Journals    
Present Issue 
Past Issues 
 

THESMANEWS   
Present Issue 
Past Issues 
 

SMJ Editorial Board 

Letters to the Editor

Instructions to Authors 
 

Singapore Med J 1999; Vol 40(03):

Temporomandibular Disorders - An Overview
A U J Yap, V C L Ho

ABSTRACT

Temporomandibular disorders (TMD) have been an area of increased clinical and scientific inquiry in dentistry. This is due to increased patient awareness and desire for treatment as well as scientific advances in the fields of epidemiology, neurobiology and diagnostic imaging. This article

sets out to introduce this disorder and describes its aetiology and management.

Keywords: temporomandibular joint disorders, temporomandibular joint pain dysfunction syndrome, craniomandibular disorders

INTRODUCTION

Aetiology

The aetiology of TMD is still widely disputed in the literature and claims of success have been made for a wide variety of treatment modalities ranging from psychotherapy to complex occlusal rehabilitation. There are several possible reasons for these disagreements, some of which are obvious. Firstly, such patients are treated by diverse medical and dental specialties which will invariably view the problem from different perspectives. Psychological stress, which is an important element in TMD, renders patients susceptible to placebo effects of any treatment carried out. In fact, placebo effects for a variety of dental treatments has been shown to be effective in 40% - 60% of cases treated(6). It is thus essential that only objective signs such as mandibular movements, and not subjective ones, be used as a measure for success. Finally, there exists the problem of standardisation of diagnostic criteria. Complicating this issue even further, is the fact that patients are often not diagnosed on initial presentation. The two major concepts that have evolved pertaining to the aetiology of TMD, are morphofunctional and psychological.

Morphofunctional concept

Historically, a number of occlusal factors have been linked with TMD. These include the number of teeth in contact, loss of vertical dimension and orthodontic malocclusion. Over the past two to three decades, occlusal interferences (contacts between teeth that interrupt the free sliding movement of the mandible) and poor intercuspal contacts (the contact between cusps of opposing teeth) have been considered of prime importance. Based on comparative anatomy and histology, Robinson(7) concluded that the temporomandibular joints are not intended to be stress bearing. As one can postulate that a fairly intact dentition with an adequate intercuspal position can dissipate forces produced by the masticatory muscles during function and parafunction, it is conceivable that posterior teeth loss can predispose to overloading of the joints. The mode of action of interferences and deflective contacts have been attributed to the induction of parafunction activity(8) and aberrant function(9). Aberrant function may be defined as changes in functional movements and mandibular posture that occur as a result of subconscious avoidance of aberrant tooth contacts.

Psychological

Psychological stress has been shown to cause masticatory muscle hyperactivity(10). Muscle hyperactivity may be expressed in parafunctional activities such as clenching and grinding; leading to pain in the muscles as well as repeated overloading of the joints. A study by Moody and co-workers(11) suggests that patients suffering from TMD experienced a greater number of life crises and health changes (life-change units - LCU) over a given period of their lives than patients with other illnesses. There are a number of possible explanations as to why TMD patients have higher LCU totals. One explanation may be that as the number of life changes being experienced by a patient increases, so does psychological stress, which is an aetiologic factor in TMD. Another explanation may be that as life changes increases, the patient’s ability to cope with existing symptoms decreases. Rao and Glaros(12) also indicated in their report that TMD patients have significant life stress but unlike non-patients, they do not exhibit the usual habitation responses to stress. In either case, the symptoms are accentuated to the extend that the patient will seek professional help.

The current most widely accepted theory however, is that the symptoms of TMD are primarily a group of psycho-physiological disorders in which an injury producing activity may be initiated, resulting in an overload of the temporomandibular joint and its supporting musculature and surrounding soft tissues. Such injury-producing activities include both acute trauma (any incident that stretches and loosens the disc attachment) and chronic trauma (any factor that cause excessive loading of the joint or masticatory muscles). Examples of acute trauma are overstretching from iatrogenic dental and oral surgical procedures and direct injuries to the face and jaw. Chronic trauma can arise from unilateral chewing habits, frequent mastication of hard foods, lack of occlusal stability and stress-induced muscle tension and bruxism/clenching. Arthritic diseases like rheumatoid arthritis and osteoarthritis may also precipitate TMD. Pathology and pain occurs when the reparative capacity of the tissue is exceeded. Other systemic diseases like systemic lupus erythromatosus, scleroderma and psoriatic arthritis also give rise to inflammatory joint diseases and should be considered when assessing joint pain.

Diagnosis

Joint disorders

• explanation of the disorder to the patient, reassurance and counselling

• rest and isokinetic exercises for the jaw

• physiotherapy modalities eg. moist heat, ultrasonic energy, transcutaneous electrical nerve stimulation (TENS) (Fig 1)

• orthopaedic appliance therapy (occlusal splints) (Fig 2 and Fig 3)

• rehabilitation of dental deficits if such inadequacies in dentition result in excessive masticatory effort or pathology

• Medication eg. analgesics, non-steriodal anti-inflammatory drugs (NSAIDS), muscle relaxants, tri-cyclic anti-depressants (TCA)

Unless the psychological side of the aetiology is not too dominant, correctly carried out phase 1 treatment should provide a successful and conservative way of helping TMD patients. From a study of 154 patients, it was concluded that most TMD patients have minimal recurrent symptoms 7 years after conservative treatment(13). Although symptoms can resolve swiftly in some patients, in others, however, treatment may need to continue for a number of months. Efforts should be directed towards the reduction of both initiating and perpetuating factors. It is important that stage 1 joint disorders be differentiated from stage 2 disorders. Patients should be referred for specialist treatment if they do not respond to phase 1 treatment, if stage 2 disorders are diagnosed and, in particular, if there is any suggestion of emotional illness.

• occlusal equilibration (modification tooth form with the intent of equalising stress)

• orthodontic therapy (correction of bite discrepancies by movement/realignment of teeth with braces, removable and functional appliances)

• restorative therapy (replacement of lost tooth structure, teeth or oral tissues with crowns, bridges, overlay prostheses, dentures etc)

• orthognathic surgery (surgical repositioning of all or parts of the maxilla and/or mandible)

• combination of the above treatments

• arthrocentesis (joint "washout" procedures)

• arthroscopy (closed surgical procedure using an arthroscope)

• arthrotomy (open surgical intervention on the temporomandibular joint ranging from discoplasty, discal repositioning and repair, or disectomy with or without replacement to arthroplasty)

Muscular disorders

Pain from the musculature of the head and neck is very commonly perceived in the region of the mouth and the associated structures(14) and consequently, dental professionals are frequently approached for management. After a complete history has been recorded, this may include a psychological or psychiatric evaluation, masticatory and neck musculature are examined for the presence of trigger points which may be referring pain to the temporomandibular joint or other facial structures. Trigger points can be localised by application of pressure to the muscle with the tip of the finger or by squeezing between the thumb and the forefinger. This often accentuates the pain both locally and at the referral area. Autonomic concomitants may include blurred vision, excessive lacrimation, rhinitis, conjunctival reddening and congestion of the maxillary sinus. Management of muscular disorders include:

• patient education, awareness of physical and emotional components

• restriction of extreme mandibular movement and soft diet

• moist heat applications followed by stretching exercises

• deactivation of trigger points [vapocoolant spray and stretch, trigger point injection with local anaesthesia, ultrasound, ischaemic pressure, acupuncture (Fig 4) or TENS]

• orthopaedic appliance therapy, if clenching or parafunctional activities are present

• a well designed self-care programme to maintain the benefits of therapy, eg. passive stretching exercises, good posture and avoidance of prolonged contraction of muscle groups

Behaviour modification

CONCLUSIONS

TMD is undoubtedly a highly controversial area of dentistry and it is impossible to discuss all the issues involved in this single article. It is however, important for us, health professionals, to know that this group of psycho-physiological problems do exist and that the majority of TMD patients get better with time. Only a minority of patients require surgical interventions. However, it is still advisable that referrals to the relevant specialists be undertaken when in doubt about its diagnosis. Treatment protocols in general, are conservative, non-invasive and reversible.

Dr A U J Yap