Imaging the 3D vibration patterns of ultrasonic scaler probes

Objectives: Despite the available information relating to the longitudinal vibrations of dental ultrasonic scalers probes, their 3-dimensional vibration patterns have not been fully characterised. One of the reasons for this is the difficulty to perform 3D measurements. The aim of this study was to ascertain the phase-related, 3-dimensional vibration data of an ultrasonic scaler via mirror-reflected measurements using a scanning laser vibrometer.

Methods: A P-style probe (EMS, Nyon, Switzerland) was fixed in place with its anterior surface vertical and perpendicular to the vibrometer laser. A metallic, first surface reflecting mirror was positioned to enable the side of the probe to be viewed through the vibrometer camera simultaneously with the front of the probe. Measurement points were superimposed over both aspects of the scaler probe. The scaler was operated using a MiniPiezon ultrasound generator at a medium power setting and scanned with the vibrometer.

Results: Phase-related, 3-dimensional models of the scaler probe motion, for both its fundamental oscillation frequency (29kHz) and its second harmonic (87kHz) were produced. The acquired data demonstrated 3D node/antinode points along the probe length and provided an insight into the complex motion of the probe.

Conclusions: Laser vibrometry, used in conjunction with mirrors, is able to characterise the 3-dimensional movement of oscillating ultrasonic scaler probes. Future work will investigate how these patterns will change when the probes are contacted against hard and soft surfaces and inserted in periodontal pockets. Better understanding of their movement may lead to future designs with improved cleaning efficiency whilst minimising potential tooth damage.

This work was supported by a project grant from the EPSRC (no: GR/T22551/01).