Cavitation occurs around dental ultrasonic instruments. Previous work using luminol solutions has shown that the greater amount of cavitation will occur at the upper bend of the ultrasonic scaler probe with less occurring at the working tip and that the shape of the probe can also affect cavitation production. However, it has also indicated that tip cross-section may be a factor. The aim of this work was to determine whether a change of tip cross-section would change the position of the cavitation occurrence.
Methods:
Six TFI-10 ultrasonic scaler tips were ground (3 x front surface and 3x side surface) so that their cross section was altered from circular to half round. Three scaler tips were left unmodified to act as a control. A scanning laser vibrometer was used to measure the movement of the tips before and after grinding at various generator power settings (under unloaded conditions). The occurrence of inertial cavitation was mapped using luminol solution and the activity was photographed, using a CCD camera, in a light proofed room. Photographs were obtained using an exposure time of 60 seconds.
Results:
Laser vibrometry showed that modifying the shape of the ultrasonic probes' cross-section altered the instruments oscillation including, under certain conditions, a shift in the nodal point of the vibration. The luminol measurements showed that the occurrence of cavitation changed with shape change of the tip and was also affected by the generator power setting. The nature of the modification (side versus front surface alteration) appeared to also affect cavitation production.
Conclusion:
The positioning of cavitation around the probe of the tip is influenced by the cross sectional shape and the generator power driving the instrument. Further work is necessary to determine whether this will be useful clinically.
Supported by EPSRC Grant No: EP/C536894 & EP/F020090