Core-Shell Ceramic Dental Restorations Without Milling Wear
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Solution Overview
Problem
Existing methods for producing ceramic dental restorations face challenges such as high wear of milling tools, time-consuming processes, and risks of cracks and deformations during debinding, which complicate the production of aesthetically demanding restorations with natural appearances.
Innovation Solution
A method involving additive manufacturing of a one-piece framework structure and veneering structure separately, using CAD/CAM technology to create digital design models, and assembling them with matching thermal expansion and sintering shrinkage properties to ensure precise fit and reduce errors, followed by debinding and sintering to achieve high strength and detail accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional milling methods are used to produce ceramic dental restorations, then manufacturing precision can be achieved, but the process becomes very time-consuming and causes high wear of milling tools
Solution Approach 1:
The patent replaces conventional mechanical milling methods with additive manufacturing (stereolithography) to produce ceramic dental restorations. The slurry containing ceramic particles is selectively cured by UV light to build three-dimensional structures layer by layer, eliminating the need for mechanical cutting and grinding operations that are time-consuming and cause tool wear.
Solution Approach 2:
The patent changes the physical state and properties of the ceramic material from solid blocks requiring mechanical removal to liquid/slurry state that can be selectively deposited and cured. By adjusting parameters such as slurry viscosity, particle size distribution, and UV curing conditions, the process achieves both high precision and improved productivity.
2Manufacturing precision
If ceramic materials are milled, then manufacturing precision is maintained, but tool wear increases significantly due to the hardness of ceramic
Solution Approach 1:
The patent replaces mechanical milling tools with a photopolymerization-based additive manufacturing system. Instead of using hard milling tools that wear down when cutting ceramic materials, the system uses UV light to selectively cure ceramic-containing slurry, completely eliminating mechanical contact and tool wear.
3Manufacturing precision
If the framework and veneer are assembled before sintering, then precise positioning is required, but this increases the risk of errors due to different shrinkage behavior
Solution Approach 1:
The patent divides the dental restoration into separate framework and veneer components that are manufactured independently using additive manufacturing. Each component is produced separately with its own digital model, allowing for independent optimization and reducing the complexity of positioning and alignment during assembly.
Solution Approach 2:
The patent adjusts the slurry composition and printing parameters for both framework and veneer to achieve similar shrinkage behavior during sintering. By controlling factors such as ceramic particle content, binder type, and layer thickness, the differential shrinkage between components is minimized, reducing positioning errors.
4Productivity
If additive manufacturing is used to produce ceramic components, then productivity increases and tool wear is eliminated, but cracks and deformations may occur during debinding
Solution Approach 1:
The patent employs a multi-stage debinding process where different heating rates and temperature holds are applied at different stages. The initial stage uses a slow heating rate to allow gradual removal of organic binders from the green body, preventing rapid gas evolution that could cause cracks. Subsequent stages increase the heating rate once the majority of binders are removed.
Solution Approach 2:
The patent incorporates preliminary support structures and optimization of layer adhesion during the additive manufacturing process to prevent deformations during debinding. The green body is designed with appropriate support elements that are removed after debinding, and the printing parameters are optimized to ensure strong inter-layer bonding that can withstand the debinding process.
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 method produces ceramic dental restorations with high strength and aesthetic appeal, minimizing tool wear, process time, and reducing the risk of defects, while allowing for precise alignment and natural tooth-like appearance.
Implementation Method 1
comprising a monomer (a), a photoinitiator (b) and ceramic, glass and/or glass-ceramic particles (c)
Implementation Method 2
Transform Optical Energy to Chemical Energy
Implementation Method 3
The green body is then sintered into a dense ceramic molded part
Implementation Method 4
assembling them with matching thermal expansion and sintering shrinkage properties
Implementation Method 5
sintering shrinkage properties
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method for manufacturing an all-ceramic dental restoration with a one-piece core and shell structure, in which a digital design model of the dental restoration is created, the resulting CAD dataset is then divided into at least two separate CAD subsets, one defining the contours of the core structure and the other defining the contours of the shell structure. A green body of the core structure is produced using the first CAD subset, and a green body of the shell structure is produced using the second CAD subset. The core and shell structures are then joined in their green state, the green body is subjected to heat treatment to remove the binder, and the component is subsequently sintered to obtain the finished dental restoration.The process enables the production of dental restorations with improved aesthetic properties without significant additional effort compared to the production of one-piece restorations.