Effect of $ \mathrm{B_2}\mathrm{O_3} $ addition on structure of nepheline glass-ceramics for dental applications

This study investigates the effect of substituting \mathrm{Al_2}\mathrm{O_3} with \mathrm{B_2}\mathrm{O_3} (0-4mol%) in nepheline-based glasses intended for advanced dental applications. Differential scanning calorimetry, X-ray diffraction, Raman spectroscopy, dilatometry and scanning electron microscopy were used to examine the structural and thermal evolution of the modified compositions. Increasing B2O3 content decreased the glass transition and softening temperatures and suppressed nepheline crystallisation, leading to the enhanced amorphous stability. Raman analysis revealed progressive network depolymerisation due to the conversion of Al-O-Si linkages to BO3 structural units, while dilatometry demonstrated improved thermal expansion compatibility with zirconia and metal substructures. SEM confirmed that higher \mathrm{B_2}\mathrm{O_3} levels reduced crystal formation and yield smooth, homogeneous microstructures ideal for aesthetic dental applications. The results show that \mathrm{B_2}\mathrm{O_3} contents of 2-3mol% provide optimal thermal behaviour, translucency potential and structural uniformity, positioning these compositions as promising candidates for use in dental veneering porcelains, pressable glass-ceramics and CAD/CAM restorative materials.