Intentionally perforating the pulp chamber floor promotes M2 macrophage polarization in the dental pulp following tooth replantation in mice

Objectives: Perforation of the pulp floor prior to tooth replantation promotes tertiary dentin formation and reduces bonelike tissue formation in the pulp cavity. However, the mechanisms remain largely unclear. This study aimed to elucidate the effects of this method on macrophage dynamics and angiogenesis in dental pulp. Methods: The bilateral maxillary first molars of TetOP–H2B–GFP mice were extracted. The left molar was immediately replanted, serving as the control group (CG), whereas the pulp floor of the right molar was perforated using a tungsten carbide bur prior to tooth replantation, serving as the experimental group (EG). Immunohistochemical analysis of F4/80, CD206, erythroblast transformation-specific-related gene (ERG), and GFP was performed on days 3, 5, and 7. Results: The F4/80-positive area in the coronal pulp of the CG on days 3 and 7 was larger than that of the EG. The area of CD206 positivity, a specific marker of M2 macrophages, in the coronal pulp of the EG on day 7 was larger than that of the CG. The number of cells positive for ERG, a transcription factor expressed in vascular endothelial cells, in the coronal pulp of the EG on days 5 and 7 was higher than that of the CG. GFP-positive cells were distributed around the pulp floor on day 5 of the EG. Conclusions: This study demonstrates that perforation of the pulp chamber floor prior to tooth replantation induces early revascularization and vascular stabilization as well as promoting M2 macrophage polarization in the coronal pulp.