title: Irradiation time and ablation rate of enamel in contact and non-contact irradiation with Er:YAG laser.
abstract: OBJECTIVE
  The relationship between changes in ablation rate of enamel with irradiation time was investigated to find the most effective irradiation time for tooth ablation by Er:YAG laser.
  
  
  BACKGROUND
  Previous studies have shown that the Er:YAG laser has the ability to ablate tooth material effectively, but that the efficiency and effectiveness of ablation are determined by various parameters such as energy, pulse frequency, the amount of water, and irradiation time.
  
  
  METHODS
  Contact and non-contact irradiation of the Er:YAG laser were carried out respectively for 1, 3, 5, and 7 s on the enamel surface of each specimen using a combination of a 400 mJ/pulse at 20 Hz and water flow rate of 6.75 mL/min, and quantitative measurements using a mass balance were performed to compare the resulting ablation rates.
  
  
  RESULTS
  The ablation weight, by taking the mean of both contact and non-contact irradiation, generally increased with irradiation exposure time, but no significant increases in ablation were seen in specimens that had been exposed for > 3 s in either the contact or non-contact irradiation group. Results in the non-contact irradiation group indicated superior ablation of enamel compared to that in the contact irradiation group.
  
  
  CONCLUSIONS
  Irradiation exposure of < or = 3 s per application of laser beam is recommended to ablate enamel effectively in both non-contact and contact irradiation.
authors.affiliation: Department of Oral Medicine, College of Dentistry and Medical Laser Research Center, Dankook University, Chunan, Korea. kimks@dku.edu
authors.forename: K S
authors.initials: KS
authors.lastname: Kim
authors.forename: M E
authors.initials: ME
authors.lastname: Kim
authors.forename: E J
authors.initials: EJ
authors.lastname: Shin
mesh_terms: D003737:Dental Cavity Preparation / Q000379:methods; D003743:Dental Enamel / Q000528:radiation effects*; D006801:Humans; D007834:Lasers; D008963:Molar / Q000528:radiation effects; D011829:Radiation Dosage; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water