Heavy force with corticotomy increased tooth movement at days 7 and 14 but did not show any difference in alveolar bone change or root resorption.

Objectives: To evaluate the amount of hyalinization and root resorption after application of light and heavy forces during corticotomy-assisted tooth movement. Materials and Methods: Forty-eight male Wistar rats were used. Eight animals were the control group (day 0). The other 40 animals were randomly divided into two groups using the split-mouth technique: (1) corticotomy combined light force (CLF) and (2) corticotomy combined heavy force (CHF). Nickel-titanium closed coil springs that generated 10 g (light force) and 50 g (heavy force) were used for maxillary first molar movement. three-dimensional root volume was evaluated at 0, 14, and 28 days. Percent hyalinization was analyzed at 0, 3, 7, 14, 21, and 28 days by histomorphometric analysis. Results: The CHF group showed significantly lower cervical root volume than the CLF group at 28 days. Compared with day 0, the CHF group showed significantly less root volume in both distobuccal and distopalatal roots at 28 days. The hyalinization percentages in the CHF group were significantly higher than the CLF group at days 3 and 21. Conclusions: Heavy force combined with corticotomy produced more periodontal ligament hyalinization and root resorption than the light force combined with corticotomy.