Quantitative Assessment of Dentinal Tubule Disinfection in Absence of Biofilm on Root Canal Walls: An in vitro Study

Svetlana Fedorovna Byakova; Viktoria Andreevna Dezhurko-Korol; Nina Evgenievna Novozhilova; Irina Mikhailovna Makeeva; Alexandr Nikolaevich Lukashev; Ludmila Vasilievna Akhmadishina; Alexandr Mikhailovich Semenov; Mikhail Mikhailovich Moisenovich; Anastasiya Yurievna Arkhipova; Evgenii Nikolaevich Ponirovsky

doi:10.22037/iej.v15i3.27453

Quantitative Assessment of Dentinal Tubule Disinfection in Absence of Biofilm on Root Canal Walls: An in vitro Study

Iran Endod J. 2020 Summer;15(3):155-165. doi: 10.22037/iej.v15i3.27453.

Affiliations

¹ Department of Therapeutic Dentistry, Institute of Dentistry, I.M. Sechenov First Moscow State Medical University (Sechenov University) of the Ministry of Health of the Russian Federation, Mojaiskii val str, Moscow, Russia.
² E.I. Martsinovsky Institute of Medical Parasitology and Tropical Medicine, I.M. Sechenov First Moscow State Medical University (Sechenov University), M. Pirogovskaya str., Moscow, Russia.
³ Department of Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russia.

Abstract

Introduction: This study aimed at assessing the quantitative effect of calcium hydroxide, 2% chlorhexidine gel, and 1.5% chlorhexidine linked to xanthan gel specifically against intratubular bacteria.

Methods and materials: Fifty-two semi-cylindrical bovine dentin specimens were infected with Enterococcus (E.) faecalis by centrifugation with subsequent 7-days incubation. The surface of specimens was disinfected with 3% H₂O₂. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and the count of bacterial colony-forming units (CFU/mg) were used to assess dentin infection. A total of 40 specimens were incubated for 2 weeks with one of the intracanal medication applied (10 samples for each group): 1) calcium hydroxide, 2) 2% chlorhexidine gel, 3) 1.5% chlorhexidine linked to xanthan gel and 4) sterile saline. Final passive ultrasonic irrigation with 3% sodium hypochlorite was performed in half of the total specimens. The effect of intracanal medications and irrigation against intratubular bacteria was assessed by bacterial culturing of dentin shavings. Two-Way ANOVA model was applied followed by post-hoc Tukey's test for multiple pair-wise comparisons of mean CFU/mg values.

Results: SEM, CLSM, and bacterial culturing confirmed the absence of the surface biofilm on the root canal wall and showed vital intratubular bacteria at the depth up to 700 m. Two-week application of 1.5% chlorhexidine with xanthan gel and 2% chlorhexidine gel significantly decreased intratubular bacterial counts compared with saline (P=0.0003 and P=0.0005, respectively). Subsequent passive ultrasonic irrigation with 3% sodium hypochlorite significantly reduced the number of intratubular bacteria in all groups except for the group with 1.5% chlorhexidine-xanthan gel (P=0.0054).

Conclusion: This modified ex vivo model study showed ultrasonically activated irrigation with sodium hypochlorite had greater effect on intratubular bacteria counts compared with 2-week application of intracanal medications.

Keywords: Confocal Laser Scanning Microscopy; Electron Scanning Microscopy; Enterococcus faecalis; Root Canal Irrigants.