In the production of dental zirconia blocks, the pressing process directly determines the internal structure of the green body and its subsequent performance characteristics.
At our facility, after dry pressing, the zirconia blocks do not proceed directly to pre-sintering. Instead, we incorporate an additional **Cold Isostatic Pressing (CIP)** step.
Although this step increases production costs and process time, it is crucial for achieving the stability, consistency, and controllability that dental laboratories truly value.
Traditional dry pressing offers high efficiency and rapid forming, but inevitably introduces the following issues within the green body:
Variations in density across different locations
Potential presence of microscopic voids in localized areas
These variations tend to amplify during subsequent pre-sintering and final sintering processes
The purpose of cold isostatic pressing is not merely “pressing again,” but to homogenize the entire formed zirconia block through isotropic pressure.
Following dry pressing, zirconia blocks undergo cold isostatic pressing with the following key parameters:
Equipment: Isostatic Press
Pressure Range:
Minimum: 200 MPa
Maximum: 260 MPa
Typical Intermediate Value: 240 MPa
Single Pressing Duration: Approximately 2 minutes
Number of Blocks Pressed per Cycle: 8 dental zirconia blocks
Under these pressure conditions, the green bodies experience uniform pressure from all directions within a sealed environment, rather than unidirectional mechanical compression.
Based on long-term mass production and practical feedback, this process primarily delivers the following improvements:
Isotropic pressure significantly reduces density variations within the zirconia block, providing a more stable foundation for subsequent sintering.
CISP helps compact micro-voids potentially remaining after dry pressing, minimizing the risk of pore enlargement during sintering.
A more uniform green body structure minimizes strength fluctuations post-sintering, delivering greater batch-to-batch consistency.
For dental laboratories, deformation often impacts usability more directly than “strength parameters.”
A more uniform green body structure helps mitigate deformation caused by irregular shrinkage during sintering.
After cold isostatic pressing, zirconia blocks proceed to the **pre-sintering** stage.
Here, blocks are sintered to a hardness suitable for CAD/CAM milling while maintaining excellent machinability.
The preceding cold isostatic pressing provides more stable, predictable blank conditions for pre-sintering.
At our facility, all dental zirconia blocks undergo this CSP process, including:
White zirconia blocks
Pre-stained zirconia blocks
Multi-layer zirconia blocks
Series products with varying strengths and translucency grades
This is not a process reserved for a specific “premium model,” but rather an integral part of our foundational quality control.
Cold isostatic pressing isn't a technical term discussed daily in dental labs, yet it directly impacts:
- Stability during milling
- Consistency of shape after sintering
- Reproducibility across batches
For the factory, it's a cost-increasing process;
For the lab, it often manifests as a long-term experience of “more stable performance.”
