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tmj_disorders

temporomandibibular joint disorders

see also:

Introduction:

  • The TMJ is susceptible to all the afflictions of other joints. Conversely, there are no articular conditions unique to the jaw joint. The same rules apply to the masticatory muscles.
  • The central presenting symptom of most conditions in the constellation of TMJ disorders is acute or chronic pain.
  • For decades, the dental occlusion has been a central theme in the debates about TMJ disorders. These disorders were often attributed to malocclusions, and treatment focused on altering the occlusal form and function. The assumption that the teeth must be responsible for some head pains was probably a natural one because of the unique anatomy. The maxilla and mandible are the only bones with their own adnexa, the teeth. The TMJ is the only synovial joint with a fixed end point of closure (i.e., when the teeth occlude). The fact that no one has an ideal occlusion added fuel to the fire because some malocclusion could be identified in every patient with head and neck pain. The simultaneous occurrence of pain and malocclusion was assumed to be a cause-and-effect relationship, but this did not explain the majority of malocclusions that were not associated with any pain disorder.
  • The teeth are now thought to be innocent victims rather than wanton malefactors. Treatment of the occlusion is usually geared toward protecting the dentition and periodontium from the effects of misuse, such as bruxism.

TMJ disorders

muscular disorders

  • Most patients with myogenic pain have normal TMJs
  • Abnormalities of the masticatory muscles can be divided into organic and functional conditions.
  • Because organic diseases such as hemifacial hypertrophy or atrophy rarely cause pain or require comprehensive craniomaxillofacial evaluation and treatment, they are not considered here.
  • True spasms, involuntary convulsive muscular contractions, of the masticatory muscles are also rare. When they occur, central neurologic pathology must be ruled out.
  • Most painful disorders of the chewing muscles are functional in nature and lack discrete organic pathology.
  • Pain of the masticatory muscles must be considered to be the result of hyperactivity or hyperfunction. As such, these conditions should be classified as strains, injury by overuse or improper use.
  • Many patients presenting for treatment of muscle pain give a history of nocturnal or diurnal bruxism (i.e., jaw clenching). Some patients may have clinical evidence of such behavior (i.e., attrition of the dental occlusion) but are unaware of its occurrence. A third group may have myogenic pain without a history or signs of masticatory strain. Surface EMG of symptomatic patients yields a wide range of results and cannot be used as a diagnostic tool. EMG is thought to be useful as a baseline for biofeedback training.
  • Rx: rest, soft diet, moist heat, muscle relaxants, NSAIDs, oral splint of flat plane type, behavioural training, stress Mx, hypnotics
  • see also fibromyalgia

internal derangements:

  • see below for disk displacement & ligament injury
bony or synovial disorders:
  • degenerative arthritis:
    • the loss of articular tissues. This usually means destruction of the articular fibrocartilage of the condyle and fossa, in part or whole, and metaplastic or destructive changes in the disk and its attachments.
    • may have secondary synovitis which is thought to be the result of particulate debris buildup following microfibrillation with resultant microtrauma and the production of inflammation mediators via the arachidonic acid cascade.
    • may present with preauricular pain, otalgia, lateral and endaural palpation tenderness, or crepitant joint sounds on auscultation. Radiographs can confirm the diagnosis
    • Ix: OPG tomograms or CT
    • Rx: NSAIDs, physical therapy, arthrotomy, joint replacement, orthognathic occlusal reconstruction
  • inflammatory arthritis (eg. Rh A):
    • Rx: NSAIDs, corticosteroids, autogenous or alloplastic reconstruction, orthognathic occlusal reconstruction
  • congenital deformities (eg. condylar aplasia)
  • developmental deformities (eg. condylar hyperplasia)
  • ankylosis:
    • is divided into fibrous and bony types. Fibrous ankylosis may be the result of chronic inflammation or disuse. Various degrees of fibrosis are seen with disk displacements. Bony ankylosis may reflect partial ossification of the joint complex or complete fusion of the mandible to the temporal bone.
    • Ix: OPG tomograms or CT
    • Rx: arthrotomy with disc reconstruction; costochondral graft or total joint replacement
  • fractures
  • neoplasms

Key points in Mx of TMJ disorders:

  • Temporomandibular joint syndrome is an outdated concept.
  • Most TMJ pain is muscular rather than joint pain.
  • Early intervention for disk displacements is the key to success.
  • Imaging is indicated for confirmation of disk pathology and bone status before surgery or to establish a treatment baseline.
  • Early surgery is conservative therapy for painful disk disease.
  • Disk repair surgery is the mainstay for disk displacement.
  • Arthrocentesis and arthroscopy are effective for early nonreducing disk displacement.
  • Conchal cartilage is an excellent donor source for replacement of articular cartilage and interpositional tissue mass.
  • Ankylosis and secondary arthritic deformities can be successfully treated with autogenous reconstruction.
  • Reconstructive procedures can be combined to satisfactorily restore form and function in lieu of a U.S. Food and Drug Administration (FDA)-approved joint prosthesis.
  • Orthognathic surgery may be necessary to restore the occlusion after prolonged disease or occlusal-oriented therapy.
  • The ability to diagnose and treat diseases and disorders of the TMJ and stomatognathic complex has never been more thorough or accurate. Predictable treatment regimens are available, and appropriate therapies can be instituted without delay. Surgery is no longer considered a treatment of last resort. In some cases, surgery should be considered the primary, conservative intervention.
  • The importance of working with a well-trained team or referral group cannot be overemphasized. Generic referral to the patient's dentist is no longer appropriate after ear disease has been ruled out as a cause of preauricular or panfacial pain. All the components of multimodal treatment are necessary for the most reliable outcome and the quickest success.

TMJ disk displacement & ligament injury:

  • disk displacements are caused by disruption of the ligamentous attachment of the disk to the condyle and the subsequent pull of the lateral pterygoid muscle.
  • usually a condition of young adult women.

mechanisms of ligament stretch or tear:

  • acute blunt trauma to the mandible
  • systemic joint hypermobility
    • autoradiographic studies have demonstrated estrogen receptors in the ligaments of the primate TMJ and confirmed sexual dimorphism in the concentration of these sex hormone receptors. This dovetails nicely with the high female-to-male ratio of TMJ disk derangements. Clinical studies have confirmed an increased frequency of generalized joint hypermobility in the population of patients with TMJ internal derangements. Hypermobilities are more common in women than in men.
  • structural weakness
  • mandibular hyperextension which may be caused by:
    • prolonged dental appointments
    • forceful third molar removal
    • difficult intubation
    • subluxation during tonsillectomy
    • prolonged oral sex with hyperextension
  • by far, the most common vector of displacement of the disk is in the anteromedial direction because of the orientation of the lateral pterygoid muscle.
  • the degree of displacement correlates with clinical symptoms.
  • the exact cause of the pain component is thought to be part mechanical and part chemical. With the disk displaced anteriorly, the meniscotemporomandibular frenum (i.e., retrodiskal pad) is stretched over the condyle and compressed between the bony components. The chronic irritation causes inflammation of the synovium and release of noxious peptides (e.g., substance P) into the synovial fluid.

a classification for these anterior disk displacements:

overview of this classification:
  • these types represent the clinical progression of the stages in chronic disk derangement. A patient with a type II derangement often gives a history of having passed through the phases of type Ia and Ib, and many type III patients present with a history that recapitulates the type I and type II signs and symptoms.
  • outcome predictors correlate well with the stage of derangement. The best prognosis is for a nonpainful click that occurs early in the opening motion. (The earlier the click, the less displaced is the disk.) A painful, late click is less likely to respond to primary intervention, and a type III derangement almost always requires surgical treatment for clinical improvement to take place within a reasonable period. Because duration of symptoms is highly weighted in the prognosis equation, early treatment or referral is imperative for disk derangements. A surgeon should be included in the early phase of treatment planning to ensure proper sequencing of nonsurgical and surgical modalities.
type Ia internal derangement:
  • presents with a non-painful click during the opening or closing movements of the mandible. The noise occurs as the condyle moves under the anteriorly displaced disk during opening and again as the disk is held anteriorly while the condyle moves posteriorly during closure.
  • no imaging needed
  • Rx: none or antero-posterior splint
type Ib derangement:
  • is the same as type Ia but has pain as part of the condition.
  • Ix: MRI if unresponsive to primary Rx
  • Rx: none, NSAIDs or antero-posterior splint
type II displacement:
  • has the same clinical presentation as the type Ib patient. The maximal oral opening is the normal interincisal distance of 40 to 50 mm, and there are clicking sounds during opening or closing. Unlike the type I patient, the type II patient gives a history of locking (i.e., inability to open the mouth fully). The closed lock is caused by the inability of the condyle to translate under the disk. The disk therefore becomes a mechanical obstacle to normal condylar movements. This may occur intermittently due to changes in disk position, distortion of the normal disk morphology, or changes in the normal synovial lubrication of the joint.
  • Ix: MRI if unresponsive to primary Rx
  • Rx: NSAIDs, antero-posterior splint, surgical disc repair or physical therapy
type III displacement:
  • a persistent closed lock. In this patient, there is no translation of the condyle under the displaced disk. Hence, there are no joint clicks, and the maximal opening is reduced.
  • Ix: MRI or arthrotomy
  • Rx: NSAIDs, arthrocentesis, arthroscopy, or arthrotomy

References:

  • WILLIAM C. DONLON in Head & Neck Surgery—Otolaryngology 2001 Lippincott Williams & Wilkins
tmj_disorders.txt · Last modified: 2009/09/09 22:34 (external edit)