Lithium Silicate Glass Ceramic Composition for Easy Machining
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Solution Overview
Problem
Conventional lithium silicate glass ceramics are difficult to machine due to their high strength, leading to tool wear and slow processing, which is problematic for single-session dental restorations.
Innovation Solution
A lithium silicate glass ceramic with lithium metasilicate as the main crystal phase, comprising specific oxide components and a molar ratio of SiO2 to Li2O between 2.5 to 5.0, allowing for easy machining and subsequent conversion to high-strength dental products with excellent optical and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional lithium silicate glass ceramics are used, then high strength is achieved, but machining difficulty increases and tool wear increases
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass ceramic, specifically setting SiO2 content to 70-80 wt.%, Li2O content to 8-14 wt.%, and controlling the molar ratio of SiO2 to Li2O between 2.5 to 5.0. These parameter changes create a composition that balances machinability during fabrication with strength after crystallization to lithium disilicate phase.
2Strength
If conventional lithium silicate glass ceramics are used, then high strength is achieved, but machining speed decreases
Solution Approach 1:
The patent optimizes the chemical composition with specific ranges of SiO2 (70-80 wt.%) and Li2O (8-14 wt.%), along with controlled molar ratios, to create a glass ceramic that can be machined at higher speeds before crystallization while maintaining the capability to transform into a high-strength final product.
3Productivity
If lithium metasilicate glass ceramic is used for easy machining, then machining speed improves, but final strength is insufficient
Solution Approach 1:
The patent performs preliminary shaping and machining operations on the glass ceramic in its non-crystallized or partially crystallized state where it is more machinable. After the desired shape is achieved, a subsequent heat treatment step transforms the material into the high-strength lithium disilicate crystal phase, ensuring both easy machining and high final strength.
Solution Approach 2:
The patent utilizes phase transition by controlling the crystallization process. The glass ceramic is first processed in a more ductile phase for machining, then undergoes heat treatment to transform into the lithium disilicate crystal phase which provides high strength. This phase transition approach allows the material to exhibit different properties at different processing stages.
4Productivity
If conventional glass ceramics are machined, then tool wear increases, but if softer material is used, then machining speed decreases
Solution Approach 1:
The patent performs all necessary machining operations on the glass ceramic before it undergoes crystallization to the high-strength lithium disilicate phase. This preliminary action allows machining to be performed on the softer, more ductile glass or partially crystallized material, minimizing tool wear. After shaping is complete, the material is heat-treated to achieve the final high-strength crystalline structure.
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 glass ceramic can be machined quickly into complex dental restorations and transformed into high-strength lithium disilicate glass ceramics with minimal tool wear, offering excellent mechanical and optical properties.
Implementation Method 1
it has lithium metasilicate as main crystal phase... can be machined faster than the known lithium metasilicate glass ceramics and can subsequently be converted into high-strength dental products
Data Source
AI summary
A lithium silicate glass ceramic having lithium metasilicate as main crystal phase and having not more than 30 wt.-% of lithium metasilicate crystals and having the following components in the amounts indicated:ComponentWt.-%SiO271.0 to 82.0Li2O6.0 to 14.0MeI2O4.0 to 15.0Al2O32.0 to 10.0P2O50.5 to 7.0,wherein MeI2O is selected from Na2O, K2O, Rb2O, Cs2O and mixtures thereof, andwherein the molar ratio of SiO2 to Li2O is in the range of 2.5 to 5.0.