Effects of Contemporary Irrigant Activation Schemes and Subsequent Placement of an Interim Dressing on Bacterial Presence and Activity in Root Canals Associated with Asymptomatic Apical Periodontitis.

Alexandre P L Carvalho,Fernanda P Bruno,Heitor M Honório,Fernanda S Fernandes,Ericka T Pinheiro,Giulio Gavini,Luiza R Paz,Márcia P A Mayer,Laura C L Nardello,Elaine F Iglecias

doi:10.3390/jcm9030854

Alexandre P L Carvalho, Fernanda P Bruno + Show 8 more

Open Access

https://doi.org/10.3390/jcm9030854

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Abstract

New tools for activating endodontic irrigants have evolved, yet their impact on root canal disinfection, in comparison to the passive placing of an inter-visit medication, have not yet been fully elucidated. The use of DNA- and rRNA-based methods may cast some new light on this issue, as they allow a comparison to be made between microbial presence and activity. Therefore, the aim of this single-arm intervention trial is to evaluate the antibacterial effect of endodontic procedures using both molecular methods. Root canal samples were obtained from 20 patients with asymptomatic apical periodontitis after each treatment step: access cavity, chemo-mechanical preparation, adjunctive procedures (XP-endo Finisher file and passive ultrasonic irrigation), calcium hydroxide medication, and 2nd-visit root canal preparation. DNA and cDNA from the samples were subjected to quantitative polymerase chain reaction with universal primers for the bacterial 16S rRNA gene. Chemo-mechanical preparation promoted a drastic reduction in bacterial levels and activity, whereas the adjunctive procedures did not make a significant contribution to further disinfection. At the 2nd visit, bacteria were active after the use of calcium hydroxide medication; however, they were significantly reduced after a 2nd-visit preparation. Consequently, the lowest bacterial levels were found at the end of the treatment. This clinical trial, which used an rRNA and rDNA combined approach, confirmed previous studies showing that root canal preparation represents the main strategy for root canal disinfection.

Highlights

The aim of endodontic treatment of teeth with apical periodontitis is to reduce viable bacteria to levels that are compatible with apical healing
RDNA-based quantitative polymerase chain reaction may provide important information on the bacterial load remaining after treatment, they are not suitable for assessing bacterial viability [5]
This single-arm intervention trial compared the antimicrobial effects of endodontic procedures on the first and second treatment visits

Summary

Introduction

The aim of endodontic treatment of teeth with apical periodontitis is to reduce viable bacteria to levels that are compatible with apical healing. Since an endodontic microbial community comprises many as-yet-uncultivated/difficult-to-culture bacteria [2], molecular methods that target viable cells [3] or culturomic analysis [4] may be useful strategies for monitoring bacterial load during endodontic treatment. Most molecular-based studies have used assays that target bacterial ribosomal RNA genes (rDNA), usually the 16S rRNA genes [4]. QPCR assays that target bacterial ribosomal RNA (rRNA) could be useful for this purpose [6]. As rRNA levels are related to the bacterial activity, the abundance of rRNA transcripts in relation to their corresponding genes (rDNA) has been used to search for active bacterial cells in microbial communities [3,7,8,9,10]

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