Lithium Silicate Glass Ceramic Machinability
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Solution Overview
Problem
Conventional lithium disilicate glass ceramics are difficult to machine due to their high strength, leading to significant tool wear and requiring a further crystallization step for achieving high strength, which is problematic for chairside dental restoration treatments.
Innovation Solution
A lithium silicate glass ceramic with lithium disilicate as the main crystal phase, comprising no more than 40 wt.-% of lithium disilicate crystals, exhibiting low strength and toughness for easy machining and excellent mechanical, optical, and chemical stability without additional heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional lithium disilicate glass ceramic is used to ensure high strength, then mechanical strength is improved, but machining difficulty increases and tool wear increases
Solution Approach 1:
The patent changes the crystal phase composition parameter by limiting lithium disilicate to ≤40 wt.-% and introducing alternative crystal phases (such as lithium metasilicate, lithium phosphate, or barium disilicate), thereby reducing material strength to enable easy machining while maintaining sufficient mechanical performance for dental applications
Solution Approach 2:
The patent creates a composite glass ceramic material containing multiple crystal phases (lithium disilicate combined with other crystalline phases like lithium metasilicate, lithium phosphate, or barium disilicate) in specific proportions, achieving a balance between machinability and mechanical strength
2Ease of manufacture
If lithium metasilicate glass ceramic is used to enable easy machining, then machining ease is improved, but further heat treatment is required to achieve high strength
Solution Approach 1:
The patent performs preliminary action by pre-forming the desired crystal phase composition (including ≤40 wt.-% lithium disilicate and other crystalline phases) during the initial glass ceramic formation process, so that the material achieves both machinability and sufficient strength without requiring subsequent heat treatment to convert lithium metasilicate to lithium disilicate
Solution Approach 2:
The patent extracts the requirement for further heat treatment by directly forming the final multi-phase crystal structure during initial processing, eliminating the need for subsequent crystallization steps to convert lithium metasilicate to lithium disilicate
3Strength
If lithium disilicate glass ceramic with high crystal content is used to ensure high strength, then mechanical strength is improved, but machining speed decreases and tool wear increases
Solution Approach 1:
The patent changes the crystal phase composition parameter by limiting lithium disilicate to ≤40 wt.-% and introducing alternative crystal phases, thereby reducing material hardness and enabling faster machining with reduced tool wear while maintaining sufficient mechanical strength for dental restorations
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
Enables fast and efficient machining of complex dental restorations with improved mechanical and optical properties, and excellent chemical stability, allowing for immediate use without further heat treatment, thus enhancing chairside treatment capabilities.
Implementation Method 1
comprises lithium disilicate as main crystal phase and comprises no more than 40 wt.-% of lithium disilicate crystals
Data Source
AI summary
A lithium silicate glass ceramics having lithium disilicate as main crystal phase and having not more than 40 wt.-% of lithium disilicate crystals.