ORTHODONTIC TREATMENT WITH Nd-Fe-B MAGNETS

Abstract

The aim. The development of methodology for experimental and theoretical assessment of interaction forces between magnets in an orthodontic apparatus, the test of corrosion resistance of protective oxide and nitride coatings deposited on Nd-Fe-B magnets surface. Materials and methods. The Nd-Fe-B permanent magnets with saturation magnetization Ms≈1100 G and bilayer ZrN / ZrO2 coatings were used. To experimental measure of interaction forces between magnets the device was assembled on the base of analytical balance. The distance between the magnets was varied using non-magnetic plates. The ZrO2 and ZrN coatings have been analyzed for their corrosion properties in 0.9 % NaCl quasi-physiological solution. Results. An original method was proposed for calculating of magnetic interaction forces for materials with high magnetic anisotropy, which has good agreement with experimental measurement of forces. The theoretical model takes into account the size of the magnets and the mutual influence of their opposite faces. An increase of corrosion resistance of magnetic materials can be provided by zirconium oxide or nitride compounds, which contribute to inhibition of electrochemical corrosion of Nd-Fe-B magnets. Conclusions. A method for calculating of interaction forces between permanent magnets, which are used for correction of malocclusion in orthodontic, has been developed. The passivation of the Nd-Fe-B permanent magnets surface can be achieved by applying of bilayer ZrN / ZrO2 coating.