ZrO2-Modified Lithium Silicate Glass Ceramic for Crack-Free Zirconia Bonding
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Solution Overview
Problem
Lithium silicate glass ceramics known for their use in dental restorations are not suitable for coating zirconium oxide ceramics due to cracking issues during the viscous flow process, which compromises their mechanical properties essential for dental applications.
Innovation Solution
A lithium silicate glass ceramic with a high content of ZrO2 (at least 6.1% by weight) and specific compositions that include P2O5 as a nucleating agent, reducing the formation of undesirable crystal phases and enhancing mechanical properties, allowing for a crack-free coating with improved bonding and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If lithium silicate glass ceramics are used for coating zirconium oxide ceramics, then the coating provides desired optical properties, but cracks and fissures form during the viscous flow process compromising mechanical properties
Solution Approach 1:
The patent changes the chemical composition parameters of the glass ceramic by increasing ZrO2 content to at least 6.1 wt% and adjusting other oxides (SiO2, Li2O, Al2O3, P2O5, etc.) to specific ranges. This compositional parameter change modifies the material's viscosity-flow characteristics during coating, preventing crack formation while maintaining optical properties.
Solution Approach 2:
The patent creates a composite glass ceramic system combining multiple oxide components (ZrO2, SiO2, Li2O, Al2O3, P2O5, and others) in specific proportions. This composite formulation synergistically provides both the viscous flow behavior needed for crack-free coating and the mechanical strength required for dental applications.
2Ease of manufacture
If glass ceramics are pressed onto zirconia ceramic in a viscous state, then coating application is achieved, but cracks and fissures form compromising the bond's mechanical properties
Solution Approach 1:
The patent modifies the rheological parameters of the glass ceramic by adjusting its chemical composition, particularly ZrO2 content (≥6.1 wt%) and other oxide ratios. This creates an optimized viscosity window that allows easy pressing and coating application while preventing crack formation that would compromise bond reliability.
3Strength
If high ZrO2 content is used in glass ceramic, then mechanical properties and crack resistance are improved, but the composition complexity increases
Solution Approach 1:
The patent systematically adjusts multiple compositional parameters within defined ranges (ZrO2: ≥6.1%, SiO2: 55-71%, Li2O: 9-17%, Al2O3: 0.5-5%, P2O5: 0.5-12%, and others) to achieve optimal fracture toughness. While this involves multiple parameters, each has a defined range that guides manufacturing, balancing complexity with performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The high ZrO2 content and optimized composition result in a glass ceramic with enhanced mechanical properties, such as high fracture toughness and translucency, enabling a strong, crack-free bond with zirconium oxide ceramics suitable for dental restorations without the formation of amorphous-amorphous phase separation.
Implementation Method 1
P2O5 as a nucleating agent, in particular, promotes the formation of desired lithium disilicate crystals and, on the other hand, largely avoids the formation of ZrO2-containing crystal phases
Implementation Method 2
Subsequent heat treatment transforms the metasilicate phase into the high-strength disilicate phase
Data Source
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AI summary
Lithium silicate glass ceramics and glasses are described which can be advantageously applied to zirconia ceramics, in particular by pressing in the viscous state, and form a strong bond with them.