Long Span Implant Retained Bridges - Problem With Breaking

[JohnWilson]

Bernard thanks.
HI John,
I agree with many of your pros and cons, would love to discuss a little more.
1. Weight, we stopped providing conventional hybrid restoration in 1990 due to breakage of teeth and or acrylic. At that time we moved all these cases to porcelain to gold. Some patient with severe bone loss would require 22-23 mm of restorative material. I remember cases that had close to 3 ounces of gold in the casting. That said, we never ever had a patient comment on weight.
4. You're right about the best verification jigs having a possible discrepancy. That said, Isn't it more about tension on the implant-bone interface than the tension on the CAD base?

I hear you Bob, so glad the days of 65sf casted bars and substructures are a thing of the past. I always think of the one bar I did when we calculated the wax weight we needed to throw 3.6oz just for the pattern and then double that for the runner bar/sprue and button. I watched the casting tech do this one and I am sure having me watching made it even worse. Thank god for no splash and the thing worked but I always hoped for a better way.

As to the verification I mentioned, I noticed that when a verification jig gives a false reading its because the analog is often too LOW in the model and this allows the jig to seat in the mouth and unless the client is taking perfect radiographs at exactly a right angle to the fixture the film will look like everything is correct.

This leads to the screw constantly pulling and essentially extracting the cad base from the zirconia as its constantly under tension and is not bottomed out in the morse taper of the implant. This is when I see things start to go sour down the line.

 

[JohnWilson]

By the way John Wilson doing these cases with Ti bar and Zi top [davis bridge] you can reduce the the bulk greatly .I have done cases with only 6-7 mm in height in places the case is going strong for over 5 years now ,you can also save a lot of headaches on the really thick ones doing it this way.I actually charge less for zi ti because its more straight forward and a lot less manufacturing probs.

And you can fit the case in a much smaller disk as well I have a few in the lab that I am trying some interesting paths with right now.

 

[Labwa]

We are getting a little off topic but there are Interesting points everyone is bringing up and I think all interesting.
as a bit of background we do a heap of immediate AO4 using milled titanium frames in house Pressed with ivobase. We would like to think they are on the higher end of what is done in 48 hours post surgery but also up there with what would take 3-4 weeks (going to Nobel for frame) and we have had really good results over the last 4 years in terms of breakages (touch wood). To put a number on it we would be at less than 1 percent adjustment (mainly to tissue contacting areas) or repair of teeth which has been due to occlusion in most cases.
As the technology has become more accessible we are able and should be able to produce these types of restorations more efficiently to price them under zirconia as an option. Is it a final? Yes I think so. Are floating cast bars or PMMA's finals. No I don't think so.
We price the full zirconia arches above our hybrids based on the level of difficulty and cost of experience. I would be interested to understand if others see things differently.

 

[Affinity]

lachlan, you charge more for zr, but what is the difference in labor? It seems like it would be faster, labor-wise, to process a zr arch, as opposed to milling a bar, waxing up and cutting teeth, boilout, process, polish etc.

 

[Labwa]

Not at all I find Zirc full arches a lot more time consuming. I probably spend 50 percent less time on a hybrid than a full arch Zirc.

 

[BobCDT]

So many labs are doing the screw retained full denture tooth set-up for a try-in before going to a full zirconia case. If this is the workflow any of you use there are obvious labor savings to simply convert that to a hybrid.