Temporomandibular disorders (TMDs) involve musculoskeletal pain disorders and functional disharmony of the masticatory system. TMD is one subcategory of orofacial pain that includes intracranial pain, headache, neuropathic pain, intraoral pain, and all other pains associated with the head and neck.< ?xml:namespace prefix = "mbp" />1 The preliminary role of the dental practitioner is to discern whether the patient’s clinical presentation reveals a diagnosis of pathology or dysfunction that is within the realm of dental treatment and/or if the clinical diagnosis requires allied medical collaboration for effective management. Once the problem has been verified to be within the realm of dental therapy, the clinician must identify the source of the problem and treat accordingly. Often the originating source and symptomatic site of the pain are incongruous, which differs from conventional dental diagnosis. Unless the primary site from which the pain emanates is addressed by therapy, control of the problem will remain elusive.2 Hence, history and examination are critical to diagnosis, but also unlike most dental diagnoses, the importance of the patient’s history of the disorder is far more indicative than presenting signs. Keen diagnostic skills in the treatment of TMD are the key to successful management, as TMD is often a combination of etiologies rather than a single anatomical or functional disharmony. Combination of etiologies often complicates successful treatment and can frustrate the clinician and patient.
Many diagnostic systems and algorithms of TMD have been proposed since otolaryngologist James Costen first published his findings in 1934. Costen3 described a small group of patients with ear/sinus symptoms in conjunction with functional disturbance of the temporomandibular joints (TMJs). Okeson2 has emphasized the importance of determining whether the presenting signs or symptoms are truly emanating from the region of complaint or whether the symptoms originate from a distant site by virtue of interaction of nerve fibers that coalesce in the upper spinal cord and brain stem. He applied the terms primary pain and secondary or heterotopic pain to these two phenomena, respectively. Successful delineation of primary and secondary pain can mean the difference between treatment success and failure, since quality treatment can unequivocally fail if applied to the incorrect site or misdiagnosed clinical situation. Consider a patient experiencing left-sided mandibular pain as a result of a myocardial infarction who is treated via delivery of a maxillary splint, which provides a perfect mutually protected occlusal scheme. The infarct remains of fatal potential despite apparent harmony of the masticatory system.
TMDs can be classified into several subcategories2:
• Masticatory disorders including protective co-contraction, persistent local muscular soreness, myofascial or trigger-point pain, myospasm, chronic myositis, and fibromyalgia. These disorders predominate in frequency and are each managed differently.
• Dysfunction of the joint complex itself including disc displacements, disc/condyle/fossa incompatibilities including adhesions, and subluxation/dislocation. These problems may require surgical co-therapy and can often be anatomically documented by modern imaging techniques.
• Inflammatory conditions including capsulitis, synovitis, retrodiscitis, arthroses, and posttraumatic sequelae. Many are self-resolving and require little therapeutic management if diagnosed correctly.
• Hypomobility including ankylosis, muscle dysfunction, and anatomical impedance ranging in need from continued surveillance to initiation of collaborative care with multiple co-therapists.
• Growth disorders including congenital bone and muscle disorders.
Accurate diagnosis and classification are critical to proper management to determine therapeutic modalities and to assess the need for involvement of allied specialists. For example, as chronicity of TMD increases, so do the number of therapists needed for effective management given increasing difficulty in management. In general, dental practitioners are most effective at managing acute muscle problems but require increased collaboration to provide effective care as joint involvement and chronicity increases.
The intent of this chapter is to address the most common questions pertaining to TMD that arise in dental practice. Hence, the approach to these questions is intended to be practical and applicable to routine care delivery.
1 When is treatment indicated for TMD?
The presence of joint sounds is insufficient reason to implement therapy. Consequently, the persistence of joint sounds alone is an inadequate criterion for success or failure of therapy. Pain and/or loss of function are the hallmarks of need for treatment.2 As other weight-bearing joints of the body emit joint sounds during function, the TMJs are no exception. Thus, signs and symptoms of TMJ dysfunction are common but well tolerated and are often ignored by the patient. Although statistics vary, Dolwick and Dimitriulis4 report that 60% to 70% of the population display at least one sign of TMD and 25% display at least one symptom. It is more often seen in females than males. Furthermore, TMD is a phenomenon most commonly noted during the patient’s reproductive years with peak frequency between the ages of 25 and 44 years, and only 0.7% by age 65. Hence, it is logical to infer that signs and symptoms self-resolve without or in spite of therapy. This phenomenon has been termed regression to the means and occurs frequently in nature.2
Disc position is also not critically related to the success or failure of treatment. A recent study has shown that although approximately 75% of those who have undergone arthroscopic surgery for difficulties in opening may have improvement with significant pain reduction, subsequent MRI imaging of the joints of these patients has demonstrated no true change in disc position.5 Condylar position and occlusion may not be highly correlated. A recent investigation has revealed that there is a significant difference in the occlusal position of asymptomatic patients when comparing maximum intercuspation to condylar-dictated occlusion within the same patient.6
2 What is the role of occlusal disharmony in TMD?
Multiple investigations have indicated that malocclusion and functional disharmony have little role in the etiology of TMD. A review of the literature reveals that most studies exploring this topic are retrospective rather than prospective, and many are viewpoint in nature rather than evidence based. In a recent article involving questionnaire format and multivariate regression analyses of 4290 adults examined for TMD, there was no significant relationship to occlusal factors with respect to temporomandibular symptoms.7 This finding is the norm rather than the exception.
There has been one non-treated clinical population that may have a predisposed profile for TMD. Pullinger et al.8 observed that there was a significantly high probability of nonreducing disc displacement in growing patients with unilateral posterior crossbite. These authors attributed this tendency toward adaptation of mandibular position, which may account for the condylar displacement. Thilander9 also recommended early correction of posterior crossbite to resolve facial asymmetry, normalize muscle activity, and avoid disc displacement resulting from asymmetric skeletal form. A later study7 using a small subject size determined that pretreatment asymmetric joint spaces and asymmetric mandibles resolved by maxillary expansion, thus supporting early correction of posterior crossbite.
There is also insufficient evidence to indicate that occlusal adjustment is effective treatment for TMD unless there is a single tooth in hyperocclusion or is severely mobile.7,8,10
Okeson2 has introduced the term orthopedic stability to describe the simultaneous relationship between condyles that are seated in a musculoskeletally stable position as the teeth are in maximum intercuspation. If the position of the teeth prevents superior-anterior seating of the condyles and the complex is loaded by trauma or parafunction, the loading will occur in an unstable joint relationship. This is called orthopedic instability. The joints, muscles, or teeth are adversely affected. Although many patients demonstrate orthopedic instability, the key factors in the development of symptoms are loading and host susceptibility. There are multiple methods of loading unstable joints inclusive of trauma and parafunction. Host susceptibility remains an elusive factor but may include gender, history, or emotional factors.
3 When are occlusal splints indicated in therapy, and when are alternative forms of management of TMD appropriate?
Some authors advocate the use of splints to diagnostically determine the position of the condyle prior to orthodontic correction or prosthetic rehabilitation.11
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