Accurate diagnosis is the most important single step in the management of TM disorders of all types. The therapy is empirical at best and becomes little more than a trial-and-error procedure without it. This has been the weakest link in temporomandibular joint management since the beginning—and remains so. That substantial improvement in diagnosis is more predictive treatment that can be expected in the future.
The radiographic methods which are applicable to temporomandibular joint diagnosis may be grouped into several categories, each having certain advantages and disadvantages. Frequently, it is more than one category which is required to properly visualize the condition present.
- Panoramic projection
- Transorbital projections
- Computed tomography (CT scanning)
- Arthrotomography (contrast tomography)
- Scintigraphy (nuclear scanning).
The need for visualization of the TMJ should be established on the basis of selection criteria. Selection criteria represent those clinical signs and symptoms that suggest that a radiographic examination would contribute to the proper diagnosis and care of the patient. They provide a rationale for selecting among the various imaging modalities, with the goal of obtaining the necessary diagnostic information without unnecessary patient expense or radiation exposure. The most appropriate imaging procedures are those that provide new information that will influence patient care. Selection of an examination is influenced by many, sometimes competing, factors. The decision should be made after considering the history and clinical findings, clinical diagnosis, cost of the examination, amount of radiation exposure, and results of prior examinations, as well as the tentative treatment plan and expected outcome.
A variety of diseases affect the temporomandibular joint including : congenital and developmental malformations of the mandible/cranial bones; acquired disorders, which include neoplasia, fractures, dislocations, ankylosis and disk displacement; inflammatory diseases that produce synovitis and capsulitis; a wide range of arthritides; and various post-treatment conditions. Diagnosis of these conditions frequently cannot be made with clinical examination alone.
In broad terms, the aim of imaging the temporomandibular joint is the same as in any other region of the body, namely, to evaluate the integrity of the structures when disease is suspected, to confirm the extent of known disease, to stage the progression of known disease, or to evaluate the effects of treatment. With respect to the TMJ this involves assessment of the integrity and relationships of the hard and soft tissues, including the mandibular condyle, the glenoid fossa and articular eminence of the temporal bone, and the articular disk and its attachments.
All imaging techniques are not equally effective for each of the many conditions that affect the TMJ. Efficacy of any imaging examination rests not just with its technical adequacy but also with its diagnostic accuracy, a complex interaction between the image and the person interpreting it. In addition to this, there has been sophistication of imaging technique that does not guarantee better management of the patient.