Sameer Puri D.D.S. Bruxzir by Glidewell has become one of the most popular restorative options for clinicians. Bruxzir as we all know is a full contour zirconia restoration and zirconia is an extremely strong material. As the cost of gold went up and up, laboratories started to use zirconia copings instead of metal copings to eliminate the variable of gold cost from the restorations. This resulted in a less expensive restoration for the lab to produce and the doctor to purchase. The problem with these early zirconia restorations however was the layering porcelain that was used to cover the opaque zirconia copings.
While zirconia is a strong material, it is also opaque and un-esthetic. To overcome this, labs would layer the zirconia copings with traditional feldspathic porcelain which would give the material its esthetics. This worked great until the weaker layering porcelain started fracturing at a high rate. The failure rate of early zirconia based crowns was catastrophic in some studies as the layering porcelain sheered off in case after case. This was when the folks at Glidewell decided to create a full contour zirconia crown with no layering porcelain. Granted while some of their early restorations were not the most esthetic, newer versions of their Bruxzir restorations are more esthetic by making the zirconia more translucent. Bruxzir has become Glidewell's best selling restoration by a long shot because clinicians have a strong restoration that they do not need to bond and can cement it. The success rate with this material is extremely high. The natural question then leads to- why can't we mill full contour zirconia restorations chair side? Well, technically we CEREC users can. We have had access to Sirona's line of full contour zirconia blocks for years. They are called the inCoris blocks which you can see below. They are available in blocks for single units and longer blocks for bridge frameworks.
The problem with milling zirconia chair side is not the milling of the zirconia- the problem is sintering the material so that it can be placed in the patients mouth. Zirconia in its "green state" as its referred to is a soft material. Very easy and fast to mill. But in this state, it is so soft that it won't last in the patients mouth. You have to have it go through a phase transformation by placing it in a special oven which not only shrinks the material to its final size but also gives it its final strength. Similar to eMax as its milled in the softer state and crystalized in an oven to give it its final strength and characteristics.
To do this previously required a huge oven and at least a few hours of sintering time, often times overnight in the oven. This left the process of doing chair side crowns made from full contour zirconia a laboratory procedure. Today, Sirona has recently introduced its fast zirconia sintering oven, the inFire HTC Speed. This oven can sinter a zirconia crown in about 10 minutes. This essentially means that creating a zirconia crown takes no longer to do than to create any other type of crown in any other type of material with the CEREC.
This innovation in sintering zirconia means that those clinicians who will only place metal or a Bruxzir in a patients mouth now have the opportunity to buy a CEREC and use an extremely strong material in the patients mouth. Innovations like this simply mean that CAD/CAM is no longer only for those clinicians who are comfortable with bonding and using all ceramic on molars. Many clinicians prefer cementation and using a Bruxzir type material. Those clinicians can now look at CEREC as an option in their practice.
