FC ZI breakage

[subrisi]

I got two cases lately from the same Dr. That came back a month after seating with the FC ZI broken. The patients came in the office with the crown in their hands. There is not a smidge of cement inside the crown. I try to troubleshoot but am clueless. I have the feeling they broke because the crowns loosened and got canted, then one hard bite could have broken the crown??!! I also get confusing info on how to fire the ZI. Currently I use inSync for stain and glaze and it does not require a cooling cycle, but some say Zi's should get a cooling cycle especially at the glaze bake. I called Jensen, but they said no.
Please give me some input. Is this my fault or the Dr? How can this get fixed. I do only a very few FC ZI's. So getting 2 broken crowns back, this is like 30% remake.

 

[NicelyMKV]

I had a few break from one account. Couldn't figure it out until I happened to be in his office one day during a seating. The assistant had sparks flying across the room grinding on false markings. Had the crown a millimeter out and was still grinding. Micro fractures that eventually propagated and split the crown in pieces. Possibility?

Jason

 

[Andrew@KillianDental]

^ That's what i was thinking too. I Always wonder how some zirconia could even break in the mouth, thick bridges crowns or what not.

Grinding on the crowns with diamond tools without water cooling, maybe there was an existing fracture missed that spread? Have seen crowns look fine then a few glaze cycles and a fracture occurs or spreads.

As a dental tech who takes pride in his work seeing one of my crowns come back I assume its the doctors fault, have seen some pretty shady dentists. Cutting a crown in half and saying it broke in half... or after they cemented the wrong crown onto an abutment ask for it to be remade at lab expense.... soooo ya

But cant deny sometimes there are just things that cant be seen or missed.

For the sintering temps, always use the recommended rise and cooling temps for the zirconia used. There can be some variance in max temp but talking with the manufacturers of your zirconia will help you home that in. For glazing that's probably up to inSync. Whenever I have some questions or concerns I go right to the source. No time for RnD, i'm sure the RnD has been done, just have to find it.

 

[JohnWilson]

I am telling you its very very hard to have these units fracture. You all have seen the Glidewell sledgehammer video. We did it here in the lab to a crown with occ clearance of just 1.5 mm and I could not break it.

However two things affect fractures. Improper handling of the material in the green state and rapid heat up by adjusting improperly both in the lab and in the op. Improper tooling and use by assistants/clients lead to our biggest headaches. When a client starts off with me I call them and we have a conversation about the material. I ask poignant questions leading the client to see how much experience they have with the product and if they have the proper tooling to adjust and polish the restorations.

After we complete the conversation I make notes in the customer file about when and what we talked about. If a problem comes up I ask them to tell me their procedure for adjusting, if they deviated from the proper protocol I inform them again what the right way is and explain that the material while very tough is still all ceramic and needs to be treated correctly or the potential for fracture now and or after the delivery WILL be increased.

Lots of labs feel their job is over once they make a pretty crown. Picking up the phone to make sure you clients are on the same page on these things BEFORE they become a problem is both proactive and will set you apart from the big box labs.

It seems so basic but I can assure you that many labs rarely communicate in this fashion.

 

[charles007]

Great idea John.
Today I accidently got to see a FCZ being adjusted... the talk I had and free adjusting kit I gave last year ????????

WHY ME WHY ME WHY ME

 

[grantoz]

we have all been there is it me or him. just ask yourself one question is it happening with any other of you clients.if you are doing the same thing with all your crowns the only variable or as i like to call it random act is the dentist

 

[corona]

I got two cases lately from the same Dr. That came back a month after seating with the FC ZI broken. The patients came in the office with the crown in their hands. There is not a smidge of cement inside the crown. I try to troubleshoot but am clueless. I have the feeling they broke because the crowns loosened and got canted, then one hard bite could have broken the crown??!! I also get confusing info on how to fire the ZI. Currently I use inSync for stain and glaze and it does not require a cooling cycle, but some say Zi's should get a cooling cycle especially at the glaze bake. I called Jensen, but they said no.
Please give me some input. Is this my fault or the Dr? How can this get fixed. I do only a very few FC ZI's. So getting 2 broken crowns back, this is like 30% remake.

I think you better go back to finding out Exactly what the protocol is for heating and cooling FCZ. I believe the info you have been given is totally incorrect . The short of it all is zr has a very low thermal conductivity. So it takes loooonger to heat and you have to give it looonger time to cool down . IMO you definately need a cooling time for your FCZ. Go back to jensen or who ever makes your FCZ and get the right info . That is where the lab could be at fault. Chairside its all about what and how they adjust , Like John said , get a protocol from them .

Either way , get YOUR part right . you dont want ALL of your FCZs to come back . good luck . corona