Leucite glass-ceramics are extensively used in Dentistry to produce dental prostheses including dental crowns, bridges, inlays and veneers and demonstrate favorable aesthetics. Undesirable brittle failure however, is associated with uneven leucite crystal distribution, and the thermal mismatch between the glass matrix and larger leucite crystals. The aims of the present study were to design and synthesis high strength, aesthetic, reliable and processable leucite glass-ceramic with controlled microstructures.
Alumino-silicate glasses were designed using Appen Factors to control the thermal expansion coefficient (TEC) and refractive index and produced using melt-quench methods. Glasses were ground and characterized using Dilatometry, Light Microscopy, Differential Scanning Calorimetry and High Temperature X-ray Diffraction. A series of crystallization heat treatments were carried out on all glasses to control the leucite crystal size, morphology and volume fraction. The biaxial flexural strength (BFS) of the experimental and commercial control IPS Empress Esthetic glass-ceramic was measured using the ball on ring test.
TEC predictions using Appen Factors corresponded well with experimental measurements. Leucite glass-ceramics with evenly distributed fine tetragonal leucite crystals (Mean (SD) 0.15 (0.09) ?m2) were achieved by ball milling of the parent glass followed by optimized two-step heat treatments. The glass-ceramic showed minimal matrix microcracking and a high BFS value of 252.4 (38.7) MPa and m value of 8.7, which is statistically higher than the IPS Empress Esthetic glass-ceramic with a BFS of 165.5 (30.6) MPa and m value of 6.3. Leucite crystal size, morphology and distribution depended on the parent glass composition and the thermal heat treatment. Highly crystallized leucite microstructures with orientated fibres, spheres and rosette shaped domains were synthesized based on different glass compositions, and showed a high BFS of 212.2 (28.2) MPa and m value of 8.5. High strength, reliable and translucent leucite glass-ceramics were successfully heat extruded to produce dental restorations.