## 3 Results
### Assessment of Cell Proliferation in the Dental Pulp of Replanted Tenth by Ki-67 Immunostaining  
The proliferative activity of pulpal cells after application or absence of L-PRP before replantation was evaluated using Ki-67 immunohistochemistry from day 1 to week 2 after IR and at weeks 1 and 2 after IDR. Following immediate replantation, the number of proliferative cells seemed to be slightly lower in the EG group, particularly in the root pulp, at day 1 (Supplementary Figure S3A,D). At day 3, the positive cells were slightly higher in the crown and root pulp of the EG (Supplementary Figure S3B,E), and in the root pulp at day 5 (Supplementary Figure S3C,F). No significant differences were found at week 1 (Figure 4A,B) or 2 (Figure 4C,D) after replantation. In contrast, quantitative analysis of Ki-67 in the samples from the IDR injury model indicated that the L-PRP treatment did not improve the pulpal cell proliferation activity in the coronal or root pulp one week after replantation (Figure 4E,F); however, cell proliferation was decreased in the EG at week 2, particularly in the coronal pulp (\(p<0.047\)) (Figure 4G,H). Figure 1: Hematoxylin–eosin (H&E) (**A,D,G,J**) and AZAN (**B,E,H,K**) staining, and immunohistochemistry for Nestin (**C,F,I,L**) in samples from the CG (**A–C,G–I**) and EG (**D–F,J–L**) one week after IR (**A–F**) and IDR (**G–L**). (**A,G**) The dental pulp of the CG after IR and IDR shows eosinophil amorphous matrices and small hemorrhagic areas in the odontoblast layer (arrowheads in **G**). (**D,J**) Fewer inflammatory lesions and more blood vessels are observed in the dental pulp of samples from the EG after IR and IDR. (**J,K**) Some samples show early deposition of newly formed hard tissue (arrows) in certain areas of the pulpal floor after IDR. (**B,E**) Collagen-related blue areas are consistently detected by AZAN staining in the CG and EG after IR. (**H,K**) Weak AZAN staining is observed in the dental pulp of samples from the CG and EG after IDR. (**C,F**) Samples from the CG and EG show a positive reaction for Nestin in odontoblast-like cells, pulpal cells, and filamentous structures after IR. (**I,L**) Nestin immunoreaction is more intensely detected in the whole dental pulp in samples from the CG and EG after IDR. DP: Dental pulp. Scale bars: 100 μm (**A–L**). Figure 2: H&E (**A,D,G,J**) and AZAN staining (**B,E,H,K**), and immunohistochemistry for Nestin (**C,F,I,L**) in samples from the CG (**A–C,G–I**) and EG (**D––F,J–L**) at week 2 after IR (**A–F**) and IDR (**G–L**). (**A,D,G,J**) Newly formed hard tissue is observed in the dental pulp of the CG and EG after IR and IDR. (**B,H**) Collagen-related blue areas in the hard tissue areas are evident following AZAN staining in samples from the CG. (**E,K**) AZAN-positive areas are more abundant in the pulpal tissue of the EG following IR and IDR. (**C,F,I,L**) Nestin expression is localized in the odontoblast-like cells aligned beneath the newly formed tertiary dentin in samples from the CG and EG after IR and IDR. (**F,I**) Bone-like tissue formation in some samples of the CG and EG lacks Nestin immunoreactivity following either IR or IDR. B: Bone-like tissue, DP: Dental pulp, TD: Tertiary dentin. Scale bars: 100 μm (**A–L**). Figure 4: The percentage of Ki-67-positive cells in the crown (**A**,**C**,**E**,**G**) and root pulp (**B**,**D**,**F**,**H**) at weeks 1 (**A**,**B**,**E**,**F**) and 2 (**C**,**D**,**G**,**H**) after IR (**A**–**D**) and IDR (**E**–**H**). (**A**,**B**) There are no significant differences in the number of proliferating cells at week 1 in the crown and root pulp between CG and EG after IR. (**C**,**D**) Similarly, no significant differences are noted between groups at week 2 after IR. (**E**,**F**) Cell proliferation appears slightly higher in the CG in the coronal and root pulp at week 1 after IDR. (**G**,**H**) The proliferative cells further decrease at week 2, whereas a significant difference between the CG and EG is observed in the coronal pulp at this stage (\(p<0.047\)).