Effect of Manipulation Methods and Storage Environments on the Microstructural, Chemical, and Mechanical Properties...

This study aimed to evaluate the impact of different manipulation methods and storage environments on the microstructural, chemical, and mechanical properties of calcium-enriched mixture (CEM) cement. Four sample groups were examined, including nondried (ND-I) and dried (D-I) groups placed directly in an incubator, dried samples stored in phosphate-buffered saline (PBS) (D-P), and dried samples stored in distilled water (D-W). Various analyses, including Vickers microhardness, compressive strength, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) were conducted after incubating the samples for 7 days. The data were analyzed by Shapiro-Wilk, Levene, independent t, one-way ANOVA, and Tukey HSD tests. Key findings include the ND-I group exhibited a significantly longer setting time but the lowest microhardness and compressive strength. D-P showed the highest microhardness, while D-W displayed the highest compressive strength. FTIR analysis revealed vibration modes related to (PO4)^3- ions and Si compounds in all groups, with dried groups showing more vibrations of (PO4)^3- ions and OH groups, and D-P and D-W groups displayed vibration modes of (CO3)^2- ions. XRD analysis indicated increased tri/dicalcium silicate reflections in CEM groups exposed to PBS or distilled water. D-I and D-W groups presented hexagonal or rectangular cubic and needle-like crystals, while D-P showed a homogeneous globular structure covered with fine crystals. The order of the weight percentage of major elemental constituents of D-P group was oxygen, calcium, phosphorus, zirconium, barium, carbon, silicon, and sulfur. Incremental placement, drying each increment, and exposing CEM to PBS/tissue fluids result in a faster set and more tolerant cement with a more uniform microstructure. The formation of hydroxyapatite can occur on the surface of the set cement.