Histological study of platelet-rich fibrin combined with MTA for direct pulp capping of rabbit teeth

To investigate the outcomes of a novel direct pulp capping agent containing platelet-rich fibrin (PRF) and mineral trioxide aggregate (MTA).

A total of 32 New Zealand rabbits were randomly divided into 4 groups, namely, the PRF+MTA group (P+M group), PRF group (P group), MTA group (M group) and blank control group (BC group), with 8 rabbits per group. Dental pulp exposure and direct pulp capping were performed, and complete crown square sealing was performed on 2 mandibular central incisor teeth of each rabbit. Four rabbits from each group were euthanized after each observation period (7 and 28 days). The experimental teeth were subjected to HE staining. Inflammatory cell infiltration, calcified bridge formation and pulp tissue disorganization were observed and graded.

Inflammatory cell infiltration: on the 7^th day, group P+M and group M were lighter than group BC (P＜0.05); on the 28^th day, group P+M was lighter than group P and group BC (P＜0.05); group P+M and group M did not significantly differ (P＞0.05). Calcified bridge formation: on the 7^th and 28^th days, group P+M was lighter than group P, group M and group BC (P＜0.05); on the 28^th day, group M was higher than group BC (P＜0.05). Under microscope, the calcified bridge contained cellular components and was surrounded by odontoblast-like cells, sharing a structure resembled osteodentin; dentin tubule-like structure could not be observed in calcified bridge, and the calcified bridge resembled certain points of osteodentin. Pulp tissue disorganization: on the 7^th day, group P+M and group M were lighter than group BC (P＜0.05); on the 28^th day, group P+M was lighter than group P and group BC (P＜0.05). group P+M and group M did not significantly differ (P＞0.05).

The combination of PRF and MTA for direct pulp capping provided light inflammatory cell infiltration, stable pulp status and a strong ability of pulp tissue to form calcified bridge, and the calcified bridge resembled certain points of osteodentin.