Quantitative Assessment of the Efficacy of Two Irrigation Activation Systems in Reducing the Bacterial Load in Teeth With Post-treatment Apical Periodontitis: A Clinical Study

Eligibility criteria The study population consisted of 20 patients (9 women and 11 men, aged 19-66 years) presenting to the endodontic clinic at Istanbul Medipol University Dental School, for nonsurgical endodontic retreatment of teeth with apical periodontitis lesions. 20 previously root canal-treated teeth exhibiting clinical and radiographic evidence of chronic apical periodontitis lesions were included in this study. Radiographically, the diameter of the periapical radiolucency ranged from 2 to 7 mm. Teeth with post-treatment apical periodontitis had endodontic therapy completed more than 2 years earlier and required retreatment. Termini of the root canal fillings ranged from 0-4 mm short of the radiographic apex, with no overfilling. The teeth had intact coronal restorations, with no obvious exposure of the root-filling material to the oral cavity. Selected teeth had enough crown structure for adequate isolation with a rubber dam and showed an absence of periodontal pockets or attachment level deeper than 4 mm. Exclusion criteria were also applied, as follows: teeth from patients who had received antibiotics within the previous 3 months or who had any general disease, teeth that could not be properly isolated with rubber dam, teeth with absence of coronary sealing, teeth with periodontal pocket depth >4 mm; and teeth with crown/root fracture. Only one tooth was included from each patient.

Root canal treatment procedures and sampling Rubber dam and an aseptic technique were used throughout the endodontic retreatment. After plaque removal and rubber dam isolation, the operative field was cleaned with 3% hydrogen peroxide and disinfected with 2.5% NaOCl solution. Then, all coronal restorations, posts and carious defects were removed and access preparation was completed when the root canal filling was properly exposed. Afterwards, the tooth (including the pulp chamber), clamp, and adjacent rubber dam were once again disinfected with 2.5% NaOCl, followed by inactivation with 10% sodium thiosulfate in order to avoid interference with bacteriological sampling. Sterility control samples (SR1) were taken from the tooth surface with a sterile Omni Swab (Whatman FTA, Sigma-Aldrich) with an ejectable head. Paper points were transferred to cryotubes containing phosphate buffered saline (PBS) solution stored at -20°C. In each case, a single root canal was sampled in order to confine the microbial evaluation to a single ecological environment. In multirooted teeth, the root with the periapical lesion was selected. If there were periapical lesions in all roots, the wider canal was selected. Two of the canals included in this study were from single-rooted teeth, 3 were buccal canals in maxillary premolars, 1 palatal canal in maxillary molar, and 10 distal canals in mandibular molars.

Old root fillings were removed using Gates-Glidden drills (Dentsply Maillefer, Ballaigues, Switzerland) and endodontic files without the use of chemical solvents. The working length (WL) was established 1-mm short of the apical foramen with an apex locator (Raypex6; VDW GmbH, Munich, Germany), and then periapical radiographs were taken to ensure that all filling material was removed. Irrigation with sterile saline solution was performed in order to remove any remaining materials and to moisten the canal prior to sample collection. Next, the canal was left filled with saline, and a small hand instrument was placed at the WL and used to gently file the canal walls. An initial microbiologic sample (S1) was taken from the root canal with sterile paper points consecutively placed at the WL. Three sterile paper points were inserted into the root canal for sampling. Each paper point was left in the canal for about 1 minute. Both the paper points and the endodontic hand instrument, without the handle, were transferred to cryotubes containing 300 μl of PBS solution stored at -20°C. The samples were transferred to genetic analysis laboratory for further analysis in cold chain.

Root canals were prepared by using the Revo S files and irrigated with 2.5% NaOCl. The canals were apically enlarged to size 35 (AS35) at the working length. Between each instrument change, the root canal was irrigated with 5 ml of 2.5% NaOCl solution by using 30-gauge side-vented needle, which was placed 1 to 2 mm short of working length. Hence, a total of 30 mL of the irrigating solution was used. After instrumentation was completed, the smear layer was removed with 2 mL 17% EDTA, which was left in the canal for 3 min, followed by 2.5% NaOCl. The root canal was dried with sterile paper points and flushed with 2 ml of 10% sodium thiosulfate for 1 min to inactivate the NaOCl solution. Next, a sample (S2) was taken from the canals as described for S1. Following this, the NaOCl was agitated/activated as described below.

XPF group: The instrument XP-Endo Finisher (FKG Dentaire, size #25, taper .00) was cooled down (Endo-Frost; Roeko, Langenau, Germany) in order to keep it straight and measure the WL. The canals were flushed with 2.5 mL 2.5% NaOCl for 30 s and activated by a XPF instrument that was placed in the canal to 1 mm short of the WL and powered by the motor at 800 rpm (1 N-cm torque) for 30 s according to the manufacturer's instructions (in slow up-and-down movements at approximately 7-mm amplitude in continuous rotation). Then the canals were rinsed with 2.5 mL of 2.5% NaOCl, followed by activation of the substance with the XPF instrument for 30 seconds, the same way as above. A new XP-endo Finisher file was used for each canal.