Comparison of irrigation solutions and activation methods for calcium hydroxide removal in a patient-derived three-dimensional printed internal root resorption model: an in vitro study

Complete removal of calcium hydroxide from internal root resorption cavities remains challenging because of their complex and irregular morphology. This study compared the effectiveness of different irrigation solutions and activation methods for calcium hydroxide removal using a patient-derived three-dimensional printed internal root resorption model. A cone-beam computed tomography (CBCT) scan of a tooth with internal root resorption was used to generate standardised three-dimensional printed resin models. Before the main experiment, the chemical stability of the printed resin following exposure to the tested irrigation solutions was verified by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). The models were filled with calcium hydroxide and randomly assigned to four irrigation solutions (17% EDTA, glycolic acid, Dual Rinse HEDP, and RISA) combined with three activation methods (conventional needle irrigation, passive ultrasonic irrigation, and XP-Endo Finisher). Calcium hydroxide removal was quantified using CBCT volumetric analysis, and the percentage of removal was calculated. Data were analysed using a two-way ANOVA with HC3 heteroscedasticity-consistent standard errors followed by Tukey-adjusted pairwise comparisons (α = 0.05). ATR-FTIR analysis confirmed that none of the tested irrigation solutions produced detectable chemical alterations in the printed resin. Both irrigation solution and activation method significantly affected calcium hydroxide removal, with a significant interaction between the two factors (all P < 0.05). The effect size was larger for activation method (η²ₚ = 0.827) than for irrigation solution (η²ₚ = 0.304). XP-Endo Finisher achieved significantly greater calcium hydroxide removal than passive ultrasonic irrigation and conventional needle irrigation. Overall, glycolic acid and EDTA demonstrated significantly greater removal than Dual Rinse HEDP and RISA, whereas no significant difference was observed between glycolic acid and EDTA. Within the limitations of this in vitro study, activation method had a larger overall effect on calcium hydroxide removal than irrigation solution, with XP-Endo Finisher providing the highest removal efficiency. Glycolic acid showed calcium hydroxide removal efficacy comparable to that of EDTA under the present experimental conditions. The patient-derived three-dimensional printed model provided a standardised platform reproducing the morphology of an actual internal root resorption defect.