title: The effect of wear on ultrasonic scaler tip displacement amplitude.
abstract: OBJECTIVE
  During clinical usage, scaler tips may become worn and reduced in length. It is unknown what effect wear has on the magnitude of scaler tip vibrations when they are utilized under typical clinical loads. The aim of this investigation was to assess the effect of simulated wear on ultrasonic scaler tip displacement amplitude, using a scanning laser vibrometer.
  
  
  METHODS
  A Cavitron SPS (Dentsply) ultrasonic generator and three scaler insert designs (FSI-100, FSI-1000 and FSI-SLI-10S) were selected for the investigation. Tip vibration displacement amplitude was assessed unloaded and then contacting against tooth surfaces with loads of 0.5 and 1.0 N. Tips were then ground down by 1 mm and then 2 mm and scans were repeated.
  
  
  RESULTS
  For all tips, load and length were found to be significant variables (p<0.0001). The scaler tips showed a fall in displacement amplitude with a reduction in tip length. However, all scaler tips showed variability in the amount oscillation that occurred. This was most pronounced with FSI-SLI-10S.
  
  
  CONCLUSIONS
  This investigation demonstrated that tip wear could affect the performance of dental ultrasonic scaler inserts by reducing their vibration displacement amplitude. Clinicians should be aware of this variability, which may be significant enough to affect clinical procedures.
authors.affiliation: School of Dentistry, The University of Birmingham, St. Chad's Queensway, Birmingham, UK. s.lea@bham.ac.uk
authors.forename: Simon C
authors.initials: SC
authors.lastname: Lea
authors.forename: Gabriel
authors.initials: G
authors.lastname: Landini
authors.forename: A Damien
authors.initials: AD
authors.lastname: Walmsley
mesh_terms: D003755:Dental High-Speed Technique; D003762:Dental Instruments; D012534:Dental Scaling / Q000295:instrumentation*; D003799:Dental Stress Analysis; D004867:Equipment Design; D017743:Equipment Reuse; D006801:Humans; D007834:Lasers; D009991:Oscillometry; D014464:Ultrasonic Therapy / Q000295:instrumentation; D014732:Vibration