Multi-Layer Zirconia Mill Blank for Rapid Dental Sintering
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Solution Overview
Problem
Existing dental mill blanks require lengthy final sintering processes, which hinder chairside applications and result in dental restorations with unsatisfactory optical properties when attempts are made to shorten the process.
Innovation Solution
A pre-sintered multi-layered dental mill blank composed of zirconia and yttria layers with varying yttria content and a sintering activator, allowing for rapid sintering to full density in under 45 minutes while maintaining desirable optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional multi-layered dental mill blank is used, then the dental restoration can be prepared with adequate mechanical properties, but the final sintering process takes several hours which significantly increases preparation time
Solution Approach 1:
The mill blank is pre-sintered to approximately 70% of final density before machining, performing the time-consuming sintering operation in advance. This preliminary action allows the material to achieve adequate mechanical properties while leaving only a short final sintering period (5-15 minutes) to complete the restoration, thereby significantly reducing total preparation time.
Solution Approach 2:
The invention modifies the composition parameters of the mill blank by incorporating specific sintering activators (zinc oxide, gallium oxide, or aluminum oxide) and controlling yttria content gradients (4.5-6.1 wt% at bottom, 6.2-7.9 wt% at intermediate layers, 8.0-11.0 wt% at top). These parameter changes enable the material to reach full density much faster during the final sintering process while maintaining mechanical integrity.
2Productivity
If the final sintering time is significantly reduced, then chairside application becomes possible, but the optical properties become unsatisfactory with unnatural appearance
Solution Approach 1:
The mill blank employs a graded composition where yttria content and sintering activator distribution vary by layer (bottom layer: 4.5-6.1 wt% yttria; intermediate layers: 6.2-7.9 wt% yttria; top layer: 8.0-11.0 wt% yttria). This local quality variation enables different regions to sinter at optimally different rates, ensuring uniform optical appearance and natural translucency gradients even during rapid sintering.
Solution Approach 2:
Sintering activators (zinc oxide, gallium oxide, or aluminum oxide) serve as intermediary substances that catalyze the sintering process. These activators enable the ceramic material to reach full density and develop proper optical properties much faster than conventional materials, making chairside application feasible while maintaining aesthetic quality.
3Ease of manufacture
If pre-sintering is performed to improve machinability, then the mill blank becomes easier to work with, but the final sintering process still requires several hours
Solution Approach 1:
The mill blank undergoes pre-sintering to achieve approximately 70% of final density before machining operations. This preliminary treatment significantly improves machinability and workability, allowing for efficient CAD/CAM processing. The remaining 30% densification is achieved during a short final sintering period, thereby maintaining ease of manufacture while minimizing total time loss.
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
Enables chairside production of dental restorations with a graded optical appearance, achieving natural translucency and color transitions, and reducing overall preparation time.
Implementation Method 1
the top layer comprising 0.02 to 0.8 wt.%, based on the total weight of the top layer, of a sintering activator which is zinc oxide, gallium oxide, or a combination thereof
Implementation Method 2
sintering activator which is zinc oxide, gallium oxide, or a combination thereof
Implementation Method 3
the yttria content of the layers increases from the bottom layer to the top layer
Data Source
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AI summary
The present invention relates to a pre-sintered multi-layered dental mill blank comprising a top layer, a bottom layer, and at least one intermediate layer. The pre-sintered multi-layered dental mill blank or a part prepared thereof has one or more desirable properties when being fully sintered by a speed sintering process. The present invention also relates to a process for preparing a dental restoration using the pre-sintered multi-layered dental mill blank as well as to a dental restoration as such. The present invention further relates to a process for sintering a dental restoration precursor.