Lithium Disilicate Glass-Ceramic Microstructure for Strength and Transparency
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Solution Overview
Problem
Existing lithium disilicate glass-ceramics used for dental restoration suffer from low bending strength, limited light transparency, and inadequate fracture toughness, making them prone to cracking and fracturing, and are limited in their application to posterior teeth.
Innovation Solution
A lithium disilicate glass-ceramic with controlled crystal grain size and morphology, optimized composition, and adjusted heat treatment to achieve a three-dimensional interweaving microstructure, enhancing strength and fracture toughness while maintaining high transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If lithium disilicate glass-ceramic is used for dental restoration, then aesthetic effect and optical matching are improved, but bending strength is insufficient leading to cracking and fracturing
Solution Approach 1:
The patent creates a composite microstructure consisting of lithium disilicate crystals (3-10 μm) embedded in a glass matrix, forming a two-phase composite material. This composite structure combines the optical transparency of the glass phase with the mechanical strength of the crystal phase, achieving both aesthetic effect and sufficient bending strength (450-750 MPa).
Solution Approach 2:
The patent applies local quality by creating regions with different properties: the glass matrix provides optical transparency and aesthetic appearance, while the distributed lithium disilicate crystal phases provide localized reinforcement and crack resistance. The crystal size (3-10 μm) is specifically controlled to be smaller than the wavelength of visible light to maintain transparency while providing mechanical reinforcement.
2Illumination intensity
If crystal size is reduced to improve transparency, then light transmittance is improved, but three-dimensional interweaving microstructure is compromised reducing strength
Solution Approach 1:
The patent optimizes the crystal size parameter to a specific range (3-10 μm) that is smaller than the wavelength of visible light (400-700 nm), ensuring light can pass through without significant scattering. Simultaneously, this controlled size enables the formation of a three-dimensional interweaving microstructure with high crystal density, achieving both high light transmittance (10-80%) and high fracture toughness (>3.5 MPa·m1/2).
Solution Approach 2:
The patent transitions from two-dimensional crystal arrangement to a three-dimensional interweaving microstructure. The lithium disilicate crystals are distributed throughout the glass matrix in three dimensions, creating a network that provides mechanical reinforcement while maintaining optical transparency. This 3D arrangement allows light to pass through the smaller crystals without significant scattering.
3Strength
If second phase impurity is added to increase strength, then bending strength is improved, but refractive index mismatch reduces light transparency
Solution Approach 1:
The patent maintains homogeneity by using lithium disilicate crystals with the same chemical composition and refractive index (1.55) as the surrounding glass matrix (1.50). This compositional homogeneity ensures optical matching, allowing light to pass through the crystal-glass interface with minimal scattering. The uniform distribution of lithium disilicate phases throughout the glass matrix further enhances optical homogeneity while providing mechanical reinforcement.
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 lithium disilicate glass-ceramic achieves a three-point bending strength of 450-750 MPa and fracture toughness above 3.5 MPa·m1/2, with light transmittance adjustable from 10% to 80%, effectively reducing chipping risk and simulating natural tooth properties.
Implementation Method 1
The ZrO2 microcrystals may undergo a phase transition from tetragonal phase to monoclinic phase during cooling to result in volume expansion, thus forming an extrusion effect on the surrounding lithium disilicate crystals.
Implementation Method 2
a heat treatment to fully react MgO with Al2O3 and SiO2
Implementation Method 3
Lithium disilicate glass-ceramic is a microcrystalline glass having uniformly distributed crystal phase and glass phase
Data Source
AI summary
The present disclosure discloses a lithium disilicate glass-ceramic with high strength and high transparency and a preparation method and use thereof. A raw material composition of the lithium disilicate glass-ceramic comprises: 63-75 wt % of SiO2, 13-18 wt % of Li2O, 1-6 wt % of Al2O3, 1-10 wt % of K2O, 2-6 wt % of P2O5, 0-4 wt % of an additive and 0-10 wt % of a colorant; a main crystal phase of the lithium disilicate glass-ceramic is lithium disilicate crystals, and an impurity phase of the lithium disilicate glass-ceramic is any one or a combination of at least two selected from the group consisting of lithium metasilicate, lithium phosphate and quartz; the lithium disilicate crystal has a size larger than 700 nm and a length-diameter ratio not less than 3.