EFFECTS OF ORTHODONTIC MAGNETS ON CUTANEOUS EPITHELIAL THICKNESS AND TIBIAL BONE-GROWTH IN RATS

The use of permanent magnets in orthodontic treatment has increased si gnificantly over the past years, triggered by the introduction of rare earth magnetic alloys. Concerns about possible side effects have been expressed relating to their use in orthodontic treatment. In previous experimental studies evidence of a reduction in bone formation and ep ithelial turnover close to rare earth magnets has been presented. The aim of the present study was twofold: to confirm earlier results and t o study whether the observed changes are reversible. One hind leg in e ach of 45 rats was fitted with aluminum rings with Co5Sm magnets, wher eas the other hind leg was fitted with sham rings. After 8 weeks 25 ra ts were killed, and the rings in the remaining rats were removed. The latter group was killed after another ii weeks. The epithelial and bon e reactions were evaluated histomorphometrically. Previous results sho wing thinner epithelium and retarded rate of bone formation close to C o5Sm magnets were confirmed. These effects were also shown to be large ly reversible. It was concluded on the basis of this and the magnitude of the effects that any local side effects from orthodontic rare eart h magnets appear negligible when extrapolated to the clinical situatio n.