Osteoblast viability and detachment following exposure to ultrasound in vitro

Ultrasound has been used in dentistry for over 40 years and has recently be en proposed for cutting bone. The purpose of this study was to establish th e effects of ultrasonic instruments on osteoblasts. A 25 kHz magnetostricti ve ultrasound generator and a TFI-1 tip (Dentsply, UK) were used as the ult rasound generating instruments. Primary osteoblast cultures were establishe d from the parietal bones of two-day-old Albino Wistar rats grown on tissue culture (TC) petri dishes (Corning, UK) in alpha MEM (Sigma, UK). Once con fluent, the osteoblasts were harvested using 0.05% trypsin in 0.02% EDTA th en 1.7 x 10(5) cells in 2.5 ml of alpha MEM were either re-seeded immediate ly onto TC dishes and allowed to adhere for 24 h or kept in suspension befo re application of ultrasound with different tip displacements prior to re-s eeding the cells. Osteoblast viability was assessed using 0.4% Trypan Blue following the initial dose of ultrasound then periodically over a 20 h peri od for both adherent and suspension osteoblasts. This study demonstrated th at ultrasound caused osteoblast detachment and loss of viability in vitro, both when adherent to a substrate or in suspension. Loss of osteoblast viab ility was related to the maximum displacement of the ultrasonic tip and con tinued throughout the 20 h period observed for osteoblasts adherent to TC d ishes. (C) 2001 Kluwer Academic Publishers.