Osteogenesis in the glenoid fossa in response to mandibular advancement

The purpose of this study was to identify the temporal sequence of cellular changes in the glenoid fossa and to quantify the amount of bone formation in response to mandibular advancement. One hundred 35-day-old female Spragu e-Daw[ey rats were randomly divided into 5 experimental groups (15 rats eac h) and 5 control groups (5 rats each). In the experimental groups, function al appliances were used to create continuous forward mandibular advancement . The rats were killed after 3, 7, 14, 21, and 30 days. Sections were cut t hrough the glenoid fossa in the parasagittal plane and stained with periodi c acid and Schiff's reagent for evaluation of bone formation and with hemat oxylin and eosin for observation of cellular response. The results showed t hat, in the control rats, bone formation was initially higher in the poster ior and middle regions than in the anterior region then decreased over time in all regions, In the experimental group, bone formation significantly in creased from day 7 to day 30 compared with control rats. Day 21 marked the highest levels of bone formation in the middle (+184%) and posterior region s (+300%). Mandibular protrusion resulted in the osteoprogenitor cells bein g oriented in the direction of the pull of the posterior fibers of the disc and also resulted in a considerable increase in bone formation in the glen oid fossa.