The physical characteristics of neodymium iron boron magnets for tooth extrusion

Impaction and non-eruption of teeth is a common problem encountered in orth odontics and many techniques have been proposed for the management of this condition. It has been advocated that a system utilizing magnets would supp ly a continuous, directionally sensitive, extrusive force, through closed m ucosa and thus provide not only a physiological sound basis for successful treatment, but also reduce the need for patient compliance and appliance ad justment. This ex vivo investigation examined in detail the physical charac teristics of neodymium iron boron magnets employed in attraction in order t o assess their usefulness in the clinical situation. Attractive force and m agnetic flux density measurements were recorded for nine sets of magnet pai rs with differing morphologies. The effect of spatial relationship on force was assessed by varying vertical, transverse and horizontal positions of t he magnets relative to each other, and by altering the pole face angles, The data obtained suggest that magnets with larger pole face areas and long er magnetic axes provide the best performance with respect to clinical usef ulness. It was possible to formulate a specific relationship between force and flux density for each magnet pair. This relationship can be used in the clinical management of unerupted teeth to predict the force between the ma gnets by measuring the magnetic flux density present at mucosal level. The results indicate that magnetic systems may, indeed, have a place in the tre atment of unerupted teeth.