Osteoarthritis of the Temporomandibular Joint
Osteoarthritis (OA) of the temporomandibular joint is a unilateral, degenerative disease of the jaw joint. It is characterized by breakdown of the articular cartilage, architectural changes in bone, and degeneration of the synovial tissues causing pain and/or dysfunction in functional movements of the jaw. Figures 1 and 2 illustrate an MRI and an annotated drawing of a normal joint, while Figure 3 presents an MRI of osteoarthritis of the TMJ. Until recent years, OA of the temporomandibular joint was confusing, relatively unrecognized, and difficult to diagnose and manage. Scientific research had found neither a common cause, nor a clinically useful and differentiable diagnostic test. This resulted in a diagnostic journey full of frustration, pain, and expense. Due to its multifaceted nature, the disease has no defined or linear progression of symptoms. The symptom complex is not the same from one patient to another: it can exist in a quiet state until it is set off by an array of events or it can be painful from the start.
With osteoarthritis, the jaw joint can be the first joint to get the disease, whereas in rheumatoid arthritis it is the last joint to be affected. It can be anywhere from a 3:1 or 6:1 female-to-male ratio.1 The cost of the pathology was estimated to be $16.7 billion in 1984.2 Of the patients presenting to University Florida Parker Mahan Pain Center, 16.8 percent of the patients each year have OA of the jaw joint, of which 90 percent are female with an average age of 48.3.3 Of the patients who presented to Raleigh Facial Pain Services in the years 2000 and 2001, 11 percent had OA of the jaw joint, with 86 percent being females and an average age of 51. In another pain center study, of the 200 patients having jaw joint problems, 67 percent had disc displacement with reduction, 22 percent disc displacement without reduction, and 10 percent had OA.4 Diagnosis is complicated in that there is a lack of correlation between damage and pain with radiographic evidence.5
One of the most important events in the diagnosis of osteoarthritis was the establishment of a new specialty called orofacial pain. The orofacial pain specialist is familiar with the different presentations of osteoarthritis and can coordinate the different specialties necessary to manage the problem. However since OA of the TMJ does have several different presentations, it has taken time for the diverse specialties of rheumatology, orofacial pain, physical therapy, and psychology to coordinate the requisite patient care. With the advent of new scientific and clinical knowledge, we are entering a new era of increased awareness, improved care, and improved quality of life for people afflicted with OA.
The patients who develop OA present with a variety of symptoms including pain on opening, limited movement to the opposite side, coarse grinding noise on function, history of clicking that has now stopped, and deviation on opening to the affected side. An unusually large percentage of those diagnosed are women around the age of 35.6 In addition, 31.6 percent have had a macrotrauma usually from a maximal voluntary contraction (MVC) force or even a blow to the mandible. The clinical findings are pain on palpation of lateral pole, decreased range of motion, flattened condyle, osteophytes on condyle, heavy occlusion on second molar on the affected side, facial asymmetry, and tipped Curve of Wilson. Some other indicators include loss of condylar bone which traumatizes the posterior molar on the same side, pain referral pattern to the ear, pain on eating, talking, or function of the jaw joint, jaw locking, and pain in the front tooth of a bridge due to torque forces on two molars. In summary, a picture of pain, dysfunction, and disability is involved in osteoarthritis of jaw joint.
The typical patient may have years of jaw pain, joint clicking with or without pain, disc displacement, joint dysfunction, and eventually osteoarthritis. Unfortunately, most patients are not typical. Our common perception of OA is a 70-year-old man in a nursing home with osteoarthritis of knees and hips getting OA of the jaw joint also. In reality, the most common person with OA of the jaw joint is a 33-year-old female with two kids, husband, dog, and job. Even a third grader (10-year-old female) can get OA of the jaw joint. The following is a sampling of the variations in presentations that may occur to the medical and dental professionals.
Patient #1 had recurrent unilateral ear pain for years. Frequent trips to the doctor provided no evidence of ear inflammation and rounds of antibiotics provided no benefit. Eventually, an ENT specialist then referred the patient to an orofacial pain specialist.
Patient #2 went to a dentist for frequent fractured teeth, toothaches, and recurrent abscessed teeth on the posterior teeth on one side. After several root canal, crowns, or extracted teeth on the left lower posterior area, the dentist referred the patient to an endodontist. The endodontist, feeling another root canal would not be appropriate, referred the patient to an orofacial pain specialist.
Patient #3 had years of left jaw pain with the pain suddenly shifting to the right with limited opening. The panograph revealed the left joint was severely eroded but the right joint looked apparently normal.
Patient #4 having just completed 14-unit precision bridge work on the all the upper teeth, developed pain in tooth #12 on cementation. After months of fine tuning the bridge work, she was sent to an endodontist for root canal therapy on the painful tooth. The endodontist felt it was not the tooth and recommended referral to an orofacial pain specialist, but at the insistence of the patient, performed root canal therapy with no benefit. A visit to the orofacial pain specialist confirmed OA of the temporomandibular joint.
Patient #5 presented with a bite that had suddenly changed but without any pain. This patient was correctly diagnosed with OA of the temporomandibular joint when a dentist took a panograph and found a smaller deformed condylar ball on the same side as the bite change.
Disease Inception and Progression
OA of the temporomandibular joint is a disease having a great deal of variation in progression, symptoms, epidemiology, pathophysiology, and presentation. The rate of progression from a healthy joint to a severely damaged joint of OA can vary from a very short time to decades. The fourth and fifth decades of life are the most prominent age to get OA of the jaw joint.
The pattern and rate of progression relates to the set of initiators, aggravators, and perpetuators and how they interplay with each other. There are five known factors related to the onset of—or set the stage for—osteoarthritis. These contributing factors are parafunction, occlusion, psychosocial aspects, macrotraumas, and genetics.