粪肠球菌再感染根尖周炎病程进展分析

Progression analysis of periapical periodontitis caused by repeated root canal infection with Enterococcus faecalis

目的构建粪肠球菌(Enterococcus faecalis,E.faecalis)再感染大鼠根尖周炎模型,通过观察实验牙根尖区骨质破坏面积、根尖区炎症状态及TNF-α表达,分析E.faecalis再感染大鼠根尖周炎的病程进展。方法 SD大鼠30只,采用双侧上颌第一磨牙开髓后置入细菌内毒素脂多糖并自然暴露于口腔正常菌群4周的方法建立混合菌初次感染慢性根尖周炎模型,建模成功后对实验牙行根管预备、封药消毒2周,其后去除填充物,根管内注入E.faecalis菌悬液,封闭洞口1周建立E.faecalis再感染大鼠根尖周炎模型,之后连续观察3周。E.faecalis再感染根尖周炎组大鼠在建模成功后1周、2周、3周时,以及混合菌初次感染慢性根尖周炎组正常培养6周后、慢性根尖周炎氢氧化钙治疗组经氢氧化钙治疗6周后,各组随机处死6只大鼠,通过X线测量法、H-E染色和免疫组化染色分别检测实验牙根尖周区骨质破坏面积、根尖周区炎症状态及炎症因子TNF-α的表达量。结果 (1)E.faecalis再感染大鼠根尖周炎建模成功后连续观察3周发现根尖周骨质破坏面积持续增加,骨破坏边界仍不清晰,而根尖周炎症1～2周时达重度炎症,在3周时已转为慢性炎症状态,TNF-α表达量在2周后下降。(2)混合菌初次感染慢性根尖周炎组根尖周骨质破坏面积较小,骨破坏边缘清晰,根尖炎症程度低,TNF-α表达量少。(3)慢性根尖周炎氢氧化钙治疗组根尖周骨质破坏面积最小,炎症消退,可见根尖周牙骨质和牙槽骨新生明显,TNF-α极少量表达。结论 E.faecalis具有较强的破坏根尖周组织的能力,在慢性炎症时,根尖周组织仍有进行性溶骨破坏的现象。

Objective To develop a rat model of periapical periodontitis caused by repeated root canal infection with Enterococcus faecalis （E. faecalis）, and to evaluate the disease progression by observing the periapical lesion area, inflammation, and TNF-a expression in the root apex. Methods Thirty Sprague Dawley rats were used in this study. The pulps of the bilateral first maxillary molar teeth of each rat were exposed, absorbent cotton with lipopolysaccharides （LPS） was implanted, and then the teeth were exposed in the oral environment for four weeks to induce periapical periodontitis of primary root canal infection with mixed bacteria. Then the root canal was subjected to disinfection treatment for two weeks, followed by inoculation with E. faecalis suspension for one week to produce repeated root canal infection model with E. faecalis for a 3 week observation. X-ray, H-E staining and immunohistochemical staining were used to observe the periapical lesion area, inflammation, and TNF-a expression in the root apex at one week, two weeks, three weeks after establishment of repeated root canal infection model; the above parameters were also observed for periapical periodontitis caused by primary root canal infection with mixed bacteria （6 weeks later） and for root canal disinfected by Ca （OH）2 （for 6 weeks）. Results （1） Periapical periodontitis caused by repeated root canal infection with E. faecalis had gradually increased periapical lesion area, with unclear damage border; the infection reached a severe level during the 1-2 weeks and became chronic inflammation at week three; and the expression of TNF-a began to decrease after two weeks. （2） The periapical periodontitis caused by primary root canal infection with mixed bacteria had a smaller periapical lesion area, with clear damage border, slighter infiltration of inflammatoryceils, and less TNF-a expression. （3） The periapical periodontitis with root canal disinfected by Ca （OH）2 had the smallest periapical lesion area, with disappeared inflammation, slight TNF-a expression, and hyperplasia of cementum and alveolar bone. Conclusion E. faecalis has a strong periapical damaging effect, with continuous bone absorption observed even under the chronic inflammatory status.