GaAlAs laser irradiation induces active tertiary dentin formation after pulpal apoptosis and cell proliferation in rat molars

J Endod. 2011 Aug;37(8):1086-91. doi: 10.1016/j.joen.2011.05.020.


Introduction: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Bromodeoxyuridine / metabolism
  • Cell Proliferation
  • Dental Pulp / cytology*
  • Dental Pulp / physiology
  • Dentin, Secondary / metabolism*
  • Female
  • HSP27 Heat-Shock Proteins / biosynthesis
  • In Situ Nick-End Labeling
  • Intermediate Filament Proteins / biosynthesis
  • Lasers, Semiconductor* / adverse effects
  • Molar
  • Nerve Tissue Proteins / biosynthesis
  • Nestin
  • Odontoblasts / physiology*
  • Rats
  • Rats, Wistar
  • Wound Healing


  • HSP27 Heat-Shock Proteins
  • Hspb1 protein, rat
  • Intermediate Filament Proteins
  • Nerve Tissue Proteins
  • Nes protein, rat
  • Nestin
  • Bromodeoxyuridine