A study on the effects of Electrical stimulation by the miniature Electric device on the tooth movement and tissue remodeling / 대한치과교정학회지

Electric current is a highly probable way as a clinical tool for tooth movement. The purposes of this study were to determine the usefulness of exogenous electric currents in accelerating orthodontic tooth movement and to investigate the effects of electric-orthodontic treatment on the remodeling of the periodontal tissue histologically. The study was performed with six male cats weighing around 3kg. The electric device which is providing the direct electric current of 20microA was inserted to the removable appliance. The right and left maxillary canines were assigned as control and experimental sides respectively. The control canine was provided with orthodontic force (75gm) only and the experimental side was given the same amount of force and electricity. The lingual buttons were bonded to the maxillary canines and both sides of canines were retracted with NiTi coil spring. The electric device was adjusted to provide 20microA direct current to the experimental canines 5 hours a day. The amount of the canine movement was measured with electronic caliper every week. After 4 weeks of tooth movement, the animals were sacrificed and the histologic study was performed. The results of this study were as follows : 1. The application of a direct current to the experimental tooth significantly increased the final amount of orthodontic tooth movement. The amount of tooth movement after 28-day was 37% more in the experimental side. 2. The electrically stimulated tooth showed histologic evidence of significant increases in the amount of bones and matrix deposition in the area of tension. 3. In the compression side, the electric-orthodontic treatment stimulated bone resorption more extensively in the experimental canines. 4. After 28 days of electricity exposure and orthodontic force, the experimental side demonstrated significantly more osteoblasts, osteoclasts, capillaries and osteoid tissues, reflecting an increase in the local tissue's cellular activity. 5. Intermittent electrical stimulation (five hours a day) had effects to enhance orthodontic tooth movement and tissue remodeling. These results suggested that the low-intensity exogenous electric current by the miniature electric device might accelerate orthodontic tooth movement and bone remodeling in vivo and have the possibility to reduce the orthodontic treatment duration.

The effect of parathyroid hormone on cyclic AMP level and distribution in periodontal cells in tension sites during orthodontic treatment / 대한치과교정학회지

Parathyroid hormone (PTH) is known to exert its effects on bone cells through the mediation of adenosine 3', 5'-monophosphate (cAMP) Orthodontic forces have also been shown to alter the cAMP content of paradental cells, particularly the alveolar bone osteoblasts. The objective of this experiment was to determine whether a combined orthodontic treatrnent-PTH administration regimen would have an additive effect on cAMP content in paradental cells in sites of periodontal ligament (PDL) tension. Seven groups of 4 one year old female cats each were treated for 1,3,6,12,24 h, 7 and 14 d by tipping one maxillary canine. PTH was administered twice dally, 30u/kg. Maxillary horizontal sections were stained immunohistochemically for cAMP and the degree of cellular staining intensity was determined microphotometrically as per cent light transmittance at 600nm. Alveolar bone osteoblasts, progenitor cells, PDL fibroblasts and cementoblasts in tenion sites were measured and the data were analyzed statistically by a mixed model analysis of variance. PTH administration increased the cAMP staining of non-orthodontically treated paradental cells in comparison to cells untreated by force or hormone. Cells in PDL tension sites of PTH-treated cats demonstrated significantly darker cAMP staining than cells in non-orthodontically-treated sites. Osteoblasts demonstrated the greatest response in terms of cAMP elevation, while in PDL fibroblasts orthodontic force did not Increase cAMP levels above those measured m non-stretched hormonally-treated cells. These results demonstrate that PTH increases cAMP levels in paradental cells, particullarly in osteoblasts, and that the effects of PTH and orthodontic forces on paradental target cells may approach additivity.