Disinfecting and shaping type I C-shaped root canals: a correlative micro-computed tomographic and molecular microbiology study

ABSTRACT Introduction This ex vivo study compared the disinfection and shaping abilities of two preparation protocols in C-shaped canals. Methods Mandibular second molars with type I C-shaped canals were pair-matched based on micro-computed tomographic (micro-CT) analysis, and distributed into 2 groups. The canals were contaminated with a mixed bacterial culture and prepared by two protocols, both with 2.5% NaOCl irrigation: XP-E (XP-Endo Shaper supplemented with XP-Endo Finisher) and BR-Hed (BioRaCe supplemented with a Hedstrom file). Micro-CT scans and intracanal bacteriologic samples were taken before (scan #1 and S1) and after preparation (scan #2 and S2), and after the supplementary step (scan #3 and S3). Canal shaping was evaluated by micro-CT and disinfection was assessed by quantitative polymerase chain reaction. Results Micro-CT data from XP-E (n=21) and BR-Hed (n=23) revealed no significant differences between groups regarding shaping parameters (canal volume, surface area, structure model index [SMI], and prepared walls) after preparation and after the supplementary step (P > .05). All these parameters significantly increased after each preparation step (P .05). Bacteriologic data from XP-E (n=21) and BR-Hed (n=22) groups showed that 14 (66.7%) and 10 (45.5%) S2 samples still had detectable bacteria, respectively. Corresponding figures for supplementary steps with XP-Endo Finisher and Hedstrom file were 11 (52.4%) and 10 (45.5%), respectively. Bacterial counts in S1 significantly decreased in S2 and S3 in both groups (P .05 for both groups). Quantitative bacterial reduction was not different between groups (P > .05). Conclusions XP-Endo Shaper and BioRaCe systems have similar disinfecting and shaping abilities in C-shaped canals. Supplementary steps with Hedstrom file and XP-Endo Finisher were similarly effective in improving shaping, but this was not sufficient to enhance disinfection. About half of the cases, in both groups, still harbored detectable amounts of bacteria.