TISSUE-RESPONSE TO SPACE CLOSURE IN MONKEYS - A COMPARISON OF ORTHODONTIC MAGNETS AND SUPERELASTIC COIL SPRINGS

Interest in using magnets for generating orthodontic forces started wi th the widespread availability of rare earth magnetic alloys. In vivo studies have indicated that a static magnetic field and/or corrosion p roducts from the magnetic materials may induce biological effects when in close contact with cells or tissues. In the clinical situation, or thodontic magnets are often situated some distance away from the gingi va and bone. Consequently, the previously observed biological effects may not be found in an experimental situation mimicking the clinical s etting. Thus, the present experimental study was undertaken to test th is hypothesis using commercially available cobalt-samarium magnets for orthodontic treatment in comparison to treatment with Sentalloy close d coil springs with respect to possible side effects on alveolar bone growth, gingival epithelial thickness as well as rate of space closure . Corrosion of the uncovered areas of the magnets was already evident after 6 weeks. No statistical differences were found between the magne t and coil spring specimens with respect to rate of space closure, bon e formation or epithelial thickness. The only two variables that diffe red significantly between magnet and coil spring specimens was that th ere were more resorption and more tetracycline labelled osteocyte lacu nae under the magnets. In conclusion, although some marginal statistic al differences were found between the magnet and coil spring specimens with respect to cell and tissue reactions, the near lack of cell and tissue effects of the magnets in the present clinical experimental sit uation compared to previous studies in which the magnets were position ed in close contact with the tissue under study, indicate limited adve rse clinical effects.