Penetration depth of different final irrigants into the root canal dentinal tubules after bypassing a separated instrument in the apical third – An in vitro confocal microscopic study

Aim: The aim of the study was to evaluate and compare the depth of penetration of 0.1% Rhodamine B labeled 17% ethylenediaminetetraacetic acid (EDTA), 0.2% chitosan, and 18% 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) root canal irrigants into the dentinal tubules in the apical third using manual dynamic activation and sonic activation under Confocal Laser Scanning Microscopy. Methods: Forty-eight single-rooted mandibular premolars were decoronated and root canal preparations were done up to Protaper F1. Rotary Protaper F2 files of 3 mm were fractured at the apical third and bypassed using hand files and rotary path files. The samples were distributed into four groups (n = 12) based on final irrigants: Group I – Normal saline, Group II – 17% EDTA, Group III – 0.2% chitosan, and Group IV – 18% HEDP. Each group was subdivided into two subgroups (n = 6) based on the activation system: Subgroup A – Manual Dynamic Activation and Subgroup B – Sonic activation. The root samples were embedded in acrylic and 1 mm thin sections were taken from 1 mm to 3 mm from apex. The extent of penetration of the irrigant was analyzed using Confocal Laser Scanning Electron Microscopy with the aid of Image J software. Results: A 0.2% chitosan showed more depth of penetration at 1 mm section compared to 18% HEDP and 17% EDTA and at 3 mm section both 0.2% chitosan and 18% HEDP showed more depth of penetration compared to 17% EDTA. Sonic activation showed more depth of penetration in all four groups at 3 mm from the root apex and at 1 mm section there was no significant difference between the activation systems. Conclusion: A 0.2% chitosan can be used as an alternative final irrigant after instrument bypassing, both at 1 mm and 3 mm from the apex. Irrigant activation is inevitable during bypassing fractured instruments.