Long Span Implant Retained Bridges - Problem With Breaking

CAD-CAM Jedi

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First off, I want to start by saying how appreciative I am for the regular posters on this forum. I have for a long time been just a lurker, but have learned so much from the information you guys continue to provide online. I should definitely help and post more often. I just wanted to start off by thanking the regular guys that post on this sub like JohnWilson, Al., rkm_rdt, CatamountRob, Sideshowbob, Sevan, Bob-CDT, Travis, CoolHandLuke, zero_zero, JMN etc. I know I am missing a few, but please know your knowledge is appreciated.

The reason why I am writing today is that I have been having some major issues with long span zirconia bridges breaking. I am at a loss for what is causing it and was hoping maybe you guys can help shed some light. I took some time today to read through the Zirconia forum to see if anyone else has experienced similar issues, but it is hard to isolate what exactly is causing this.

Basically, the situation I am having is that doctors are sending me back broken bridges that are sectioned clean. I don't know what in my manufacturing process is causing them to do that. Some of these bridges cracked after just 2-3 weeks. I will detail my process as follows:

So we follow the basic protocol of verifying the cast with a series of jigs, verification bridges, etc. Our final master cast is verified using a stone jig, due to how brittle stone is. We noticed when we were using PMMA alone, there was still slight flex that would occur, that would cause the final zirconia prosthesis not to seat. Since then, we have been using gypsum stone verification jigs to make sure that the implant coordinates are properly recorded. If there is any variance at all, the stone will break, and we will correct the master cast.

After we have verified the master cast, design, aesthetics, etc. We then go to producing the final zirconia bridge off of the verified scans, etc. When producing the bridge, we almost always use a Roland DWX-50 with a set of CAP Ultra burs that are specifically used for small amounts of time, and only for these large bridges. After the bridge is milled, we will use a carbide bur to cut it out of the disk and shave down the sprues. To complete the removal of sprues, we will then use a bur made for smoothing zirconia to remove any last traces of the sprues.

After removing the sprues, we will stain the bridge using Zirkon Zahn stains. It then gets placed under a heat lamp for 40 min - 1 hour. After it is dried, we sinter using either a Sirona inFire Speed or a Sintra furnace. The zirconias we are using for these bridges are the Katana ML and DentalDirekt BioZX. The cycles used in either furnace are posted as images. When using the cycle for DDBioZX, we use the long program (3.2) and we have a max temp of 1530 degrees Celsius. When running the katana cycle, it recommends a max temp of 1500 degrees, but we run it at 1550 degrees Celsius. All of our furnaces are calibrated as well, so the units are getting to the proper temperature.

After the bridges come out of the furnace, we have a guy that finishes them. There is a bit of a language barrier but I spoke with him today on his finishing process. He is using an older porcelain oven with vacuum (NEY Centurion Q100) when applying glaze and finishing these bridges. He has a low temp of 1000 degrees Fahrenheit, and a high temp of 1680 degrees Fahrenheit. He cools for about 30 minutes and dries for 30 minutes. When he cools, he cools at a rate of 100 degrees Fahrenheit per minute. I think he may be cooling too rapidly, but don't know enough about the stain/glaze cycles to say otherwise. He also may run this cycle a number of times depending on how he finishes the case, how many times he has to glaze, etc. I don't know if this is where the integrity of the zirconia is being weakened to where it breaks intraorally. I have had close to 6 long span, monolithic implant bridges break like this on me and I have no idea what to do to resolve the issue going forward. I dont want to just keep milling the same thing and following the same procedure just to lead to a frustrated dentist, and an unhappy patient. If anyone has any advice, or suggestions at all it would be greatly appreciated. Thank you for taking the time to read my long post!

tl;dr:
Monolithic long span zirc bridges are breaking left and right. Following the same manufacturing protocol everyone else seems to use. CCan'tfigure out what in the manufacturing process is causing a defect in the zirconia for it to break like this. IMG_0944.JPG IMG_0945.JPG IMG_0944.JPG IMG_0945.JPG IMG_0946.JPG IMG_0947.JPG IMG_0948.JPG
 

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Sda36

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First off, I want to start by saying how appreciative I am for the regular posters on this forum. I have for a long time been just a lurker, but have learned so much from the information you guys continue to provide online. I should definitely help and post more often. I just wanted to start off by thanking the regular guys that post on this sub like JohnWilson, Al., rkm_rdt, CatamountRob, Sideshowbob, Sevan, Bob-CDT, etc. I know I am missing a few, but please know your knowledge is appreciated.

The reason why I am writing today is that I have been having some major issues with long span zirconia bridges breaking. I am at a loss for what is causing it and was hoping maybe you guys can help shed some light. I took some time today to read through the Zirconia forum to see if anyone else has experienced similar issues, but it is hard to isolate what exactly is causing this.

Basically, the situation I am having is that doctors are sending me back broken bridges that are sectioned clean. I don't know what in my manufacturing process is causing them to do that. Some of these bridges cracked after just 2-3 weeks. I will detail my process as follows:

So we follow the basic protocol of verifying the cast with a series of jigs, verification bridges, etc. Our final master cast is verified using a stone jig, due to how brittle stone is. We noticed when we were using PMMA alone, there was still slight flex that would occur, that would cause the final zirconia prosthesis not to seat. Since then, we have been using gypsum stone verification jigs to make sure that the implant coordinates are properly recorded. If there is any variance at all, the stone will break, and we will correct the master cast.

After we have verified the master cast, design, aesthetics, etc. We then go to producing the final zirconia bridge off of the verified scans, etc. When producing the bridge, we almost always use a Roland DWX-50 with a set of CAP Ultra burs that are specifically used for small amounts of time, and only for these large bridges. After the bridge is milled, we will use a carbide bur to cut it out of the disk and shave down the sprues. To complete the removal of sprues, we will then use a bur made for smoothing zirconia to remove any last traces of the sprues.

After removing the sprues, we will stain the bridge using Zirkon Zahn stains. It then gets placed under a heat lamp for 40 min - 1 hour. After it is dried, we sinter using either a Sirona inFire Speed or a Sintra furnace. The zirconias we are using for these bridges are the Katana ML and DentalDirekt BioZX. The cycles used in either furnace are posted as images. When using the cycle for DDBioZX, we use the long program (3.2) and we have a max temp of 1530 degrees Celsius. When running the katana cycle, it recommends a max temp of 1500 degrees, but we run it at 1550 degrees Celsius. All of our furnaces are calibrated as well, so the units are getting to the proper temperature.

After the bridges come out of the furnace, we have a guy that finishes them. There is a bit of a language barrier but I spoke with him today on his finishing process. He is using an older porcelain oven with vacuum (NEY Centurion Q100) when applying glaze and finishing these bridges. He has a low temp of 1000 degrees Fahrenheit, and a high temp of 1680 degrees Fahrenheit. He cools for about 30 minutes and dries for 30 minutes. When he cools, he cools at a rate of 100 degrees Fahrenheit per minute. I think he may be cooling too rapidly, but don't know enough about the stain/glaze cycles to say otherwise. He also may run this cycle a number of times depending on how he finishes the case, how many times he has to glaze, etc. I don't know if this is where the integrity of the zirconia is being weakened to where it breaks intraorally. I have had close to 6 long span, monolithic implant bridges break like this on me and I have no idea what to do to resolve the issue going forward. I dont want to just keep milling the same thing and following the same procedure just to lead to a frustrated dentist, and an unhappy patient. If anyone has any advice, or suggestions at all it would be greatly appreciated. Thank you for taking the time to read my long post!

tl;dr:
Monolithic long span zirc bridges are breaking left and right. Following the same manufacturing protocol everyone else seems to use. CCan'tfigure out what in the manufacturing process is causing a defect in the zirconia for it to break like this. View attachment 26674 View attachment 26675 View attachment 26674 View attachment 26675 View attachment 26676 View attachment 26677 View attachment 26678
Can't say for sure but your porcelain furnace has a clam shell opening mechanism? Could be too rapid a cooling rate or uneven cooling. I would seriously shut the power off on your furnace, at the end of the cycle and leave until you know it's likely at room temp. The biggest thing with these babies is slow up and down.

Hope this helps you[emoji4]
 
RCKSTR

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Are you using a stabilizer block when it sinters? My bet is the bridge is twisted slightly, when it gets torqued down puts pressure on the zirconia, eventually, it will snap.
 
R

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Do you know what temp your sintering oven opens at? I find sometimes sintering ovens open up at too high of a temp with these type of restorations. The mass of zirconia is not cool enough when the door opens which can cause cracking.

Also, your heat and cool rate for applying porcelain should be around 20 - 30 degrees per minute depending on the volume of material.

I hope this helps
 
CatamountRob

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I just wanted to start off by thanking the regular guys that post on this sub like JohnWilson, Al., rkm_rdt, CatamountRob, Sideshowbob, Sevan, Bob-CDT, etc. I know I am missing a few, but please know your knowledge is appreciated.

You'd have had way more credibility here if you hadn't included CatamountRob on that list......
 
CAD-CAM Jedi

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Can't say for sure but your porcelain furnace has a clam shell opening mechanism? Could be too rapid a cooling rate or uneven cooling. I would seriously shut the power off on your furnace, at the end of the cycle and leave until you know it's likely at room temp. The biggest thing with these babies is slow up and down.

Hope this helps you[emoji4]

This specific porcelain furnace we are using does not use a clamshell opening mechanism. I do think it might be too rapid a cooling rate or uneven cooling, I just need to figure out how I can isolate that as the problem. The issue is that there is no visible sign showing the integrity of the zirconia has decreased. They look perfect when they leave the lab, and then come back looking like the pictures. Do you have any recommendations on cooling rates for zirconia? Either in the sintering or in the glazing

Are you using a stabilizer block when it sinters? My bet is the bridge is twisted slightly, when it gets torqued down puts pressure on the zirconia, eventually, it will snap.

Yeah, we are always using a stabilizer block. I read in a previous post that you only want to have no more than 4-5 sprues holding the bridge to the block so I will try reducing the sprues from here on out.
 
CAD-CAM Jedi

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Do you know what temp your sintering oven opens at? I find sometimes sintering ovens open up at too high of a temp with these type of restorations. The mass of zirconia is not cool enough when the door opens which can cause cracking.

Also, your heat and cool rate for applying porcelain should be around 20 - 30 degrees per minute depending on the volume of material.

I hope this helps

The Sirona inFire Speed oven opens first around 900 degrees Celsius. It opens just a crack and slowly opens very little as the temp decreases.
The Sintra stays closed completely until about 400 degrees Celsius until it starts to open and come down.

When you talk about the heat and cool rate for the porcelain, are the temperatures in F or C? Most of these bridges that broke on me all were monolithic zirconia. Some with pink porcelain.
 
CAD-CAM Jedi

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You'd have had way more credibility here if you hadn't included CatamountRob on that list......

hahaha you're a funny guy! I hear you are the go to DLN hunting expert as well!
 
Contraluz

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Basically, the situation I am having is that doctors are sending me back broken bridges that are sectioned clean. I don't know what in my manufacturing process is causing them to do that. Some of these bridges cracked after just 2-3 weeks. I will detail my process as follows:

I don't have too much knowledge in respect to the milling and sintering. Others have chimed in not that. However, there are so many things that can go 'wrong' with bridges this size. You have to adhere to a very tight protocol. From start to finish!

Just a few points, I think are important:

After sintering, make sure you don't grind into the connectors and, make sure your connectors are as 'big' as possible. If using high speed, always use a hand piece with water cooling. In general, be very gentle when grinding on a frame like that! Have you tried those green 'diamond stones' from Jota?
Use a very slow heating and cooling program, when firing porcelain, or glazing. You mention something of an old furnace that is used to glaze. If you can not dial in precisely the firing parameters, I would refrain from using it. Also, I always do a 'regeneration' firing, after refinishing the frame.

One other factor, on lower arches, the flex of it can cause problems, too.

Hope this helps
 
CAD-CAM Jedi

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I don't have too much knowledge in respect to the milling and sintering. Others have chimed in not that. However, there are so many things that can go 'wrong' with bridges this size. You have to adhere to a very tight protocol. From start to finish!

Just a few points, I think are important:

After sintering, make sure you don't grind into the connectors and, make sure your connectors are as 'big' as possible. If using high speed, always use a hand piece with water cooling. In general, be very gentle when grinding on a frame like that! Have you tried those green 'diamond stones' from Jota?
Use a very slow heating and cooling program, when firing porcelain, or glazing. You mention something of an old furnace that is used to glaze. If you can not dial in precisely the firing parameters, I would refrain from using it. Also, I always do a 'regeneration' firing, after refinishing the frame.

One other factor, on lower arches, the flex of it can cause problems, too.

Hope this helps

Contraluz,

Thanks for your response. I will make sure to lower my heating and cooling rates. I am able to dial in the parameters on my furnace. How do you like the diamond stones from Jota? Also what do you mean by 'regeneration' firing?
 
Contraluz

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Contraluz,

Thanks for your response. I will make sure to lower my heating and cooling rates. I am able to dial in the parameters on my furnace. How do you like the diamond stones from Jota? Also what do you mean by 'regeneration' firing?

This is from an older thread:
It is a firing cycle before applying your first layer of porcelain, after adjusting your framework (which should be minimal, anyway (one can dream...) The following quote is from an article (found here: http://dentalnews-articles.blogspot.com/2015/03/how-to-prevent-failure-of-veneered.html):

"E.max ZirCAD and VITA In-Ceram YZ don’t allow sandblasting or grinding the framework, since this can damage the surface leading to undesired phase transformation and jeopardize the bond with the layering ceramic. In case of minor correction after sintering, a thermal treatment (regeneration firing) can reverse any phase transformation."

I like the Jota stones very much. Although rather on the expensive side, since they don't last as long as others. They grind gently at low speed. It feels less aggressive than the regular green diamond stone.
 
R

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The Sirona inFire Speed oven opens first around 900 degrees Celsius. It opens just a crack and slowly opens very little as the temp decreases.
The Sintra stays closed completely until about 400 degrees Celsius until it starts to open and come down.

When you talk about the heat and cool rate for the porcelain, are the temperatures in F or C? Most of these bridges that broke on me all were monolithic zirconia. Some with pink porcelain.

The temps are in Celsius.

In regards to the sintering. I think the open temp is way too high and could be a big part of the issue. I have always waited until the oven reaches at least 300 c before the table drops.
 
Affinity

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Maybe you should start thinking about using a material other than zirconia..
 
Ken Knapp

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First off, I want to start by saying how appreciative I am for the regular posters on this forum. I have for a long time been just a lurker, but have learned so much from the information you guys continue to provide online. I should definitely help and post more often. I just wanted to start off by thanking the regular guys that post on this sub like JohnWilson, Al., rkm_rdt, CatamountRob, Sideshowbob, Sevan, Bob-CDT, Travis, CoolHandLuke, zero_zero, JMN etc. I know I am missing a few, but please know your knowledge is appreciated.

The reason why I am writing today is that I have been having some major issues with long span zirconia bridges breaking. I am at a loss for what is causing it and was hoping maybe you guys can help shed some light. I took some time today to read through the Zirconia forum to see if anyone else has experienced similar issues, but it is hard to isolate what exactly is causing this.

Basically, the situation I am having is that doctors are sending me back broken bridges that are sectioned clean. I don't know what in my manufacturing process is causing them to do that. Some of these bridges cracked after just 2-3 weeks. I will detail my process as follows:

So we follow the basic protocol of verifying the cast with a series of jigs, verification bridges, etc. Our final master cast is verified using a stone jig, due to how brittle stone is. We noticed when we were using PMMA alone, there was still slight flex that would occur, that would cause the final zirconia prosthesis not to seat. Since then, we have been using gypsum stone verification jigs to make sure that the implant coordinates are properly recorded. If there is any variance at all, the stone will break, and we will correct the master cast.

After we have verified the master cast, design, aesthetics, etc. We then go to producing the final zirconia bridge off of the verified scans, etc. When producing the bridge, we almost always use a Roland DWX-50 with a set of CAP Ultra burs that are specifically used for small amounts of time, and only for these large bridges. After the bridge is milled, we will use a carbide bur to cut it out of the disk and shave down the sprues. To complete the removal of sprues, we will then use a bur made for smoothing zirconia to remove any last traces of the sprues.

After removing the sprues, we will stain the bridge using Zirkon Zahn stains. It then gets placed under a heat lamp for 40 min - 1 hour. After it is dried, we sinter using either a Sirona inFire Speed or a Sintra furnace. The zirconias we are using for these bridges are the Katana ML and DentalDirekt BioZX. The cycles used in either furnace are posted as images. When using the cycle for DDBioZX, we use the long program (3.2) and we have a max temp of 1530 degrees Celsius. When running the katana cycle, it recommends a max temp of 1500 degrees, but we run it at 1550 degrees Celsius. All of our furnaces are calibrated as well, so the units are getting to the proper temperature.

After the bridges come out of the furnace, we have a guy that finishes them. There is a bit of a language barrier but I spoke with him today on his finishing process. He is using an older porcelain oven with vacuum (NEY Centurion Q100) when applying glaze and finishing these bridges. He has a low temp of 1000 degrees Fahrenheit, and a high temp of 1680 degrees Fahrenheit. He cools for about 30 minutes and dries for 30 minutes. When he cools, he cools at a rate of 100 degrees Fahrenheit per minute. I think he may be cooling too rapidly, but don't know enough about the stain/glaze cycles to say otherwise. He also may run this cycle a number of times depending on how he finishes the case, how many times he has to glaze, etc. I don't know if this is where the integrity of the zirconia is being weakened to where it breaks intraorally. I have had close to 6 long span, monolithic implant bridges break like this on me and I have no idea what to do to resolve the issue going forward. I dont want to just keep milling the same thing and following the same procedure just to lead to a frustrated dentist, and an unhappy patient. If anyone has any advice, or suggestions at all it would be greatly appreciated. Thank you for taking the time to read my long post!

tl;dr:
Monolithic long span zirc bridges are breaking left and right. Following the same manufacturing protocol everyone else seems to use. CCan'tfigure out what in the manufacturing process is causing a defect in the zirconia for it to break like this. View attachment 26674 View attachment 26675 View attachment 26674 View attachment 26675 View attachment 26676 View attachment 26677 View attachment 26678
It's not surprising.
1) Zirconia does not bend it will break in tension.
2) Delayed tension break from preloaded tension. Bridge was in tension when cemented and normal stress cycling (tension/compression) pushed it over the edge to failure.
3) The larger the span the higher probability of encountering a defect/void in the zirconia and hence failure. There are defects and voids in every block of zirconia, varies among supplier and process. Small defects are not noticeable in single units and most bridges. However, large spans have a greater chance of a defect and also have higher tensile stresses.

Were the implant abutments cemented first to the zirconia and then torqued or bridge was cemented over torqued abutments?
 
JohnWilson

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Ill chime in

I have a fair bit of experience with these big arches, everything I read in your post sounds great. Just be certain that its true.

I see some interesting things from the pictures.

When ever I see a fracture and one of the cad bases are out its a model verification issue in my opinion. Another observation is the cad bases that has all the stain/tarter on it below the seating surface again leads me to believe the prosthetic was not fully seated. When I look closely at the cad bases it appears they are rounded over hexed units and not prefab Non eng cad bases???? Maybe its the picture? All of these things will lead to have instability and torque to the appliance.

Anyhow your protocol on your side based on your description of how you verify the cast sounds great but are you putting you clients to the test prior to moving on with ANY design? Really hard to fool a stone jig but not impossible.

Everyone of my 450 arches that I have in the mouth over the last 3.5 years have confirmation sent to me. I have had some fail early on and MANY MANY fail in the lab but I know when I look at why in the lab failures happen its always human error.

I need quality images of EVERY fixture and they must be taken at a right angle to the table of the fixture or I will not proceed to a beta let alone a final restoration. Too often the film is taken with a descending angle which can give you a false sense of accuracy.

Hold them accountable. Use the correct zirconia for the case, minimize post sinter modification, and above all else maintain the correct dimensions by doing a survey with your 2d cross section tool. This material is super strong and for it to midline fracture is rare, generally its distal extensions that fail due to poor ap and techs/dr's pushing to get more occlusion than they should. Also that case with gingiva is not designed appropriately for a bunch of reasons and the dimensions are not suitable in my opinion. Not saying thats why it broke but anyhow.

Its super frustrating to have failures and super dangerous when these sorts of cases fail in the mouth, ask more questions and above all else learn to say NO when you know things are not ideal. Good luck
 
Ken Knapp

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Ill chime in

I have a fair bit of experience with these big arches, everything I read in your post sounds great. Just be certain that its true.

I see some interesting things from the pictures.

When ever I see a fracture and one of the cad bases are out its a model verification issue in my opinion. Another observation is the cad bases that has all the stain/tarter on it below the seating surface again leads me to believe the prosthetic was not fully seated. When I look closely at the cad bases it appears they are rounded over hexed units and not prefab Non eng cad bases???? Maybe its the picture? All of these things will lead to have instability and torque to the appliance.

Anyhow your protocol on your side based on your description of how you verify the cast sounds great but are you putting you clients to the test prior to moving on with ANY design? Really hard to fool a stone jig but not impossible.

Everyone of my 450 arches that I have in the mouth over the last 3.5 years have confirmation sent to me. I have had some fail early on and MANY MANY fail in the lab but I know when I look at why in the lab failures happen its always human error.

I need quality images of EVERY fixture and they must be taken at a right angle to the table of the fixture or I will not proceed to a beta let alone a final restoration. Too often the film is taken with a descending angle which can give you a false sense of accuracy.

Hold them accountable. Use the correct zirconia for the case, minimize post sinter modification, and above all else maintain the correct dimensions by doing a survey with your 2d cross section tool. This material is super strong and for it to midline fracture is rare, generally its distal extensions that fail due to poor ap and techs/dr's pushing to get more occlusion than they should. Also that case with gingiva is not designed appropriately for a bunch of reasons and the dimensions are not suitable in my opinion. Not saying thats why it broke but anyhow.

Its super frustrating to have failures and super dangerous when these sorts of cases fail in the mouth, ask more questions and above all else learn to say NO when you know things are not ideal. Good luck
Great information.

What is the yield% on this product?

I have never made one and wouldn't. I have done an extensive amount of zirconia flexural strength testing though. I don't believe a zirconia ceramic framework for large span implant supported bridge is reliable enough.

What about a titanium framework with zirconia onlay and porcelain?

During 2005-2007 I vapor deposited a titanium esthetic porcelain adhesion layer over several titanium full arch implant supported frameworks for a lab. Seemed to work out.

Ken
 
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I have a question, before removing fractured appliance did any one checked if there was any space betwin parts. If yes, would this show that the abutments are in a slitely different position then on the master cast?
And does this happens mostly on mandibular arch?

Sent from my SM-G935V using Tapatalk
 
JMN

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First off, I want to start by saying how appreciative I am for the regular posters on this forum. I have for a long time been just a lurker, but have learned so much from the information you guys continue to provide online. I should definitely help and post more often. I just wanted to start off by thanking the regular guys that post on this sub like JohnWilson, Al., rkm_rdt, CatamountRob, Sideshowbob, Sevan, Bob-CDT, Travis, CoolHandLuke, zero_zero, JMN etc. I know I am missing a few, but please know your knowledge is appreciated.

The reason why I am writing today is that I have been having some major issues with long span zirconia bridges breaking. I am at a loss for what is causing it and was hoping maybe you guys can help shed some light. I took some time today to read through the Zirconia forum to see if anyone else has experienced similar issues, but it is hard to isolate what exactly is causing this.

Basically, the situation I am having is that doctors are sending me back broken bridges that are sectioned clean. I don't know what in my manufacturing process is causing them to do that. Some of these bridges cracked after just 2-3 weeks. I will detail my process as follows:

So we follow the basic protocol of verifying the cast with a series of jigs, verification bridges, etc. Our final master cast is verified using a stone jig, due to how brittle stone is. We noticed when we were using PMMA alone, there was still slight flex that would occur, that would cause the final zirconia prosthesis not to seat. Since then, we have been using gypsum stone verification jigs to make sure that the implant coordinates are properly recorded. If there is any variance at all, the stone will break, and we will correct the master cast.

After we have verified the master cast, design, aesthetics, etc. We then go to producing the final zirconia bridge off of the verified scans, etc. When producing the bridge, we almost always use a Roland DWX-50 with a set of CAP Ultra burs that are specifically used for small amounts of time, and only for these large bridges. After the bridge is milled, we will use a carbide bur to cut it out of the disk and shave down the sprues. To complete the removal of sprues, we will then use a bur made for smoothing zirconia to remove any last traces of the sprues.

After removing the sprues, we will stain the bridge using Zirkon Zahn stains. It then gets placed under a heat lamp for 40 min - 1 hour. After it is dried, we sinter using either a Sirona inFire Speed or a Sintra furnace. The zirconias we are using for these bridges are the Katana ML and DentalDirekt BioZX. The cycles used in either furnace are posted as images. When using the cycle for DDBioZX, we use the long program (3.2) and we have a max temp of 1530 degrees Celsius. When running the katana cycle, it recommends a max temp of 1500 degrees, but we run it at 1550 degrees Celsius. All of our furnaces are calibrated as well, so the units are getting to the proper temperature.

After the bridges come out of the furnace, we have a guy that finishes them. There is a bit of a language barrier but I spoke with him today on his finishing process. He is using an older porcelain oven with vacuum (NEY Centurion Q100) when applying glaze and finishing these bridges. He has a low temp of 1000 degrees Fahrenheit, and a high temp of 1680 degrees Fahrenheit. He cools for about 30 minutes and dries for 30 minutes. When he cools, he cools at a rate of 100 degrees Fahrenheit per minute. I think he may be cooling too rapidly, but don't know enough about the stain/glaze cycles to say otherwise. He also may run this cycle a number of times depending on how he finishes the case, how many times he has to glaze, etc. I don't know if this is where the integrity of the zirconia is being weakened to where it breaks intraorally. I have had close to 6 long span, monolithic implant bridges break like this on me and I have no idea what to do to resolve the issue going forward. I dont want to just keep milling the same thing and following the same procedure just to lead to a frustrated dentist, and an unhappy patient. If anyone has any advice, or suggestions at all it would be greatly appreciated. Thank you for taking the time to read my long post!

tl;dr:
Monolithic long span zirc bridges are breaking left and right. Following the same manufacturing protocol everyone else seems to use. CCan'tfigure out what in the manufacturing process is causing a defect in the zirconia for it to break like this. View attachment 26674 View attachment 26675 View attachment 26674 View attachment 26675 View attachment 26676 View attachment 26677 View attachment 26678
One thing that catches my red flag level attention is your comment that you've gone to stone jigs because you found pmma jigs flexing. There is the likelyhood that somewhere in the impression and model generating process process there may be a protocol problem if you noticed jigs flexing frequently enough to change methods.

Do the fractures happen with every clinician, every office? Or more prevalent with specific practitioners. (By percentage-don't let volume metrics conflate)

How are impressions made and supplied? Is it the same at every office? Can you get permission from them to be present at impressioning to verify how/if they lute the impression posts together intraorally before impressing using [wire pieces and coldcure/lightcure resin/thread and composite]? This can prevent many issues from generating that would cause the case foundation to be faulty and doom you from the start. If they are, check material expation/contraction on the IFU, not all are created equal.

Are you familiar with the one screw test method of verification? If not, you put only one screw in the jig and verify that all abutments are seated, then remove the screw and go to the next implant ... Doing that all the way around will show well and clearly if any of the analogs in your model are incorrectly posistioned.

I know it's hard to see in the distal, and to keep from aking your patient to glow with 5-7 extra xrays, you can pick up a simple USB IO camera on ebay for less than $50USD. Just the first one I found in case you were unaware of them: http://m.ebay.com/itm/8MP-USB-2-0-6...Oral-Digital-Micro-check-Camera-/322540016966

In short, of course John Wilson is right ;)
 
TheLabGuy

TheLabGuy

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I want to share some things as well... I say the mandibular bar that broke could have been easily mandibular flexure, I'm not a big fan of zirconium bars on the mandible for this reason. As John stated, the bases look awful dirty to me, makes me scream that the verification jig wasn't accurate, or Doc didn't get the right x-ray pics to verifying it seated correctly, etc... I'd suggest shadowing said Doctor(s) in this stage, include lunch, a great way to work on the communication in team building....and before you say, the doc in lives in a different state...I fly to my Docs offices all the time, include it in the bills and price accordingly. Lastly, I'm curious what the occlusion was on this before they snapped...anterior breakage in almost the same place for all your bridges is most likely a sintering/verification issue, but occlusion should be mentioned here. Why not start using a high performace polymer (pekkton) or titanium instead of zirconium? Are you guys trending this way for large frameworks?
 

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