Mandibulofacial adaptations in a juvenile animal model of temporomandibular joint arthritis

Juvenile rheumatoid arthritis (JRA) is a chronic systemic disease of childhood that affects synovial joints including the temporomandibular joint (TMJ). Individuals with JRA of the TMI frequently show aberrations in mandibulofacial development. Since the basis for these developmental perturbations is poorly understood, they remain a perplexing clinical problem to manage. To begin dissecting the mechanisms for altered craniofacial development in JRA of the TMJ, we characterized the gross morphologic adaptations in the facial skeleton in a juvenile animal model of TMJ arthritis. Arthritis was induced in ten 87-day-old male rabbits by intra-articular challenge with ovalbumin. Eight sham-challenged and 4 unchallenged rabbits were used as controls. Serial lateral head cephalograms, taken at 73 (T1), 87 (T2), 108 (T3), 129 (T4), and 150 (T5) days of age, were evaluated by linear measures of maxillary, mandibular, and posterior dental height dimensions. Differences in the absolute dimensions and relative percent incremental changes were compared by ANOVA and Fisher's test. The body weights, as well as the absolute measures and incremental changes in maxillary and posterior dental height dimensions, were not significantly different between the antigen-challenged and control groups. In contrast, absolute measures of posterior mandibular height, condylar neck height, and total mandibular length were significantly smaller (P < 0.05) in antigen-challenged rabbits than in both control groups at T5. Furthermore, the antigen-challenged rabbits demonstrated significantly smaller (P < 0.05) relative increases in all measures of mandibular length, and in total posterior mandibular and condylar neck heights. Cephalometric superimpositions on the cranial base and tantalum implants confirmed these quantitative observations. This investigation demonstrates mandibulofacial developmental aberrations in experimental JRA-like disease of the TMJ that are similar to those observed in humans with this disease.