Can Heated Distilled Water Effectively Prevent Precipitate Formation between NaOCl and CHX?

Introduction. The present study aimed to investigate the capacity of different irrigation protocols using heated distilled water at 65°C (HDW), in preventing the formation of the brown–orange precipitate observed after the interaction between sodium hypochlorite (NaOCl) and chlorhexidine (CHX). Methods. Forty human canines were selected, prepared, and cleaved in two halves. Images of delimited areas in each root canal thirds were obtained through a stereomicroscope (16x and 40x). After reassembly, the teeth were distributed into four groups (n = 10) according to the final irrigation protocol: G1 (no HDW): EDTA + NaOCl + CHX with conventional irrigation (CI); G2 (HDW + CI): EDTA with passive ultrasonic irrigation (PUI) + NaOCl (PUI) + HDW (CI) + CHX (PUI); G3 (HDW + PUI): EDTA + NaOCl + HDW + CHX with PUI; G4 (HDW + CUI): EDTA (PUI) + NaOCl (PUI) + HDW with continuous ultrasonic irrigation (CUI) + CHX (PUI). After irrigation, the teeth were re-separated and images of the same delimited areas were obtained again. Scores were assigned according to the amount of precipitate observed, comparing the initial and final images. The data were submitted to Kruskal–Wallis, Dunn and Friedman statistical tests (α = 5%). Results. G1(no HDW) showed the highest scores in the analysis between groups (p<0.001), with a greater amount of precipitate in the cervical and medium thirds (p<0.001). The thirds of the other experimental groups did not differ from each other (p>0.05). Conclusion. The intermediate irrigation with heated distilled water at 65°C prevented the formation of brown–orange precipitate, regardless of the use of ultrasonic activation (PUI or CUI).