慢性根尖周炎患牙根尖外表面的细菌生物膜

Bacterial biofilm on the apical external root surfaces of human teeth associated with chronic periradicular lesions

目的:对慢性根尖周炎患牙根尖外表面的生物膜进行细菌学研究和形态学观察,了解生物膜中细菌的种类、组成及其超微结构。方法:选择临床诊断为慢性根尖周炎且不能保留的患牙10例,包括未经治疗及根管治疗失败的患牙各5例,同时将5例因正畸减数拔除的健康前磨牙作为对照组。所有样本的牙冠部无菌消毒后进行根管内取样、接种、厌氧培养后检测根管内的细菌种类。患牙拔除即刻3%(体积分数)戊二醛固定,取距根尖5 mm的牙根经梯度脱水、临界点干燥、喷金处理后进行扫描电镜观察。结果:10例慢性根尖周炎患牙拔除前根管内细菌培养均为阳性,其中微小消化链球菌和具核梭杆菌检出率较高。在5例未治疗的慢性根尖周炎患牙中仅有1例根尖外表面存在生物膜结构,主要由球菌组成;而在5例根管治疗失败的根尖周炎患牙的根尖外表面均可观察到浓密的细菌膜状结构,由球菌、杆菌及/或丝状菌组成,并且在超填的牙胶尖表面还观察到由球菌和丝状菌组成的典型的"玉米棒芯"样结构。对照组中则未有细菌存在。结论:慢性根尖周炎患牙的根尖外表面存在细菌生物膜结构,该生物膜的存在与临床上难治性慢性根尖周炎密切相关。

Objective：To investigate the patterns of microbial infection on the apical external root surfaces of treated and untreated teeth associated with chronic apical periodontitis and to study bacteria in the biofilm in order to find out the species, constitution and origination of bacteria in periapical biofilm. Methods： Ten teeth with chronic apical periodontitis from patients of the Department of Stomatology of People＇s Hospital, Peking University： 5 untreated teeth with a radiographically visible chronic periradicular lesions and 5 teeth with extensive carious lesions, radiolucent lesions of varying sizes and attached periradicular tissues were selected for study. Using aseptic techniques and sterile instruments, bacterial samples of the root canals were taken, inoculated and separated according to usual practice. After extraction, ten teeth were fixed and the apical 5 mm portion of one root was sectioned. Root tips were dehydrated, sputter coated with gold, and then examined for the occurrence of bacteria on the apical root surfaces using scanning electron microscope. Five healthy teeth with vital pulp were used as controls. Results： Microbial study showed that ten specimens yielded bacterial growth. The most prevalent bacteria were P. micros and F. nueleatum. In the 5 untreated teeth, bacterial cells were usually observed close to the apical foramen in only 1 specimen. Morphologically, these bacteria consisted of cocci. In the 5 treated teeth, a dense bacterial aggregation composed mainly of cocci and rods was observed surrounding the apical foramen of all specimens. Besides rods, ding coaggregations of cocci and filaments, other bacterial morphological types were recognized, inclu- characterizing a fully developed ＂corn-cob＂. No microorganisms were found in the healthy controls. Conclusion：Bacterial biofilm was always present in teeth with post-treatment endodontic disease. The presence of apical bacterial biofilm is clinically important, and it may cause failure of endodontic treatment as a consequence of persistent infection.