Chronic temporomandibular joint dysfunction: an area of debate

Introduction Temporomandibular joint dysfunctions present with a variety of symptoms that comprise pain in the joint and its surroundings, jaw clicking, limited jaw opening or locking and headaches. The management of chr-onic temporomandibular joint dysfunction may be defined as simple or complex. The preference of the treatment, based on the aetiology, may be characterized as psychosomatic or operational. Conservative treatment is helpful in most cases. This up-todate review focuses on the pathogenesis and management of this multifactorial clinical entity. Conclusion Chronic TMD is a complex clinical condition of yet unknown pathogenesis. Further research is required to investigate the aetiological patterns. On examination, the most common features are tenderness upon palpation of the joint or muscles of mastication, diminished mouth opening, side-to-side movement and clicking or grating sounds in the joint upon movements of the mandible4,5. Lack of tenderness in the external auditory canal could be an additional diagnostic feature of the pain syndrome4. An acute episode of pain generally has a sudden onset due to local tissue inflammation and it usually resolves within 4–12 weeks6. The conversion from acute to chronic pain may result from the body’s inability to restore normal physiological function7,8. Historically, there have been several TMD classifications emphasizing either mechanical or psychological concepts. Classifying TMD has been a difficult task and several suggestions exist in the literature. One of the oldest classification systems distinguishes two categories of TMJ pain: (a) masticatory pain (musclerelated) and (b) TMJ arthralgia (jointrelated). The former is subdivided into splinting, spastic and inflammatory pain while the latter into discal, retrodiscal, capsular and arthropathic pain9,10. Later, TMJ non-arthritic arthralgia was re-classified as a deep somatic pain of disc attachment11. Currently, the Research Diagnostic Criteria (RDC)/TMD is the most accepted classification; it was reported by Dworkin and LeResche12 and it differentiates the TMD entities along two axes. The first axis (axis I) refers to the clinical evaluation of TMD conditions. It is divided into three main groups: (a) muscular involvement, (b) disc displacement and (c) arthritic origin of the condition. The second axis (axis II) considers pain-related disability and psychological status in association with TMD12. Good to excellent reliability results were found using these criteria in an adolescent study for each category of RDC/ TMD13. RDC/TMD and, more specifically, the jaw disability checklist, evaluates the jaw function and determines in depth the extent of interference caused by TMD12. Eating, yawning and chewing were found to be the most common jaw functions that interfered with TMJ using RDC/TMD14,15. Another classification, reported by Goldstein16, separates the condition into general groups of: (a) rheumatoid changes with synovitis, (b) arthralgia, (c) condylar degeneration, (d) open bite deformity, (e) chronic pain with link to behaviour, (f) myofascial pain and dysfunction and (g) internal derangement with displacement and reduction. A more recent classification system, reported by Ogle and Hertz17 and which relates TMD to masticatory myofascial pain in association to TMJ pain with or without joint sounds, suggests that myofascial pain dysfunction, masticatory myalgia, masticatory myositis, tendonitis and whiplash TMJ are all variations of the myofascial pain syndromes. This review discusses the impact of different factors on chronic TMJ dysfunction. Pathogenesis There is a lack of scientific evidence regarding the pathological origin of chronic TMJ dysfunction, and aetiology is unknown in up to 95% cases16. Currently, there are observation studies indicating a multi-part aetiology of the disease. Nowadays, the involvement of psychological factors in the aetiology of many TMJ disorders is well established; these implicate emotion, behaviour and personality disorders as major contributors to the pain dysfunction syndrome18. Furthermore, * Corresponding author Email: [email protected] 1 Department of Oral Surgery and Radiology, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece 2 Department of Oral and Maxillofacial Surgery, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece 3 UCLH Head and Neck Unit, University College London Hospitals, London, UK Or al & C ra ni oM ax ill of ac ia l