Lithium Disilicate Dental Block for Chip-Resistant Machining
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Solution Overview
Problem
Existing dental prostheses materials lack good machinability, particularly those with a lithium disilicate main crystalline phase, making it difficult to process complex shapes without faults like chipping, and requiring additional heat treatment for improved strength.
Innovation Solution
A block for dental prostheses with a lithium disilicate main crystalline phase, limited to 21% area of crystals over 0.5 μm, composed of 60-80% SiO2, 10-20% Li2O, 3-15% Al2O3, and 4.2-10% P2O5, with optional additives, allowing machining without heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the block contains a lithium disilicate main crystalline phase with high crystal content, then the strength and chemical durability are improved, but the machinability deteriorates making it difficult to process complex shapes without chipping
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystal proportion parameter (limiting crystals ≥0.5μm to 21% or less of total area) and optimizing chemical composition parameters (SiO2: 60-80 mass%, Li2O: 10-20 mass%, Al2O3: 3-15 mass%, P2O5: 4.2-10 mass%). This resolves the contradiction by finding the optimal parameter range that provides sufficient strength while maintaining good machinability for complex shape processing.
Solution Approach 2:
The patent applies local quality by creating a non-uniform crystal distribution where smaller crystals (＜0.5μm) are distributed throughout the matrix providing strength, while limiting larger crystals (≥0.5μm) that cause machining difficulties. This local differentiation of crystal sizes allows the material to exhibit both high strength and good machinability in different aspects.
2Strength
If additional heat treatment is applied to improve strength, then the mechanical properties are enhanced, but the processing time and production efficiency deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the crystal composition and size distribution during block fabrication, so that the final product achieves the required strength without needing additional post-processing heat treatment. The crystals are carefully controlled to be ≥0.5μm in size and limited to 21% or less of total area, which provides sufficient strength inherently, eliminating the need for time-consuming heat treatment steps and improving productivity.
3Strength
If the crystal size is increased to improve strength, then the mechanical durability is enhanced, but the machining quality deteriorates causing chipping and faults
Solution Approach 1:
The patent applies parameter changes by establishing a critical crystal size threshold of 0.5μm and limiting the proportion of crystals at or above this size to 21% or less of the total area. This parameter control ensures that crystals are large enough to provide mechanical durability while remaining small enough to avoid causing chipping during machining of complex shapes.
Solution Approach 2:
The patent applies local quality by differentiating crystal sizes into two categories: smaller crystals (＜0.5μm) that are distributed throughout the matrix to provide strength without causing machining issues, and larger crystals (≥0.5μm) that are strictly limited in proportion. This local differentiation resolves the contradiction between mechanical durability and machining quality.
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 block enables efficient machining of dental prostheses with improved machinability and strength, maintaining shape accuracy without additional heat treatment, comparable to conventional materials.
Implementation Method 1
a main crystalline phase of the block being of lithium disilicate, and when the block is observed in a field of view of a partially enlarged cross section of the block, a proportion of a total area of crystals having a length of at least 0.5 μm
Data Source
AI summary
A block for dental prostheses is in the form of a column or a board, a main crystalline phase of the block being of lithium disilicate, and when the block is observed in a field of view of a partially enlarged cross section of the block, the proportion of the total area of crystals having a length of at least 0.5 μm, the crystals appearing in the field of view, to an area of the field of view is at most 21%.