Effects of Hypothalamic Obesity-associated Orthodontic Tooth Movement on the Periodontal Tissues in Rats: An Experimental Study

Abstract

Aims: This study aimed to evaluate whether hypothalamic obesity associated with orthodontically induced tooth movement can influence the rate of tooth movement and the histological structure of periodontal tissues in rats. Study Type: Experimental research. Methodology: Forty female pups Wistar rats were used. Twenty pups received subcutaneous injections of monosodium glutamate (4g/kg/day) in the cervical region for the first five days of life to induce obesity (MSG group). The remaining twenty animals received hyperosmotic saline solution (1.25g/kg/day) and served as the non-obese control group (CTL). Animals were divided into four groups (n=10/group): Group1: Non-obese rats without induced tooth movement (CTL); Group 2: Non-obese rats with induced tooth movement (CTL+ITM); Group 3: Obese rats without ITM (MSG); Group 4: Obese rats with ITM (MSG + ITM). At day 90, the ITM device was installed. At day 97, animals were weighed, euthanized, and the right hemimaxillae were collected, fixed in 10% formalin, and histologically processed. Results: Obese animals showed a higher Lee index and more retroperitoneal and perigonadal fat than controls. The MSG + ITM group exhibited a reduced tooth movement rate compared to CTL + ITM. No acute or chronic inflammation was observed. MSG + ITM animals showed more external root resorption, multinucleated giant cells, and disorganized periodontal ligament. The highest incidence of hyalinization was found in ITM groups, while vascular alterations were more frequent in obese animals. Conclusion: Orthodontic tooth movement associated with hypothalamic obesity reduces rate of tooth movement and increased occurrence of periodontal alterations and external root resorption.