Real-time Co-site Optical Microscopy Study on the Morphological Changes of the Dentine’s Surface after Citric Acid and Sodium Hypochlorite. A Single-tooth Model.

Abstract BackgroundTo this day, the mechanisms of action and the effects of sodium hypochlorite and chelating agents during the smear layer removal, remain unclear. The study aimed to analyze the dentine's surface treated with 40% citric acid and 5.25% sodium hypochlorite according to two irrigation protocols. Materials and MethodsThe study employed a computer-controlled Nikon Eclipse LV100 optical microscope. Ten roots split longitudinally with canals prepared mechanically using the MTwo system to a size of 40/04 were observed. The root halves were divided into two study groups, one half in each of the groups. According to two irrigation protocols, the dentine's surface was irrigated with 40% citric acid and 5.25% sodium hypochlorite, separated with water. Dentine surface was observed in a fixed place and photographed in 500x magnification after each irrigation stage. The obtained images were then analyzed using computer software (NIS-Elements AR, GIMP-2.6, ImageJ 1.45s). ResultsVarious speed of removal of the smear layer and varied morphological changes of the dentine's surface were observed in both examined groups. Double irrigation of the dentine with citric acid for 30 seconds resulted in complete removal of the smear layer, and double irrigation for 60 seconds resulted in increased mean diameter of the dentine tubules (degradation of the dentine's surface).Conclusions Double alternating irrigation with citric acid and sodium hypochlorite for 30 seconds yielded satisfactory results, while double irrigation for 60 seconds resulted in increased mean diameter of the dentine tubules. A real time assessment of the dentine’s surface changes after both tested solutions can improve understanding of the phenomena that occur during the irrigation and as a result it might help to improve clinical outcomes in root canal treatment.