| Objective: To establish the experimental periapical periodontitis model in rats by Enterococcus faecalis, and study the expression of Bcl-2 in the process of SD rats periapical lesions,to investigate the effect of Enterococcus faecalis.Methods: 40 male Sprague- Dawley(SD) rats were selected as the experimental object. Selecting the right mandibular first molar oeclusal for experiment, rats was anesthetized by an intraperitoneal injection of 10% chloral hydrate, pulp exposure were made at the occlusal surface of mandibular first molars with small round bur. Randomly divided them into 2 groups: group A and group B, 20 for each groups. Group A(no bacterium group) : clean up the pulp cavity after the surgery,in the rat medullary cavity sealed sterile cotton PBS buffer solution; Group B(bacterium group): clean up the pulp cavity after the surgery, soaked sterile cotton with Enterococcus faecalis and PBS buffer in the medullary cavity is sealed. Then all the medullary cavity was sealed by imported glass ionomer. The left side mandibular first molar of the rat as the control group. Conventional uniform feeding after 1week, 2 weeks, 3 weeks, 4 weeks time, 5 rats were randomly selected of each group. Ether anesthesia, then the animals were killed by paraformaldehyde buffer. To separate the left and right along the mandibular mid-line. Mandibular first molars was then retrieved with the surrounding bones and soaked into 10% EDTA. Tissue shaping molding, regular histological processing(dehydration, transparent, paraffin), paraffin embedding, parallel to the long axis of the teeth sagittal, paraffin section. Five-micrometer-thick sections were cut for the experiment. HE staining was used to stain on apical tissue of rats and the characteristics of pathology observation of tissue apical inflammation, degree of immunohistochemical staining distribution method to detect Bcl-2 in periapical tissues of rats and the expression. Using statistic method to analysis the results.Results:1.HEHE stain result indicates experimental lateral mandibular first molar root tip tissue showed serous exudation and vasodilatation in different degree, inflammatory cell infiltrates formed, it shows a small amount of neutrophil infiltration; with disease progression scope of inflammatory infiltration expands, which contains a large number of neutrophils; On the 4 weeks after operation the scope of inflammatory cell range continues to expand, the number of lymphocytes increases. Pathological examination results shows that the periapical periodontitis model in rats was successfully established.2.Immnohistochemisty(SP)(1) immunohistochemical result shows that the positive expression of Blc-2 can be observed in periapical inflammation region in both A and B group, the positive signal was mainly expressed in the lymphocyte and neutrophil cytoplasm. Part of the expression in the nucleus, the positive signals behave as brown or brown yellow deep dyeing. At 2 weeks intense Bcl-2 immunoreaction was observed. Bcl-2 began to express quantity decreased gradually in 3 weeks.On the other hand, only weak Bcl-2 immunoreactivity was detected at 4 weeks after pulp exposure. The control group showed a small amount of Bcl-2 positive cells.(2) At 1, 2, 3 and 4 weeks after operation, the positive expression of Bcl-2 in B group campared with each other, with statistically significant(P<0.05). At 2 and 3 weeks after operation, the positive expression of Bcl-2 in A group campared with other time point, with statistically significant(P<0.05); at 1 and 4 weeks after operation, th e positive expression of Bcl-2 in A group campared with each other,without statistically significant(P>0.05).(3) At 1, 2, 3 and 4 weeks after operation,the positive expression of Bcl-2 in A group was higher than that in control group, with statistically significant(P<0.05).(4) At 1, 2, 3 and 4 weeks after operation,the positive expression of Bcl-2 in B group was higher than that in control group, with statistically significant(P<0.05).(5) At 1, 2, 3 and 4 weeks after operation, the positive expression of Bcl-2 in B group was higher than that in A group, with statistically significant(P<0.05).Conclusion:1. The study demonstrated that the expression of Bcl-2 was positively correlated with the area of the lesion.2. Enterococcus faecalis can influence the pathological and physiological process of periapical periodontitis, stimulate the expression of Bcl-2 increased. |
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