Abstract: Objective: To investigate the effect of platelet-rich fibrin(PRF)on promoting periodontal healing by replantation of canine dislocation. Methods: 10 adult mongrel dogs were selected and the upper and low-er anterior teeth were pulled out at intervals. Whole blood was extracted from jugular vein to prepare PRF and PRP. The dislocated teeth were randomly divided into groups according to 30min, 1h and 2h after dry placement in vitro. The infected teeth in each group were replanted with PRF, PRP or without any graft, and immediate replantation was used as the control group. Histological observation was used to evaluate the periodontal healing in each group. Results: The first group presented normal periodontal membrane structure. No inflammatory changes and inflammatory absorption, no inflammatory changes and inflamma-tory absorption occurred in groups 3 and 4, and the difference in normal periodontal membrane and sur-face absorption was not statistically significant(P>0.05). The periodontal membrane structure of the fourth group and the seventh group had relatively dense collagen fiber structure and strong directivity. There was no significant difference in normal periodontal membrane between the fourth group and the seventh group and the first group(P>0.05). Normal periodontal membrane of the 7th group was higher than that of the 6th group, while surface absorption was lower than that of the 6th group, and the difference was statistically significant(P<0.05). There was no significant difference in surface absorption between the 9th group and the 10th group(P>0.05), but surface absorption was mostly repaired and static. Conclusion: The effect of PRF on periodontal healing was more obvious than that of the group without grafting and the group using PRP. After 2h of dislocation, PRF/PRP was difficult to promote periodontal healing.

Key words: platelet-rich fibrin, the dog, dislocated replantation, the periodontal ligament, the heal-ing effect