GaAlAs laser‐induced pulp mineralization involves dentin matrix protein 1 and osteopontin expression

Objectives GaAlAs lasers induce pulp mineralization by promoting reparative dentinogenesis. This study analyzed the expression of dentin matrix protein 1 ( DMP 1) and osteopontin in GaAlAs laser‐irradiated rat molars, to examine the hypothesis that these proteins play a role in the laser‐induced reparative dentinogenic process. Materials and methods The mesial surfaces of the upper first molars of 8‐week‐old Wistar rats were irradiated with a pulsed GaAlAs laser. After 1–14 days, mRNA expression of DMP 1 and osteopontin in the coronal pulp was analyzed using real‐time PCR . DMP 1, osteopontin, and heat shock protein 25 ( HSP 25) were immunolocalized at 1–21 days. Results The pulp exhibited a degenerative zone in its mesial portion on days 1–3, and progressive formation of reparative dentin lined with HSP 25‐immunoreactive odontoblast‐like cells, from day 7 onwards. DMP 1 and osteopontin mRNA expression were significantly upregulated on days 1–7 and 3–7, respectively. From day 7 onwards, DMP 1 and osteopontin immunoreactivity colocalized along the boundary between the primary and reparative dentin. Conclusion GaAlAs laser irradiation of rat molars induced upregulated DMP 1 and osteopontin mRNA expression in the coronal pulp, followed by the formation of reparative dentin and the colocalization of DMP 1 and osteopontin immunoreactivity at the site at which this tissue first appeared.