Ultrasonic Scaler Tip Oscillation and the Effect of Water Flow

Objectives: Ultrasonic scalers change their vibrational behaviour when operated at different power settings. The aim of this study was to investigate two designs of ultrasonic scaling tip and their vibration characteristics under different operating situations.

Methods: Displacement amplitude measurements were made of two piezoelectric (EMS A and P; EMS, Switzerland) and two magnetostrictive (TFI-3 and FSI-SLI-10S; Dentsply, USA) probes operated in air and with water flowing over the tip at a water flow rate of 26 ml/min. Operating conditions included low, medium and high power settings. A 2D Scanning Laser Vibrometer (SLV) was used to record displacement amplitudes and to locate nodal points along each tip. For loading measurements the free end of the probe was allowed to contact a molar tooth that was embedded in resin. The measurements were repeated with water flowing over the tip and with loading of 100g and 200g.

Results: Displacement amplitudes between the working scaler tips demonstrated a 29% reduction in movement at the free end when water was flowing over the tip compared to the instrument working in air. For the water flow measurements further reductions occurred when the tip was working under loading. These reductions were on average 33% below those recorded in air. It was also noted that the nodal positions moved further away from the tip. The only tip to remain with the same nodal point was the FSI-SLI-10S tip.

Conclusion: This work shows that measurements undertaken in air are not representative of how ultrasonic tips perform when used in simulated clinical conditions of water flowing over the tip and during contact with the root surface.

This work is supported by a project grant from the EPSRC (EP/C536894/1).