A 22-year-old patient was referred by her dentist to an orthodontist for evaluation and management of a worsening class II, open bite deformity which was also associated with TMJ pain and dietary limitations. She underwent a combined orthodontic and two-jaw surgical treatment with good results (Fig. 3.2a, b). Several months after debanding, she started to develop an anterior open bite again. Ultimately, there was significant degenerative change within bilateral TMJs (Fig. 3.2c) due to continued condylar resorption resulting in progressive mandibular retrusion (Fig. 3.2d, e).
The patient had pre-existing, active TMJ condylar degeneration which was a source of the developing open bite and a progressive class II dentofacial deformity. In the presence of an active resorptive disease process, relapse and redevelopment of the malocclusion should have been expected.
Fig. 3.2 (a, b) Intraoral views of the 8-month postoperative occlusion of a patient (immediately after removal of orthodontic appliances) who underwent combined orthodontic and orthognathic surgical treatment for correction of an open bite, class II skeletal and occlusal deformity. (c) Sixteen-month postoperative panoramic radiograph showing advanced bilateral resorption of condyles. (d, e) Relapse has occurred 4 months later due to continued TMJ condylar resorption
Evidence of condylar resorption in a young person manifested by a progressive change in occlusion or radiographic evidence of TMJ degeneration should alert the surgeon to the potential for progressive condylar resorption (PCR) or a systemic arthritide unless proven otherwise. Specific causes of condylar degeneration include rheumatoid arthritis, internal derangement, use of steroids, trauma, systemic auto- immune/connective tissue (CT) diseases (e.g., lupus, psoriasis, scleroderma), orthodontic treatment, and orthognathic surgery [16, 17].
The etiology and pathogenesis of condylar resorption remains unclear. It may be classified into primary (idiopathic) and secondary (known etiology) depending on the presence of predisposing factors . In PCR, the patient usually presents with a progressively retruded chin, mild TMJ pain with and open bite deformity. In contrast, many patients with TMJ resorption due to CT disease have significant preauricular joint and myofascial pain. Connective tissue diseases that can affect the TMJ are broadly divided into rheumatoid arthritis (RA) and the seronegative spondyloarthropathies. The latter can include conditions such as psoriatic arthritis, lupus arthritis, scleroderma, ankylosing spondylitis, arthritis associated with inflammatory bowel disease, and reactive arthritis. Juvenile idiopathic arthritis can be positive or negative for rheumatoid factor and also affects the TMJ in younger individuals leading to destruction of the condylar growth center with subsequent disturbances in mandibular growth [19, 20]. The metabolic diseases of gout and pseudo gout are also similarly known to affect the TMJ. The effects of these systemic autoimmune/CT diseases on the TMJ may induce a plethora of characteristic radiographic (MRI) findings such as abnormal disc position, abnormal disc morphology, osseous changes in the mandibular condyle, deformity of the articular eminence, and glenoid fossa, besides an abnormal bone marrow signal of the mandibular condyle . If a patient is suspected to be having TMJ disorder secondary to a CT disease, rheumatology consultation is recommended.
If the resorption occurs in a bilateral fashion, there is a symmetric posterior shift of the mandible with class II skeletal and dental malocclusion. On the other hand, asymmetric bilateral or unilateral disease processes may result in a dental and skeletal mandibular midline shift, contralateral posterior open bite, and ipsilateral cross bite. Irrespective of the etiology, it is critical to determine whether the disease is active or not by a thorough history and serial clinical and radiographic evaluations. Computed scans and MRI provide static information and cannot provide information about disease activity. A technetium 99 MDP study can be useful in determining metabolic activity in the condyles. The treatment of TMJ condylar resorption remains controversial and will depend on the extent and stage of the disease. Although it may occasionally be self-limiting, it can be reactivated by orthodontics or orthognathic surgery [22-24]. Most clinicians agree that the TMJs must be stable prior to any orthognathic surgery. Potential treatments for patients with active PCR patients include the following: (1) observation for disease arrest (“burn out”) followed by maxillary orthognathic surgery to close the open bite and/or chin camouflage surgery to improve facial profile, (2) TMJ replacement with autogenous tissues (most commonly costochondral grafts) with delayed orthognathic surgery, and (3) TMJ replacement with alloplastic joints with delayed or concomitant orthognathic surgery.