Cultured Cementoblast Stimulation by Low- and High- Intensity Pulsed Ultrasound

Root resorption is a side-effect of orthodontic tooth movement. Recently, it has been shown that ultrasound (US) stimulation accelerates repair of orthodontically induced root resorption in an in vivo human study. The effect of US stimulation on cellular metabolism is highly dependent on its intensity, therefore, it is hypothesized that mineralization of cementoblasts located on the root surface is affected by the intensity of US. Objectives: This study was designed to investigate the principal role of US exposure on the mineralization process of cementoblast by using two different intensities of pulsed US. Methods: The murine cementoblastic cell line (OCCM-30) was used for this study. Cultured cementoblasts received single-US exposure with 30 (low-) or 150mW/cm2 (high-) intensity. Real-time PCR analysis was carried out to quantify the gene expression of bone differentiation markers at 1, 4, 12 and 24hrs after exposure. Furthermore, using cultured cementoblasts received US stimulation per day for 6 days, the assay for collagen synthesis was performed. Results: At 24h after US exposure, both pulsed intensities produced a significant (p < 0.01) increase in the expression of collagen type I (COL I) and alkaline phosphatase (ALP) mRNA levels, compared with sham controls. Furthermore, the high intensity US enhanced the expression more significantly (p < 0.01) than the low-intensity US did for both genes. The synthesis of collagen was also significantly (p < 0.01) upregulated using a high-intensity US. Conclusion: These results here demonstrated that both the low and high-intensity pulsed US stimulates cementoblast by regulating genes related protein. Although more studies are necessary, high-intensity pulsed US might be a better candidate as a medical remedy to accelerate repair of root resorption.