Vibration characteristics of ultrasonic scalers assessed with scanning laser vibrometry.
OBJECTIVE
Scanning laser vibrometry is a non-invasive method of accurately measuring the vibratory characteristics of oscillating objects. The aim of this study was to observe, using a scanning laser vibrometer (SLV), the vibration patterns of dental ultrasonic scaler tips and to assess the effects of water flow rate and power setting on these patterns whilst operating the tips in an unloaded environment.


METHODS
A 30kHz ultrasonic scaler (TFI-10, Dentsply) was fixed in position and a laser beam from the SLV was focused onto the tip. The laser, guided by a virtual measurement grid, was scanned over the oscillating tip surface. Scans were taken with the laser beam perpendicular to the long axis of the front face of the tip.


RESULTS
Oscillation frequencies and the displacement amplitude at the unconstrained end of the tip were measured for various power/water settings. Vibration nodal positions were recorded for the various settings and were found to occur approximately 4mm from the free end of the tip. At low and medium power settings, tip displacement amplitude was reduced by increased water flow. At high power settings, combined with a high flow rate, the water leaves the body of the instrument as a jet. This left the tip relatively unconstrained, allowing it to oscillate at increased displacement amplitudes.


CONCLUSIONS
This study shows that the SLV is able to accurately characterise the movement of oscillating ultrasonic scaler tips. The tips are affected by power setting and water flow rates.
Lea
S C
SC
School of Dentistry, The University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, UK. s.lea@bham.ac.uk
Landini
G
G
Walmsley
A D
AD
D000704:Analysis of Variance; D012534:Dental Scaling / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017078:Laser-Doppler Flowmetry / Q000295:instrumentation; D007834:Lasers; D008422:Materials Testing; D009068:Movement; D009991:Oscillometry / Q000295:instrumentation; D012212:Rheology; D013223:Statistics as Topic; D013499:Surface Properties; D014464:Ultrasonic Therapy / Q000295:instrumentation*; D014732:Vibration; D014743:Videotape Recording; D014867:Water / Q000737:chemistry
D014867:Water