中文摘要：

目的采用16s r DNA PCR和实时荧光定量聚合酶链反应（RTFQ-PCR）分析和比较牙髓卟啉单胞菌（P.endodontalis）在原发性感染和再感染根管中的定植情况。方法将120例慢性根尖周炎患者的120颗单根管患牙按原发性感染和再感染分为2组,每组60颗。采用16s r DNA PCR分析P.endodontalis在两种感染根管内的检出率,对于P.endodontalis检出阳性者用RTFQ-PCR比较P.endodontalis在两种感染根管内的DNA相对表达量。结果 P.endodontalis在原发性感染根管内的检出率明显高于再感染根管的检出率（P=0.001）。RTFQ-PCR检测结果表明P.endodontalis在原发性感染根管内的DNA表达量和再感染根管内DNA表达量差异无统计学意义（P=0.303）。结论 P.endodontalis在原发性感染和再感染根管内均有定植,但与原发性感染根管关系更为密切。

英文摘要：

Objective This study aims to assess and compare the prevalence ofPorphyromonas endodontalis （P. endo- dontalis） in root canals associated with primary and secondary endodontic infections by using 16s rDNA PCR and real-time fluorescence quantitative polymerase chain reaction （RTFQ-PCR）. Methods A total of 120 adult patients with one radio- graphically documented periapical lesion were included. Sixty teeth presented with primary endodontic infections and 60 with secondary endodontic infections requiring retreatment. P. endodontalis was identified by using 16s rDNA PCR techni- ques. The positive DNA expression ofP. endodontalis in two types of infected root canals were quantitatively compared by using SYBR GREEN I RTFQ-PCR. Results The prevalence ofP. endodontalis in the root canals with primary endodontic infections was significantly higher than that in root canals with secondary endodontic infections （P=-0.001）. However, RTFQ- PCR results showed no significant difference in DNA expression quantities between the primary and secondary endodontic infections root canals （P=-0.303）. Conclusion P. endodontalis is more highly associated with root canals having primary endodontic infections, although P. endodontalis colonize in both root canals with primary and secondary chronic apical periodonfitis.