Porcelain build up technique

Dental ceramics is applied with specific brushes (of various shapes and sizes), in multiple layers. Each layer has to be separately fired in special furnaces at high temperatures (up to 1000 degrees Celsius or 1830 Fahrenheit). During the combustion process, porcelain and metal alloys develop extremely strong chemical bonds between them.

porcelain furnace

specific brushes used for porcelain build up

Dental porcelain shrinks during firing ; therefore, the dental technician must build artificial teeth about 25% bigger to compensate the shrinking process.

First, the powder corresponding to the desired shade is mixed with water. When porcelain is applied, it may have different colors (white, purple, pink) depending on the manufacturer. The final shade is obtained only after firing.

restoration after porcelain build up and before firing

Dental ceramics is applied in several layers (normally 4 but it can be more). During build up, the technician takes into account all the information received from the dental office (shade, other details).

Layer 1 - Primary or opaque layer

It is a thin layer positioned directly on the metal framework. It consists of specific ceramics that block the passage of light. The main objective is to mask the black color of the metal. After build up, the layer is fired at specific temperatures.

Layer 2 - Base Layer

It is the thickest layer, which gives the basic shape of the crown and defines its shade. Normally, the gum areas have a darker shade while the top areas a lighter one.

dental ceramics build up

Porcelain is applied on all desired sides of teeth, the proximal contacts are adjusted (these are the contacts with the adjacent teeth) and the occlusal side is defined (with cusps and grooves).

When the build-up is completed, the restoration is placed in the ceramic furnace for firing.

Layer 3 - Characterization layer

In this layer, specific features may be added to further improve the aesthetics and give the artificial teeth a close to natural look. Special colors may be added to mimic various anatomical or physiological conditions. For example :

• If teeth abrasion is present, a darker coloration can be given to the peak area to mimic the process.

• Colorations may be added to mimic various stains : nicotine staining, color changes caused by tartar, erosions etc.

• Sometimes, because of excessive bone loss or gingival recession, artificial teeth would appear "too long" or "over-stretched".

  In this case, a pink or red colored porcelain may be applied to the top areas to mimic the gums. This way, artificial teeth will not look "over-stretched".

red colored porcelain applied to the top areas.
if tooth-shade porcelain had been applied, artificial teeth would have appeared "over-stretched" and unsightly

slight brown colorations
on the occlusal side of a porcelain crown

Proximal contacts, occlusal contacts (both static and dynamic), gingival tissue contacts, the surface texture and the overall contour of the restoration are adjusted.

After the firing process, the restoration can be sent to the dental office for the final fitting appointment.

Layer 4 - Finishing or glaze layer

The glaze layer is the last layer and it is extremely thin. The glaze layer gives the restoration a smooth surface and the translucency that mimics the enamel or dentin. In this layer, minor shade adjustments can still be made (if required).

porcelain bridge
after glaze layer build up

porcelain crown
after glaze layer build up

It is possible to process dental porcelain using the CAD/CAM systems. As described in the previous chapter, there are some differences between the two techniques, each having certain advantages and drawbacks.