Biofilms and Apical Periodontitis: Study of Prevalence and Association with Clinical and Histopathologic Findings

Introduction: This study evaluated the prevalence of bacterial biofilms in untreated and treated root canals of teeth evincing apical periodontitis. The associations of biofilms with clinical conditions, radiographic size, and the histopathologic type of apical periodontitis were also investigated. Methods: The material comprised biopsy specimens from 106 (64 untreated and 42 treated) roots of teeth with apical periodontitis. Specimens were obtained by apical surgery or extraction and were processed for histopathologic and histobacteriologic techniques. Results: Bacteria were found in all but one specimen. Overall, intraradicular biofilm arrangements were observed in the apical segment of 77% of the root canals (untreated canals: 80%; treated canals: 74%). Biofilms were also seen covering the walls of ramifications and isthmuses. Bacterial biofilms were visualized in 62% and 82% of the root canals of teeth with small and large radiographic lesions, respectively. All canals with very large lesions harbored intraradicular biofilms. Biofilms were significantly associated with epithelialized lesions (cysts and epithelialized granulomas or abscesses) (p < 0.001). The overall prevalence of biofilms in cysts, abscesses, and granulomas was 95%, 83%, and 69.5%, respectively. No correlation was found between biofilms and clinical symptoms or sinus tract presence (p > 0.05). Extraradicular biofilms were observed in only 6% of the cases. Conclusions: The overall findings are consistent with acceptable criteria to include apical periodontitis in the set of biofilm-induced diseases. Biofilm morphologic structure varied from case to case and no unique pattern for endodontic infections was identified. Biofilms are more likely to be present in association with longstanding pathologic processes, including large lesions and cysts. (J Endod 2010;36:1277-1288)