Long-term effects of orthodontic magnets on human buccal mucosa - a clinical, histological and immunohistochemical study

The aim of this intra-individual study was to examine human buccal mucosa clinically, histologically and immunohistochemically after 9 months' exposure to orthodontic magnets. In each of eight subjects (17.8-42.4 years), a magnet and a demagnetized equivalent of parylene coated neodymium-iron-boron was bonded alternately on the left and right side, to the buccal surface of maxillary premolars. The buccal mucosa was clinically examined and photographed, and three punch biopsies (6 mm diameter) of the buccal mucosa were taken from each subject at the site of contact with the magnet (test), in contact with the demagnetized magnet (control), and also at a site on the control side without contact with the demagnetized magnet (normal). The biopsies were snap-frozen for histological and immunohistochemical investigation, using antibodies to PD7 (lymphocyte 'naive T'), UCHL1 ('memory T'), HLADR, ELAM-1 and ICAM-1. Clinically, the buccal mucosa showed normal features before and after the experimental period. In four of the eight subjects, the epithelium was 1.4-2.3 times thicker in the control and test tissues than in normal tissues. The difference between controls and tests was negligible, and there were no signs of increased keratinization or other surface abnormalities. Compared with normal sites, all control and test sites showed slightly increased ELAM-1/ICAM-1 vascular staining, accompanied in th ree subjects by small infiltrates of PD7/UCHL1-positive lymphocytic cells and in all subjects by focal keratinocyte HLADR-staining. The minor tissue reactions found in test and control tissues were interpreted to be a result of microtrauma (contact irritation) and not caused by the static magnetic field per se, since there was no difference between test and control tissues.