感染根管优势菌致病能力的实验研究

目的研究感染根管优势菌在根尖周炎发病过程中的作用，探讨不同细菌致病能力的差异。方法选择牙髓卟啉单胞菌（Porphyromonas endodontalis，P．e）、牙龈卟啉单胞菌（Porphyromonas gingivalis，P．g）、具核梭杆菌（Fusobacterium nucleatum，Pn）分别接种于SD大鼠第一磨牙髓腔内，以生理盐水和髓腔开放作为对照。术后1、2、4、8周处死大鼠，取上、下颌骨拍摄X线片，测量并比较各组第一磨牙根尖周透射影面积；组织学切片观察各组根尖周组织病理变化，评价根尖周组织炎症程度。结果X线片测量结果显示根尖阴影面积在术后8周最大，组织学评价结果为术后4周根尖周炎症程度最重，骨吸收最为活跃。各观察阶段，Pg、P．e组X线片和组织学评价结果均与生理盐水组无统计差异（P〉0．05）；术后4周，F．n组x线片和组织学评价结果与Pe组、P．g组及生理盐水对照组有显著差异（P〈0.01），前者骨吸收面积和炎症程度均高于后者；但在所有组中，髓腔开放组根尖周炎症程度最重（P〈0．01）。结论P．g或P．e单独感染牙髓，导致根尖周炎发病能力较弱，Fn相对较强。多种细菌混合感染是根尖周炎形成、发展的主要原因。

The pathogenic potential of oral anaerobic microorganisms in rat periapical lesions

Objective To evaluate the pathological effect of three oral anaerobic bacterial species on periapical lesions.Methods Porphyromonas endodontalis,Porphyromonas gingivalis and Fusobacterium nucleatum were inoculated into the first molars′ pulp of SD rats respectively,and saline inoculated as control.Another group of molars′ pulp was open to the oral cavity without any inoculation.The maxillary and mandibular bone was harvested at 1,2,4,8 weeks,and periapical X-ray was taken and the absorption area of the periapical bone measured and analyzed.The periapical lesions were sliced and their pathology was observed.Results The periapical bone absorption area was increased with time and became biggest at 8 weeks.There were no significant difference in area of periapical lesions and in inflammation degree between the P.e group,P.g group and saline group at 1,2,4,8 weeks(P>0.05).At 4 weeks,the bone absorption area of F.n group was bigger than that of P.e group and P.g group(P<0.01).The inflammation degree in F.n group was severer than that in P.e or P.g group.Conclusion Compared with P.g and P.e,the F.n plays an more important role in the progress of apical periodontitis.Mixed infection of several kinds of bacteria was the main cause of periapical diseases.