Background This in vitro study aimed to evaluate the persistence of calcium hydroxide (CH) associated with different vehicles on the artificial cavities after removing with sonic activation or conventional needle irrigation (CNI). Methods Seventy-two extracted single-rooted teeth were instrumented with ProTaper Universal rotary system up to F4. The roots were split longitudinally, and standardized cavities were prepared. The roots were assigned into 3 groups (n=24), according to vehicles used; distilled water, glycerin, and propylene glycol. In each group, cavities were filled with CH mixed with the respective vehicle. After reassembly, the removal of CH dressing was performed with either sonic activation (with EDDY) or CNI (n=12).The remnants of CH was assessed under a microscope with x40 magnification. A four-grade scoring system was used to evaluate. Kruskal-Wallis and Mann-Whitney U-tests were used to compare the data. (p <0.05). ResultsThere was a significant difference among groups (p<0.05). Complete removal of CH was found in the distilled water and propylene glycol groups when EDDY was used (p<0.05).EDDY was significantly more effective than CNI in the removal of CH mixed with distilled water and propylene glycol (p<.05).Whereas no significant difference was found between EDDY and CNI in the glycerin group (p>0.05).The lowest CH remnants were found in the distilled water group when CNI was used (p<0.05).Conclusion The vehicle associated with CH and irrigation activation is important for its retrieval. EDDY provided the complete removal of CH when mixed with distilled water or propylene glycol.