Synthesis and characterization of bioactive calcium niobate particles derived from non-hydrolytic sol-gel for application in dental adhesives.

This study aimed to synthesize and characterize calcium niobate (CaNb₂O₆) particles via a non-hydrolytic sol-gel method and evaluate their incorporation into an experimental adhesive system. CaNb₂O₆ was characterized using transmission electron microscopy (TEM), laser diffraction (LD), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Particle dissolution was assessed through pH and Ca²⁺ release analyses at varying pH levels (4 and 7) over 28 days. The formation of hydroxyapatite precipitates on the particle surface was monitored using SEM, FTIR, and XRD. Cell viability was also evaluated. CaNb₂O₆ was incorporated into a self-etching adhesive at concentrations of 5 and 10 wt% and tested for cohesive strength (CS), surface microhardness (SMH), microtensile bond strength (µTBS), hydroxyapatite formation, antibacterial activity, and cell viability. The particles exhibited an irregular shape with an average size of 4.68 µm. EDS showed a Ca/Nb ratio of 3:1 with Cl ions from precursor reagents. FTIR and XRD confirmed the semi-crystalline nature of CaNb₂O₆, with high Ca²⁺ release (48 mM/Ca after 28 days) and buffering capacity (pH 10 after 1 h). Hydroxyapatite precipitates were detected on the particle surface. The incorporation of CaNb₂O₆ did not significantly affect the mechanical properties of the adhesive (p = 0.363). SEM-EDS analysis confirmed the presence of Ca and P precipitates in the adhesive. The non-hydrolytic sol-gel process proved effective for synthesizing CaNb₂O₆, which promotes hydroxyapatite formation when added to the adhesive.