title: Comparison between the removal effect of mechanical, Nd:YAG, and Er:YAG laser systems in carious dentin.
abstract: OBJECTIVE
  The purpose of this study was to compare the effectiveness of carious dentin removal by using an Er:YAG laser irradiation and Nd:YAG laser under a continuous water spray with that of the conventional mechanical treatment in vitro.
  
  
  BACKGROUND
  Lasers are being considered as a potential replacement of conventional mechanical systems to remove diseased and healthy dental hard tissues.
  
  
  METHODS
  First, one half of the 10 carious lesions were treated with the round steel bur and then removed. The other half were treated with the Er:YAG laser at 200-mJ pulse energy at 2 Hz. After that, one half of another set of 10 teeth was subjected to the round steel bur in which the other half was removed using the Nd:YAG laser at 6-W output power, 20 pps, and under a continuous water spray (120 mL/min). Thermal change during each treatment and the time required for carious dentin removal was determined, and the surface characteristic was observed using the scanning electron microscopic (SEM).
  
  
  RESULTS
  The Er:YAG or Nd:YAG laser irradiation time was almost two or three times longer than the bur treatment, respectively. From the SEM study, it was found that the lased cavity surface revealed various patterns of microirregularity, and there was also no smear layer.
  
  
  CONCLUSIONS
  It can be suggested that under adequate water spray and with a careful irradiation technique, cavities without sign of thermal damage to the surrounding tissues as well as dental pulp could be produced with the Er:YAG and Nd:YAG laser.
authors.affiliation: Department of Endodontics, Showa University School of Dentistry, Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamada
authors.forename: M
authors.initials: M
authors.lastname: Hossain
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: N
authors.initials: N
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D003731:Dental Caries / Q000473:pathology / Q000601:surgery*; D003804:Dentin / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D053685:Laser Therapy / Q000379:methods*; D016896:Treatment Outcome