Abstract: Objective · To investigate on the difference of the orthodontic tooth movement rate and pressure side bone remodeling between diet-induced obese rats and diet-resistant rats. Methods · Forty male Sprague-Dawley rats were randomly divided into two groups, including the normal diet (ND) group and high-fat diet (HFD) group. And then the HFD group was subdivided into diet-induced obese (DIO) group (n=10) and diet-resistant (DR) group (n=10). Orthodontic applications were placed between the left upper first molar and incisors in rats respectively. After orthodontic treatment for 14 d, the rats were executed and their maxillae were harvested bilaterally. The number of osteoclasts in 3 groups were observed by tartrate-resistant acid phosphatase (TRAP) staining. The expression of osteocalcin in 3 groups was observed by immunohistochemical staining. The tooth movement distance and trabecular bone parameters on the pressure side were measured by Micro-CT. Results · The rate of orthodontic tooth movement was significantly lower in the DR group than that in the DIO and ND groups (P=0.000, P=0.005). After orthodontic treatment for 14 d, the bone mineral density, percentage trabecular bone volume/total volume, trabecular number and trabecular thickness in the DR group were significantly higher than those in the DIO group (P=0.001, P=0.000, P=0.005, P=0.000). The number of osteoclasts in the DR group was significantly lower than that in the ND group and DIO group (P=0.005, P=0.001). The expression of osteocalcin was higher in the DIO group than that in the ND group (P=0.047). Conclusion · High-fat diet-induced obesity or obesity-resistance may affect bone remodeling process during orthodontic treatment by promoting or inhibiting osteoclastogenesis, thereby affecting the rate of tooth movement.

Key words: obesity, obesity resistance, Micro-CT, orthodontic tooth movement, osteoclast, rat