OZA – What is it, and is it Viable?

November 5, 2009

OZA™  - One-piece Zirconia Abutment

I’m trademarking the name, just in case today’s pseudo-experiment is a viable restorative option.

Here’s the deal -

We have clients who occasionally request one-piece screw-retained prostheses.  We usually fill the order in one of two ways.  Most commonly a  metal abutment featuring an anatomical coronal portion that has been cut back for porcelain application is cast in a ceramic alloy and then veneered.  Like most everyone else I know, we’ve had our fair share of ceramic chipping around the screw hole, so we gently insist that the screw channel be waxed into occlusion.  This leaves exposed metal on the occlusal surface of the restoration, but that’s the compromise we make…

We’ve also done a few cases involving single anteriors where a zirconia abutment is milled – again, with an anatomical coronal portion – and then veneered with Creation Zi-F or Vita’s VM9.  Leaving the screw channel in zirconia isn’t that big of an issue in these cases because the lingual surface of upper anterior teeth aren’t usually consider part of the “.

I never liked the exposed metal screw channel on posterior restoration’s done in the manner described above, and then I started thinking about how our shaded Full Zirconia Crowns (Crystal) are becoming increasingly popular, so I decided to try putting the two ideas together.

Using 3Shape’s D700 scanner, and their abutment software, I managed to create an OZA™ -

Here’s a buccal view of my proposal -

And, an occlusal view -

(Please note that the software really isn’t geared towards this particular use, so I had to do a fair amount of on-screen manipulation of the original abutment proposal – I think i could do a little better job on the tooth morphology, but I have a few other things that need to be done today)

Now, here’s the proposal with the screw hole shown -

Of course, I would have preferred the screw hole to be a little more centrally located, but this isn’t a practical case, so I will live with this result.

Here’s a buccal view where I’ve dialed up the translucency of the individual elements so you can see what’s going on below the tissue -

I have no idea whether or not this type of restoration would be viable in the mouth.  One problem that I need to look into is  - can the milling center shade the zirconia used in fabricating the abutments?  I can’t imagine why not, but I will check and if they can I’m going to remit an OZA™ for them to mill, and will post the results.

In the meantime – if anyone has any thoughts on whether or not zirconia would hold up under these circumstances, I would like to hear from you.

© 2009, Jeff Saylors. All rights reserved.