Pulsed electromagnetic field prevents tooth relapse after orthodontic tooth movement in rat models

Relapse after orthodontic treatment remains a crucial problem. Pulsed electromagnetic fields (PEMFs) accelerate osteoblastogenesis and inhibit osteoclastogenesis. However, their effect on tooth movement during the retention phase of orthodontic treatment has not been studied. This study investigated the role of PEMF stimulation in preventing tooth relapse after orthodontic tooth movement (OTM) in rat models.

Thirty-six male Wistar rats were divided into control, PEMF 7, and PEMF 14 groups. The maxillary first molar was moved mesially with a 50 g force of a Nickel Titanium closed coil spring for 21 days. Therefore, PEMF stimulations, including a frequency of 15 Hz and intensity of 2.0 mT, were applied to a retention phase for 2 h daily for 7 and 14 days. The tooth relapse distance was evaluated on days 1, 3, 7, and 14; the number of osteoblasts, osteoclasts, and fibroblasts was assessed by hematoxylin and eosin staining; and the expression of fibroblast growth factor 2 (FGF-2) and type I collagen (Col-I) was evaluated by immunohistochemistry. The data were analyzed using one-way analysis of variance and post hoc test with p < 0.05 considered statistically significant.

Tooth relapse distance was significantly decreased in the PEMF 7 and PEMF 14 groups compared to the control group. A significant increase was detected in osteoblasts, fibroblasts, FGF-2, and Col-I in both PEMF groups, while osteoclasts decreased (p < 0.05).

The reduction of tooth relapse could be attributed to PEMF stimulation for 7 and 14 days by accelerating alveolar bone formation and periodontal ligament remodeling.