[Image analysis of condylar cartilaginous adaptation to mandibular protrusion in rats]

To quantify chondrogenesis in condylar cartilage in response to active forward positioning of mandible.

Identical bite-jumping appliances were fixed to upper incisors of animals in experimental groups, causing a continuous mandibular forward positioning. Histological sections were performed through mandibular condyle and were stained with HE under the same condition. Chondrogenesis was quantified by measuring the area of cells in resting, proliferative, hypertrophic and erosive zones in the superioposterior region, through computer-assisted image analyzing system (Q550IW, Leica) with the advanced software (Leica Qwin Pro, V2.2). Statistical analysis was performed with GraphPad 3.0.

1. comparison among experimental groups revealed a fluctuation in proliferative zone, with 21-day group being the greatest (0.058 +/- 0.004 mm2) and 14-day the least (0.012 +/- 0.001 mm2). A change in erosive zone was also depicted by a peak of 0.112 +/- 0.001 mm2 in 7-day group and a bottom of 0.018 +/- 0.002 mm2 in 14-day group (P < 0.001). 2. comparison among the control groups manifested stable zonation, except for a slump of proliferative zone descending from 0.069 +/- 0.005 mm2 in 3-day group to 0.009 +/- 0.001 mm2 in 21-day group (P < 0.001). 3. comparison between experimental and control groups demonstrated significant discrepancy in proliferative zone, hypertrophic zone and erosive zone (P < 0.001).

Mandibular forward positioning stimulates and accelerates cartilaginous remodeling in mandibular condyle.