IRRIGATION PROTOCOLS IN THE REMOVAL OF FILLING MATERIALS DURING ENDODONTIC RETREATMENT: SCANNING ELECTRON MICROSCOPY ANALYSIS

ABSTRACT Endodontic retreatment is often the first choice when initial root canal therapy fails. However, removing filling materials remains a clinical challenge. This study aimed to evaluate, using scanning electron microscopy (SEM), the cleanliness of dentinal tubules in straight canals after retreatment with four different complementary irrigation techniques. Fifty-four single-rooted teeth were instrumented with the ProTaper Next system (X1–X4) and obturated using the single-cone technique with AH Plus sealer. Retreatment was performed using the ProTaper Universal Retreatment system (D1–D3), followed by re-instrumentation with the X5 file. Samples were divided into four groups according to the complementary irrigation method: Ultrasonic tip E1 (Irrisonic), Tip E62 (WAK), Easy Clean, and XP-Endo Finisher. Roots were sectioned longitudinally, and the most preserved half was selected for SEM analysis to quantify clean and unobstructed dentinal tubule. No statistically significant differences were observed in the degree of dentinal tubule cleanliness among the apical, middle, and cervical thirds within the tested groups (p > 0.05). Intergroup analysis revealed significant differences only between the control group and the experimental groups (p < 0.05), with no significant differences among the tested irrigation methods (p > 0.05). All complementary irrigation techniques contributed to cleaning and dentinal tubule de-obstruction during retreatment. However, none of the protocols were able to completely remove the filling material from the root canal system.