Heating-stability, physical and chemical analysis of calcium silicate-based endodontic sealers.

Abstract

AIM\nTo evaluate possible modifications in root canal sealers subjected to a variety of heating conditions using vibrational spectroscopy and analysis of physical and chemical properties.\n\n\nMETHODOLOGY\nEndoSequence BC Sealer HiFlow, Bio-C Sealer, BioRoot RCS, and AH Plus were analysed chemically using Raman spectroscopy (25-220 °C) and Fourier-transform infrared spectroscopy (FT-IR) (37-100 °C ). For FT-IR, the materials were tested individually and mixed with root dentine powder. Scanning electron microscopy (SEM) and coupled-energy dispersive spectroscopy (EDS) were used to evaluate surface and chemical elements. ISO 6876-2012 specifications were followed to evaluate flow, setting time (moist and dry), solubility, radiopacity. Also, pH analysis at 37 °C and 100 °C was performed. Shapiro-Wilk and Mixed ANOVA (within and between the effects of the subjects), Levene, and a post hoc analyses with Bonferroni correction were performed (P < 0.05).\n\n\nRESULTS\nVibrational spectroscopy exhibited peaks of tricalcium silicate, dicalcium silicate, and zirconium dioxide. Chemical changes in the Raman spectra during heating were discrete, as the inorganic-content predominated the signaling for all root canal sealers. FT-IR analysis exhibited spectral changes in water absorption for EndoSequence BC Sealer HiFlow and Bio-C Sealer, probably related to dehydration. For BioRoot RCS and AH Plus, no significant chemical changes were observed. Bio-C Sealer exhibited a band of polyethylene glycol band only after heating at 100 °C, probably related to its thermal decomposition. SEM/EDS analysis corroborated the composition results observed in vibrational spectroscopy for all materials. Heating at 100 °C significantly changed the flowability of all calcium silicate-based sealers with a wide variation in setting times at both temperatures, along with solubility levels above ISO-standard. For all tested sealers, radiopacity fulfilled the requirements, and pH exhibited alkaline values.\n\n\nCONCLUSIONS\nThe tested calcium silicate-based sealers were affected by heating. Calcium silicate-based root canal sealers exhibited high solubility which may represent a concern regarding their clinical use. AH Plus was the only root canal sealer that was stable after heating.