Methods: Three piezoelectric (EMS Piezon A, P and PS) and three magnetostrictive (Dentsply TFI-3, TFI-10 and FSI-SLI-10S) ultrasonic probes were operated at low, medium and high generator power settings in a water bath. The bubble activity was observed by a 2D Scanning Laser Vibrometer (SLV) with a video camera attached. Nodal points along the tips were detected and compared with acoustic streaming patterns when operated in water. The occurrence of bubble production, activity and behaviour was determined.
Results: The only tips to produce stable cavitation bubbles were the piezoelectric EMS Piezon P and PS and the magnetostrictive FSI-SLI-10S tip. It was observed that bubbles travel along the side of the oscillating scaler tip via acoustic streaming and remain mostly at nodal points. As generator power increased from medium to high settings, the stationary bubbles collapsed and disappeared. The EMS Piezon A tip and Dentsply TFI-3 and TFI-10 did not produce any observable bubbles.
Conclusion: The occurrence of stable cavitation bubbles depended on the type and geometry of the ultrasonic scaler used. The slimmer tips produced stable cavitation. This is in agreement with previous work (Lea et al., Ultrason. Sonochem., 2005, 12, 233) which showed that broader tips produce inertial cavitation. Stable cavitation bubbles were moved away from the tip to nodal points along the probe.
Supported by EPSRC grants EP/C536894/1 and EP/C536908/1