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目的应用聚合酶链式反应-变形梯度凝胶电泳（PCR—DGGE）技术检测慢性根尖周炎患牙根管内中间普菌和链球菌定植情况，分析根管内细菌与患牙症状间关系。方法2011年12月至2013年5月于北京大学深圳医院口腔科就诊的27例慢性根尖周炎患牙根管内细菌样本，提取DNA，利用16SrDNA引物进行PCR—DGGE技术分析。结果27例共检出细菌菌属17种。中间普菌在17例有症状组中检测出16例（94．1％），在10例无症状组中检测出6例（60．0％），两组检出率差异有统计学意义（P〈0．05）。链球菌在17例有症状组中均未检测出，在10例无症状组中检测出4例（40．0％），两组检出率差异有统计学意义（P〈0．05）。结论慢性根尖周炎患牙以厌氧菌感染为主，根管内中间普菌、链球菌与临床症状相关。

Determination and analysis of Prevotella intermedia and Streptococcus in the infected root canals of teeth with chronic periapical periodontitis

Objective To detect preponderant bacterium in the root canals of chronic periapical periodontitis by a polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE）approach, and analyze the relationship between Prevotella intermedia, Streptococcus and the clinical symptoms. Methods Clinical samples were collected from the root canals of 27 teeth with chronic periapical periodontitis. DNAs were extracted from the samples and identified by PCR-DGGE. Results All samples were positive in the presence of bacteria and 17 samples contained one or more of the detected bacterium （62.96%）.The detection rates of PrevoteUa intermedia were higher in symptomatic cases while Streptococcus lower （P 〈 0.05）.Conclusion Anaerobic organisms are detected from canal samples of periapical periodontitis at high rates. In the root canals, Prevotella intermedia and Streptococcus have significant relationship with the presence or absence of clinical symptoms.