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Biomedical subjects

A Linder-Aronson

Publications and source records attributed to A Linder-Aronson.

5 recordsLinked to original sources
PubMed1996

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 with the widespread availability of rare earth magnetic alloys. In vivo studies have indicated that a static magnetic field and/or corrosion products from the magnetic materials may induce biological effects when in close contact with cells or tissues. In the clinical situation, orthodontic magnets are often situated some distance away from the gingiva and bone. Consequently, the previously observed biological effects may not be found in an experimental situation mimicking the clinical setting. Thus, the present experimental study was undertaken to test this hypothesis using commercially available cobalt-samarium magnets for orthodontic treatment in comparison to treatment with Sentalloy closed 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 magnet and coil spring specimens with respect to rate of space closure, bone formation or epithelial thickness. The only two variables that differed significantly between magnet and coil spring specimens was that there were more resorption and more tetracycline labelled osteocyte lacunae under the magnets. In conclusion, although some marginal statistical 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 situation compared to previous studies in which the magnets were positioned in close contact with the tissue under study, indicate limited adverse clinical effects.

Alveolar Process↗
PubMed1995

Effects of orthodontic magnets on cutaneous epithelial thickness and tibial bone growth in rats.

The use of permanent magnets in orthodontic treatment has increased significantly 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 epithelial turnover close to rare earth magnets has been presented. The aim of the present study was twofold: to confirm earlier results and to study whether the observed changes are reversible. One hind leg in each of 45 rats was fitted with aluminum rings with Co5Sm magnets, whereas the other hind leg was fitted with sham rings. After 8 weeks 25 rats were killed, and the rings in the remaining rats were removed. The latter group was killed after another 11 weeks. The epithelial and bone reactions were evaluated histomorphometrically. Previous results showing thinner epithelium and retarded rate of bone formation close to Co5Sm magnets were confirmed. These effects were also shown to be largely reversible. It was concluded on the basis of this and the magnitude of the effects that any local side effects from orthodontic rare earth magnets appear negligible when extrapolated to the clinical situation.

Animals↗
PubMed1995

Effects of static magnetic fields on human periodontal fibroblasts in vitro.

In orthodontic treatment, the use of mechanical forces generated by magnetic fields have increased significantly over the past years, triggered by the introduction of rare earth permanent magnetic alloys. Rare earth magnets, initially made from cobalt-samarium alloy and later from neodymium-iron-boron alloy generate high mechanical forces in relation to their small size. Relating to their use in orthodontic treatment, queries about possible side effects have been expressed. This study was undertaken in order to determine if cell growth and attachment in vitro is affected over time in a static magnetic field of a magnitude comparable to that used clinically. Significantly and progressively impaired attachment and growth over a 5 week period was observed when human periodontal fibroblasts were cultured in a static magnetic field. These results indicate that a static magnetic field itself is capable of influencing vital cell functions, although they do not exclude the possibility of corrosion products from the magnets contributing to previously observed cytotoxic in vitro and biological in vivo effects.

Alloys↗
PubMed1992

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.

Alveolar Process↗