Effect of the chelating agent Alendronic acid vs EDTA on the physicochemical properties of dentine

Objective: The present study aimed to evaluate the changes in the physicochemical properties of dentine after irrigation with a solution of 0.22% alendronic acid (AA) as a chelating agent vs 17% ethylenediaminetetraacetic acid (EDTA).
Methods: A total of 48 extracted premolars and molars that were intact, free of caries or cracks, without root canal treatment and restorations were collected. The roots were randomised into three groups (n=16): Group A: Distilled Water (dH2O); Group B: 17% EDTA, and Group C: 0.22% AA. Longitudinal sections of the dentine with a root of 1x1x10 mm were made with a diamond disc and a low-speed handpiece for bending tests (n=9). For morphological analysis, images were taken with a scanning electron microscope, crystallographic analysis with X-ray diffraction, and chemical analysis with Fourier Transform Infrared Spectroscopy (FTIR) and Vickers Hardness. For this purpose, cross-sections were made through the root using the Isomet to obtain 3 mm thick dentine discs (n=14). The samples were stored in dH2O for up to 24 h before use and dried at room temperature before exposure to chelating solutions for 1 h in a Stuart STR6D mixer at 50 rpm. For data comparison, the Kruskal-Wallis statistical test was used (α=0.05).
Results: The chelating solutions of EDTA and AA cause alterations in the physicochemical structure of dentine, attacking mainly the inorganic part (Hydroxyapatite), which was observed in the decrease in intensity of the peaks in the X-ray diffraction pattern of hydroxyapatite. This generated a greater exposure of the collagen fibres that were observed in SEM and the increase in the bands characteristic to Collagen Type I in the infrared spectrum at 1645, 1550, and 1240 cm-1 belonging to amide I (C=O), amide II (N-H) and amide III (C-N), significantly affecting its dentine hardness (p=0.001).
Conclusions: AA can be used as a chelating agent in the area of dentistry. It does not generate a significant demineralising effect that modifies the physicochemical properties of dentine, as observed with EDTA.