Studies Of MMP-3 And CCN2 In The Process Of Dental Pulp Injury And Repair—Experimental Observation Of The Effect Of Pulp Capping Agent

Objective:Establishing model of pulp mechanical damage- repair of rats,covered Matrix metalloproteinase 3( MMP-3) and Connective tissue growth factor CCN2(CTGF/CCN2) in the injuried pulp and observe the histomorphology changes of rat dental pulp at different points in time,research the role of MMP-3 、CCN2 on the reparative dentin and odontoblasts after injury.Methods:Forty-eight male wistar rats were randomly divided into three groups according to different pulp capping agent(n = 16) : the control group(PBS pulp capping), the experimental group(MMP- 3 pulp capping), the experimental group(CCN2 pulp capping),again each group were randomly divided into 3, 7, 14 and 28 d four subgroups(n = 4) according to the observation time. Each wistar rat was prepared with a cavity on the occlusal surface of maxillary first molars on left side. PBS group applied PBS on the exposed pulp, MMP-3 group applied MMP-3 on the exposed pulp,CCN2 group applied CCN2 on the exposed pulp.Each groups rats were put to death respectively on the 3rd, 7th, 14 th and 28 th day after operations and collected teeth specimen.The teeth were stained with HE and immunohistochemical to generate dentin sample. Observe the expressions of reparative dentin and odontoblasts in each sample.Results:HE staining results showed that compared with the PBS group:After three days,a few inflammatory cells under the exposed pulp in MMP- 3 group,the inflammatory cells under the exposed pulp were no less in CCN2 group,but obviously blood vessels and the expansion of new blood vessels can be observed in both the experimental groups. Then inflammatory cells were decreased after 7 days and a small amount of prophase dentin formed between fibroblasts and dentin. After injury of 14 days the calcified bridge was observed and the inflammatory cells disappeared. 28 days after injury reparative dentin can be observed. Immmunohistochemical staining results showed that: thepositive expression of DMP- 1 and DSP was gradually strengthen after 3, 7, 14 days in MMP-3 group and CCN2 group, besides, two experimental groups presented a significant statistical difference(p<0.05) compared with the PBS group at the same time point. After 28 days, DMP-1 and DSP expression were decreased in three groups.Conclusion:MMP-3 and CCN2 are placed in exposed pulp can increase the activity of odontoblasts and improve the ability of the reparative dentin formation.This study suggests matrix metalloproteinases 3 as well as connective tissue growth factor are good pulp capping agents and can be applied to clinical associated with calcium hydroxide. It can provides theoretical basis and new ideas for development of pulp capping agent.