Adjunctive Steps for Disinfection of Teeth With Primary Endodontic Infections

The success of endodontic treatment in teeth with necrotic pulp and apical periodontitis depends on the reduction of viable microorganisms of root canals by endodontic disinfection procedures. This study aims to evaluate by molecular methods the effect of different disinfection procedures on reduction, diversity and microbial metabolic activity. Patients with necrotic pulps and apical periodontitis in single-rooted teeth will be selected. Microbiological samples will be taken from root canals after access cavity (S1), after chemomechanical preparation with Reciproc System and 2.5% NaOCl (S2), after irrigant activation using the XP-Endo Finisher instrument (S3a) and ultrasonic activation (S3b); and after intracanal medication with calcium hydroxide for 14 days (S4), followed by 2nd-visit root canal preparation (S5). DNA and RNA will be extracted from root canal samples, and complementary DNA (cDNA) synthetized using reverse transcription reaction. The effect of treatment protocols on total microbiota levels will be determined by DNA-based quantitative polymerase chain reaction (qPCR) using universal primers for Bacteria domain. RNA of root canal samples will be used to determine the diversity of metabolically active microbiota by Reverse Transcriptase Reaction (RT), followed by amplification (PCR) and high throughput sequencing of the hypervariable region V4-V5 of 16S rRNA gene. The metabolic activity of the most prevalent species / taxa will be calculated by rRNA- and DNA-based molecular methods. Ratios between rRNA and DNA levels will be calculated to search for active bacteria (rRNA/DNA ≥ 1) in root canal samples. Data will be analyzed by statistical tests, with 5% significance level.

Inclusion criteria

• Teeth with necrotic pulps and asymptomatic apical periodontitis

Exclusion criteria

• patients who had received antibiotics during the previous 3 months or had any general disease,
• teeth that could not be properly isolated with rubber dam,
• non-restored teeth,
• periodontal pockets depths greater than 4 mm,
• previous endodontic treatment,
• open apex,
• crown/root fracture
• root resorption or calcifications.