Effect of Irrigation Activation Techniques on Periapical Organic Tissue Dissolution in Simulated Immature Teeth: An Ex Vivo Study

<b>Background/Objectives</b>: Effective removal of organic tissue extruded beyond the apex is crucial in regenerative endodontics, particularly in teeth with immature apices; therefore, this study aims to compare the efficacy of standard needle irrigation (SNI), ultrasonic irrigation (UI), photon-induced photoacoustic streaming (PIPS), and shock wave-enhanced emission photoacoustic streaming (SWEEPS) techniques in dissolving periapical tissue in a simulated model. <b>Methods</b>: Sixty single-rooted human premolars and sixty bovine palatal mucosa specimens were used. A custom model was created by placing mucosal tissue in contact with the apical area. Specimens were divided into four groups (n = 15) according to the irrigation method: SNI, UI, PIPS, and SWEEPS. Each canal received 15 mL of 2% NaOCl. Tissue samples were weighed before and after treatment. One-way ANOVA and Tukey's post hoc test were used for statistical analysis (<i>p</i> < 0.05). <b>Results</b>: UI showed significantly less tissue dissolution than the other methods (<i>p</i> < 0.05). SNI, PIPS, and SWEEPS showed no significant differences (<i>p</i> > 0.05). <b>Conclusions</b>: All methods led to tissue loss, but UI was significantly less effective. SNI, PIPS, and SWEEPS performed similarly.