Cleaning and Disinfecting Oval-Shaped Root Canals: Ex Vivo Evaluation of Three Rotary Instrumentation Systems with Passive Ultrasonic Irrigation

Abstract

Background and Objectives: Successful root canal treatment depends on the thorough removal of biofilms through chemomechanical preparation. This study aimed to investigate and compare the cleaning and disinfecting efficiency of oval-shaped root canals using XP-endo Shaper (XPS), ProTaper Next (PTN), and HyFlex CM (HCM) in combination with passive ultrasonic irrigation (PUI). Materials and Methods: Ninety extracted teeth were contaminated and randomly divided into three groups: XPS, PTN, and HCM. Each group was assigned to three subgroups: subgroup A (sterile saline), subgroup B (3% sodium hypochlorite and 17% ethylenediaminetetraacetic acid), and subgroup C (3% sodium hypochlorite, 17% ethylenediaminetetraacetic acid, and PUI). Bacterial sampling was conducted both from baseline samples and samples after chemomechanical preparation. Scanning electron microscopy (SEM) was used to evaluate the residue bacterial biofilms, hard tissue debris, and smear layers on the buccolingual walls of oval-shaped root canals. Results: When combined with sterile saline, XPS demonstrated a higher reduction of bacterial counts and was more effective in eradicating Enterococcus faecalis in the middle third of the canals compared to the other instruments (p < 0.05). Additionally, when used with antimicrobial irrigants, XPS was more effective in disinfecting the coronal third of the canals than the other instruments (p < 0.05). Furthermore, XPS reduced hard tissue debris more effectively in the middle third of canals than in the apical third (p < 0.05). Conclusions: XPS outperforms PTN and HCM in disinfecting oval-shaped root canals. Despite the fact that combining XPS and PUI improves cleaning and disinfecting, removing hard tissue debris from the critical apical area remains challenging.

Keywords: endodontic disinfection; endodontic irrigation; oval-shaped root canal; passive ultrasonic irrigation; scanning electron microscope.

Figure 1

Flow diagram showing the selection of eligible subjects and the conduction of the trial. Abbreviations: BHI: brain heart infusion broth; CBCT: Cone-beam computed tomography; HCM: HyFlex CM; PTN: ProTaper Next; PUI: passive ultrasonic irrigation; SEM: scanning electron microscope; XPS: XP-endo Shaper.

Figure 2

Representative scanning electron microscopy (SEM) images of E. faecalis colonization of the root canal before chemomechanical instrumentation. (a) A transverse section of dentinal tubules (3000×); (b) A longitudinal section of dentinal tubules (7000×). Bar = 1 μm.

Figure 3

Representative SEM images of the buccolingual canal walls after rotary instrumentation in the coronal, middle, and apical thirds. The images were taken at a magnification of 5000×, and yellow arrows indicate bacteria residue. In the whole group, only isolated bacteria were observed on the canal wall surface in the coronal thirds (a,d,g). In all groups, bacterial residue on the buccolingual canal walls in the coronal and middle thirds were lower than the apical third. In the middle third, a few agglomerating bacteria with signs of viability were observed in the dentinal tubules of all three groups (b,e,h), whereas in the apical third, the bacterial density was higher, with more agglomerating bacteria in the tubules (c,f,i). Bars = 1 μm. Abbreviations: HCM: HyFlex CM; PTN: ProTaper Next; SEM: scanning electron microscope; XPS: XP-endo Shaper.

Figure 4

The bar charts showing SEM scores of bacterial biofilms (a–c), smear layer (d–f), and hard tissue debris (g–i) on the buccolingual walls of the root canal in the coronal, middle, and apical thirds, after chemomechanical preparation with different irrigants and rotary systems. (a,d,g) Subgroup A: Sterile saline; (b,e,h) Subgroup B: 3% NaOCl and 17% EDTA; (c,f,i) Subgroup C: 3% NaOCl, 17% EDTA, and PUI. Different lowercase letters indicate a significant difference at p < 0.05. Abbreviations: HCM: HyFlex CM; PTN: ProTaper Next; PUI: passive ultrasonic irrigation; SEM: scanning electron microscope; XPS: XP-endo Shaper.

Figure 5

Representative SEM images showing bacteria residue on the buccolingual canal walls after chemomechanical preparation combining PUI in the coronal (a,d,g), middle (b,e,h), and apical thirds (c,f,i) (5000×). No bacteria cells on the surface of the root canal and dentinal tubules. Bars = 1 μm. Abbreviations: HCM: HyFlex CM; PTN: ProTaper Next; PUI: passive ultrasonic irrigation; SEM: scanning electron microscope; XPS: XP-endo Shaper.

Figure 6

Representative SEM images showing smear layer on the buccolingual canal walls in the coronal third after chemomechanical preparation with different irrigants and rotary systems. (a–c) Subgroup A: Sterile saline; (d–f) Subgroup B: 3% NaOCl and 17% EDTA; (g–i) Subgroup C: 3% NaOCl, 17% EDTA, and PUI. The images are magnified at 1000×. Bars = 10 μm. Abbreviations: HCM: HyFlex CM; PTN: ProTaper Next; PUI: passive ultrasonic irrigation; SEM: scanning electron microscope; XPS: XP-endo Shaper.