3D Investigation of Ultrasonic Scaling Tip Motion

Objectives: Previously recorded data of the oscillation of ultrasonic scalers has only looked at their motion in 2 dimensions. The aim of this study was to introduce a novel method for characterising ultrasonic scaler tip motion in 3 dimensions.

Methods: A 30 kHz magnetostrictive FSI-SLI-10S (Dentsply, USA) scaler was fixed in position and three laser beams of a 3D Scanning Laser Vibrometer were brought into focus to record the movement of the tip. The probe was operated in air with three power settings (low, medium, high) and with its free end contacting the root of a canine of an artificial tooth model. The tip was placed 2 mm subgingivally within the artificial gum. Loading of 150g was applied and the water flow was set at 25 ml/min.

Results: At high power and in air, maximum displacement amplitudes of 18 ± 0.7 µm were recorded along the y-axis. This correlates with previously collected 2D data (Lea et al. 2003). Tip movement was also recorded along the x-axis (max.: 38 ± 0.9 µm) and z-axis (max.: 19 ± 0.6 µm). This demonstrated that the tip oscillates in an ellipsoidal movement envelope at its free end. A nodal point was detected at 2.6 mm from the free end of the tip and remained at this position when the tip was loaded during subgingival contact. Motion of the free end of the tip was undetectable when operated subgingivally.

Conclusion: This study confirms that ultrasonic scaler tips exhibit ellipsoidal movement with a large movement along the x-axis when working in air. However, this motion is lost when the tip contacts the tooth in an artificial pocket. Therefore excessive loading is to be avoided during routine ultrasonic scaling.

This work is supported by project grants from the EPSRC (GR/T22551/01, EP/C536894/1 and EP/D500834/1).