Functionally Graded Dental Bulk Block for Machinability and Translucency
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Solution Overview
Problem
Existing dental crown materials, such as lithium disilicate glass-ceramics, face challenges in machinability due to coarse crystalline phases, leading to reduced dimensional accuracy and aesthetic issues, and require time-consuming heat treatments, limiting their ability to replicate the multi-gradation and light transmittance of natural teeth.
Innovation Solution
A dental bulk block with a crystalline phase in an amorphous glass matrix, featuring a gradient of crystalline sizes and light transmittance, is manufactured through controlled heat treatment, allowing for direct machining and improved structural stability via functional grading of mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lithium disilicate glass-ceramics with coarse crystalline phases are used to achieve high strength, then strength is improved, but machinability deteriorates and dimensional accuracy is reduced
Solution Approach 1:
The patent applies parameter changes by controlling the crystallization temperature (400-850°C) to transform the crystalline phase from coarse lithium disilicate to fine-grained lithium metasilicate. This temperature parameter adjustment fundamentally changes the material's microstructure, enabling both high strength and excellent machinability without compromising dimensional accuracy
2Strength
If secondary crystallization heat treatment is performed to improve strength, then strength is improved, but manufacturing time increases and process complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the lithium metasilicate crystalline phase during the initial crystallization process (400-850°C) to create a machinable intermediate structure. This preliminary crystallization enables direct machining without requiring subsequent secondary heat treatment, thereby eliminating time loss and reducing process complexity while maintaining the ability to achieve high strength through the controlled fine-grained structure
3Strength
If conventional lithium disilicate glass-ceramic is used to achieve high strength, then strength is improved, but light transmittance and aesthetics deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the crystallization temperature (400-850°C) to form a fine-grained lithium metasilicate crystalline phase with grain sizes of 0.5-5 μm. This parameter control creates a microstructure that allows light to pass through more effectively compared to coarse lithium disilicate, thereby improving light transmittance and aesthetic appearance while maintaining high strength through the refined crystalline structure
4Strength
If coarse crystalline phase is used to achieve high strength, then strength is improved, but machinability deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting the crystallization temperature to 400-850°C, which transforms the crystalline phase from coarse lithium disilicate to fine-grained lithium metasilicate. This parameter modification creates a microstructure with grain sizes of 0.5-5 μm that is significantly easier to machine while maintaining the high strength required for dental applications
Solution Approach 2:
The patent applies local quality by creating a uniform distribution of fine-grained lithium metasilicate crystals throughout the glass matrix. This localized refinement of the crystalline structure at the micro-scale enhances machinability throughout the entire material volume while preserving the strength properties needed 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
The dental bulk block enables efficient CAD/CAM machining, replicating the multi-gradation of natural teeth, enhancing aesthetics and structural stability without additional processes, and reducing manufacturing time.
Implementation Method 1
performing a primary heat treatment on a glass composition at 400 to 850° C. The primary heat treatment results in the generation of a lithium disilicate crystalline phase and a silica crystalline phase
Implementation Method 2
it is necessary to primarily form a lithium metasilicate crystalline phase (machinable crystalline), and then secondarily form a high-strength lithium disilicate crystalline phase through heat treatment
Data Source
AI summary
Provided is a dental bulk block made from a glass-ceramic material having a crystalline phase embedded in an amorphous glass matrix. The crystalline phase includes eucryptite and at least one lithium silicate-based crystalline phase selected from the group consisting of lithium metasilicate and lithium disilicate. The dental bulk block is a functionally graded material having a crystalline size gradient with respect to a depth thereof and having no interface at a point of change in main crystalline size gradient value. The bulk block that is heat-treated at 820° C. for 40 minutes exhibits a characteristic peak of a spodumene crystalline phase in an X-ray diffraction analysis result graph unlike the bulk block that is heat-treated at 820° C. for 2 minutes.