Coronoid process hyperplasia leads to limitation of mouth-opening due to contact of the enlarged coronoid process of the mandible with posterior surface of the body of the zygomatic bone and inner surface of the zygomatic arch. Patients suffering from coronoid process hyperplasia are often misdiagnosed and treated as cases of temporomandibular joint disorder because trismus secondary to coronoid process hyperplasia is relatively rare. To diagnose coronoid process hyperplasia, it is important to gather complete clinical information such as current medical history and clinical presentation, and to perform appropriate imaging tests. Coronoid process hyperplasia is characterized by comorbidity of other diseases related to the temporomandibular joint and masticatory muscles.

This paper summarizes the clinical characteristics of coronoid process hyperplasia and the differences of coronoid process hyperplasia from other diseases with similar symptoms such as temporomandibular joint disorder.

Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) was published in 2014 after a rigorous literature review and verification of reliability and validity through multicenter clinical trials, and is now an internationally standardized system for diagnosing temporomandibular disorders. DC/TMD has a two-axis diagnostic system based on a biopsychosocial model, and targets only the most frequent TMD. Recently, DC/TMD for children and adolescents was announced. This was completed by discussing the necessary revisions of DC/TMD for use in children and adolescents using the Delphi method. The revision of the axis I evaluation is outlined as follows. "Distinguish between children (6-9 years old) and adolescents (10-19 years old) according to the WHO definition, and prepare screening and full versions for both", "Health Questionnaire for Children, Parents and Adolescents, a modified symptom questionnaire, and clinical diagnostic classification of DC/TMD are prepared", "Accepting simple and easy-to-understand explanations for children and adolescents regarding instructions (commands) at the time of examination", "Clinical examination of adolescents is almost the same as that for adults", "Clinical examination of children is limited to mouth-opening movement only, and limited mouth opening is considered to be 32 mm or less", and "Joint noise examination is limited to opening and closing mouth movements". Furthermore, in the axis II evaluation, the questionnaire was changed significantly. In this article, we review DC/TMD for examining and diagnosing TMD in children and adolescents, which was published after a consensus was reached by international experts on TMD.

A newly-identified mechanism of chronic pain is "nociplastic pain, " which can be triggered by central sensitization, dysfunction of the mesolimbic dopamine system, and/or descending pain inhibiting pathway. This is a "third type of brain-generated pain" caused by unpleasant emotions, with or without peripheral injury, and is classified as chronic primary pain (MG30.0) in ICD-11. Fibromyalgia is a typical example, but temporomandibular disorders (TMD) are also included in this category, specifically burning mouth syndrome (BMS) and persistent idiopathic dentoalveolar pain (PIDAP). Psychosocial factors are often involved in patients with chronic pain, in which case an accurate assessment of these factors and a corresponding cognitive-behavioral approach are required. I introduced an original psychosocial flags system, which was developed by members of the Policy Research Project of the Ministry of Health, Labour and Welfare on chronic pain. The "psychosocial flags framework" originated in the U.K. for the multidisciplinary treatment of musculoskeletal pain, and is recommended in neck and back pain guidelines in Europe. I focused on the yellow flags (i.e., psychosocial factors used to screen for cognitive-behavioral therapy), which will be an appropriate operation system for motivated therapists.

In the present case, the occlusal position that had been established by articular disc displacement for a long period of time was suddenly restored to the normal position, resulting in inadequate mouth closure of the molars. A rare case of disc transposition in which inadequate mouth closure was improved by external anterior transposition is reported.

The patient, a 42-year-old woman, was aware of bilateral temporomandibular joint noises for about 15 years, and for about 3 years, she was aware of inadequate mouth closure after large openings and during meals, but left it untreated because it improved on its own. On the day before her first visit, she again experienced a sudden inability to close her mouth and the problem did not resolve, so she came to our department. At the time of the initial examination, both the left and right sides of the molar teeth were separated by 1 to 3 mm, the maximum opening range was 30 mm, and there was pain during right-sided jaw movement. On imaging examination, the mandibular head was located in the mandibular fossa on both sides but deviated anteriorly and inferiorly. And there were no bone or disk abnormalities, inflammatory findings, or joint effusion in the right temporomandibular joint. On the day after the first visit, the posterior open bite that had persisted for about 36 hours improved; an MR scan was performed, which showed anterior and lateral dislocation of the right-side disc and marked joint effusion. About 5 months have passed since then, and there has been no occurrence of posterior open bite, and the maximum aperture was 40 mm.

The cause of the inadequate mouth closure in this case was thought to be the change in thickness of the articular disc due to the adaptation of occlusion to the long-term dislocation, extension of the posterior connective tissue as the articular disc moved forward and downward, and interference with the position of the mandibular head caused by superimposition when the disc returned to the normal position.

A 43-year 6-month-old female with the chief complaints of severe trismus and difficulty in chewing with the anterior teeth visited our clinic. The patient presented bimaxillary protrusion and had the symptoms of trismus, with pressure pain in the masticatory muscles and temporomandibular joint. MR images indicated bone deformities of flattening and osteophytes on the surfaces of both condyles. The diagnosis was myalgia of the masticatory muscles (Type I), arthralgia of the temporomandibular joint (Type II), suspected temporomandibular joint disc derangement without reduction (Type IIIb), and osteoarthritis of the temporomandibular joint (Type IV) on both sides according to the criteria of the Japanese Society for Temporomandibular Joint. First, guidance for tooth contacting habit (TCH), oral myofunctional therapy (MFT) for parafunctions, mouth-opening exercises, massage of masticatory muscles, and stabilization appliance therapy were recommended. After confirming that the symptoms of the temporomandibular disorders (TMDs) had been relieved and the mental condition had calmed, orthodontic treatment was started. Orthodontic treatment with multi-bracket appliances on the upper and lower dentition were formulated, especially in consideration of TMDs, avoiding mechanical stress on the temporomandibular joint. Since an acceptable occlusion was attained 2 years later, all orthodontic appliances were removed and the retention period was started. Throughout the orthodontic treatment, all the symptoms of TMDs remained stable. The development or deterioration of TMDs makes it difficult for orthodontic treatment to proceed properly. Therefore, accurate diagnosis and appropriate therapy for TMDs in cooperation with specialized institutions according to the severity of the disease are important.

We describe the clinical course of a pediatric patient with unilateral temporomandibular joint (TMJ) ankylosis who underwent successful open TMJ surgery with gap plasty and follow-up to adulthood. The patient was a 12-year-old girl with ankylosis of the right TMJ (Sawhney Classification Type III) secondary to a condylar fracture. At the initial visit, her mandible was slightly deviated to the affected side, and mouth opening range (MOR: interincisal distance) was 11 mm. At the age of 14 years, she firmly decided to carry out postoperative mandibular motion exercises with pain, and open TMJ surgery was performed. The first step of the surgical procedure was gap plasty for the bony ankylosis of the outer side of the right TMJ while preserving the normal TMJ structure in its inner site, and a temporal muscle/fascia flap was inserted into the gap. Then, the healthy-side temporal muscle was detached from the coronoid process, resulting in the achievement of 50-mm MOR. From the day after surgery, mandibular-motion exercises were started, and the MOR reached 40 mm within 10 days postoperatively. Thereafter, she continued mandibular-motion exercises, and we recognized no facial asymmetry or mandibular-motion disorders with 40-mm MOR at the 6-year follow-up after surgery. In conclusion, the mandibular mobility that was achieved, together with preservation of the normal TMJ structure, through our surgery and postoperative continuous mandibular-motion exercises were crucial factors that prevented growth disturbance of the mandible in our patient.