Fig. 9.1 OPT showing idiopathic condylar resorption.

Trismus

•   Classically, an inability to open mouth due to muscular spasm, but commonly used to refer to limited mouth opening.

•   Normal inter-incisal mouth opening is 35–45mm.

•   Extra-articular causes:

    •   odontogenic infection;

    •   facial trauma including dento-alveolar surgery;

    •   myofascial pain/TMJDS;

    •   following ID LA block;

    •   depressed fractured zygoma/arch;

    •   radiation fibrosis;

    •   tetanus;

    •   quinsy;

    •   local malignancy;

    •   submucous fibrosis;

    •   coronoid hyperplasia;

    •   malignant hyperpyrexia.

•   Intra-articular causes:

    •   ankylosis—bony/fibrous;

    •   facial trauma—effusion, fracture;

    •   meniscus displacement;

    •   osteophyte formation;

    •   septic arthritis.

Myofascial pain

•   Synonyms: myofacial pain/facial arthromyalgia.

•   Spectrum of facial pain disorders secondary to parafunctional habits, without signs and symptoms of TMJ internal derangement.

Temporomandibular joint dysfunction

•   Most common non-infective pain disorder of the oro-facial region.

•   Meta-analysis show that the overall prevalence of TMJDS in population studies ranges from 30–45%.

•   More common in ; : ratio of 1:3.

•   Mean age is between 30 and 40 years.

•   Pain is typically diffuse, cyclical and distributed in multiple sites, especially the muscles of mastication; it is frequently worse in the morning.

•   Related to stress and parafunctional habits.

•   Associations: depression, back pain, tension headaches, migraine, irritable bowel syndrome, fibromyalgia.

Features

•   Pain.

•   Clicking.

•   Locking.

•   Crepitus.

•   Trismus.

Clinical findings

•   Tenderness of the pre-auricular region and muscles of mastication.

•   Clicking, usually with abnormal path of opening.

•   Evidence of parafunctional activity—such as clenching causing dental attrition, linea alba affecting the buccal mucosa, scalloped tongue, masseteric hypertrophy, and biting of finger nails.

Internal derangement

•   Occurs where the articular disc within the joint interferes with smooth functioning of the joint.

•   Clicking usually indicates reducible displacement of the disc.

•   Clicking is usually related to abnormal paths of opening, with protrusion and/or lateral deviation.

•   Some patients will go on to develop locking.

•   Closed lock: mouth cannot open beyond around 25mm as the head of the condyle impinges on an anteriorly displaced disc.

•   Open lock: patient unable to close the mouth without manipulation, since condyle is trapped in front of posteriorly displaced disc.

•   Locks may be reducible (patient can manipulate the jaw to regain mobility) or irreducible.

•   Disc may perforate (associated with joint crepitus and the development of osteoarthritis).

Investigations

•   Routine radiography does not change management in classical TMJDS.

•   An OPT may eliminate dental pathology radiating to the ear in a non-classical pain pattern.

•   Radiographic features of OA:

    •   narrowing of joint space;

    •   bone cyst (geode) formation;

    •   remodelling;

    •   osteophyte formation.

•   MRI is the gold standard imaging for the TMJs. It can be useful in the assessment of patients with trismus where a closed lock (or other pathology) is suspected (Fig. 9.2).

•   Approximately a third of asymptomatic patients have anterior displacement of their discs on MRI scan.

•   CT scanning is superior for assessing bone detail.

Management/treatment

•   Reassurance and explanation.

•   Education regarding parafunctional habits.

•   Jaw exercises, e.g. straight line to eliminate click.

•   Physiotherapy.

•   Analgesia.

•   Heat.

•   Rest/soft diet/relaxation.

•   Splints/bite guards/bite raising appliances:

    •   variety of materials, designs, and for either jaw;

    •   possible mechanisms of action include reduction of bruxism and other parafunctional habits, production of a gap between the condyle and fossa to free the disc, and possible placebo effect.

Other interventions

Tricyclic antidepressants

•   Have analgesic and muscle relaxant effects independent of their antidepressant action.

•   No RCTs show efficacy in TMJDS.

Occlusal rehabilitation

•   Most patients with abnormal occlusions do not suffer TMJ pain.

•   No evidence of benefit.

•   Orthodontic treatment or orthognathic surgery is not a treatment for TMJDS.

Arthrocentesis and manipulation

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