title: Controlling dental enamel-cavity ablation depth with optimized stepping parameters along the focal plane normal using a three axis, numerically controlled picosecond laser.
abstract: OBJECTIVE
  The purpose of this study was to establish a depth-control method in enamel-cavity ablation by optimizing the timing of the focal-plane-normal stepping and the single-step size of a three axis, numerically controlled picosecond laser.
  
  
  BACKGROUND
  Although it has been proposed that picosecond lasers may be used to ablate dental hard tissue, the viability of such a depth-control method in enamel-cavity ablation remains uncertain.
  
  
  METHODS
  Forty-two enamel slices with approximately level surfaces were prepared and subjected to two-dimensional ablation by a picosecond laser. The additive-pulse layer, n, was set to 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70. A three-dimensional microscope was then used to measure the ablation depth, d, to obtain a quantitative function relating n and d. Six enamel slices were then subjected to three dimensional ablation to produce 10 cavities, respectively, with additive-pulse layer and single-step size set to corresponding values. The difference between the theoretical and measured values was calculated for both the cavity depth and the ablation depth of a single step. These were used to determine minimum-difference values for both the additive-pulse layer (n) and single-step size (d).
  
  
  RESULTS
  When the additive-pulse layer and the single-step size were set 5 and 45, respectively, the depth error had a minimum of 2.25 μm, and 450 μm deep enamel cavities were produced.
  
  
  CONCLUSIONS
  When performing three-dimensional ablating of enamel with a picosecond laser, adjusting the timing of the focal-plane-normal stepping and the single-step size allows for the control of ablation-depth error to the order of micrometers.
authors.affiliation: 1 Center of Digital Dentistry, Faculty of Prosthodontics, Peking University School and Hospital of Stomatology and National Engineering Laboratory for Digital and Material Technology of Stomatology and Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health , Beijing, China .
authors.forename: Fusong
authors.initials: F
authors.lastname: Yuan
authors.forename: Peijun
authors.initials: P
authors.lastname: Lv
authors.forename: Dangxiao
authors.initials: D
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Sun
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
mesh_terms: D003731:Dental Caries / Q000601:surgery*; D003743:Dental Enamel / Q000528:radiation effects*; D006801:Humans; D053685:Laser Therapy / Q000295:instrumentation*; D046509:Tissue Culture Techniques