title: Effects of water flow on dental hard tissue ablation using Er:YAG laser.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of water on dental hard tissue ablation using Er:YAG laser as it relates to energy and pulse repetition rate, and determine the water flow rate that produces the most effective ablation at a given irradiation condition.
  
  
  BACKGROUND
  Er:YAG laser application leads to volumetric expansion and micro-explosions that result in hard tissue ablation. Ablation efficiency is improved when combined with fine water spray.
  
  
  METHODS
  Extracted, healthy human molars were sectioned into two pieces and categorized into small groups related to water flow rate (1.69, 6.75, and 13.5 mL/min), pulse energy (250 and 400 mJ), and pulse repetition rate (5, 10, and 20 Hz). Within the combination of irradiation parameters, a laser beam was applied over enamel and dentin surfaces of the specimens, and the ablation amount was determined by differences in weight before and after irradiation.
  
  
  RESULTS
  At a pulse energy of 250 mJ, the most effective ablation resulted from a water flow rate of 1.69 mL/min in both enamel and dentin. With 400 mJ/pulse, dentin removal was most effective at the water flow rate of 1.69 mL/min, whereas the efficiency of enamel ablation was the highest at 6.75 mL/min. Dental hard tissue ablated better as energy and pulse repetition rate increased.
  
  
  CONCLUSIONS
  Effective ablation of dental hard tissue using Er:YAG laser requires that the appropriate water flow rate correspond properly to irradiation conditions. The results of this study suggest the following parameters; a water flow rate of 1.69 mL/min for enamel and dentin ablation at a pulse energy of 250 mJ and for dentin ablation at 400 mJ/pulse, and a water flow rate of 6.75 mL/min for enamel ablation at a pulse energy of 400 mJ, regardless of pulse repetition rate of 5, 10, and 20 Hz.
authors.affiliation: University Dental School, Chunan, Choongnam, Korea. meunkim@dku.edu
authors.forename: Mee-Eun
authors.initials: ME
authors.lastname: Kim
authors.forename: Deuk-Jin
authors.initials: DJ
authors.lastname: Jeoung
authors.forename: Ki-Suk
authors.initials: KS
authors.lastname: Kim
mesh_terms: D003814:Dentistry, Operative / Q000379:methods*; D006801:Humans; D053685:Laser Therapy / Q000379:methods*; D012212:Rheology / Q000295:instrumentation*; D014070:Tooth / Q000601:surgery*; D014867:Water
chemical_list: D014867:Water