In this superiority randomized clinical trial with a parallel design, 75 asymptomatic maxillary anterior teeth with 2-5 mm periapical lesions and a history of primary root canal treatment (PRCT) at least four years earlier were included. Patients were randomly assigned, using a randomization sequence generated on www.random.org, and divided into three groups. In all patients, existing canal fillings were removed using Remover rotary file (Coltene, MicroMega) and hand files. Working lengths were determined with an apex locator and canals reshaped using the step-back technique. For the final irrigation, side-vented needles were positioned 2 mm short of the working length. Activation was performed with Ultra X (Eighteeth) in the ultrasonic group, EDDY (VDW) in the sonic group, and an Er:YAG laser (LightWalker, Fotona) in SWEEPS mode (2940 nm, 5 μs, 20 mJ, 15 Hz) in the laser group. In all groups, each irrigant (EDTA followed by NaOCl) was activated in three cycles of 20 seconds. All canals were obturated with gutta-percha and a bioceramic sealer, and restored with composite. Pain levels were recorded using the Visual Analog Scale (VAS) 0, 6, 12, 24, 48, and 72 hours, and on day 7. The completed forms were collected by another independent investigator blinded to the group assignments. At the end of the treatment, periapical radiographs were obtained and recorded from all patients. Patients whose treatment was completed will be recalled at the 6th, 12th, and 24th months for follow-up periapical radiographs, and the comparison of healing among the groups will be evaluated as a secondary outcome based on changes in the PAI index.

This randomized controlled trial, employing a double-blind, single-center, parallel-group superiority design, was conducted and reported in line with the Preferred Reporting Items for Randomized Trials in Endodontics (PRIRATE) 2020 guidelines. Ethical approval was obtained from the Ege University Clinical Research Ethics Committee, Izmir, Turkey (Approval No: 24-3/86). Participant recruitment took place at the Department of Endodontics, Ege University Faculty of Dentistry, between December 2024 and June 2025. Prior to inclusion, all participants received verbal and written information about the study's objectives, procedures, potential benefits, and risks, and provided signed informed consent. Sample-size estimation was based on postoperative pain on the VAS as the primary outcome. Using G*Power 3.1.9.6 for a repeated-measures ANOVA (between-within interaction; three groups; seven time points), with α=0.05, power=95%, and an effect size f=0.358, the required total sample size was 75 (n=25 per group; allocation ratio 1:1:1). Medically healthy individuals aged 18-65 who agreed to participate and attend follow-up visits were enrolled in this randomized controlled trial. Only asymptomatic maxillary anterior teeth with completed root development, a history of root canal treatment performed at least four years earlier, and periapical lesions measuring 2-5 mm, with healthy periodontal status and no mobility, were included. Patients with systemic disease, pregnancy, or known allergies to treatment materials, as well as teeth presenting symptoms, lesions smaller than 2 mm or larger than 5 mm, open apices, advanced periodontal disease, or mobility, were excluded. All treatment procedures were performed by a single operator (B.G.), with two years of clinical practice in the endodontics department. Under rubber dam isolation, existing restorations and carious lesions, if present, were removed. Previous root canal fillings were removed using a rotary Remover file (Coltene MicroMega, Besançon, France) and a Hedström file (Dentsply Maillefer, Ballaigues, Switzerland). Due to the passive tip design of the Remover file, a retention space of 1-2 mm was first created within the filling material using a #3 Gates-Glidden drill. The Remover file was used with an X-Smart Plus endodontic motor (500 rpm, 2.5 Ncm) in 3 mm strokes to remove filling material from the coronal and middle thirds. The remaining 3 mm of filling material in the apical third was removed using a Hedström hand file of a size corresponding to the tooth's apical diameter. Working length was determined with an apex locator (RayPex 6, VDW, Munich, Germany) and canals reshaped using the step-back technique. Between each file change, canals were irrigated using a 30-gauge irrigation needle (Kerr Hawe Sa, Bioggio, Switzerland) with 2 mL of 2.5% sodium hypochlorite (NaOCl) (Wizard, Rehber Kimya, Turkey) and 2 mL of 17% ethylenediaminetetraacetic acid (EDTA) (Sigma Chemical Co., St. Louis, MO, USA). In total, 20 mL of NaOCl and 8-10 mL of EDTA were used during the removal and reshaping procedures for each tooth. The master gutta-percha cone of the determined apical size was fitted to the working length until tug-back was achieved, and a periapical radiograph was taken for confirmation. The sequence of the final irrigation protocol for each patient was pre-assigned at the start of the study using the automated randomization method available at www.random.org. Allocation was concealed until this stage to maintain blinding. In the ultrasonic group, an Ultra X device (Eighteeth, Changzhou Sifary Medical Technology Co., Ltd.) equipped with silver 21 mm, 0.2-taper irrigation tips was used. The tip was positioned 2 mm short of the working length and moved in an up-and-down motion to activate 17% EDTA for three 20-second cycles (3 × 2 mL), followed by 2.5% NaOCl for three identical cycles. In the sonic group, a polyamide EDDY tip (20 mm, 0.05 taper; VDW, Munich, Germany) was mounted on a sonic air scaler (TA 200, Micron, Japan). The tip was inserted 2 mm short of the working length and agitated in an up-and-down motion, activating 17% EDTA for three 20-second cycles (3 × 2 mL), followed by 2.5% NaOCl for three identical cycles. In the laser group, an Er:YAG Lightwalker device (Fotona, Ljubljana, Slovenia) in Shock Wave Enhanced Emission Photoacoustic Streaming (SWEEPS) mode (2940 nm, 20 mJ, 15 Hz, 0.3 W, 25 μs pulse duration) was used. A SWEEPS fiber tip mounted on the H14 handpiece was positioned in the access cavity with air and water pressures set to zero, and irrigation activation was performed in the same manner as in the other two groups. Canals were finally rinsed with 5 mL of distilled water and dried with paper points. Root canal obturation was then performed using the master cone gutta-percha (Diadent Group International Inc., South Korea) and BioRoot RCS sealer (Septodont, France) with the lateral compaction technique. The canal orifices were sealed with a 3-mm layer of flowable composite (RubyFlow, Rubydent) and the coronal restorations were completed with resin composite (Solare X, GC). Final radiographs were taken using a parallel film holder to ensure the same positioning as the initial periapical images. Patients whose treatment was completed will be recalled at the 6th, 12th, and 24th months for follow-up periapical radiographs, and the comparison of healing among the groups will be evaluated as a secondary outcome based on changes in the PAI index.

Inclusion Criteria:

• Systemically healthy patients
• Patients between 18 and 65 years of age
• Patients with previously root canal-treated teeth who are asymptomatic
• Patients with maxillary anterior teeth presenting with periapical lesions measuring between 2-5 mm
• Teeth with completed root development and healthy periodontal status
• Patients who agreed to participate in the study

Exclusion Criteria:

• Patients with any systemic disease
• Pregnant patients
• Patients with allergies to the materials used during the procedure
• Patients with previously root canal-treated teeth who are symptomatic
• Teeth in the maxillary anterior region with periapical lesions smaller than 2 mm or larger than 5.1 mm
• Teeth with open apices
• Teeth with advanced periodontal disease and mobility
• Patients who did not consent to participate in the study