[Morphological and histological adaptation after mandibular functional positioning only in vertical dimension].

PURPOSE:To elucidate the role of mandibular vertical functional positioning in condylar adaptive remodeling. METHODS:Forty female Sprague-Dawley rats at the age of 5 weeks were randomly divided into 4 control and experimental groups. All the animals were sacrificed on day 3, 6, 9 and 12 (n=5). Bite plates on upper posterior teeth were fitted on the experimental animals to induce functional repositioning of the mandible. Morphological and histological analysis was carried out to quantitatively analyze the amount of the adaptive changes of condylar cartilage. Independent-samples t test and One-Way ANOVA using SPSS11.0 software package were performed. RESULTS:Twelve days after mandibular vertical functional positioning the condylar height increased. Nine days after mandibular vertical functional positioning the thickness of prechondroblast layer and chondroblast layer increased significantly compared with control groups. However the thickness of hypertrophic layer decreased significantly after 6 days' mandibular repositioning. No change was found in the thickness of mesenchymal layer during the experimental period. CONCLUSIONS:Mandibular vertical functional positioning could enhance the growth of condyle. The resulted adaptive remodeling in condylar cartilage plays an important role in the treatment mechanism of mandibular deficiency via functional appliances.