Mandibulofacial adaptations in a juvenile animal model of temporomandibular joint arthritis

Juvenile rheumatoid arthritis (JRA) is a chronic systemic disease of childh ood that affects synovial joints including the temporomandibular joint (TMJ ). Individuals with JRA of the TMI frequently show aberrations in mandibulo facial development. Since the basis for these developmental perturbations i s poorly understood, they remain a perplexing clinical problem to manage. T o begin dissecting the mechanisms for altered craniofacial development in J RA of the TMJ, we characterized the gross morphologic adaptations in the fa cial skeleton in a juvenile animal model of TMJ arthritis. Arthritis was in duced in ten 87-day-old male rabbits by intra-articular challenge with oval bumin. Eight sham-challenged and 4 unchallenged rabbits were used as contro ls. 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 ma xillary, mandibular, and posterior dental height dimensions. Differences in the absolute dimensions and relative percent incremental changes were comp ared by ANOVA and Fisher's test. The body weights, as well as the absolute measures and incremental changes in maxillary and posterior dental height d imensions, 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 significantl y smaller (P < 0.05) in antigen-challenged rabbits than in both control gro ups at T5. Furthermore, the antigen-challenged rabbits demonstrated signifi cantly smaller (P < 0.05) relative increases in all measures of mandibular length, and in total posterior mandibular and condylar neck heights. Cephal ometric superimpositions on the cranial base and tantalum implants confirme d these quantitative observations. This investigation demonstrates mandibul ofacial developmental aberrations in experimental JRA-like disease of the T MJ that are similar to those observed in humans with this disease.