Effects of occlusal hypofunction and its recovery on PDL structure and expression of VEGF and bFGF in rats.

Abstract

The purpose of this study was to clarify whether occlusal hypofunction and its recovery affect the structure of the periodontal ligament (PDL) and expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in rats. Forty-eight Wistar rats aged 5weeks were used and randomly divided into three groups: the hypofunctional group (HG), recovery group (RG), and control group (CG). In HG and RG, appliances were attached to the maxillary and mandibular incisors. In HG, appliances were set for 11weeks. In RG, appliances were set for 7weeks. Appliances were then removed at 0, 1, 3, 7, 14, and 28days. Untreated rats served as CG. Histological sections were prepared and immunohistochemically stained for VEGF and bFGF. Three groups were evaluated for PDL area and the number of VEGF and bFGF immunopositive cells in PDL. The number of immunopositive cells and PDL area in CG and RG were significantly larger when compared with HG, and PDL area in RG was similar to that in CG. In the recovery process, PDL area and number of VEGF-positive cells in PDL increased from days 0 to 7 and decreased from days 7 to 28. Conversely, the number of bFGF-positive cells in PDL increased significantly after day 1 and peaked at 28days. This study suggests that occlusal stimuli regulate PDL area through expression of VEGF and bFGF in rat PDL. Occlusal stimuli are able to regulate the expression of VEGF and bFGF in PDL cells, and these growth factors may lead to alveolar bone remodeling in PDL.