Zirconia framework for implant supported hybrid denture – crowns too! How are they milled?

Zirconia framework and zirconia milling

Zirconia framework option for an all on 4 can be a great framework option for an all on 4. The properties of  zirconia make it one of the most common dental ceramic in use.  It’s strong, like really strong, and the esthetics are improving.

Zirconia framework milling for an all on 4.

We can use a zirconia framework for a full arch restoration supported by implants and without the porcelain, the framework looks like this. To learn more about the laboratory side of zirconia frameworks and research on zirconia frameworks check out our zirconia substructure page.

Picture of a milled zirconia framework.

Zirconia framework

The patient’s story for the above all on 4 is found here.

Zirconia dental crown milling.

The full contour zirconia crowns are looking better and better.  One popular name brand is Bruxzir.  This material was my go to for posterior restorations for years. There are now even more esthetic options like Prettau anterior, which I use in both the posterior and the anterior. A very esthetic and natural looking case of zirconia crowns on 6 dental implants can be seen here.

A milled zirconia dental crown.

Milled zirconia dental crown

So how does a lab or dental office mill a zirconia framework or a zirconia crown?

These products are CAD CAM, and a lab will either soft or hard mill the product from a puck.  The process involves scanning and digitizing the area we plan on restoring either directly or of off a model or impression of that area.  Digital impressions for dental implants are still not as accurate as traditional impressions but I am sure that will change. Once the area is in a digital form we use the software to design the prosthesis (crown or framework).  Finally we use a 5-axis mill to fabricate the prosthesis.

Hard milling of zirconia

When hard milling we presinter the zirconia and process by hot isostatic pressing. We then mill the zirconia with a more powerful milling system.  When hard milling, the milling components wear out faster when the zirconia is in a harder state, therefore almost everyone that mills does soft milling.

Soft milling of zirconia

In soft milling the process is very similar but we sinter after milling.  There is significant shrinkage when sintering (typically 20-25% depending on exact make up of zirconia) so we use computer software to ensure the final product is accurate.

 

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