Bacterial Reduction After Supplementary Disinfection Procedures in Infected Root Canals

Sample Size Calculation Sample size was calculated by STATISTICA v8.0 software (StatSoft, Tulsa, OK, USA), that demonstrated 23 teeth per group are needed to show a 5% difference in bacterial levels at 90% power. Considering possible losses, ninety adult subjects will be selected.

Case Selection and Eligibility Criteria Participants will be recruited at the Endodontic Clinic at the University of Iowa. The inclusion criteria will be patients 18 years or older, teeth with intact pulp chamber walls, no response to cold and electric pulp testing and apical periodontitis.

Teeth with vital pulp, incomplete root formation, extensive crown destruction, previous endodontic treatment or intervention (pulp debridement), acute/ chronic apical abscess, internal or external resorption, non-odontogenic facial pain, periodontal probing deeper than 4 mm, advanced untreated periodontal disease or recent periodontal surgery, teeth with mobility score > 2, fracture or visible crack, patients with diabetes or immune-compromised conditions, patients who received systemic antibiotics within the last three months, or taking corticosteroids, and pregnancy will be excluded.

Study Intervention Root canal samples will be taken under strict asepsis, as described by Rodrigues et al. (21). Operative field will be disinfected using 3% hydrogen peroxide and 3% NaOCl under rubber dam isolation. Once the access cavity is prepared, 10% sodium thiosulfate solution will be injected into the pulp chamber, and the sterility control (SC) will be taken from the access cavity walls' internal surfaces using sterile paper points. This sample will be transferred aseptically to a cryotube containing RNA later (Ambion, Austin, TX) and stored at -20°C.

The first sample (S1) will be taken as the baseline quantity of bacteria before chemomechanical preparation. One ml of 10% sodium thiosulfate solution will be injected into the canal, and a sterile paper point will be introduced up to that length for 1 minute, transferred in cryotubes containing RNA later, and stored at -20°C.