Introduction of temporomandibular diseases - 謝明吉、姜厚任 顎顏面 美學 重建 專科診所-風華整形聯合診所
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Physiology and pathology of the TMJ
Introduction of temporomandibular diseases


Temporo-Mandibular disorders/ TMD)

Temporomandibular disorders (TMD) are a collective term embracing a number of clinical problems that involve the temporomandibular joint and associated structures. Naming of TMD does not contain the word "joint" meaning the cause of the syndromes are not only limited to TMJ, but related to abnormalities of the whole masticatory system. The textbook "Orofacial pain, guidelines for assessment, diagnosis, and management" published by American Academy of Orofacial Pain (AAOP) combining a clinical overview of orofacial pain and TMD (i.e. pain or function disorders of cranio-cervi0-facial area) has become the standard guidelines for oral and maxillofacial surgeons to diagnose and treat TMD and related diseases.


Related epidemiological studies show that about 40% human population has experienced at least one TMD symptom in life. Among them, about 55% showed TMD signs after clinical examination and 5-10% were in need of active treatment. The commonly seen clinical signs of TMD are:

  1. Head and neck pain and stiffness
  3. Joint popping, clicking or crepitus
  5. Limited mandibular movements or locking
  7. Tinnitus or earache (no other primary cause has been found)
  9. Difficulty and pain while chewing and swallowing


Few severe or long-term TMD may develop permanent damage of articular disc and condyle or condylar head resorption, resulting in persistent or chronic TMJ pain, trismus, malocclusion (e.g. open bite) and facial asymmetry.

Diagnosis of TMD is mainly based on detailed history taking, physical examination, coupled with imaging examinations, e.g. panoramic film or TMJ film, computed tomography (CT) and cone beam computed tomography (CBCT). CBCT allows accurate evaluation of TMJ structure and identification of any lesion, fracture or adhesion, with the advantages of great reduction of exposure to radiation and finest image resolution. Nevertheless MRI is the main diagnostic tool for TMJ disc displacement nowadays.



According to AAOP (2013), the etiology of TMD can be divided into 3 types: cranial bone abnormalities, articular disorders and masticatory muscle disorders. TMJ specialists are capable of further identifying the symptoms of TMD caused by masticatory muscle disorders are related to intra- or extra-articular muscles. Different cranial bone abnormalities that may cause TMD include congenital TMJ aplasia, hypoplasia, hyperplasia or dysplasia, acquired articular tumors and bone fractures.

It is commonly accepted that the etiology of TMD is complicated and multifactorial. Known causes of TMD include trauma, malocclusion, mental stress, poor posture, congenital growth abnormalities, autoimmune diseases, and hormone related disorders. In the author's view, all these causes can be grouped into 3 p-factors, i.e. physical factors, physiologic factors, and psychological factors. For example, malocclusion and facial asymmetry are the commonly known causes of TMD that lead to misalignment of teeth, jaws and TMJ can be categorized as physical factors. Though in fact very few people have perfect teeth and jaw alignments, and not every patient with malocclusion exhibits signs of TMD. Researchers at Tokyo Medical and Dental University found that when the mouth is closed and relaxed, most people do not have tooth contact between the upper and lower teeth. Close contact between teeth happens only during dining or intentionally hard bites. The time of close contact between teeth within a day was estimated to be about 20 minutes. But the time and the stress undertaken by TMJ may increase due to mental stress (e.g. stress at work or study) that leads to tightness in craniocervial muscles and signs of TMD (e.g. teeth clenching and bruxism), which further magnifies the influence of other physical factors, e.g. malocclusion resulting in misalignment of the jaws. In this case, if coupled with poor joint adaptability, congenital diseases or hormone influence, chances of developing arthritis and joint pain will increase substantially.


Results of surgery vary among patients. Please consult your doctor.
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Results of surgery vary among patients. Please consult your doctor.