| Dental pulp tissue is the parenchyma in the pulp chamber. To preserve vital dental pulp is a basical of conservative dentistry. But the ability to self-restore is weak because of the special structure of dental pulp. calcium hydroxide has usually been used as pulp capping agent, but it can not help to restore the dental pulp tissue very well, and it is found that calcium hydroxide had some harmful impact on dental pulp tissue. Based on the experimental research, there has been a movement in conservative dentistry that the healing of dental pulp injury is regulated by many growth factors and ectocytic matrix which can induce hard tissue bridge formation at the exposure site in human dental pulp and provide an effective long-term seal against harmful stimulation. So calcium hydroxide, while still popular, is challenged by stimulation of reparative dentine. transforming growth factors (TGF-β), platelet derived growth factor (PDGF), bone morphogenetic protein (BMP) are the most popular kinds of growth factors. It has been reported by some research that bone morphogenetic protein (BMP) can induce cellular proliferation and differentiation, and stromosecretion as well. BMP-2 and TGF-β1. But how to resolve the difficult problems on the immunoreaction of the extrinsic growth factor and the buildup of the different growth factors is still unknown. In this study we investigated the biological effects of the platelet-rich plasma (PRP) as autologous growth factors on dental pulp fibroblasts and the histopathological effects of PRP as pulp –capping agents in dog teeth. We try to probe into the possibility of the application of PRP as pulp capping agents through the tow parts. Part one: Effects of PRP on the attachment and proliferation of dental pulp fibroblastsMethods: Primary cell culture technique,PRP isolation technique and MTT colorimetric method were used to study the influence of PRP on dental pulp fibroblasts attachment and the influence of different PRP concentration on dental pulp fibroblasts proliferation. Results: The dental pulp cells grew well and sound; In the experiment of attachment, the mean OD value of the PRP group was significantly higher than that of the control group. In the experiment of proliferation, the mean OD values of the different concentration of PRP groups were significantly higher than that of the control group. Conclusion: the PRP can promote the attachment and proliferation of dental pulp fibroblasts. Part two: The experimental study of PRP as pulp –capping agents in dog teethMethods: 50 teeth in two dogs were subjected to methanical pulp exposure. The exposed sites were capped with PRP, MTA, Dycal, PRP compounded with MTA, PRP compounded with Dycal, and restored with glass-ionomer cement. Teeth were extracted after 12weeks and histopathological studies of the response to exposed dental pulp of dogs were completed. Results: Ten teeth in PRP compounded with MTA group were found complete dentinal bridge; one tooth in PRP compounded with Dycal group was found complete dentinal bridge; no complete dentinal bridge was found in PRP group; three teeth in Dycal group were found complete dentinal bridge; six teeth in MTA group were found complete dentinal bridge. Conclusion: The results suggest that PRP compounded with MTA appears superior to pure MTA or Dycal for mechanically exposed dog pulps and may have potential for clinical application, although many issues remain to be further investigated. PRP is not an appropriate dental material to be used alone in direct pulp capping for mechanically exposed dog pulp.
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