cracked zirconia bridge

[Ryan Gottlieb]

i need a little help on this one.
this was milled with Cap FZ
colored with ZirckonZahn water based liquids
dried under heat lamp for about 1 hour
sintered in sintra plus (parameters pictured below)
i inspected the green state under microscope and didn't see any cracks prior to sintering.
i inspected the bridge after sintering and it looked and fit fine.
came in this morning (48hrs later) and was shocked to find this crack.
ideas?

 

[ts4341]

Sorry Ryan to see this.. so much time invested into these cases
Im not a fan of Sintra Plus..

I would have used this program for that big bridge:
4c up - 900c hold 60mins - 2c up 1560c 2hr hold - 4c down to 900c hold 30mins - 6c to natural

 

[JohnWilson]

I prefer a tripod style of bar placement and less mass in the sintering brace. We do it with 3mm bars and only 3, I am not saying thats what caused this to fracture. Weiland has a PDF somewhere that states you only need two but it scares me too much.

We all know there are times we do absolutely everything right and things fail. BTW Tads program is similar to mine and the SINTRA is a fine machine that did not cause this. Is this the recommended program for large bridges from CAP?

good luck

 

[Ryan Gottlieb]

I prefer a tripod style of bar placement and less mass in the sintering brace. We do it with 3mm bars and only 3, I am not saying thats what caused this to fracture. Weiland has a PDF somewhere that states you only need two but it scares me too much.

We all know there are times we do absolutely everything right and things fail. BTW Tads program is similar to mine and the SINTRA is a fine machine that did not cause this. Is this the recommended program for large bridges from CAP?

good luck

can you explain the tripod style?

 

[JohnWilson]

You can mill with as many bars as you like but see how I have 3 larger sinter bars and a hollow brace. I also use drops and sinter horizontally. I section the other bars prior to sintering

 

[ts4341]

I know the Sintra didn't cause the crack... Prob the mass and sintering program..
I had issues with our Sintra that makes me pull my hair out, but we have over come most of them now. The MS6000 other than size capacity has been perfect. Next up, we are looking at the Vario S400

 

[Sevan P]

Ryan can you post a pic of the incisal view straight down? How think is the in between area? Maybe it snapped cause it was too thin.

 

[Ryan Gottlieb]

I will post more pics tomorrow.
The interesting thing is that there is an actual gap (you can see light pass through).

 

[Sevan P]

I will post more pics tomorrow.
The interesting thing is that there is an actual gap (you can see light pass through).

yeah, most likely to thin and with the Zr trying to sinter 360 degrees, pop!

 

[Patrick Coon]

I know with our materials we would recommend drying something this large 4+ hours before sintering. Not sure if this would cause it crack 48 hours after sintering though. I would expect problems sooner (during sintering),but maybe the crack started during sintering and propagated as it sat.

I would also agree with John on the sintering support. The behind the support is that you have approximately the same mass in it as you do in the restoration, this helps to even the contraction of the material as it sinters and cools. We would definitely recommend the cuts as John show in his picture, You can even place units in this area to mill and cut them out prior to sintering, avoiding some unused material.

 

[Ryan Gottlieb]

How do I create that type of support bar using sum 3d?

 

[Sevan P]

How do I create that type of support bar using sum 3d?

You can't that's the only support type there is in there.

 

[JKraver]

Did one of your employees pick it up?/drop it?

 

[zero_zero]

How do I create that type of support bar using sum 3d?

I believe is possible using the curve functions to design custom support bars...might need to tweak the strategies too... alternatively it can be created and attached with ease by most CAD software out there...

 

[grantoz]

Its simple round off in between the teeth along the incisal edge its way to sharp and the crack starts there.You wouldnt do that with any other ceramic.

 

[Ryan Gottlieb]

I fired it without any support bar and the fit was absolutely perfect.