Cavitation Analysis

The team at Birmingham (Dr Simon Lea and Prof AD Walmsley) have analysed the occurrence of cavitation around dental ultrasonic scalers and powered toothbrushes.

Many techniques exist for the quantification of cavitation including methods which monitor its chemical effects. Of these, oxidation reactions such as in the Weissler reaction or Fricke’s dosimeter have been used  in dentistry to assess the occurrence of cavitation around dental ultrasonic instruments.

During cavitation bubble collapse, OH radicals are produced. The terephthalate dosimeter is a system that specifically measures the OH radical yield. The system uses an aqueous solution of terephthalic acid, which reacts with hydroxyl radicals to form 2-hydroxyterephthalate. The hydroxyterephthalate product is fluorescent and may be detected using fluorescence spectroscopy where an excitation wavelength of 310nm causes the hydroxyterephthalate to fluoresce at 425nm.

Figure 1. The reaction of terephthalic acid with hydroxyl radicals to form 2-hydroxyterephthalate.

Using this method of cavitation detection it was demonstrated that the occurrence of cavitation around dental ultrasonic scalers is highly dependent upon the design of the instrument, generator power setting and duration of instrumentation.

It was also shown that inertial (transient) cavitation did not occur in any detectable quantity around the powered toothbrushes investigated .

Further work is presently underway to investigate further the occurrence of cavitation around dental ultrasonic instruments.

Details of cavitation work are given in the following publications:

• Lea SC , Price GJ & Walmsley AD. Does Cavitation Occur around Powered Toothbrushes? Journal of Clinical Periodontology, 2004; 31: 77-78.
• Lea SC , Price GJ & Walmsley AD. A Study to Determine whether Cavitation Occurs around Dental Ultrasonic Scaling Instruments. Ultrasonics Sonochemistry, 2005; 12: 233-236.