The effect of surgically induced anterior disc displacement of the temporomandibular joint on the midface and cranial base.

OBJECTIVE: The purpose of this study is to investigate the effect of unilateral TMJ disc displacement on the midface and cranial base. STUDY DESIGN: Thirteen 10-week-old rabbits, eight controls and five experimental were included in this study. The five experimental rabbits had surgically created unilateral disc displacement. Animals were sacrificed at 22 weeks and frontal, occlusal, and lateral oblique radiographs were made of the skulls. RESULTS: The occlusal radiograph demonstrated that the glenoid fossa on the experimental side was located more anterior. The oblique radiograph demonstrated the root of the zygomatic arch the experimental side was inferior. The anterior aspect of the fossa was more inferior on the frontal radiograph. CONCLUSIONS: A previous study suggested a shortening in the ramal height. This study suggests an alteration of the cranial articular fossa. Thus, it is suggested that disc displacement is capable of producing asymmetry in the developing mandible and cranial base.

Loose joint bodies of the temporomandibular joint: a case report.

Osteochondral loose bodies are an uncommon finding in the temporomandibular joint (TMJ), but occur relatively frequently in large joints such as the knee, elbow, hip, wrist, and ankle. Loose joint bodies can be divided in three groups: 1) synovial chondromatosis; 2) osteochondral fracture fragments and; 3) cases of degenerative arthritis or avascular necrosis. The most common clinical features of loose joint bodies are pain, swelling, joint noise and impaired joint movements. A case of loose joint bodies of the temporomandibular joint is presented. The pantomograph and lateral cephalograph revealed several irregularly shaped, variably sized radiopaque structures in the region of the right temporomandibular joint. CT and MR scans confirmed the initial diagnosis. The dimensions of the loose joint bodies varied from 1-2 to 5-6 mm. In this patient, the loose joint bodies may have been secondary to osteoarthritis, may have preceded and caused the degenerative changes, or may be only a coincidental finding.

Effect of a surgically created disk displacement on mandibular symmetry in the growing rabbit.

PURPOSE: The purpose of this study was to evaluate the contribution of unilateral disk displacement to growth changes in the young New Zealand White rabbit. METHODS: Ten female rabbits aged 10 weeks were included in this study. The five experimental rabbits had unilateral anterior disk displacement surgery. The five controls had no surgery. The rabbits were killed at 22 weeks of age, and the mandibles hemisected and radiographed. Cephalograms were digitized and analyzed by conventional methods. RESULTS: The gross appearance showed shortening and flattening of the articulating surface in the experimental group (P < 0.05). No significant shortening and flattening was found in the control group. CONCLUSION: These observations suggest that surgically created internal derangement can produce altered growth in the mandible.

Temporomandibular joint: surgically created disk displacement causes arthrosis in the rabbit.

To document a causal relationship between temporomandibular joint disk displacement and arthrosis, the disk was surgically displaced in one temporomandibular joint in each of three rabbits. The rabbits were sacrificed after 4 weeks and the mandibular condyles were studied radiographically and histologically. All three joints that underwent disk displacement had radiographic and histologic evidence of arthrosis, which included erosion of the bone, irregularity and fissure formation of the articular soft tissue cover, disruption of the subchondral layer of cartilage cells, and chondrocyte proliferation. No radiographic or histologic changes occurred in the joints that were untouched. The results suggest that surgically created disk displacement can cause arthrosis in the temporomandibular joint of the rabbit.

Use of protrusive splint therapy in anterior disk displacement of the temporomandibular joint: a 1- to 3-year follow-up.

Sixty-eight patients, who were determined clinically (by the presence of audible and palpable-joint sounds) and arthrographically to have meniscus displacement with reduction, had protrusive splints constructed, and the results were evaluated for a minimum of 1 year to a maximum of 3 years. Eighteen additional patients, arthrographically determined to have meniscus displacement with reduction, served as a nontreatment group for comparison. Odds ratios were calculated to compare the proportions of subjects who experienced follow-up symptoms on the two regimens. Results indicated that with splint therapy there was a statistically significant reduction of the intensity of jaw joint pain, temporal headache, ear pain, and pain in front of the ear, and there was a decrease in the probability of a closed lock condition developing. Splint therapy is less likely to reduce frontal headache, neck pain, and clenching of teeth.

Animal model for disk displacement.

This paper describes the soft-tissue changes associated with surgically created, nonreducing disk displacements in the New Zealand white rabbit. Four rabbits, one control and three experimental, were used. The disk of the control animal had thick posterior and anterior bands separated by a thinner intermediate zone. The disk in the one animal sacrificed immediately after surgical disk displacement was buckled downward at the intermediate zone, with the posterior band lying inferior to the anterior band. The disks in the two animals sacrificed 2 months after surgical disk displacement were grossly deformed and clearly had abnormal internal architecture. Tissue reactions seem to be similar to those observed in human disk displacement specimens, namely disk remodeling and degenerative joint disease. This animal model will aid in the understanding of the progression of this disorder.

Arthrographically assisted splint therapy: a 6-month follow-up.

After repositioning splint therapy, 51 patients were evaluated for a minimum of 6 months. Forty-five (88%) of the patients were considered to have been treated successfully, whereas six (12%) patients required surgery to correct meniscal displacement. A detailed analysis of signs and symptoms before and after splint treatment is in progress.