Dental Magnetic Retainers with a Closed Magnetic Path

Abstract

In this study, models of closed magnetic circuit were investigated. The Sm-Co magnet was fitted in a yoke (a cap of soft ferromagnetic materials covering the magnet, which is made of high purity high chrome stainless steel or permalloy). A disk of soft ferromagnetic stainless steel was used as a model of the root cap, and the relation between magnetic force and the size of a york was examined. To prevent corrosion of the exposed surface of the Sm-Co magnet, the surface of the magnet was covered with stainless steel or titanium foil.
The magnetic force of the closed circuit was stronger than that of the open circuit. The magnetic attractive force mainly depended on the diameter of the yoke.
Corrosion on the magnet surface was prevented by covering it with thin foil made of stainless steel or titanium using 4-META resin as an adhesive. The magnetic attractive force was 450〜630 g in this case.
As a ferromagnetic part, the disk of high purity high chrome stainless steel was used in combination with common dental casting alloys. These root caps had a satufactory ferromangnetic quality and excellent corrosion resistance.