The Impact of Calcination on the Structure, Bioactivity, and Biocompatibility of Sol-Gel-Derived Glasses

Bioactive glasses (BG) are promising materials for bone tissue engineering due to their bonding ability to biological tissues. In this study, a BG was synthesized via a modified sol-gel method that incorporated fumed silica. Two thermal treatments were applied: stabilization at 36.5 °C and calcination at 700 °C. X-ray diffraction analysis revealed the amorphous nature of BG stabilized at 36.5 °C, while calcination induced the formation of crystalline calcite. Nitrogen adsorption-desorption analysis revealed a specific surface area of 62 m² g^-1 for the stabilized BG, which decreased to 32 m² g^-1 after calcination. Thermogravimetric analysis indicated that the calcined sample exhibited lower thermal stability than the stabilized sample. Both BG samples exhibited the capacity to form a hydroxyapatite layer upon immersion in a simulated body fluid for a period of 48 h, being corroborated by X-ray diffraction, FTIR, and scanning electron microscopy. Additionally, cell viability assays with HaCaT keratinocytes showed enhanced cell proliferation compared to the control at 1, 4, and 7 days. A toothpaste containing 3 w/w% BG was also formulated with the calcinated sample and tested for dentin hypersensitivity, showing promising dentinal tubule occlusion, remineralization potential, and cytocompatibility. These results indicate that both samples prepared retains excellent surface properties, bioactivity, and cytocompatibility, even without high-temperature processing, highlighting its potential for biomedical applications.