关键词: 粪肠球菌, 根尖生物膜, 根管治疗后疾病

Abstract:

Objective This study aims to develop andobserveamodel systemofthe periapicalbiofilm structure of Entero-coccus faecalis (E. faecalis). Methods  A total of 24 intact human single-rooted premolars extracted for orthodontic reasons were collected and randomly divided into eight groups (n=3). The specimens were subjected to ultraviolet disinfection, ino-culated with E. faecalis (ATCC 29212) suspension adjusted to 1×108CFU•mL-1, and incubated at 37 ℃ for 1, 2, and 7 d. Specimen groups were prepared for scanning electron microscope to examine the biofilm formation. The specimens in the confocal laser scanning microscope (CLSM) groups were stained with propidium iodide (PI) and ConA-fluorescein iso-thiocyanate (ConA-FITC) to examine the biofilm formation. The images were randomized, and biofilm coverage (%) was assessed using Photoshop CS5. Results  The biofilm coverage (%) on the cementum increased with increasing incubation period. The biofilm coverage of the 7 d group was significantly higher than those of the 1 and 2 d groups (P<0.05). The values of the latter two groups were not significantly different (P>0.05). Dense aggregations composed of E. faecalis and the amorphous matrix were observed on the root cementum surfaces of the specimens in the 7 d group. The bacteria were stained red by PI, and the matrix was stained green by ConA-FITC under CLSM observation. The biofilm coverage (%) on the samples inthe7 d group was17.23%±1.52%, showing multi-level space structure andwaterchannels. Conclusion  E. faecalis forms bacterialbiofilmsontherootcementumsurfacein7d. Thebiofilmswerecomposedof E. faecalis andtheamorphousmatrix.

Key words:  Enterococcus faecalis, periapical biofilm, post-treatment endodontic disease