Abstract:

Objective　To detect colonization of four anaerobic bacteria in infected root canals with 16S rDNA-PCR. Methods　Thirty freshly extracted teeth were selected for this study （10 teeth with pulpitis; 10 teeth with periapical lesions; 10 teeth with failed root canal treatment）. Each root canal was divided into two sections：the corona and middle section （6 mm to root tip），and the tip section （3 mm to root tip）. Bacterial genomes of every section were extracted，and classes of bacteria were detected with 16S rDNA-PCR；the detection rate was calculated and statistical analysis was made. Results　P.endodontalis （P.e），F.nucleatum （F.n） ，E.faecalis（E.f）and P.intermedia （P.i） were detected in corona and middle section of pulpitis group，with P.e detected in most canals（P＜0.05），while only P.e was detected in the tip section. In group of periapical lesions，no statistically significant difference was found in the detection rate of P.e，F.n，P.i or E.f（P > 0.05）. In group of failed root canal treatment，detection rate of E.f in the tip section （60%） was higher than that in the corona and middle section （10%），with obvious statistical difference （P < 0.05）. Conclusion　Colonization of anaerobic bacteria of pulpitis canals is mostly in the corona and middle section，with the highest detection rate in P.e. In periapical inflammation canals，no statistically significant difference is found  in the detection rate of P.e，F.n，P.i or E.f，with P.i as the main bacteria. In endodontic treatment failure canals，E.f is the main bacteria，and is most often detected in the tip section.

Key words: P.endodontalis, P.e；F.nucleatum, F.n；P.intermedia, P.i；E.faecalis, E.f；16S rDNA

摘要：

目的　应用16S rDNA-PCR技术检测不同类型感染根管内4种厌氧菌的定植状况。方法　于南京大学医学院附属口腔医院收集临床上拔除的新鲜离体牙30颗，分为3组：牙髓炎组、根尖周炎组、根管治疗失败组，每组10颗。将各组牙齿的根管分为根管冠中段（离根尖6 mm）和根管尖段（离根尖3 mm），提取每个根管段的细菌基因组DNA，用PCR扩增细菌16S rDNA基因片段的方法检测细菌种类，计算检出率并进行统计学分析。结果　在牙髓炎组，根管冠中段能检测到牙髓卟啉单胞菌（P.endodontalis， P.e）、具核梭杆菌（F.nucleatum，F.n）、粪肠球菌（E.faecalis，E.f）和中间普氏菌（P.intermedia，P.i），其中P.e的检出率最高（P < 0.05），根管尖段只检测到P.e的存在。在根尖周炎组，4种厌氧菌（P.e、F.n、E.f、P.i）在根管冠中段和尖段的检出率差异无统计学意义（P > 0.05）。在根管治疗失败组，E.f在根管尖段的检出率（60%）比在根管冠中段的检出率（10%）高，差异有统计学意义（P < 0.05）。结论　牙髓炎的根管细菌主要定植在冠中段，P.e检出率最高；根尖周炎的根管冠中段和根管尖段4种细菌检出率无明显差别，都是以P.i为主；根管治疗失败的根管细菌以E.f为主，主要集中于根管尖段。

关键词: 牙髓卟啉单胞菌, 具核梭杆菌, 中间普氏菌, 粪肠球菌, 16S rDNA