Effect of ultrasonic irrigant activation and negative apical pressure in removing mature biofilm from the isthmus of curved root canal: A 3D-printed model study

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INTRODUCTION: Although the iVac® system has shown promising cleaning performance, its effectiveness in biofilm removal from anatomically complex areas remains untested in standardized 3D models, highlighting the relevance of the present study to evidence-based irrigation strategies. METHODS: A standardized 3D mandibular molar model with curvature and an isthmus was created, incorporating dentin blocks and a 21-day E. faecalis biofilm. Samples (n = 48) were randomized into four groups: syringe-needle irrigation, iVac System, ultrasonic irrigant activation (UIA), and control. All groups received NaOCl, EDTA, PBS, and sodium thiosulfate. Biofilm removal was assessed by CFU counting and SEM. RESULTS: ANOVA of CFUs showed that UIA and iVac significantly reduced bacterial counts compared to the control (p < 0.001), with no difference between them (p = 0.342). Syringe and needle irrigation showed results similar to the control (p = 0.124) and iVac (p = 0.087), but had higher CFUs than UIA (p = 0.017). These reductions corresponded to substantial decreases in bacterial load. SEM revealed that iVac and UIA groups exhibited exposed dentinal tubules with few scattered bacteria, while syringe and needle irrigation showed a dense amorphous matrix with E. faecalis-like cells covering most of the dentin, with limited exposed areas. CONCLUSIONS: Active irrigant agitation with UIA or iVac was more effective in reducing mature biofilm and promoting its disruption in the isthmus of curved root canals than syringe and needle irrigation.

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