Orthodontic tooth movement using the attractive force of rare earth magnets in rats

The aim of this study was to confirm the usefulness of magnets for orthodontic tooth movements. Computer simulation was performed to design magnets, especially for this new animal model. The flux density and attractive force of samarium-cobalt (Sm-Co) magnet and neodymium-iron-boron (Nd-Fe-B) magnet were examined. The magnet or titanium was bonded on the rat maxillary first molars. The initial distance between magnets/titanium was 1.0 mm (experimental group I/control group I, Exp. I/ Cont. I) or 1.5 mm (experimental group II/control group II, Exp. II/Cont. II). The amount of tooth movement was measured and periodontal structures were observed using microfocus X-ray CT radiographs. The distance between magnets decreased in both experimental groups. Tooth movement in Exp. II was slower than Exp. I. Horizontal sections of microfocus CT radiographs showed narrow periodontal space without root resorption on the pressure side in both experimental groups. Attractive force of the newly designed magnets caused effective tooth movement without any pathological changes in rats.