Microbial and Morphological Study on Refractory Periapical Periodontitis

Methods:Eighteen teeth suffered refractory peiapical periodontitis were recruited in this study. The microbiological samples were collected with paper points or by erasion of periapical soft tissues during the root-end surgery, then were inoculated, isolated and identified by traditional bacterial culture methods. The resected root ends were immediately immersed in 2.5% glutaraldehyde solution and observed under scanning electron microscope (SEM).

Results:16 (88.8%)of 18 periapical lesions yielded microbial growth.17 different bacteria species and 57 bacteria strains were detected. There was no significant difference in the detection rate and the constituent ratio between Gram-positive bacteria and Gram-negative bacteria (P>0.05). No significant difference was found in the detection rate between the obligate anaerobic bacteria and facultative anaerobic bacteria (P> 0.05), however, there was significant difference in the constituent ratio between the obligate anaerobic bacteria and facultative anaerobic bacteria (P <0.05). Under scanning electron microscope, mature bacteria biofilms were observed on the surface of the resected root ends.

Conclusions:The pathogeny of refractory periapical periodontitis is obligate anaerobic bacteria dominated polyinfection. And the bacteria were existing in the form of mature biofilms.