title: GaAlAs laser irradiation induces active tertiary dentin formation after pulpal apoptosis and cell proliferation in rat molars.
abstract: BACKGROUND
  This study aimed to clarify pulpal responses to gallium-aluminum-arsenide (GaAlAs) laser irradiation.
  
  
  METHODS
  Maxillary first molars of 8-week-old rats were irradiated at an output power of 0.5 or 1.5 W for 180 seconds, and the samples were collected at intervals of 0 to 14 days. The demineralized paraffin sections were processed for immunohistochemistry for heat-shock protein (HSP)-25 and nestin in addition to cell proliferation assay using bromodeoxyuridine (BrdU) labeling and apoptosis assay using deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL).
  
  
  RESULTS
  Intense HSP-25 and nestin immunoreactivities in the odontoblast layer were weakened immediately after 0.5-W irradiation and recovered on day 1, resulting in slight tertiary dentin formation by day 14. On the contrary, 1.5-W irradiation immediately induced the loss of HSP-25 and nestin-immunoreactivities in the odontoblast layer. On day 1, numerous TUNEL-positive cells appeared in a degenerative zone that was surrounded by intense HSP-25 immunoreactivity. BrdU-positive cells occurred within the intensely HSP-25-immunopositive areas during days 2 through 5, whereas TUNEL-positive cells gradually decreased in number by day 5. HSP-25- and nestin-positive odontoblast-like cells were arranged along the pulp-dentin border by day 7, resulting in remarkable tertiary dentin formation on day 14.
  
  
  CONCLUSIONS
  The output energy determined pulpal healing patterns after GaAlAs laser irradiation; the higher energy induced the apoptosis in the affected dental pulp including odontoblasts followed by active cell proliferation in the intense HSP-25-immunoreactive areas surrounding the degenerative tissue, resulting in abundant tertiary dentin formation. Thus, the optimal GaAlAs laser irradiation elicited intentional tertiary dentin formation in the dental pulp.
authors.affiliation: Division of Cariology, Operative Dentistry and Endodontics, Department of Oral Health Science, Niigata University Graduate School of Medical and Dental Sciences, Nigata, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Shigetani
authors.forename: Natsuki
authors.initials: N
authors.lastname: Sasa
authors.forename: Hironobu
authors.initials: H
authors.lastname: Suzuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Okiji
authors.forename: Hayato
authors.initials: H
authors.lastname: Ohshima
mesh_terms: D000818:Animals; D017209:Apoptosis; D001973:Bromodeoxyuridine / Q000378:metabolism; D049109:Cell Proliferation; D003782:Dental Pulp / Q000166:cytology* / Q000502:physiology; D003809:Dentin, Secondary / Q000378:metabolism*; D005260:Female; D055551:HSP27 Heat-Shock Proteins / Q000096:biosynthesis; D020287:In Situ Nick-End Labeling; D007381:Intermediate Filament Proteins / Q000096:biosynthesis; D054023:Lasers, Semiconductor / Q000009:adverse effects; D008963:Molar; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D064231:Nestin; D009804:Odontoblasts / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014945:Wound Healing
chemical_list: D055551:HSP27 Heat-Shock Proteins; C486114:Hspb1 protein, rat; D007381:Intermediate Filament Proteins; D009419:Nerve Tissue Proteins; C577486:Nes protein, rat; D064231:Nestin; D001973:Bromodeoxyuridine