Micro-vibrations at 30 Hz on bone cells cultivated in vitro produce soluble factors for osteoclast inhibition and osteoblast activity

Objetive: It has been claimed that micro-pulse vibration can accelerate the rate of tooth movement during orthodontic treatment; however, the underlying cellular mechanism has yet to be elucidated. The purpose of this study was to understand the mechanisms underlying tooth movement acceleration by measuring alterations in a panel of intercellular signalling molecules and markers of osteoblast/osteoclast function following micro-pulse vibration for 20 min at 30 Hz. Design: Primary BALB/c mouse calvarial osteoblasts were cultivatedin vitro and subjected to micro-pulse vibration (0.25 N; 30 Hz) with the AcceleDent (R) Aura appliance for 20 min and assayed for IL-4, IL-13, IL-17, OPG, soluble RANKL and TGF-beta protein by ELISA; for PCNA in osteoblasts and caspase 3/7 in osteoclasts by immunohistochemistry; for IL-4, IL-13, and 11-17 in osteoclasts by ELISA; and for cathepsin K by flow cytometry. Results: After micro-pulse vibration, the murine osteoblast culture supernatant showed increased IL-4, IL-13, IL17, OPG and TGF-beta levels and decreased RANKL levels; PCNA in osteoblasts and caspase 3/7 in osteoclasts were also upregulated. The osteoclast culture supernatant had increased levels of IL-4, IL-13 and IL-17, and cathepsin K was upregulated in the treatment group compared with the control group. Conclusions: Micro-pulse vibration promotes the production of soluble factors that inhibit osteoclasts, promote apoptosis and activate osteoblasts in vitro, which could increase bone mineral density. Further studies should be conducted in order to understand the biological mechanism of how micro-vibration might influence tooth movement during orthodontic treatment.