Aim: This study compared the periodontal vascular changes in young and adult rats after 14 days of MDO.
Materials and methods: All procedures were performed in Bioterium of Faculty of Cs. QMCS. U. de Chile. Standardized orthodontic appliances were installed in right hemimaxilar in 2 groups of 7 rats, 16 and 46 weeks of age. Eeuthanasia by intracardiac perfusion at 14 days. In 7um paraffin sections blood vessels were identified by muscle alpha actin immunohistochemical stain. A morphologic and morphometric analysis was performed on 4x standardized microphotomicrographs. The surface of periodontal ligament space (LP) and each blood vessel area (Vs) were measured (Micrometrics SE Premium). It was determined the number of small (<500um2) and large (> 500um2) blood vessels and calculated the mean of the areas of small and large blood vessels in 13.746 μm2 periodontal surface and the total number and surface of the Vs. Differences between groups were analyzed by Wilcoxon test.
Results: On young rats, the number of large vessels was significantly higher in the tension zone (p = 0.0001), and surface of larger vessel was higher at both sides (p = 0.03, p = 0.0001). The total surface area of Vs was significantly higher at stress side (p = 0.0068) compared with the adult group.
Conclusion: After 14 days of MDO the number and area of large vessels in the periodontium of young rats are significantly higher than in adult rats which may influence the rate of bone turnover and explain the differences in the amount of MDO between different ages.