2016 Volume 59 Issue 4 Pages 370-380
Purpose: Mineral trioxide aggregate (MTA) is known to promote hard tissue formation by pulp cells in direct pulp capping. However, little is known about the reparative process of mechanically direct capping with MTA. Our previous study provided direct evidence that the canonical Wnt/β-catenin pathway is involved in the regulation of odontoblast differentiation and dentin formation. In the present study, dentinogenesis after pulp capping with MTA was examined by continuous observations and evaluated by immunohistological analyses with a Wnt10a antibody.
Methods: An occlusal cavity was prepared as exposed pulp in the maxillary molar teeth of 20 Sprague-Dawley rats. Then, MTA was placed on the exposed pulp. All cavities were restored with composite. After 5, 7, 10, or 21 days, the animals were sacrificed, and the maxillary bones were dissected, fixed with 10% paraformaldehyde for 24 hours, and processed to prepare the samples. Then, the samples were histologically observed after hematoxylin and eosin staining or immunoperoxidase staining using Wnt10a and dentin sialophosphoprotein.
Results: On hematoxylin and eosin staining, the MTA-treated groups showed significantly accentuated vascular proliferation and dentin-like hard tissue formation with an odontoblastic layer. In the 21-day specimens, there was a complete dentin bridge obliterating the exposed pulp. Wnt10a immunoreactivity was observed in the matrix, just beneath the odontoblast-like layer, at 7 days after MTA capping. In addition, dentin sialophosphoprotein immunoreactivity was observed in the odontoblast-like cells.
Conclusions: In the present immunohistological study on direct pulp capping with MTA, vascular proliferation and the differentiation of odontoblast-like cells for the formation of hard tissue were observed in pulp tissue. Furthermore, it was suggested that the Wnt signaling pathway is involved in odontoblastic differentiation in direct pulp capping with MTA.
