the precisions (sensitivity, specificity, accuracy) were determined together with area under receiver-operating characteristic curve (AUC) values. The same values were determined by three oral and maxillofacial radiologists and three dental residents. Diagnostic consistencies expressed by kappa values for the deep learning system, radiologists, and residents were also verified.

Results: Sensitivity, specificity, accuracy, and AUC of the deep learning system were 84.5%, 66.2%, 75.4%, and 0.76, respectively. Significant differences in AUC values were found between the deep learning system and residents, and between the radiologists and residents. Consistency of the deep learning system was almost perfect with a kappa value of 0.84 and superior to the intraobserver consistencies of 0.55 for radiologists and 0.31 for residents. Interobserver consistencies were 0.47 for radiologists and 0.21 for residents.

Conclusions: For diagnosis of degenerative joint disease of the TMJ on panoramic radiographs, the deep learning system showed equivalent precision to radiologists, but superior consistency compared with both radiologists and residents. Accordingly, the deep learning system has potential as an effective diagnostic support.

Objective: Hyperplasia of the coronoid process leads to restriction of mouth-opening consequent to contact of the coronoid process with the posterior surface of the body of the zygomatic bone and medial surface of the zygomatic arch. This paper describes a case of bilateral coronoid hyperplasia treated by bilateral coronoidectomies and the difficulty of postoperative management including mouth-opening exercises in a child.

Patient: An eight-year old girl consulted our department with a complaint of restricted mouth-opening. Maximum mouth-opening (MMO) was 15 mm. Computer tomography (CT) showed bilateral hyperplasia of the coronoid process which extended above the zygomatic arch. We diagnosed bilateral coronoid process hyperplasia and performed bilateral coronoidectomies under general anesthesia. The coronoidectomies were carried out through an intraoral incision, which is similar to the incision of the surgical approach for sagittal split osteotomy. After releasing the temporalis muscles, coronoidectomies were performed with an ultrasonic cutting instrument.

Mouth-closing exercises were begun on the first postoperative day. On the sixth postoperative day, mouth-opening exercises using her fingers were begun. On the eighth postoperative day, passive exercises including mouth-opening and protrusion were begun using the Yasec mouth-opening exercise device. One year after the surgery, MMO remains at 37 mm. Histopathological examinations showed normal bone tissue without any other lesions. It is suggested that neonatal or postnatal bilateral coronoid process hyperplasia may lead to the restriction of mouth-opening.

Conclusion: We report a case of bilateral coronoid hyperplasia in a child. Trismus secondary to coronoid hyperplasia in a child is rare. Long-term follow-up is needed to observe the clinical outcome.

We report a case of bilateral chronic dislocation of the temporomandibular joint with heterotopic osteoma treated by open reduction, eminectomy, discectomy, high condylectomy and tumor removal. A 39-year-old woman suffered cardiopulmonary arrest due to hanging suicide in March 2013. She was transported to our hospital emergency room and resuscitated, and then transferred to a chronic care hospital. Because reduction of repeated temporomandibular joint dislocation could not be done by the visiting dentist, she was referred to our department in September 2014. Her consciousness level was JCS (Japan coma scale) II-20, and a tracheostomy was performed at the first medical examination. She could not close her mouth, and the bilateral temporomandibular joint had collapsed. CT scan revealed that the bilateral mandibular condyles were located beyond the articular eminences and under the temporal fossa inside the zygomatic arch. In addition, discontinuous radiopaque findings were observed in the anterior and inward of the bilateral mandibular condyles. Based on the diagnosis of chronic dislocation of the temporomandibular joint and bilateral mandibular tumor, open reduction, eminectomy, discectomy, high condylectomy and tumor removal were performed under general anesthesia. The tumor was pathologically diagnosed with osteoma. Five years after surgery, no recurrence of dislocation has been noted.

Jacob's disease is defined as a condition wherein a false joint-like relationship resembling a mushroom-like osteochondroma forms between the zygomatic arch and the coronoid process that keeps increasing in size. We report a case of coincident Jacob's disease and masticatory muscle tendon-aponeurosis hyperplasia. The patient showed favorable prognosis post surgery. The patient was a 27-year-old man, who was referred to our department because of long-term trismus. The patient was observed to have an enlarged mandible with a maximum mouth opening range of 4 mm. Lateral and protrusive excursion movements on both sides of the mandible were 4 mm and 6 mm. A computed tomography (CT) scan revealed a 26 x 18 x 18 mm mushroom-like opaque lesion at the top of the left coronoid process and the zygomatic arch that was in contact with it was deformed. A magnetic resonance imaging scan revealed a strike root appearance on both masseter muscles. The patient was diagnosed with suspected left coronoid process neoplastic lesion and bilateral masticatory muscle tendon-aponeurosis hyperplasia. Under general anesthesia, left coronoidectomy was first performed using a combination of intraoral and extraoral methods. However, since a hard tension was palpated on the anterior edges of both masseter muscles at the time of mouth opening, right coronoidectomy and bilateral aponeurotomy of the masseter muscle were performed. The mouth opening range was 63 mm at the end of the operation. Histopathology of the neoplastic lesion in the coronoid process confirmed the presence of thick fibrous tissue and premature hyaline cartilage-like tissue at the tip of the lesion. An osteochondroma was noted below due to cancellous tissue with a transitive medullary cavity. Thus, the patient was diagnosed with coincident Jacob's disease and masticatory muscle tendon-aponeurosis hyperplasia. Mouth-opening training was started four days after the surgery and continued for three months. 12 months after the operation, the patient is doing well with a mouth opening range of 60 mm with no signs of recurrence.