Evaluation of a new mouse model for studying dental pulpal responses to GaAlAs laser irradiation

Abstract

ObjectivesThe molecular mechanisms regulating pulpal responses to GaAlAs laser irradiation remain to be clarified. This study aimed to assess the feasibility of a mouse model for studying pulpal responses to GaAlAs laser irradiation. MethodsMaxillary first molars of 5-week-old ICR mice were irradiated at an output power of 1.0W for 180s, and samples were collected at intervals of 0, 1, 3, 5, 7, 10, and 14 days. The demineralized paraffin sections were processed for hematoxylin and eosin staining, immunohistochemistry for nestin (a marker for odontoblast differentiation) and Ki67 (a marker for cell proliferation), and a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. ResultsThe intense nestin immunoreactivity in the odontoblast layer of the mesial pulp was weakened immediately after irradiation and was almost lost on Days 1–3, although the extent of pulpal damage was variable among individual animals. At around Day 1, numerous TUNEL-positive cells appeared in the degenerative zone and gradually decreased in number by Day 14. Active cell proliferation occurred in the mesial pulp during Days 5–10. Nestin-positive odontoblast-like cells appeared along the pulp-dentin border by Day 10, resulting in tertiary dentin formation on Day 14. ConclusionsThe current output energy induced apoptosis in the affected dental pulp, followed by active cell proliferation, resulting in tertiary dentin formation. This is the first report regarding laser irradiation of teeth in an in vivo mouse model. This model could enable further understanding of the function of certain proteins, including transcriptional factors.