Chemical and antimicrobial profiling of glycolic and etidronic acid as endodontic irrigants

This study aimed to analyze the chemical interactions between commonly used endodontic irrigants and evaluate the antimicrobial efficacy of etidronic acid (HEDP), glycolic acid (GA), and ethylenediaminetetraacetic acid (EDTA) as final irrigants. The solutions tested included 9% HEDP, 17% GA, 17% EDTA, 2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) gel, and distilled water (DW). Solutions were mixed in a 1:1 ratio and analyzed using electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QToF). The pH values were measured with a calibrated pHmeter. For the microbiological assay, ninety mandibular premolars were inoculated with Enterococcus faecalis and incubated for 5 days. Teeth were randomly assigned to five groups (n = 18), according to the final irrigation protocol: 17% EDTA, 17% GA, 9% HEDP in NaOCl, 9% HEDP in saline (SS), and SS alone. Microbial sampling was performed before and after chemomechanical preparation and final irrigation. Colony-forming units per milliliter (CFU/mL) were quantified, log-transformed, and statistically analyzed using Friedman and Dunn's post hoc tests. Chemical analysis revealed precipitate formation in the mixtures of NaOCl with CHX gel, NaOCl with EDTA, CHX gel with HEDP, and CHX with EDTA. No p-chloroaniline (PCA) or other toxic byproducts were detected. GA, HEDP and EDTA irrigants reduced bacterial load. These results highlight the potential of the solution as an effective final irrigant and underscore the importance of understanding chemical interactions among irrigants to prevent adverse effects during endodontic therapy.