Exploring new machinable, strong lithium metasilicate-based glass-ceramics for dental applications

This research aimed to create a new Li metasilicate-based glass-ceramic for dental use, prioritizing improved chemical durability (CD) and machinability while preserving good glass-forming ability (GFA) and adequate mechanical properties. Characterization also involved examining fracture strength (Sf) and fracture toughness (KIC). The experimental approach involved precise microstructural adjustments through designed compositional changes and controlled thermal treatments. Four compositions underwent scrutiny using mechanical tests, microscopy, differential scanning calorimetry, and X-ray diffraction to analyze the impact of lithium metasilicate (LS) and disilicate (LS2) crystals on these properties. Machinability was evaluated by weight loss measurements during controlled grinding experiments. The developed GCs exhibited interconnected acicular LS and LS2 crystals, which resulted in favorable Sf -300 MPa and KIC -1.7 MPa m1/2 (SEVNB). Although the KIC was smaller than that of an experimental LS-LS2 GC (285 MPa and 3 MPa m1/2(double torsion)) used as a reference, the chemical durability (126 mu g/cm2 for ML14F GC) improved by nearly 50 % compared to the reference (-220 mu g/ cm2). This study introduced three new GCs with LS as the major phase (rather than the traditional LS2), showcasing commendable GFA, chemical durability and machinability, with satisfactory flexural strength and fracture toughness.