Rat Articular Condyle Changes During and After Continuous Mandibular Advancement: A Histomorphometric Study

The purpose of this study was to investigate the histological changes in rat mandibular condyle during and after continuous mandibular advancement by using a fixed functional appliance. Materials and methods: Fifty-four male Sprague-Dawley rats (4–weeks-old), weight (100-120gm) were used for three month experimental period; control group (A=24 rats) and experimental group (B=30 rats). Group A and Group B were subdivided into 3 equal groups respectively (A1, A2, A3); (B1, B2, B3). All groups were fed ad libitum and were kept under the same environmental condition. Only group (B1, B2, B3) were subjected to a full time orthodontic inclined bite plane cemented to the incisors (fixed functional appliance) to advance the mandible, while group A still as a control group. At the end of the 1st month only group B1as a (full-time wearer)and A1 were sacrificed, while groups B2 and B3 continue as a half-day-wearer, retention period) till the end of the 2nd month, when group B2 and A2 were sacrificed. Remaining rats (Group B3) stayed without appliance, post retention period) during whole 3rd month were sacrificed at the end of third month with control (A3). Specimens of hemi-cranium for all scarified animals were cut and dissected, histopathological examination had been done. Results: An abundant cellular proliferation expressed at posterior border of the condylar cartilage in group B than in group A. Cellular proliferation without proper ossification was noticed on the condyles of young rats of group A. However, rats revealed a significant Condylar ossification and higher osteoblastic activity towards the last week of treatment and retention period with the mandibular Condylar growth was accelerated by bite-jumping appliance treatment and stable within limits after a certain period of retention. Conclusion:Mandibular Condylar changes were accelerated by using fixed functional appliances that increased osteogenesis noticed during active mandibular advancement.