Functional Appliance Under The Guidance Of The Jaw Back Experiments On The Rat Condylar Cartilage

Part oneHistological study on condylar cartilage tissue in response to posterior movement of rat's mandibleObjective To study the process of tissue response and regularity of condylar cartilage after posterior movement of rat's mandible. Methods Forty-five 28-day-old male Sprague-Dawley rats were randomly divided into four experimental groups and five control groups (5 rats in each group). In the experimental groups, functional appliances were used to create continuous posterior movement of mandible. The rats were killed after 0, 3, 7, 14 and 21 days respectively. Sections were cut through the condyle in the parasagittal plane and stained with periodic acid and Schiff's reagent for evaluation of bone formation and with hematoxylin and erosin for observation of celluar response. The changes of collagen were observed through Masson staining. Results The result showed that, in the experimental group, bone formation significantly deceased from day three compared with control rats in condylar cartilage. Mandibular retrusion resulted in the decreased thickness in condylar cartilage, especially in proliferative zone and hypertrophic zone, and osteroclasts being detected in erosion area as well. The expression of collagen was also decreased in the experimental groups as compared with the control groups.