Magnetizable abutment crowns for distal-extension removable partial dentures

I n the past 30 years much has been written on the effects and use of magnets in dentistry.lV” With the development of cobalt-samarium magnets, however, there has been renewed and increasing interest in magnet application. ‘* Photoelastic stress and retention studies of a magnetically retained partial dentureI and overdenturez’a2’ have been reported. Cobalt-samarium magnets have a high intrinsic coercivity, which means that although the magnets are small, with the poles closer together because of their size, they do not tend to demagnetize themselves. Because opinions differ as to whether an existing magnetic flux is injurious, it was decided to use a closed-field system (in which there is no magnetic field beyond the magnetic system and therefore no dissemination into the tissues) (Fig. l).22 Cobalt-samarium magnets have been used in maxillofacial prosthodontics, orthodontics,‘5*‘6 and in various types of overdentures. 3-6,*. ‘29 “a *9-21 In bilateral distalextension removable partial overdentures, lower level stresses were noted in the root abutments of magnetically retained dentures than in those with stud attachments or conventionally clasped teeth. Sufficient retentive characteristics were also observed.2’ The purpose of this study was to examine the stress and retention characteristics for a removable partial denture using two designs of magnetic abutment crowns and two magnetic arrangements as the sole method for retaining a bilateral distal-extension removable partial denture supported by vital abutment teeth.