In-vitro evaluation of the efficiency of different irrigation techniques, irrigants and time of activation in removing calcium hydroxide intracanal medicament

Calcium hydroxide Ca(OH)₂ is one of the most commonly used intracanal medicaments in multiple-visit non-surgical root canal treatments, aimed at improving treatment outcomes. However, complete removal of Ca(OH)₂ presents significant challenges and is essential before obturation to ensure a hermetic seal and prevent recontamination of the root canal. This study aimed to evaluate the efficiency of different irrigation techniques, types of irrigants, and activation times in eliminating Ca(OH)₂ from the root canal. In this in-vitro study, 90 extracted lower premolars were used. The root canals were prepared to an F3 ProTaper size and then randomly assigned to three main groups: Group 1 (Manual Dynamic Activation, MDA), Group 2 (Sonic Activation, SA), and Group 3 (Passive Ultrasonic Irrigation , PUI). Each group was further subdivided based on the irrigation solution used: saline, sodium hypochlorite (NaOCl), and a combination of NaOCl followed by EDTA. The activation times tested were 30 seconds and 60 seconds. The results indicated no significant difference in the overall percentage reduction of intracanal Ca(OH)₂ among the MDA, SA, and PUI groups. However, when assessing percentage reduction of Ca(OH)₂ in the apical 5 mm of the canal, MDA was the least effecient, while both SA and PUI showed better results, with no significant difference between the two. When it comes to the type of irrigant used, saline was significantly less efficient at removing Ca(OH)₂ from the entire canal and the apical 5mm compared to NaOCl and a combination of NaOCl with EDTA. However, there was no significant difference between the use of NaOCl alone and the combination of NaOCl with EDTA in removing Ca(OH)₂ from the canal and the apical 5mm. Furthermore, while there was no significant difference in the overall percentage reduction of Ca(OH)₂ between 30-second and 60-second activation times, the apical 5 mm demonstrated significantly better percentage reduction of Ca(OH)₂ with 60 seconds of activation compared to 30 seconds. In conclusion, there is no significant difference in the overall percentage reduction of Ca(OH)₂ among MDA, SA, and PUI, SA and PUI are more efficient than MDA in overall percentage reduction of Ca(OH)₂ at the apical 5 mm of the root canal. NaOCl and its combination with EDTA outperform saline in removing Ca(OH)₂, though NaOCl alone is equally efficient as the NaOCl-EDTA combination. Additionally, while activation time did not significantly affect overall Ca(OH)₂ removal, 60-second activation provided better percentage reduction of Ca(OH)₂ in the apical region compared to 30 seconds.