Physical and surface analysis of calcium silicate Clinker after acid challenge: a micro-CT and SEM study

The purpose of this study was to evaluate the effect of immersion in butyric acid (BA, pH 4.1) or phosphate-buffered saline (PBS, pH 7.0) on the properties of Clinker (CL) with particle sizes of 2 to 30 µm or < 2 µm associated with zirconium oxide and manipulated with distilled water (DW) or liquid with additives (LA) compared with Bio-C Repair (BCR) and Biodentine (BIO). Dentin tubes were prepared and filled with materials. After 24 hours, the specimens were immersed in BA or PBS (n = 5) for 7 and 28 days. Micro-computed tomography was used to evaluate volumetric change, porosity, and material/dentin interface. Surface analysis was performed by scanning electron microscopy (SEM). Statistical analyses included Kruskal-Wallis and Dunn, Mann-Whitney, Wilcoxon, unpaired t-test, paired t-test, and ANOVA and Tukey tests (α = 0.05). All groups exhibited volumetric changes similar to BCR and BIO (p > 0.05). BA significantly increased porosity (approximately 8%) compared with PBS (approximately 2%), except for CL 2 to 30 µm with LA (p < 0.05). After 28 days in BA, all groups showed increased porosity and gaps at the interface compared with baseline values (p < 0.05). CL 2 to 30 µm with DW showed greater porosity and interface gaps than the other groups (p < 0.05). SEM analysis revealed that all groups showed hydroxyapatite formation on the material surface in PBS, and structural loss in BA. Findings: Acidic pH damages the material/dentin interface, increases porosity, and promotes dimensional changes in calcium silicate cements. Distilled water without additives increases the Clinker's porosity, interface gaps, and volume loss.