REMOVABLE MAGNETIC KEEPER FREE FROM MRI ARTIFACT

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Dental magnetic attachments are one of the intraoral atattiments and consist of two parts, the magnetic assembly and the magnetic keeper. Both parts are made by magnetic substances and these materials can cause MRI artifact, when they are used in the imaging field. The magnetic assembly are usually mounted in the prosthesis, so the magnetic assembly are easily kept away from the imaging field by removing the prosthesis. But the keeper is casted within the root cap cemented in the root, and it can be a artifact of the MRI.The aims of this investigation were to develope the removable magnetic keeper, and to make sure the efficiency of the removable magnetic keeper clinically.1.Removable magnetic keeper assemblyThe removable magnetic keeper assembly consists of a magnetic keeper and a nonmagnetic housing. The magnetic keeper is a disk with a screw-shaped lateral wall or a bolt-shaped disk. The housing is a nut-shaped ring. The magnetic keeper is screwed into the housing and fixed tightly. In the clinical evaluation, the patients was comprised of 28 partially edentulous subjects, 17 women and 11men, provided with dental magnetic attachments with the removable keeper. They were followed up for 0.5-3 years. During this period, none of these removable keepers were dropped out and all of them were kept clean and they coould be easily removed.2.Influence on MRIA volunteer test subject with combinations of keepers in lower premolar region was examined by MRI.The images of the magnetic removable keeper and the housing were defective and showed same size of distortion as the ordinary keeper, but the images of the housing only , where the keeper was removed , showed no distortion.