In vitro techniques for evaluating smear layer removal by root canal irrigants: a literature review

Introduction: The purpose of this review is to address the most commonly used techniques for evaluating smear layer removal ability or chelating capacity of root canal irrigants, including Energy Dispersive X-Ray Spectroscopy (EDS or EDX), Atomic Absorption Flame Spectrometry (AASF), wavelength dispersive X-ray fluorescence spectrometry (WDXRF), inductive coupled plasma emission spectroscopy (ICP-AES), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR). Methods: An electronic literature search was conducted in the Pub Med / MEDLINE database of indexed journals from 1992 to 2020. The search terms included chelating, chelation, calcium chelation, smear layer, smear layer removal, and demineralizing effect. Results: All the techniques were classified in terms of their results, both quantitatively and qualitatively. Even though smear layer removal and chelating capacity are not the same parameters, most of the studies included both techniques to correlate their results. SEM is the most commonly used technique for evaluating smear layer removal using various root canal irrigants. Ethylenediaminetetraacetic acid (EDTA) (17%) was the most widely studied root canal irrigant. Conclusion: Different techniques can be used to evaluate smear layer removal and chelating capacity of root canal irrigants. All of these methods have their corresponding advantages and disadvantages. This study aimed to provide researchers with a background for the selection of technique(s) to study the irrigant´s capacity for calcium chelation, which is applicable to smear layer removal.