#1. Attractive force of magnets and magnetic fields — Strength and range of impact by the attractive force of magnets
1 Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry
2 Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry
Most of the dental magnetic attachments used in Japan utilize a closed magnetic circuit. They show very good retentive force for their small size. However, some magnetic attachments used in other countries utilize an open magnetic circuit. In this study, we investigated the attractive force of magnets and the range of impact exhibited by the magnetic fields. Cylindrical neodymium and ferrite magnets were set up in various combinations. The keeper was made of SUS XM27 stainless steel. Attractive force was measured using a measuring device that matched ISO 13017. The pattern of magnetic fields formed was observed using iron powder. In combinations that involved one type of magnet, the attractive force and range of impact by the magnetic fields increased as the number of magnets increases possibly due to a decrease in demagnetizing fields. Combinations that involved different kinds of magnets; the magnet in contact with the keeper had the greatest influence on attractive force. The range of impact by magnetic fields did not change remarkably with the combination of magnets made of different materials. It is possible to control the range of magnetic fields without altering the attractive force by combining different kinds of magnets.