November 10, 2009
First off, my apologies for being a little incommunicado the last couple of days – had a lot going on, and just didn’t get around to writing anything for the blog…
Now for the news…
Our 3Shape software was updated yesterday with a new anatomy library that has been designed specifically for use with milled Full Zirconia Crowns (FZC). I think I’ve mentioned before that the new software already sported a new library when we took delivery of the scanner – the C15 library looks great on screen, and when we output it to our 3D Systems ProJet printer. However, our vendor determined that some of the detail present in a printed pattern was being lost during the milling process due to the diameter of the some of the tooling.
This new library has anatomical pits and fissures which are designed to compensate for the limitations of the machining process. We’ll do a few a units a take some photos to show the difference in the upcoming days.
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.
November 4, 2009
Earlier this week I detailed the method for using the 3Shape D700 scanner to manufacture a custom zirconia abutment and a pressable resin pattern – all from a single scan. I remitted that scan on Monday, and we received the abutment and Perfactory resin pattern this morning.
I am very pleased with the custom abutment. It appears to be an exact duplication of the on-screen design, and the fit of the interface is perfect. As I explained in the previous post, there is a bug in the software that does not allow me to output the data for the full contour resin pattern to our in-house 3D Systems ProJet printer, so I had to have the milling center print the pattern using their Perfactory system. I’m a little disappointed – the Perfactory pattern is short of the margins a good millimeter. I’m fairly certain this has to do with some parameter settings within the software set-up, and I could easily fine tune those settings if I had control over the whole process. However, for now we will have to settle for hand waxing the margins – not a big deal.
Here are some pics -
The abutment from the lingual (Notice the lingual margin is slightly supraginigival, like I stated in the previous post).
Here’s an incisal view -
And, with the Perfactory pattern in place - you can clearly see the short margin on the buccal.
We’re going to refine the pattern and fix the margins; then we’ll press, stain and glaze a e.Max restoration using an LT ingot. I will post pics of the final restoration sometime the early part of next week.
Note: Please look for our ads in the upcoming editions of the Northern Virginia Dental Society newsletter for information and pricing on Impaks™ – our new flat fee packages including Implant Tissue Model, Implant Analog, Custom Abutment (titanium or zirconia), and your choice of final restoration – available on several platforms including Noble Replace Select, Nobel Active, Branemark, Biomet 3i Certain, Straumann Bone Level and Zimmer Screw-Vent.
Or, if you can’t wait, send me an email and I will shoot you a PDF file of the ad (Doctors Only!)
November 3, 2009
Yesterday I posted an article on the 3Shape D700 scanner’s ability to design custom abutments and the final restoration – all from one scan. I showed a brief summary of the steps involved in creating a zirconia abutment and a full contour resin pattern that could then be pressed in Ivoclar’s lithium disilicate, e.Max.
I wanted to elaborate a little on other types of restorative options that can be designed using roughly the same methodology.
First, the abutment design can be milled in either titanium or zirconia. If one were to choose a titanium abutment for a posterior implant where esthetics may be not as important, it would be simple to follow the exact same steps as described in the previous post. The resulting full contour pattern could then be cast in the alloy of your choice. Or, if current cost of gold has you wishing for alternatives, the full contour data could be used to mill a Full Zirconia Crown (FZC – See this months’ Web Special!) providing you with a strong and tooth-shaded crown. (I personally haven’t tried this – I wonder what thickness of zirconia is necessary to prevent a gray cast emanating from the titanium? I suppose you could apply an opaquer to the coronal portion of the abutment, as long as you accounted for the thickness of the opaque application in the design process.) Finally, you might consider prescribing a Press-to-Metal restoration like our Pulse Interface crowns. The 3Shape software does a fantastic job of creating an anatomical coping based on the full contour data insuring adequate support of the pressed ceramic.
In the more esthetic areas of the mouth, let’s assume you select zirconia as the material for your abutment. We’ve already demonstrated the full contour pattern being used to press e.Max. And, just as simply as the aforementioned Press-to-Metal process, we could just as easily create an anatomical zirconia coping and a pressable pattern for use with CZR Press or PM9. Lastly, we could just output the anatomical zirconia coping and hand-layer the final restoration with Vita’s VM9 or Creation Zi-F ceramics. (Almost forgot – you can even chose to have the coronal portion of your zirconia abutment designed like an anatomical coping, then bake ceramic directly to the abutment for a simple, one-piece, screw-down restoration – provided the screw access hole is positioned correctly.)
Obviously, there are many alternatives provided by 3Shape and its “partners”. However, there are a few holes, so here’s my wish list -
1. Somebody at 3M needs to give serious consideration to allowing STL files from other scanners for use with the Lava milling machines. 3M has the number one brand of zirconia in the market place, but they’re rapidly losing market share. I think a major factor, aside from the high cost of Lava zirconia, is the quality of the Lava Scan software compared to other systems like 3Shape or DentalWings. Open architecture is the way of the future – bury your head in the sand and well, get buried…
2. This one’s for 3Shape – I like the custom abutment software, but there are elements of Nobel Biocare’s NobelProcera system that I would like to see adopted. First, I like the way NobelProcera’s system allows the user to automatically taper the coronal portion of the abutment at a user-defined angulation with a touch of a button. 3Shape’s tools for manipulating the abutment head could lead you to design an abutment with an undercut with respect to the path of insertion of the final restoration if you’re not careful. Also, the lack of an automatic paralleling tool for multiple abutments makes designing cases for bridgework tedious, at best.
Hey, nobody’s perfect!
But, you’re really close….
November 2, 2009
One of the main reasons we invested in the new D700 scanner from 3Shape was the ability to bring the design of our CAD/CAM custom abutments in-house. Up to this point, we’ve been using our Lava scanner and remitting this type of restoration to Atlantis – a system which has worked very well to date. However, the 3Shape software allows us to take the CAD process one step further -
Let me demonstrate -
First, we scan the working implant model with a proprietary scanning abutment provided by Glidewell Laboratories (BTW – Saylors Dental Laboratory was the first outside laboratory to obtain the full scan kit from Glidewell). The scan of the scanning abutment is then related to a computer-generated facsimile thus insuring the accuracy of the platform’s position and orientation for subsequent modelling -
The scanning abutment is removed and the soft tissue replica is replaced on the model, which is then rescanned. Once the tissue data is captured, the technician uses various CAD tools to model the final abutment which can then be milled in either titanium or zirconia. We chose zirconia for this particular case as the final restoration is prescribed as e.Max Press, which is perfect for our demonstration.
Here’s the design of the final abutment -
You can see that we have placed the margin 1mm below the height of the tissue on the facial, mesial and distal. The lingual margin is slightly supragingival (Take my word for it, I didn’t feel like taking another picture…)
At this point, we have basically duplicated the capabilities of the Lava/Atlantis system. However, 3Shape allows us to keep on keeping on…
Once we have the abutment modeled and the margin defined, a few simple keystrokes provides us with a full contour proposal of the final restoration. Using roughly the same set of CAD tools as we used to “sculpt” the abutment, we can modify this proposal to achieve a pretty darned good image of the final restoration which can then be output to a resin printer to fabricate a pattern which can be subsequently pressed, stained and glazed.
I personally recommend that our clients do an abutment try-in to verify the fit, and to check that no change has taken place in the gingival architecture that might result in an exposed margin when the final restoration is placed. If we run into that scenario, we can simply “drop” the margin (assuming that we have adequate material on the abutment above the implant), and the resin pattern can be easily modified to fit the “new” margin prior to pressing.
FYI – there is a small bug in the software that 3Shape is currently working to fix. Right now, because of the proprietary nature of the scanning abutment interfaces, the software will not allow a scanning laboratory to remit the abutment data for milling while simultaneously outputting an STL file of the final restoration which can then be used to print or potentially mill the final restoration. All files must be remitted to the milling center for fabrication. Not a huge deal, but I expect 3Shape will find a way around this little issue.
