Low-Intensity Pulsed Ultrasound Accelerates Differentiation of Osteoblastic Cells on Roughened Titanium Surface

Abstract

Use of low-intensity pulsed ultrasound (LIPUS) as a clinical tool is expected to accelerate bone-titanium integration in dental implant therapy. This study aimed to evaluate the effects of LIPUS treatment on bone marrow cells cultured under osteogenic conditions on the roughened surface of titanium disks in vitro. Bone marrow cells, obtained from the femora of 8-wk-old rats, were suspended in osteogenic-inducing medium. Cells were cultured on acid-etched titanium disks and exposed to LIPUS of 3.0 MHz sine wave frequency, repeated at 100 Hz with a spatial average intensity of 40 mW/cm 2 for 15 min/d from day 3 after primary seeding (LIPUS group). The control group was cultivated in the same manner. Cell proliferation, expression of osteoblastic genes, synthesis of collagen, and mineralization were compared between the 2 groups. No significant difference was observed in the cell number between the LIPUS and the control groups on days 5 and 7. The expression of osteocalcin and osteopontin genes were upregulated in the LIPUS group compared with that in the control group. The production of collagen, assessed by Sirius Red staining on day 14, and mineralization, assessed with Alizarin Red S staining on day 14 and 21, were both increased in the LIPUS group relative to the control group. Treatment with LI-PUS did not affect the proliferation of osteoblastic cells cultured on roughened titanium disks, whereas it affected the acceleration of osteoblastic differentiation, synthesis of collagen, and calcification.