The effect of hyaluronic acid on the remodelling of alveolar bone during orthodontic tooth movement

Aim of this study is evaluation of high molecular weight hyaluronic acid (HMWHA) and low molecular weight hyaluronic acid (LMWHA) effects on alveolar bone remodelling and orthodontic tooth movement (OTM) velocity. In this study, 84 Wistar Albino rats were divided into six groups. Group 1 and 2 were divided into five subgroups according to time period (1,3,7,14 and 21 days) (n=6). In each of Group 3, 4, 5 and 6, six rats were studied only on day 21. In the first 3 groups orthodontic mesialization of maxillary first molars was achieved by nickel titanium closed coil springs on both sides. In Group 1 and 2, right side was injected with HMWHA and LMWHA respectively, while left side injected by normal saline. Group 3 received saline injection only on right side. Group 4 and 5 received only injection with HMWHA and LMWHA, respectively. Group 6 serves as negative control. OTM was measured on 3-dimensional digital models. Alveolar bone volume in the first molar intraradicular areas were evaluated by histomorphometric and immunohistochemical analysis of receptor activator of nuclear factor-κB ligand (RANKL), Osteoprotegerin (OPG), Alkaline phosphatase (ALP) and Osteocalcin (OCN). On day 14 and 21, osteoclasts number of experimental sides was higher than control in Group 1 and 2. In HMWHA injected group, OTM amount were 1.4 times greater than control On day 21. Both molecular weight of hyaluronic acid increased RANKL/OPG, and ALP level, but didn't altered OCN.Hyaluronic acid injection may accelerate OTM by decreasing alveolar bone density and enhancing osteoclastic activity.