Zirconia the Third

We’ve had the Katana STML zirconia for a while, but haven’t seen much of its use due to two reasons. One is that our version only comes in disc-form, so in order to mill it I’d have to break out the big MCX5 5-axis milling machine, instead of the much more convenient and faster 4-axis MCXL. Milling speed aside, the other issue is that the Katana cannot be fired using an accelerated program like SpeedFire, so it’ll take the full 5 hours to sinter. This means that I can’t use it for single-visit dentistry. First world problems, I know.

But it does look pretty, I have to admit. Here’s a sample image of my case that was presented at last year’s symposium:

Four-unit anterior bridge with monolithic zirconia and external stain only.

It wasn’t perfect, but for zirconia without layered veneer I was kind of blown away by its translucency. Here’s a more recent case from a few days ago:

Single molar crown, monolithic with external staining only.

I would say about 90% of my prosthodontic work is single-visit, so it’s rare that I get a chance stall some time with temporaries and work on something like this. Still, I think these super translucent zirconia will be quite disruptive on the CAD/CAM market once they become more ubiquitous. Even with a strength reduction due to the cubic transformation, we’re still looking at 500 – 700 MPa of flexural strength and only minor reductions in fracture toughness. In other words, still stronger than all the other strongest lithium silicate ceramics. If these new, 3rd generation zirconia can catch up in the aesthetics department, then the only real disadvantage they have is the lack of bonding.

Oh, and please get them into a SpeedFire please. If I can get me some 15-minute sinter super translucent zirconia, that’d be great thanks.