Effectiveness of supplementary antimicrobial procedures in disinfecting lateral canals as evaluated by a novel ex vivo analytical approach

Abstract

This ex vivo study devised an analytical ex vivo method for infection/disinfection of simulated lateral canals located in the middle and apical segments of the root. The antibacterial effects of supplementary approaches were tested in this model. Extracted mandibular premolars had their main root canals enlarged and then two lateral canals (100 μm in diameter) were created in the root, one in the apical and the other in the middle portion. Micro-computed tomography was used for specimen selection and to confirm the quality of the simulated ramifications. The specimens were contaminated with a mixed bacterial culture from subgingival bacterial biofilm added to pure Enterococcus faecalis strain ATCC 29212 grown overnight, using special strategies to facilitate culture medium penetration within the lateral canals. The following procedures were tested for disinfection: NaOCl/passive ultrasonic irrigation (PUI), NaOCl/XP-endo Finisher, ozonated water/continuous ultrasonic irrigation (CUI), and NaOCl/conventional irrigation with 30-G needles (control). Bacteriological samples were taken from the main canal before (S1) and after (S2) each supplementary protocol, and also from each lateral canal after treatment (S3). DNA extracted from the samples was subjected to quantitative real-time polymerase chain reaction. All S1 main canal samples were positive for bacterial presence. Bacterial counts in the main root canal substantially decreased by 99.2% after PUI, 99.1% after ozone/CUI, 99% after XP-endo Finisher, and 96% in the control group (P < 0.01 for all groups). There were no significant differences between groups (P > 0.05). The same was observed when comparing the effects of the supplementary approaches in the apical and middle lateral canals (P > 0.05). Only a few lateral canals showed no detectable bacteria. The method proposed here proved effective for ex vivo infection/disinfection studies. All supplementary approaches induced a substantial bacterial reduction in the main canal, with no significant differences between them. However, in terms of lateral canal disinfection, none of the tested approaches showed significant effects when compared to the control group.

Keywords: Apical periodontitis; Endodontic treatment; Lateral canal; Ozone; Root canal infection; Ultrasonic irrigation.

Fig. 1

Schematics of the experiment protocol for infection and disinfection of lateral canals. (A) The root length was standardized and the root canal prepared up to the R-Motion instrument size 40/04. (B) Artificial lateral canals were created using a 0.10 mm bur operated by a drilling machine. (C) Micro-CT images confirmed the successful creation of lateral canals connecting the external root surface with the main root canal lumen. (D) Apparatus and strategy to permit penetration and circulation of culture medium in the lateral canals. A barrier was used to seal the apical foramen (blue). (E) After sealing of the apical and lateral foramina with a barrier (blue) to create a closed system, the disinfection procedures were performed (passive ultrasonic irrigation, XP-endo Finisher agitation, ozonated water/continuous ultrasonic irrigation, conventional irrigation). (F) Bacteriological sample taking from the main canal before and after preparation. (G) Bacteriological sample taking from each lateral canal.