A spectroscopic assessment of interaction between 4% articaine hydrochloride with adrenaline and various endodontic irrigants

Abstract

Background: Interaction between 2% lidocaine HCl (with and without adrenaline) and sodium
hypochlorite (NaOCl) resulted in a toxic precipitate formation. The aim of this in vitro study was to
assess the interaction between 4% articaine hydrochloride with adrenaline (AHa) and commonly
used endodontic irrigants 3% NaOCl, 2% chlorhexidine (CHX), and 17% ethylenediaminetetraacetic
acid (EDTA) using spectroscopic analyses.
Materials and Methods: In this in vitro study, 3% NaOCl, 2% CHX, and 17% EDTA were mixed
with 4% AHa individually. 1.7 ml of 4% AHa from the cartridge was mixed with 1.7 ml of each test
irrigants. The solutions were subjected to a preliminary ultraviolet spectroscopic (UVS) analysis
to assess forpotential interactions (if any). If the interaction was detected, the test solutions were
further subjected to nuclear magnetic resonance (NMR) analysis for characterization. The precipitate
formed (if any) was then subjected to NMR analysis.
Results: UVS analysis revealed a bathochromic shift when 3% NaOCl and 2% CHX were mixed
with 4% AHa, respectively. This shift was not observed when EDTA was mixed with 4% AHa. 1H and
13C NMR spectra confirmed the interaction between 3% NaOCl with 4% AHa, which resulted in a
precipitate formation, methyl 3‑amino‑4‑methylthiophene‑2‑carboxylate (MAMC). The analysis of 1H
NMR spectra showed peaks at 7.1 ppm, 2.21 ppm, and 9.93 ppm, respectively, which corresponds
to aromatic ring protons. A peak at 3.8 ppm was assigned to methyl proton of methyl ester. The
characteristic appearance of peaks at 14.82 and 51.16 ppm corresponds to aliphatic carbons. The
five peaks occurring at 126, 134.5, 139.2, 156.5, and 162.9 ppm correspond to the aromatic carbon
atoms present in the thiophene unit. NMR spectra revealed no interaction between 2% CHX and
4% AHa. 1H and 13C NMR spectra confirmed that 3% NaOCl interacted with 4% AHa, leading to
the formation of a precipitate MAMC.
Conclusion: 3% NaOCl interacted with 4% AHa leading to the formation of a precipitate MAMC
which is reported to exhibit the least toxicity. Until the precipitate is studied further, it would be
advisable to avoid the immediate use of NaOCl following administration of intrapulpal anesthetic
solution with articaine hydrochloride (with adrenaline).