White vs. Pre-Colored Zirconia: Which Laboratory Processing Steps Are Different?

White zirconia and pre-shaded zirconia can both be used to produce dental restorations, but the laboratory workflow is not exactly the same.

The main difference is when the basic color is introduced. With white zirconia, technicians generally need to create the desired base shade after milling and before sintering. With pre-shaded zirconia, the basic shade has already been incorporated into the zirconia blank during manufacturing, so the conventional coloring step can often be skipped.

Understanding this difference can help dental laboratories choose the appropriate workflow for different cases.

For a typical monolithic zirconia restoration, the general workflow is:

CAD design → CAM milling → cleaning → color treatment → drying → sintering → finishing

However, the color-treatment stage is different for white and pre-shaded zirconia.

A typical workflow is:

CAD design → CAM milling → cleaning → coloring → drying → sintering → polishing/finishing

White zirconia is supplied without the final tooth shade. After milling, a coloring liquid can be applied by dipping or brushing before sintering to establish the desired base color.

The workflow can usually be simplified to:

CAD design → CAM milling → cleaning → sintering → polishing/finishing

Because the basic shade is already incorporated into the zirconia blank, additional coloring is generally unnecessary for routine cases.

Pre-shaded zirconia was developed partly to simplify shade reproduction in the laboratory.

The most obvious difference occurs after milling.

After milling, the restoration can be colored using a compatible zirconia coloring liquid.

Depending on the coloring system, the technician may:

• Dip the restoration into the coloring liquid
• Apply the liquid with a brush
• Use different liquids in different areas
• Adjust the amount of coloring liquid to create a shade or gradient

This step establishes the basic color before sintering.

The absorption characteristics of the zirconia, the coloring liquid, and the application technique can all influence the final shade.

For example, cervical and incisal areas may receive different amounts of coloring liquid when a technician wants to reproduce a more natural color transition.

With pre-shaded zirconia, the basic shade has already been incorporated into the material.

Therefore, instead of:

White zirconia → coloring liquid → final shade

the laboratory can work with:

Pre-shaded zirconia → final shade after sintering

This removes one major manual processing step.

However, "pre-shaded" does not mean that no further characterization is possible. Additional staining or glazing may still be used when a case requires more individualized surface characterization.

Drying is another important difference between the two workflows.

After white zirconia has been treated with coloring liquid, the restoration contains liquid inside its porous pre-sintered structure. It therefore needs to be properly dried before sintering.

For example, one coloring system recommends drying colored zirconia at 80°C for 60 minutes before sintering. Other systems specify different drying conditions, so the instructions for the specific material and coloring system should always be followed.

The principle is simple:

Coloring → sufficient drying → sintering

A wet restoration should not simply be placed into the sintering furnace. Manufacturer instructions specifically emphasize complete drying before sintering because residual moisture or liquid can affect the sintering process.

With pre-shaded zirconia, the conventional post-milling coloring step is usually eliminated, so the additional drying step associated with coloring can also be eliminated.

However, this does not mean that every pre-shaded zirconia restoration can be sintered immediately after milling. If the restoration has been cleaned with water, processed by wet milling, or otherwise exposed to moisture, the manufacturer's drying requirements still apply.

Both white and pre-shaded zirconia still require sintering.

Before sintering, the milled restoration remains in a porous pre-sintered state. During sintering, the material densifies and develops its final mechanical and optical properties.

Therefore, the basic sequence remains:

Milling → preparation → sintering → cooling → finishing

The important difference is what happens before the restoration enters the furnace.

For white zirconia:

Milling → coloring → drying → sintering

For pre-shaded zirconia:

Milling → cleaning/drying as required → sintering

The actual sintering temperature, heating rate, holding time, and cooling procedure should always follow the zirconia manufacturer's recommended program. These parameters are material-specific and should not be assumed to be interchangeable between different zirconia products.

The CAD/CAM design and milling stages are fundamentally similar.

Both materials require the technician to consider:

• Restoration type
• Wall thickness
• Connector dimensions
• Milling strategy
• Tool condition
• Sintering shrinkage compensation
• Nesting position

The difference is not primarily in how the restoration is designed or milled, but in what happens after milling and before sintering.

One important consideration is that the final shade of zirconia is affected by its position and thickness. Therefore, material selection and nesting can be especially important when using pre-shaded or multilayer zirconia.

This is where the workflows can overlap.

A pre-shaded restoration may already have an appropriate basic shade, but the technician may still want to add individualized characterization.

For example, additional color treatment may be used to emphasize:

• Cervical chroma
• Occlusal anatomy
• Fissures
• Incisal effects
• Surface characterization

In this situation, the workflow becomes:

Pre-shaded zirconia → milling → optional characterization → drying → sintering

Therefore, pre-shaded zirconia should not be understood as a material that completely eliminates coloring. Instead, it can eliminate the need to create the basic shade from an uncolored zirconia blank.

The most important difference can therefore be summarized as:

White zirconia:
Milling → Coloring → Drying → Sintering

Pre-shaded zirconia:
Milling → Sintering

with cleaning, moisture control, and optional characterization added according to the specific workflow.

Not necessarily in every case.

The time saved mainly comes from eliminating or reducing the manual coloring and drying procedures.

For a laboratory producing many similar restorations, this can simplify the workflow because technicians do not need to individually establish the basic shade for every restoration.

However, the overall production time still depends on:

• CAD design
• Milling time
• Number of units
• Sintering cycle
• Required characterization
• Finishing and polishing
• Laboratory quality-control procedures

Therefore, the advantage of pre-shaded zirconia should be considered as workflow simplification, rather than simply assuming that every restoration will have a shorter total production time.

The key difference between white and pre-shaded zirconia is not the CAD/CAM milling process itself. It is the coloring stage before sintering.

With white zirconia, the laboratory normally needs to establish the basic shade after milling by applying a compatible coloring liquid, followed by sufficient drying before sintering.

With pre-shaded zirconia, the basic color has already been incorporated into the zirconia blank. This allows the laboratory to skip the conventional basic coloring step and simplify the workflow.