The ectopic calcifications of non-mineralized tissues can occur in several forms throughout life, such as pulpal calcification. The presence of pulp stones is a challenge in endodontic treatment because they partially or fully obliterate the pulp chamber hindering access to root canals and their subsequent shaping. This study aimed to determine their crystallographic properties and evaluate the capacity of citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) to promote the demineralization of pulp calcifications. The samples were obtained from patients with indications of endodontic treatment, and the radiographic examination was suggestive of pulp stone in at least one permanent tooth. The samples were isolated and analyzed by scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). The Fourier Transform by high resolution-transmission electron microscopy, Raman microscopy, and X-ray diffraction (XRD) were used to identify the mineral phase and crystallographic characteristics. To evaluate the effect of CA and EDTA on the crystallinity of calcifications, they were submerged into these two individual solutions and the changes were assessed in situ by Raman spectroscopy. The SEM images obtained from calcifications demonstrated irregular morphologies. EDX of sample surfaces shows a high presence of oxygen, carbon, calcium, and phosphorous, however, other elements such as sodium, magnesium, nitrogen, chlorine, potassium, sulfur, and zinc were identified in less quantity. According to Raman, XRD, and high-resolution transmission electron microscopy, the predominant mineral phase identified in the pulpal calcification was a poor crystallinity apatite. According to in situ analyses, the effect of CA and EDTA was observed on the signals of PO4 3- and CH2 groups corresponding to inorganic and organic components. The changes with CA were evident at 7 min while the effect of EDTA was observed until 15 min of treatment. All results indicate that pulp stones have a heterogeneous composition principally composed of apatite with low crystallinity. The solubility of these pathological minerals is adequate using solutions such as EDTA or CA; however, the effectivity depends on the mineralization grade of calcifications, time, and concentration of exposition to this chemical.
Keywords: HRTEM; Raman; apatite; crystallinity; pulp stone.
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