Reconstruction of dental ultrasonic scaler 3D vibration patterns from phase-related data

Ultrasonic scalers are used in dentistry for removing mineralised plaque, known as calculus, from tooth surfaces. Though there is much information relating to the longitudinal vibrations of scaler probes, corresponding lateral data is limited. Understanding the lateral motion of ultrasonic probes is essential as, when used correctly, this motion will contribute to the cleaning process as well as to any damage caused to tooth surfaces. In this work we demonstrate the use of a single-axis scanning laser vibrometer, in conjunction with a mirror, to evaluate simultaneously the longitudinal and lateral motion of dental scaler probes oscillating at ultrasonic frequencies (approximately 30 kHz). Node/antinode patterns along the probe length were observed, as was an elliptical motion along the length of the probe. Application of a load to the tip of the instrument modified the vibration pattern of the whole probe. This technique seems an important step towards better characterisation of the three-dimensional movement of oscillating ultrasonic scaler probes, particularly when probes are contacted against teeth. Understanding the three-dimensional probe motion and how this is affected by contact with tooth surfaces may lead to future instrument designs with improved cleaning efficiency whilst minimising potential tooth damage.