Impact of sodium hypochlorite on the dissolution of soft tissue with photon-initiated photoacoustic streaming (PIPS) activation

This study aimed to investigate the effect of different sodium hypochlorite (NaOCl) concentrations on the efficacy of tissue dissolution with PIPS activation in artificial root canal models. Artificial root canal models were divided into eight groups (n = 30/group), based on irrigation method (conventional needle irrigation or PIPS) and irrigant concentration (saline, 1% NaOCl, 2.5% NaOCl, and 5.25% NaOCl). Irrigation was performed using standardized protocols. Soft tissue samples were obtained from porcine palatal mucosa and placed at coronal 1/3, middle 1/3 and apical 1/3 of the root canal. Tissue dissolution was quantified by measuring weight loss of each tissue sample. Free available chlorine (FAC), pH and temperature of irrigant were also assessed. For normally distributed data, factorial repeated measures analysis of variance (ANOVA) and Least-Significant Difference (LSD) comparison were used. Paired t-test and Wilcoxon signed-rank test were used to assess tissue dissolution after irrigation. PIPS activation contributed to significantly higher mass reduction percentage of tissue samples (p <.05). 5.25% NaOCl exhibited the highest mass reduction percentage of all irrigants under PIPS activation. The highest dissolution occurred with 5.25% NaOCl under PIPS, achieving near-complete tissue dissolution in the apical third. Decrease in pH and increase in temperature of NaOCl after irrigation were also observed. NaOCl showed greater tissue dissolving efficacy under PIPS activation than CNI. The tissue dissolving ability of NaOCl increased as the concentration increased. PIPS demonstrates superior apical irrigation efficiency compared to CNI, highlighting its clinical potential.