There is a variety of common diagnostic modalities employed by the health care practitioners to confirm (or deny) an initial diagnosis of TMJ which is based upon objective physical findings and subjective complaints. Some of these diagnostic modalities are more reliable than others. The following is a list of some of the most common ones.
- Conventional Radiography (plain x-rays, including Panorex) is quick, painless, and relatively inexpensive. However, since they only show just the bony structure of the joint, they are generally useful for ruling out obvious pathological changes and disease processes.
- Transcranial and tomographic x-rays shows “slices” through the joint. When done properly and interpreted accurately, tomograms give a better view than plain x-rays. Tomography are more accurate unlike plain x-rays. They show the status of the bone. The tomogram provides a precise view of the temporomandibular joint by taking eight postage stamp serial views of the joint, slice by slice. Each view is taken at a slightly different level, thereby allowing the health care practitioner to view the condyle and temporal bone in great detail. In addition, the advantage of a “corrected cut” is the accuracy of the subject anatomy, without artifacts, and its reproducibility before, during and after treatment. The tomogram provides an accurate picture of joint functions and is useful for evaluating evidence of deformity, tumor, osteoarthritis or a previously healed condylar fracture. It does not provide a picture of the soft tissues of the joint.
- Computed Tomography (CT or CAT Scan) provides superb detail of bone in multiple directional planes, with a minimal dose of radiation. They are fairly expensive and provide a somewhat limited view of the disc and soft tissue. They also do not image the cartilaginous disc, ligaments and muscles. The CAT scan is considered one of the least effective tests for diagnosisng TMJ because it is extremely difficult to see the meniscus on a CAT scan.
- Magnetic Resonance Imaging (MRI) produces brilliantly detailed and accurate images of bone as well as soft tissue, and is widely considered the best single way to study the TMJ. No radiation is used; however, since sophisticated equipment is needed, MRIs are expensive and can be cost prohibitive — sometimes over a $1,000 for both sides.
- Arthrography allows the study of the position and function of the joint, including the disc. It involves the injection of contrast dye into the joint, followed by imaging using plain x-rays, tomograms, videotape, or a combination. A skilled examiner is a must, and the procedure can be very uncomfortable, but if done properly, arthrography can be an extremely accurate diagnostic tool.
The thermogram is a test that records heat and is allegedly used to locate areas of pain in suspected TMJ patients. The thermogram produces a dramatic, high-color, high-tech picture of the pain. The validity of thermograms in diagnosing any condition is hotly debated. A review of the medical literature indicates a clear lack of peer review support for this diagnostic technique and it should be viewed with a great deal of suspicion when it serves as a basis for diagnosing a TMJ injury.