Effects of diabetes on tooth movement and root resorption after orthodontic force application in rats.

OBJECTIVE: To investigate the effects of diabetes on orthodontic tooth movement and orthodontically induced root resorption in rats. SETTING AND SAMPLE POPULATION: Twenty-three 10-week-old male Sprague-Dawley rats divided into control (n = 7), diabetes (n = 9), and diabetes + insulin (n = 7) groups. MATERIALS AND METHODS: Diabetes was induced by administering a single intraperitoneal injection of streptozotocin. Rats with a blood glucose level exceeding 250 mg/dl were assigned to the diabetes group. Insulin was administered daily to the diabetes + insulin group. A nickel-titanium closed-coil spring of 10 g was applied for 2 weeks to the maxillary left first molar in all rats to induce mesial tooth movement. Tooth movement was measured using microcomputed tomography images. To determine the quantity of root resorption, the mesial surfaces of the mesial and distal roots of the first molar were analyzed using both scanning electron microscopy and scanning laser microscopy. RESULTS: After 2 weeks, the amount of tooth movement in the diabetic rats was lower than that in the control rats. Root resorption was also significantly lower in the diabetic rats. These responses of the rats caused by diabetes were mostly diminished by insulin administration. CONCLUSIONS: Diabetes significantly reduced orthodontic tooth movement and orthodontically induced root resorption in rats. The regulation of blood glucose level through insulin administration largely reduced these abnormal responses to orthodontic force application.