Comparative evaluation of irrigant activation devices for removal of calcium hydroxide from artificial isthmuses connecting curved canals in 3D-printed resin molar models.

BACKGROUND: Calcium hydroxide (Ca(OH)₂), confirmed effective in studies, is frequently used as an interappointment medicament in root canal treatment. The challenges related to removing this medication from the root canals before the filling negatively influence post-treatment success. This study aimed to evaluate and compare the efficacy of different irrigant activation devices-sonic activation (EDDY), passive ultrasonic irrigation (PUI), photon-induced photoacoustic streaming (PIPS), and shockwave-enhanced emission photoacoustic streaming (SWEEPS)-in removing Ca(OH)₂ from artificial isthmuses connecting curved root canals in 3D-printed resin molar models. METHODS: Seventy resin-based upper molar models with two curved canals connected by three standardized isthmuses were 3D-printed (Hex 600, Edudent, Türkiye). After canal preparation and Ca(OH)₂ (Well-Paste, Korea) placement, samples were randomly assigned to five groups (control group n = 10, experimental group n = 15) for Ca(OH)₂ removal: conventional needle irrigation (control) (NaviTip, Ultradent, USA), EDDY sonic irrigation (VDW, Germany), PUI (Guilin Woodpecker Medical Instrument Co., LTD, China), PIPS, and SWEEPS (Fotona, Slovenia) laser-assisted irrigation. Irrigation protocols were standardized for volume and duration. The percentage of cleaned isthmus areas was quantified using pre- and post-irrigation imaging under microscopy and analyzed with ImageJ software (NIH, USA). Statistical comparisons were performed using robust ANOVA. RESULTS: Significant differences in Ca(OH)₂ removal efficacy were found between groups (p < 0.001). The SWEEPS group showed the highest median cleaning percentage (47.71%), followed by PIPS (37.96%), EDDY (29.30%), PUI (28.22%), and control (11.26%). SWEEPS showed the highest median cleaned isthmus percentage, followed by PIPS, while PUI and EDDY demonstrated comparable values. Conventional needle irrigation showed the lowest cleaning performance. Cleaning efficacy varied significantly among isthmus locations (coronal > middle > apical, p = 0.007). SWEEPS, PIPS, and EDDY showed similarly high cleaning efficacy, with PUI demonstrating comparable performance, while conventional needle irrigation showed significantly lower values. No significant differences were observed between groups in the apical isthmus. CONCLUSION: None of the irrigation activation techniques achieved complete removal of calcium hydroxide. Cleaning efficacy was significantly influenced by both irrigation method and isthmus location. Laser-activated irrigation systems showed higher efficacy in specific regions, while conventional needle irrigation consistently demonstrated the lowest performance. Overall, irrigation effectiveness in isthmus-containing root canals exhibited a clear anatomy-dependent pattern.