title: Combined UV and IR laser ablation of dentine.
abstract: OBJECTIVE
  The aim of this study was to increase the rate of removal of dentine tissue by a 213-nm laser through the introduction of an Er:YAG assisting laser.
  
  
  BACKGROUND
  The rate of dentine removal is increased by using a CO2 laser to assist a XeCl excimer laser.
  
  
  METHODS
  Extracted human teeth were sliced parallel to the crown and exposed to 213-nm laser and Er:YAG laser beams that were spatially and temporally aligned. The 213-nm laser radiation was generated using a Q-switched Nd:YAG (5 nsec, 10 Hz) and three nonlinear crystals. The Er:YAG laser was free running with a pulse duration of 100 microsec and a pulse repetition rate of 10 Hz. A fluence range of 5-18.6 J/cm2 (213 nm) and 0.6-1.3 J/cm2 (Er:YAG) was used. Axial ablation rates were measured for different pulse energies and pulse overlaps.
  
  
  RESULTS
  The ablation rate of dentine increased in most cases by a factor of two. The highest ablation rate achieved was 18.3 microm/pulse +/- 2.51, which is more than twice the highest ablation rate previously published using a 213-nm laser. Changes in the pulse superpositions that were investigated did not present a significant change in the ablation rate.
  
  
  CONCLUSIONS
  The Er:YAG laser can be used to increase the removal rate of dentine by a short-pulse ultraviolet (UV) laser.
authors.affiliation: Lions Eye Institute, Centre for Ophthalmology and Visual Science, University of Western Australia, Nedlands. hanks@cyllene.uwa.edu.au
authors.forename: H C
authors.initials: HC
authors.lastname: Sciberras
authors.forename: G T
authors.initials: GT
authors.lastname: Dair
authors.forename: P P
authors.initials: PP
authors.lastname: Vansaarloos
authors.forename: N
authors.initials: N
authors.lastname: Boyd
mesh_terms: D003804:Dentin / Q000601:surgery*; D006801:Humans; D053685:Laser Therapy; D007834:Lasers; D014466:Ultraviolet Rays