Research on the clinical application of a dental magnetic attachment

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Several types of dental magnetic attachment are commercially available at the moment, however none of them are clinically satisfactory. One problem is that they are too large, otherwise the retentive force is too weak. Furthermore, most of them do not have enough corrosion resistance, which is a crucial point in clinical use. A very small and powerful attachment has been developed by devicing a sandwich typed construction and the elliptic cross-section with aid of three dimentional FEM analysis. The attachment is sealed with a stainless steel cap laser-welded to the yoke. It has shown sufficient attractive force and stability in clinical trials. A photoelastic simulation model was fabricated to study the continuous stress distribution in the mucous membrane and the bone under a free- end typed removable partial denture. Our originally developed magnetic attachment was compared with other conventional retainers such as the O-ring attachment, wire clasp and Bear attachment. The photoelastic fringes produced when the vertical loads were applied on the canti-lever denture saddle, were continuously by video system and serial photos.Although a final conclusion has not been determined, it was clarified by this research that a dental magnetic attachment which belongs to quite new category of denture retainers, showed the same mechanical attitude as other retainers. That means the magnetic attachment can be clinically used without any special anxieties. This new attachment of which commercial name is "MAGFIT 600" has benn put on the market in August 1992 as the first domestic product in Japan.This research should be followed by the three-dimentional dynamic analysis by FEM technique to establish a basic principle to determine the actual clinical undications.