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

Zirconia frameworks and zirconia crowns

Zirconia is becoming one of the most common dental ceramic used for good reason.  It’s strong, like really strong, and the esthetics are improving.  It can be used as the framework for a full arch restoration supported by implants and without porcelain looks like this.


Zirconia framework

The completed case above can be found here.

The full contour ziroconia crowns are looking better and better.  One popular name brand is Bruxzir.  This material is my go to for posterior restorations and with Prettau anterior, or similar, may be used more and more in the anterior as well.

zirconia dental crown

Zirconia dental crown

These products are CAD CAM, completed by either soft or hard milling.  The process involves scanning and digitizing the area being restored either directly or of off a model or impression of that area.  The software then is used to design the prosthesis (crown or framework).  Finally a 5-axis mill is used to fabricate the prosthesis.

When hard milling the zirconia is presintered and processed by hot isostatic pressing. It is then machined by using a more powerful milling system.  The milling components wear out faster when the zirocnia is in a harder state so milling is primarily done by soft milling.

In soft milling the process is very similar but the sintering is done after the milling.  There is significant shrinkage when sintering (typically 20-25% depending on exact make up of zirconia) so the process must be done by computers to be accurate.

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