title: Long-term histologic analysis of bone tissue alteration and healing following Er:YAG laser irradiation compared to electrosurgery.
abstract: BACKGROUND
  The erbium-doped:yttrium, aluminum, and garnet (Er:YAG) laser is reportedly useful for periodontal therapy. However, the potential thermal damage that Er:YAG laser irradiation can produce on bone tissue has not been fully clarified. The purpose of this study was to histologically examine the effects of the Er:YAG laser on bone tissue and subsequent wound healing compared to electrosurgery in a long-term study.
  
  
  METHODS
  Calvarial bone from 30 rats was exposed to contact and non-contact Er:YAG laser irradiation (115 mJ/pulse, 10 Hz) without water coolant, or electrode contact. The treated surfaces were analyzed by scanning electron microscopy (SEM), and the healing process was histologically observed until 12 months post-surgery.
  
  
  RESULTS
  Contact irradiation resulted in substantial bone ablation, whereas non-contact irradiation produced slight tissue removal. Histologic and SEM analyses of the lased surface showed no severe thermal damage, except for the production of a superficially affected layer with a microstructured surface. The layer did not inhibit new bone formation, and the ablated defect was repaired uneventfully. Although the thickness of the layer gradually decreased, it generally remained in the cortical bone through the observation period. Electrosurgery produced a large area of thermal necrosis without ablation, and the damaged area was not replaced with new bone.
  
  
  CONCLUSIONS
  Unlike electrosurgery, Er:YAG laser irradiation without water coolant easily ablated bone tissue, and thermal alteration in the treated surface was minimal. The superficially affected layer did not interfere with the ensuing bone healing, resulting in favorable repair of the defect.
authors.affiliation: Section of Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Yoshino
authors.forename: Akira
authors.initials: A
authors.lastname: Aoki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Oda
authors.forename: Aristeo Atsushi
authors.initials: AA
authors.lastname: Takasaki
authors.forename: Koji
authors.initials: K
authors.lastname: Mizutani
authors.forename: Katia Miyuki
authors.initials: KM
authors.lastname: Sasaki
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Kinoshita
authors.forename: Hisashi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Isao
authors.initials: I
authors.lastname: Ishikawa
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Izumi
mesh_terms: D000818:Animals; D004598:Electrosurgery; D005624:Frontal Bone / Q000473:pathology / Q000601:surgery; D006097:Granulation Tissue / Q000473:pathology; D006358:Hot Temperature; D053685:Laser Therapy / Q000379:methods*; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D008297:Male; D008855:Microscopy, Electron, Scanning; D018919:Neovascularization, Physiologic / Q000502:physiology; D010011:Osteocytes / Q000473:pathology; D010012:Osteogenesis / Q000502:physiology; D010294:Parietal Bone / Q000473:pathology / Q000601:surgery; D051381:Rats; D017208:Rats, Wistar; D012886:Skull / Q000473:pathology* / Q000601:surgery; D013997:Time Factors; D014867:Water; D014945:Wound Healing / Q000502:physiology
chemical_list: D014867:Water