title: Dental hard tissue ablation using mid-infrared tunable nanosecond pulsed Cr:CdSe laser.
abstract: Mid-infrared erbium: yttrium-aluminum-garnet (Er:YAG) and erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers (2.94- and 2.78-μm, respectively) are utilized for effective dental hard tissue treatment because of their high absorption in water, hydroxide ion, or both. Recently, a mid-infrared tunable, nanosecond pulsed, all-solid-state chromium-doped: cadmium-selenide (Cr:CdSe) laser system was developed, which enables laser oscillation in the broad spectral range around 2.9 μm. The purpose of this study was to evaluate the ablation of dental hard tissue by the nanosecond pulsed Cr:CdSe laser at a wavelength range of 2.76-3.00 μm.
  
  
  
  Enamel, dentin, and cementum tissue were irradiated at a spot or line at a fluence of 0-11.20 J/cm2/pulse (energy output: 0-2.00 mJ/pulse) with a repetition rate of 10 Hz and beam diameter of ∼150 μm on the target (pulse width ∼250 ns). After irradiation, morphological changes, ablation threshold, depth, and efficiency, and thickness of the structurally and thermally affected layer of irradiated surfaces were analyzed using stereomicroscopy, scanning electron microscopy (SEM), and light microscopy of non-decalcified histological sections.
  
  
  
  The nanosecond pulsed irradiation without water spray effectively ablated dental hard tissue with no visible thermal damage such as carbonization. The SEM analysis revealed characteristic micro-irregularities without major melting and cracks in the lased tissue. The ablation threshold of dentin was the lowest at 2.76 μm and the highest at 3.00 μm. The histological analysis revealed minimal thermal and structural changes ∼20 μm wide on the irradiated dentin surfaces with no significant differences between wavelengths. The efficiency of dentin ablation gradually increased from 3.00 to 2.76 μm, at which point the highest ablation efficiency was observed.
  
  
  
  The nanosecond pulsed Cr:CdSe laser demonstrated an effective ablation ability of hard dental tissues, which was remarkably wavelength-dependent on dentin at the spectral range of 2.76-3.00 μm. These results demonstrate the potential feasibility of the use of pulsed Cr:CdSe laser as a novel laser system for dental treatment. Lasers Surg. Med. 48:965-977, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.|Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Taichen
authors.initials: T
authors.lastname: Lin
authors.affiliation: Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.|Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Aoki
authors.affiliation: Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Norihito
authors.initials: N
authors.lastname: Saito
authors.affiliation: Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Yumoto
authors.affiliation: Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Sadahiro
authors.initials: S
authors.lastname: Nakajima
authors.affiliation: Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Keigo
authors.initials: K
authors.lastname: Nagasaka
authors.affiliation: Research Center for Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
authors.forename: Shizuko
authors.initials: S
authors.lastname: Ichinose
authors.affiliation: Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Mizutani
authors.affiliation: Photonics Control Technology Team, Advanced Photonics Technology Development Group, RIKEN Center for Advanced Photonics, Riken, Wako, Saitama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Wada
authors.affiliation: Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Izumi
mesh_terms: D003739:Dental Cementum / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D003743:Dental Enamel / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D003804:Dentin / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D008855:Microscopy, Electron, Scanning
keywords: Er,Cr:YSGG laser; Er:YAG laser; cavity preparation; cementum; dentin; enamel