Histologic evaluation of canal and isthmus debridement efficacies of two different irrigant delivery techniques in a closed system

Introduction: This study compared canal and isthmus debridement efficacies between side-vented needle irrigation (SNI) and continuous ultrasonic irrigation (CUI) in the mesial root of mandibular first molars with narrow isthmuses using a closed-canal design. Methods: Micro-computed tomography scanning was used to select 20 teeth, each containing a narrow isthmus. Each root was sealed at the apex; embedded in polyvinylsiloxane to simulate a closed-canal system; and instrumented to size 40, 0.04 taper. Final irrigation was performed with either SNI or CUI (N = 10). Masson trichrome-stained sections were prepared from demineralized roots at 10 canal levels between 1.0 and 2.8 mm from the anatomic apex. The areas and debris occupied by the canals and isthmus were measured using ImageJ software (National Institutes of Health, Bethesda, MD) and statistically analyzed using repeated-measures analysis. Results: Overall, a significant difference was identified between SNI and CUI in the amount of debris remaining in the isthmus (P = .006) but not in the canal (P = .940). There was significantly more debris in the most apical three canal levels (1.0-1.4 mm) regardless of the irrigation technique (P < .001). The isthmus harbored significantly less debris in the CUI group between isthmus levels 1.0 to 2.2 mm when compared with SNI (P < .001 and P = .029). Neither technique removes debris completely from the canal or isthmuses. Conclusions: Compared with SNI, CUI removes significantly more debris from narrow isthmuses of mandibular mesial roots.