Dynamic Movement of Intracanal Gas Bubbles during Cleaning and Shaping Procedures: The Effect of Maintaining Apical Patency on Their Presence in the Middle and Cervical Thirds of Human Root Canals—An In Vivo Study

IntroductionThe vapor lock effect has been shown to limit the penetration of irrigating solutions into the apical third of root canals both in vivo and in vitro; however, little attention has been given to gas bubbles in the remainder of the root canal system.MethodsSeventy-one human root canals were randomly divided into 4 groups. Apical patency was maintained in 2 groups in both small (PS) (n = 21) and big canals (PB) (n = 15) during shaping and cleaning procedures with a 10 K-file 1 mm beyond working length but not in the other 2 groups: no patency, small canals (NPS) (n = 19) and no patency, big canals (NPB) (n = 16). Irrigation was performed with 1 mL of a solution prepared with a radiopaque contrast medium and sodium hypochlorite 5.25%. Digital images were taken, and a calibrated reader determined the presence or absence of gas bubbles in the middle and cervical thirds of the root canal system.ResultsWhen a patency file was not used, 40% of the root canals presented gas bubbles; when a patency file was used, 25% of the cases exhibited gas bubbles.ConclusionsThe presence of gas bubbles in the middle and cervical thirds of the root canal system during cleaning and shaping procedures is a common finding regardless of whether a patency file was used, although maintaining apical patency significantly leads to minimizing the presence of gas bubbles in big canals (P < .05).