Orthodontic magnets: effects on gingival epithelium and alveolar bone in monkeys.

The purpose of the present study was to examine soft and hard oral tissues in contact with or close to orthodontic magnets following an extended exposure time. Two male monkeys were used in the experiment. Individual silver splints covering the teeth from 17 to 27 in the upper jaw and 32-42 in the lower jaw were made. Co5Sm magnets were inserted with cold-curing acrylic buccally and lingually in the splints. The monkeys were injected with tetracycline at the start of the experiment and after 4 weeks. The epithelial thickness in buccal and lingual mucosa under the magnets and corresponding sites on the control side were estimated. The intensity of tetracycline fluorescence in the bone under the magnets and corresponding control sites was assessed semiquantitatively. A thinner epithelium compared to the controls and a patchy tetracycline-incorporation in the bone adjacent to orthodontic magnets in contrast to a homogeneous tetracycline fluorescent pattern in the controls were the most conspicuous findings. It cannot be excluded that the magnetic field or corrosion products from the magnetic material influenced vital processes in the epithelium and the bone close to the magnets. However, it cannot be concluded from the present study what cellular processes were affected.