Lithium Silicate Glass Ceramic Strength via Localized Ion Exchange
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Solution Overview
Problem
Current methods for enhancing the strength of lithium silicate glass ceramics in dental objects, such as bridges, face challenges in achieving high strength while maintaining good translucency and chemical stability, particularly in regions subject to tensile stress, and often require complex processes that may introduce impurities or affect aesthetics.
Innovation Solution
A method involving the application of a melt or paste containing alkali metal salts with ions larger than lithium to specific regions of the dental object, followed by heat treatment, to generate surface compressive stress by replacing lithium ions with larger alkali ions, thereby increasing strength without coating regions under tensile stress, which are instead left uncovered to prevent impurities and maintain aesthetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a coating material is applied to the entire surface of the dental object, then aesthetic appearance is improved, but strength in tensile stress regions is reduced
Solution Approach 1:
The patent applies different treatments to different regions of the dental object: coating material is applied only to compressive stress regions (not tensile stress regions), and ion exchange treatment is applied selectively to regions needing strength enhancement. This local differentiation resolves the contradiction by allowing aesthetic coating where it benefits appearance while preserving strength in critical tensile regions through ion exchange.
2Strength
If ion exchange is applied to increase strength, then flexural strength is improved, but chemical stability may be affected
Solution Approach 1:
The patent carefully controls ion exchange parameters (temperature, time, salt composition) to achieve the desired balance between strength and chemical stability. By optimizing these parameters, the ion exchange process increases flexural strength through surface compressive stress while minimizing negative impacts on chemical stability.
3Strength
If the dental object is subjected to heat treatment for ion exchange, then strength is increased, but the process complexity increases
Solution Approach 1:
The patent combines the ion exchange process with the existing heat treatment steps already required for dental ceramic fabrication (such as glazing or veneering). By integrating ion exchange into these necessary thermal processes, the patent achieves strength enhancement without adding separate, complex processing steps.
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
This method significantly increases the flexural strength of dental objects to above 500 MPa and improves chemical resistance, with flexural strength values exceeding 800 MPa and chemical solubility reduced to less than 95 μg/cm², while maintaining aesthetic appeal by avoiding coatings in tensile stress regions.
Implementation Method 1
heat treating the form body to generate a surface compressive stress through the replacement of lithium ions by alkali ions of greater diameter in the at least one region covered by the melt of paste
Data Source
AI summary
The invention relates to a method to increase the strength of a form body of lithium silicate glass ceramic, which after it has a desired end geometry and after the application of a material which influences its surface to form a coating, is subject to a heat treatment. To create a surface compressive stress through the replacement of lithium ions by alkali ions of greater diameter at least that region not covered by the application layer is covered by a melt or paste consisting of or containing a salt of an alkali metal with ions of greater diameter and the form body is in contact with the melt or paste for a period of time t at a temperature T and the melt or paste is subsequently removed from the form body.