Color-Graded Dental Ceramics Uniform Sintering
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Solution Overview
Problem
The challenge in producing dental prostheses using powder technology is achieving accurate shape retention and color gradation without shrinkage or distortion, as different ceramic powders exhibit varying sintering behaviors and color pigments can alter the ceramic's properties, leading to anisotropic shrinkage and potential distortion.
Innovation Solution
A method involving a green body composed of multiple powder mixtures with specific compositions and layering, where each layer has varying concentrations of ceramic powders and coloring agents, isostatically pressed to ensure identical volume changes during sintering, maintaining shape accuracy and achieving true-to-shape sintering by matching the green and sintering densities of the powder mixtures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple differently colored ceramic powders are used to achieve color gradation, then the aesthetic appearance of the dental prosthesis is improved, but the sintering behavior varies significantly causing shape distortion and dimensional inaccuracy
Solution Approach 1:
The patent adjusts the composition of ceramic powders in each layer to have identical sintering characteristics (shrinkage behavior, densification rate) while varying only the color pigment content. This parameter adjustment ensures that all layers undergo uniform dimensional changes during sintering, preventing distortion while achieving the desired color gradation effect.
Solution Approach 2:
The patent applies different color pigment concentrations to different layers of the ceramic green body, creating local quality variations in color while maintaining uniform sintering properties throughout. Each layer is locally optimized for its specific color requirement while the overall structure maintains consistent dimensional stability during processing.
2Illumination intensity
If color pigments are added to ceramic powders to achieve desired shades, then the aesthetic properties are improved, but the sintering behavior and other ceramic properties are altered
Solution Approach 1:
The patent carefully controls the type and concentration of color pigments added to each powder mixture, adjusting these parameters to achieve the desired color shades while maintaining consistent sintering behavior. By selecting pigments with minimal impact on densification and shrinkage, the patent preserves the stability of sintering characteristics across all colored layers.
3Illumination intensity
If powder mixtures with different compositions are used to achieve color variation, then the aesthetic appearance is improved, but anisotropic shrinkage and distortion occur during sintering
Solution Approach 1:
The patent modifies the base ceramic powder composition in each layer to compensate for the effects of different color pigments, ensuring that all layers exhibit identical volumetric shrinkage and densification behavior during sintering. This compositional adjustment eliminates anisotropic shrinkage while preserving the desired color variation across layers.
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 allows for the production of color-graded dental ceramics that maintain their shape and color integrity, ensuring precise fit and appearance, as the identical volume changes and coordinated component ratios prevent distortion and shrinkage during the sintering process.
Implementation Method 1
A green body of this type is then sintered in a shape-retaining manner
Implementation Method 2
compacted into a molded body under a pressure of up to 600 MPa. Isostatic pressing is preferred to ensure good dimensional stability
Data Source
AI summary
The invention relates to a method for producing a ceramic, a ceramic produced according to said method and to the use thereof. According to the invention, a green body, which consists of at least two different powder mixtures that are compacted to form a moulded body, is initially produced and subsequently sintered. Said powder mixtures respectively contain a ceramic powder and a coloured metal compound and/or a coloured pigment. The two powder mixtures are different in their composition from the coloured metal compound and/or the coloured pigment. The ceramics are shaped prior to sintering and/or during the intermediate step, during which sintering is interrupted and then continued after shaping. The inventive ceramic can be used as colour gradiated dental ceramics or as dental ceramics having a coloured gradient.