A comparative evaluation of irrigation methods for calcium hydroxide removal from the root canal: An in vitro study

Author(s): Masako Nakano, Yuko Yamamoto, Ami Misawa, Shunjiro Yamakawa, Takumasa Yoshida, Yasushi Yamazaki, Noriyasu Hosoya

Backgorund: The lingering COVID-19 pandemic poses significant challenges in endodontic management. Calcium hydroxide is being widely used as a long-term root canal medicament due to delays in treatment completion, however, the best choice with great efficiency for removal has yet to be developed up to the present. This study aimed to help establish a reliable irrigation protocol by comparing the removal proportions in the root canal system.

Methods: Thirty extracted maxillary central incisors were used. The root canals were enlarged, filled with Ca(OH)2, sealed, then divided into six groups. Group 1: irrigation needle with syringe (NS)with NaClO. Group 2: intracanal negative pressure needle (INP) with NaClO. Group 3: ultrasonic irrigation (UI) with NaClO. Group 4: NS with NaClO+EDTA. Group 5: INP with NaClO+EDTA. Group 6: UI with NaClO+EDTA. Removal proportions were statistically analyzed.

Results: Residual Ca(OH)2 was observed in all groups tested. Significant differences were noted between Group 1 and all other groups but not among Groups 2 to 6. In INP, the removal proportions were greater when the combined solutions were used compared to when NaClO alone was used. No significant differences were observed between INP and UI in any regions of the canal.

Conclusions: None of the irrigation protocols achieved complete removal of Ca(OH)2. When either the iNP needle or ultrasonic tip was used, the sole use of NaClO achieved high removal efficiency. Contrarily, when an irrigation needle with a syringe was used, the combined use of NaClO and EDTA was considered preferable.