Orthodontics and Temporomandibular Joint (TMJ) Disorders
The temporomandibular joint (TMJ) is the joint between the lower jaw and the base of the skull. TMJ disorders (TMDs) refer to a group of disorders with symptoms that include pain, clicking, grating in the jaw joint, and problems with chewing or opening the jaw. This condition can be known by a variety of names, including craniomandibular disorders (CMDs), and is a frequent cause of facial pain problems (Dworkin & LeResche 1992). A positive relationship between occlusal factors (the way the teeth bite together) and TMD has been suggested (Ramfjord 1961). However, the term TMD may eventually be discarded as we come to understand the underlying pathophysiology of this disorder, especially with respect to chronic musculoskeletal pain. Prevalence studies have reported approximately 75% of the population has at least one sign of joint dysfunction (abnormal jaw movement, joint noises, tenderness on palpation, etc.) and approximately 33% have at least one symptom (facial pain, joint pain, etc.) (Rugh & Solberg 1985; Schiffman & Friction 1988). It is a significant finding that in all studies except one (Talaat, El-Dibany & El-Garf 1986) females are affected more than males. There are many suggested causes of TMD, although it is generally accepted that TMD covers a significant number of conditions but with common symptoms. Various theories have been put forward that relate the occlusion (bite of teeth), trauma, and stress to TMD (Bell 1986). It is suggested that the common signs and symptoms of TMD—pain, joint sounds (clicking, grating), and limited or asymmetrical jaw movement—may have an effect on health and quality of life, which in turn can lead to anxiety.
A developing view of TMD is linked to that of low back pain. The use of the word psychogenic suggests there is no known physical cause. However a bio-psychosocial model is developing as the most heuristic approach to chronic pain (Gatchel et al. 2007). This has been related to TMD (Suvinen et al. 2005), whereby the interaction of basic neuroscience processes of pain (the bio of biopsychosocial) with psychosocial factors or the interaction of psychological and social factors with the processing of information in the central nervous system influence health. The causation related to gender predisposition may be associated with genetic variations of pain perception, although this is yet to be defined (Tedeger & Lötsch 2009). There is some data that link pain to the circulating hormones. One study in particular, although with a limited sample size, considered low levels of estrogen relating to highest levels of pain (although increased levels of pain may also be associated with the most rapid periods of change of estrogen levels) (LeResche et al. 2003).
Treatment options for TMD include reassurance (patient education, self-care, and behavior therapy); physiotherapy (such as ultrasound, megapulse, acupuncture, short-wave diathermy laser, heat exercises, and biofeedback); splint therapy, drug therapy; occlusal adjustment; surgical intervention; and combined treatment. Acupuncture has been a particular treatment modality favored by List and colleagues (1993), and there are numerous articles in the literature relation to this topic. It is, however, outside the remit of this review. Certain authors consider conservative, “low-tech” treatment, as success rates from invasive treatment do not produce a better result (Stohler & Zarb 1999). Furthermore, some authors actually debate the need for treatment: LeResche (2001) suggested only 10% of the population aged over 18 are likely to have symptoms and McNeill (1997) and Okeson (1996), using other authors’ data, estimated that 3.6%–7.0% actually need treatment.
Occlusal adjustment (OA) is the selective adjustment of the biting surface of the teeth by grinding the enamel (outer layer of the tooth) so that the upper and lower teeth fit together (the intercuspal position) harmoniously and is the subject of another Cochrane review (Koh & Robinson 2003). The summary finding, however, is that there is no consistent data to support this permanent change in the shape of the occlusal surface of the teeth to treat TMD. Cochrane reviews of other treatments (e.g., splint therapy or surgery) are also underway or are published. It is not clear if malocclusion has a causal role in TMD. However, orthodontic treatment has been used in studies to prevent TMD. There are ethical and clinical implications if orthodontic treatment is found to be ineffective in preventing or initiating TMD.
As all the muscles associated with chewing may be affected by the disorder, the pain is often felt away from the joint, so the term CMD has also been described (Dworkin, LeResche & DeRouen 1990). Okeson (1997) described TMD as a collective term including a number of clinical problems that involve the chewing muscles, the TMJ and associated structures, or both. Psychosocial factors play a major part in the causes of TMD, and by treating/managing the factors associated with stress and anxiety of the patient, the symptoms and signs of TMD can often be reduced or stopped (Greene 1995).
There is a distinct profile of the types of patients affected by TMD, and the number of people affected by the condition increases with age. It is far more common in females to the point that only females are reported in some studies, with no record of the incidence or prevalence in males affected (Landi et al. 2004; Miller, Mancl & Critchlow 2005). In a report by Lipton, Ship & Larach-Robinson (1993), TMJ pain was reported by 5.5% of the population in a survey of 45,711 U.S. households. Previous studies have indicated that approximately 75% of patients have at least one sign of joint dysfunction (abnormal jaw movement, joint noises, tenderness on palpation, etc.), and approximately 33% have at least one symptom of TMD (facial pain, joint pain, etc.).
There is a significant degree of controversy regarding the relationship of TMD and orthodontic treatment (Luther 1998a, 1998b). The use of orthodontic appliances to correct the alignment and vertical relationships of teeth has small yet significant risks: an increase in plaque buildup, leading to an increase in oral and dental disease; a reduction of bone support to the teeth; and possible root resorption (Ireland & McDonald 2003). Included in the possible risks of orthodontic treatment is the concern related to the development of TMD. There are many studies that have examined the interrelationships of the occlusion (malocclusion) and the development of TMD. The reports appear to relate to specific issues:
1. Is the malocclusion, without treatment, related to the development of TMD? The nature of the psychosocial profile of the population studied can vary, and as a consequence, the studies of two groups from differing areas in the same country may nullify each other. In the study by Sadowsky and Polson (1984), groups in both Illinois and New York are examined. In this paper, although there is a comparison between the treated and untreated groups of the socioeconomic background and ethnicities within each study, it is not reported if the two studies were compared in this respect. A 20-year follow-up using questionnaires to self-report the signs and symptoms has demonstrated that while several malocclusion traits were consistent for patients with TMD, there were no strong correlations between them, and as such, screening of malocclusion on the basis of identifying those at risk of TMD was not worthwhile (Helm & Petersen 1989).
2. Is orthodontic treatment capable of improving the signs or symptoms of TMD? A study examining adolescent girls undergoing treatment showed that in the treated group there was a significantly reduced prevalence of muscular signs after treatment but that clicking, a symptom often identified, increased in both the treated, untreated, and normal groups over the 2 years of observation (Henrikson, Nilner & Kurol 1999, 2000).
3. Does orthodontic treatment predispose to the development of TMD in later life? Long-term follow-up studies are clearly difficult but have been undertaken with some robust data acquisition. One group of researchers has followed patients until 30 years of age. They identified no link between orthodontic treatment acting as either a preventative measure or a significant cause of TMD. They did identify significant associations with TMD and general health and psychosocial well-being, as well as neuroticism and self-esteem measures (Mohlin et al. 2004). Another group has reported several papers on the longitudinal follow-up of patients for 20 years. The overall conclusion initially was that although the patients who had undergone orthodontic treatment had a reduced dysfunction index (Egermark & Thilander 1992), further follow-up indicated that orthodontic care did not predispose to the development of TMD in later life (Egermark, Magnusson & Carlsson 2003, Egermark, Carlsson & Magnusson 2005).
Many of the studies, although identifying small associations, fail to isolate a single unique aspect that can either refute or support the association of orthodontic treatment to TMD, presumably because of the diffuse nature of TMD. Thus, it appears that to date the ideal study has not yet been undertaken to assess this, and while there are small but significant risks involved in the use of orthodontic appliances, especially the more complex appliances, the use of a technique without data to support it is not considered appropriate in contemporary health care. This can be especially so if the clinicians are poorly trained in the use of such appliances. Furthermore, the use of any treatment may inappropriately raise patient expectations as well as waste valuable health-care resources (in as much as no patient benefit will be predictably and reliably achieved).
The prognosis of TMD, due to the multifactorial nature of the condition, is difficult to establish. A long-term follow-up of over 30 years (deLeeuw, Boering & Stegenga 1994) established the chronic nature of such a condition.
The working hypothesis appears to be that if the teeth bite incorrectly in the form of a malocclusion, this can then apply a restriction to the function of the TMJ or, worse still, predispose it to future pathological deterioration. By correcting the alignment and arrangement of the teeth, the TMJ will remodel to the overriding new functional needs, thus treating any disease processes or malfunction of joint integrity and allowing normal function to continue unabated for the life of the patient (Moss & Salentijn 1969). The subject can be further subdivided into two aspects or questions: Does orthodontic treatment predispose to later development or worsening of TMD? Does orthodontic treatment permanently and consistently improve the immediate signs and symptoms of TMD?
The following primary null hypothesis was tested:
Orthodontic treatment does not treat or prevent symptoms of TMD.
Specifically, the review addressed the hypotheses of no difference between orthodontic treatment and control for TMD for the following outcomes where data were available:
- overall symptoms
- relief of headache
- patient quality of life
Criteria for Considering Studies for this Review
Types of Studies
All randomized controlled trials (RCTs), including quasi-randomized clinical trials assessing orthodontic treatment in TMD, were included.
Types of Participants
Adults aged 18 years or older with clinically diagnosed TMD were included. There were no age restrictions for prevention trials provided the follow-up period extended into adulthood.
The list of symptoms (Austin & Pertes 1995) included the following:
- The occurrence of recurrent headache (equal or more than two episodes a month).
- Pain in the jaws, face, throat, neck, shoulders, or back.
- Ear symptoms (includes tinnitus, stuffiness, diminished hearing, or pain).
- Pain in the temporomandibular joint (TMJ) at rest and during chewing.
- Day and night time grinding or clenching.
- Stiffness in jaws.
- Difficulties in swallowing.
- Globus symptoms (associated with choking sensations or soreness of the throat).
- Joint sounds (including clicking and grating).
- Spontaneous luxation or locking of the jaws.
The list of signs included the following:
- Palpatory tenderness on either side of the masticatory muscles.
- Joint sounds during jaw movements, elicited by auscultation.
- Distinction between opening and closing clicks, crepitations, and reciprocal clicking (as with previous Cochrane studies of this disorder).
- Tenderness during jaw movements.
- Deviation of the mandible on opening and closing.
- Reduced mandibular range of motion.
- Presence of occlusal interference in retruded, protruded, and medio- and latero-trusion positions of the mandible.
- Wear facets.
TMD was required to be clinically absent at baseline in studies on prevention, and any signs or symptoms associated with pain of dental origin were excluded.
Types of Interventions
The treatment group received appliances that could induce stable orthodontic tooth movement by way of wear for a significant period of time which would induce permanent changes in tooth position. Therefore, patients receiving splints for 8–12 weeks, while capable of moving teeth during the short term, would not be considered.
The control groups received no treatment, placebo, or reassurance.
Studies in which splints had been used prior to placement of orthodontic appliances were excluded.
Types of Outcome Measures
The main outcomes considered were overall symptoms, pain, and headache. Relief from symptoms was assessed using global measures of symptoms. Data on pain were recorded according to frequency, severity, or duration. Where possible, data for the frequency, severity, and duration of pain were aggregated.
Similarly, data on headache were recorded according to frequency, severity, or duration. Where possible, data for the frequency, severity, and duration of pain were also aggregated.
The interval required for outcome measurement was at least 6 months after the intervention.
Limitation of movement. Other signs were ignored because they are neither unique to the disease nor associated with the progression or outcomes of TMD.
Search Methods for Identification of Studies
The subject search used a combination of controlled vocabulary and free text terms based on the search strategy developed for MEDLINE. The search was combined with the Cochrane Highly Sensitive Search Strategy for identifying randomized controlled trials as referenced in Chapter 188.8.131.52 and detailed in box 6.4.c of The Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.1 (updated September 2008).
From Electronic Searches
Databases to Be Searched
The following databases were searched: The Cochrane Oral Health Group Trials Register (to present), The Central Register of Controlled Clinical Trials (to Issue 1, 2009), MEDLINE 1950–October 23, 2009, EMBASE 1980-October 23, 2009.
The search identified all relevant studies irrespective of language. Every attempt was made for non-English papers to be translated.
Checking Reference Lists
The reference lists of all relevant trials obtained were checked, along with the reference lists of relevant review articles. In addition, reference lists from prosthetic dentistry textbooks on temporomandibular disorders and splint therapy were also checked.
The following journals were identified as being important to hand search for this review for the period 1939 to present:
- Acta Odontologica Scandinavica (1939–October 2009)
- Journal of the American Dental Association (1966–October 2009)
- Journal of Oral Rehabilitation (1974–October 2009)
- Journal of Craniomandibular Practice (1986–October 2009)
- Journal of Oral and Maxillofacial Surgery (1982–October 2009)
The review authors examined these journals following the guidance of the Training Manual for Handsearchers (2002).
A comprehensive list of relevant articles, along with the criteria for the review, was included in a letter that was sent to the first author of each paper asking for any unpublished, relevant studies not included in the list. Copies of the same letter were also sent to other experts in the field of TMD or others with an interest in the area. In addition, evidence in the form of scientific art/>