Effect of Laser-Assisted Continuous Chelation Irrigation Protocols on Sealer Penetration and Bond Strength in Root Dentin: An Evaluation Using a Calcium-Specific Fluorophore and Push-Out Test

Background: Laser-assisted irrigation may enhance chemomechanical debridement and improve the sealing of root canals during endodontic treatment. Objective: This study aimed to address the scientific deficit in understanding the laser-assisted sequential versus continuous chelation in root canal irrigation. Methods: One hundred and twenty single-rooted teeth were prepared using Reciproc R40 instruments and randomly divided into six groups ( n = 20) based on the irrigation protocol. In the sequential chelation groups, canals were irrigated with NaOCl during instrumentation, followed by 17% ethylenediaminetetraacetic acid using a needle, ultrasound, or erbium-doped yttrium aluminum garnet laser activation. In the continuous chelation groups, canals were irrigated with a mixture of 2% sodium hypochlorite and 9% hydroxyethylidene diphosphonic acid during and after instrumentation, followed by final activation using the same three techniques. Ten samples per group were used to evaluate sealer penetration with Fluo-3 dye, while the remaining samples underwent push-out bond strength testing. Statistical analyses were conducted using the Kruskal–Wallis and Friedman tests ( p < 0.05). Results: No significant differences in sealer penetration were found between sequential and continuous protocols in the apical third when needle or ultrasonic activation was used. However, laser activation combined with continuous chelation resulted in significantly higher sealer penetration and bond strength ( p < 0.001). Sealer penetration followed the trend: coronal > middle > apical ( p < 0.05) with all irrigation techniques. Conclusions: Continuous chelation protocols, especially when combined with laser activation, were as effective or superior to conventional methods in improving sealer penetration and bond strength. Continuous chelation with laser-assisted irrigation may improve clinical efficiency and shorten treatment time in root canal procedures.