Sonic irrigation for removal of calcium hydroxide in the apical root canal: A micro-CT and light-coupled tracking analysis

This study aimed to evaluate the efficacy of three sonic irrigation systems for removal of calcium hydroxide dressing from the apical root canal. A total of 96 single-rooted teeth in three categories of root canal curvatures (straight: 0-5°, moderate: 6-20°, and severe: > 20°) were allocated to four groups: conventional needle irrigation, EndoActivator, EQ-S, and Vibringe. The root canals were instrumented using Protaper NEXT and filled with calcium hydroxide. After removal of calcium hydroxide, the remaining volume of calcium hydroxide was measured by micro-CT analysis. Data were compared among root canal curvatures and irrigation systems using the Kruskal-Wallis test and Mann-Whitney test (p < .05). The oscillating range of each irrigation system was measured using light-coupled motion tracking. The volumes of calcium hydroxide remaining in the canals with severe curvature were significantly higher than in those of straight curvature (p < .05). In the canals of moderate or severe curvature, EQ-S showed the highest removal percentage, followed by EndoActivator, Vibringe, and needle irrigation (p < .05). Light-coupled tracking showed the largest oscillating range in EQ-S (p < .05). Sonically activated irrigation systems with a flexible tip can be beneficial for calcium hydroxide intracanal dressing removal in the curved apical canals.