## 3 Results
#### 3.1.1 Immediate Replantation (1 min)  
One day after replantation, expanded inflammatory reactions were evident in the dental pulp of the samples from the EG and CG, including the presence of numerous inflammatory cells and hemorrhagic areas. Blood vessel lumens disappeared from the odontoblast layer, which showed disruptive features along the pulp-dentin border of the replanted teeth (Supplementary Figure S1A,G). Nestin expression was completely absent in the odontoblast layer in the samples from the CG and EG during this observation period (Supplementary Figure S1D,J). On day 3, the inflammatory cells appeared to decrease in number in the pulpal tissue, whereas the odontoblast layer continued to show degenerative features in both groups (Supplementary Figure S1B,H). Nestin expression remained absent in the odontoblast layer; however, some Nestin-positive filamentous structures were observed in the pulpal floor, particularly in the L-PRP-treated teeth (Supplementary Figure S1E,K). On day 5, the dental pulp began to recover its characteristic features, including the presence of blood vessels, although these were primarily located in the central pulp or near the subodontoblastic layer (Supplementary Figure S1C,I). Eosinophilic amorphous matrices, particularly under the coronal cusps, were observed in the pulpal tissue of the EG (Supplementary Figure S1I). Nestin-positive cells and filamentous structures were observed in the central pulp of the CG, but not under the predentin, as the odontoblast layer was not yet re-organized (Supplementary Figure S1F). In contrast, in the EG, Nestin-positive newly differentiated odontoblast-like cells were detected in the root and pulpal floor (Supplementary Figure S1L). Quantitative analysis of Nestin immunostaining revealed a positive trend in the replanted teeth treated with L-PRP at days 3 and 5, although no significant differences were observed between the groups or time points (Supplementary Figure S2). Similarly, one week after replantation, the dental pulp of the CG showed the presence of eosinophilic amorphous matrices beneath the odontoblast layer (Figure 1A), which corresponded to areas of AZAN-positive staining (Figure 1B) and Nestin-positive filamentous structures in the central pulp. In addition, newly differentiated odontoblast-like cells beneath the predentin exhibited a positive reaction to Nestin (Figure 1C). The healing process was improved in the dental pulp in most samples of the EG, which showed more blood vessels compared with that in the CG and partial re-organization of its normal morphology, particularly in the root pulp, central coronal pulp, and pulpal floor (Figure 1D). Collagen deposition, as revealed by AZAN blue staining, was located in the subodontoblastic layer (Figure 1E), whereas intense Nestin immunoreactivity was detected in odontoblast-like cells along the dentin-pulp border as well as in cells and filamentous structures in the subodontoblast layer and pulpal floor (Figure 1F). Two weeks after replantation, a higher percentage of newly formed hard tissues was observed in the pulp ofreplanted teeth in the EG compared with that in the CG (Figure 2A,D). Collagen-related blue areas were identified in the newly formed hard tissue by AZAN blue staining, which was consistently observed in the EG. Nestin immunohistochemistry enabled the identification of the healing patterns, such as tertiary dentin and/or bone-like tissue in the dental pulp (Figure 2C,F). Analysis of the Nestin-positive perimeter, which provides insight into the progression of the pulpal healing process, showed significant differences between the first and second weeks in the CG and EG (\(p<0.002\), \(p<0.012\)) (Figure 3A). Moreover, a significant difference was observed between the CG and EG at week 2 in terms of newly formed hard tissue deposition (\(p<0.002\)) (Figure 3C).