Yttria-Stabilized Zirconia Translucency and Strength Optimization
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Solution Overview
Problem
Current dental ceramic materials, such as yttria-stabilized zirconia, face challenges in achieving optimal combinations of high flexural strength, translucency, and esthetic properties suitable for dental restorations, with existing manufacturing methods falling short in producing materials that closely mimic natural teeth in both appearance and performance.
Innovation Solution
The method involves forming ceramic green bodies using dry and wet forming processes, including uniaxial pressing, cold isostatic pressing, and slip-casting, followed by pre-sintering to create bisque bodies with controlled density and porosity, which are then sintered using novel sintering profiles to achieve enhanced physical properties like high flexural strength and translucency, and optionally colored to match dental shades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional press molding methods are used with traditional sintering processes, then manufacturing process is simple, but the resulting zirconia bodies have insufficient translucency (37-40% light transmittance)
Solution Approach 1:
The patent applies parameter changes by optimizing multiple variables including yttria content (5-6.5 mol%), particle size distribution (D10, D50, D90 values), sintering temperature (1400-1600°C), and sintering atmosphere to achieve high translucency (>40% light transmittance) while maintaining manufacturing feasibility through controlled parameter ranges
2Illumination intensity
If zirconia powder with higher yttria content is used, then translucency is improved, but flexural strength decreases below the required 500 MPa threshold
Solution Approach 1:
The patent optimizes the yttria content parameter within the specific range of 5-6.5 mol%, balancing the competing requirements for translucency and flexural strength. This controlled parameter range ensures both optical properties and mechanical strength exceed dental restoration requirements
Solution Approach 2:
The patent creates a composite microstructure by controlling particle size distribution with specific D10, D50, and D90 values, resulting in a multi-scale composite arrangement that simultaneously enhances translucency through light scattering control and maintains strength through optimized grain boundaries
3Illumination intensity
If conventional sintering processes are used, then manufacturing is straightforward, but the zirconia bodies exhibit insufficient esthetic properties and do not closely match natural teeth appearance
Solution Approach 1:
The patent implements a multi-stage sintering process with controlled temperature ranges (1400-1600°C), atmosphere control, and holding times to achieve dense microstructure with optimized optical properties. These parameter controls produce translucency and color characteristics that closely match natural teeth
Solution Approach 2:
The patent develops a composite ceramic material system combining zirconia with controlled particle size distribution and yttria stabilization, creating a multi-phase microstructure that reproduces the complex optical behavior of natural tooth structure, including light scattering and absorption characteristics
4Illumination intensity
If particle size is reduced to enhance translucency, then light transmittance improves, but manufacturing precision and control of sintering become more difficult
Solution Approach 1:
The patent controls particle size parameters by specifying D10, D50, and D90 values within defined ranges, balancing translucency enhancement with manufacturability. This statistical control of particle size distribution achieves optimal optical properties while maintaining practical manufacturing capabilities
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 approach results in sintered ceramic bodies with improved mechanical strength, translucency, and esthetic appeal, meeting or exceeding the requirements for dental restorations, with specific examples demonstrating flexural strengths greater than 500 MPa and translucency values up to 75% at 700 nm, while matching dental shades.
Implementation Method 1
The green body can then be sintered at a sintering temperature of from 1450° C. to 1600° C. to obtain a zirconia sintered body
Implementation Method 2
Ceramic slurry may be cast in a mold from which water is evacuated consolidating the solid material to form a ceramic green body
Data Source
AI summary
A zirconia ceramic material for use in dental applications is provided comprising an yttria-stabilized zirconia material stabilized with 5 mol % yttria to 8 mol % yttria, and methods for making a sintered body from the ceramic material. The zirconia ceramic materials exhibit both enhanced translucency and a flexural strength of at least 300 MPa, or at least 500 MPa, when fully sintered.