The Generation of Inertial Cavitation around loaded Ultrasonic Scalers

Objectives: Previous research has shown that inertial cavitation is generated under some conditions in the cooling water during ultrasonic dental treatment and it may assist in the removal of plaque and calculus from tooth surfaces. The aim of this study is to quantify the inertial cavitation around piezoelectric ultrasonic scalers when operated under different loads and power settings.

Methods: Three piezoelectric probes (A, P and PS, EMS, Nyon, Switzerland) were operated at low, medium and high power whilst contacted against a molar tooth (with loads of 100g and 200g) in a luminol solution. The experimental apparatus was then placed in a sealed blacked-out box. Generation of cavitation bubbles led to subsequent production of luminescence which was photographed using a Canon-EOS-D30 digital camera. A Scanning laser vibrometer (SLV), with attached video camera, was then used to record tip vibration characteristics under the same operating parameters.

Results: The P and A style tips generated most inertial cavitation under all power settings. The highest luminescence was observed around the second anti-nodes of each probe. Increased load resulted in reduced maximum displacement amplitudes at the free end of each tip. There was an increase of inertial cavitation detected at both the working end of the tip and the second anti node when the tip was loaded.

Conclusions: Of the tip shapes examined, broad, beaver-tail shapes produced higher cavitation under all conditions when compared with slimmer shaped tips. Inertial cavitation was detected at the anti-nodes and when operated under load the generated inertial cavitation increased in intensity, especially at the working end of the tip that contacts the tooth surface.

This work is supported by project grants from the EPSRC (EP/C536894/1 and EP/C536908/1).