Zirconia degrading in the oral environment

[Car 54]

One more note, These studies seem to conclude that the crystal size of the sintered restoration makes a big difference in the amount of degradation that occurs. Large crystal structures will degrade more. A 50 degree too hot furnace will result in enlarged crystal structure. 100 degrees is a massive increase in crystal size. That said, I think the accuracy of sintering temps and sintering furnace are critical to getting best results. I know many furnaces do drift up over time. We should calibrate our furnaces often and use quality furnaces and materials.

"many furnaces do drift up"...thanks Bob, as on my last calibration, it seemed to have gone up 5 degrees and made me wonder what was going on.
I was thinking more in terms of a regular porcelain furnace, where over time they seem to lose temp.

 

[BobCDT]

Fir testing, if you have a front entry furnace you should put one tab in the back and a second in the front. This will provide info on the quality of the door insulation which is ofter a problem. If there is a deviation of 30+ degrees you have a problem.

 

[JohnWilson]

Fir testing, if you have a front entry furnace you should put one tab in the back and a second in the front. This will provide info on the quality of the door insulation which is ofter a problem. If there is a deviation of 30+ degrees you have a problem.

Good info here, while we always try to load the units in the center I am now very curious to check. Thanks for the tip Bob.

 

[gallagerdental]

I'm with you John- on the positive side, look at all the residual remake work you will get, on the downside it sucks for the patient, hummm.


Sent from my iPhone using Tapatalk

 

[BobCDT]

I don't think we sill see huge failures in 5 years. Out the door, if sintered properly the HT is 1100MPa. in 5 years it.s close to 600MPa. that's still 50% stronger than e.max. Not to mention e.max strength degrades over time as well. The cases that would worry me are the large full arch cases with cantilevers, all on 4 little support opposing another implant bridge, fixed restoration or natural teeth.
Keep in mind teh new "Anterior" cubic materials do not degrade over time. I have seen only one study but it went form 650 to 634.

 

[DanM]

I don't think we sill see huge failures in 5 years. Out the door, if sintered properly the HT is 1100MPa. in 5 years it.s close to 600MPa. that's still 50% stronger than e.max. Not to mention e.max strength degrades over time as well. The cases that would worry me are the large full arch cases with cantilevers, all on 4 little support opposing another implant bridge, fixed restoration or natural teeth.
Keep in mind teh new "Anterior" cubic materials do not degrade over time. I have seen only one study but it went form 650 to 634.

What's interesting about that is I think we all agree you shouldn't do a full arch on implants with the new "Anterior" zirconia materials, but they end up at the same strength after 5 years anyways. Is there any info/thoughts on these ~1000MPa materials like Sagemax NexxZr+ or Origin Beyond+?

 

[CoolHandLuke]

What's interesting about that is I think we all agree you shouldn't do a full arch on implants with the new "Anterior" zirconia materials, but they end up at the same strength after 5 years anyways. Is there any info/thoughts on these ~1000MPa materials like Sagemax NexxZr+ or Origin Beyond+?

i don't think the consideration not to do that with anterior materials is based on strength, but rather two other factors both related to each other - translucency, and translucency.

the greyness of the implant will come through in an anterior zirconia more.

and theres too much translucency to use the anterior zirconia without a proper opaque zirconia frame or otherwize anodized ti / gold coloured np bar.

 

[eyeloveteeth]

if someone is going to rate disagree, can we at least get a comment on why?

 

[CoolHandLuke]

we already hear why, its in the post above.

 

[Xydorf]

Just about all the HT materials (1100 MPh) loose 50% of their flexural strength over 5 years. That said the new Anterior materials (about 600 MPh) made form Zepex , Tosoh powder loose virtually no strength over time. This is one of the only ceramic materials in our industry that has no degradation or loss of strength over time. lithium disilicate, feldspathic, lucite ceramics all loose strength. Most are in the 30% + range.
John, you are correct, five years form now all the full arch screw retained zirconia cases will have a decreased flexural strength of about 500-600 MPa. We will get to do many all over again.

Well, this sucks... then I wont be doing many of those...

 

[cadfan]

apples and pines adhesive cemented e-max and conventional cemented zircon have you ever made a 14 unit bridge with e-max Bob ??
the problem is not degradation the problem is the interface stump cement , crown versus bridge

 

[BobCDT]

Never done a 14 unit e.max bridge. Nor have i done a conventional 14 zirconia bridge. That said we have fabricated many 14 unit zirconia cases, implant supported using a multi abutment with cement in titanium tapered inserts.

 

[DanM]

if someone is going to rate disagree, can we at least get a comment on why?

Just simply that I think you could block it out. I have a FA here that's 2.5-3mm thick at the lateral implants. With HO cement I'm certain it wouldn't show through say Katana STML, but would I consider using STML...heck no. But based on the data above one could argue it may be a better choice. Within the past year someone posted a STML full arch that broke and they couldn't figure out why. Seemed it was obvious why, but it seems numbers are not the only factor (assuming it was fabricated properly to begin with). Even on natural dentition I wouldn't consider STML as an option for a full arch bridge.
Just saying take Katana ML 1100MPa and STML 748MPa, after 5 years they both end up around 700MPa...

 

[eyeloveteeth]

Just simply that I think you could block it out. I have a FA here that's 2.5-3mm thick at the lateral implants. With HO cement I'm certain it wouldn't show through say Katana STML, but would I consider using STML...heck no. But based on the data above one could argue it may be a better choice. Within the past year someone posted a STML full arch that broke and they couldn't figure out why. Seemed it was obvious why, but it seems numbers are not the only factor (assuming it was fabricated properly to begin with). Even on natural dentition I wouldn't consider STML as an option for a full arch bridge.
Just saying take Katana ML 1100MPa and STML 748MPa, after 5 years they both end up around 700MPa...

Ah, now i understand.


Yeah we would never mill a connect full arch on STML either. Actually, we tend to break em up into groups or even better singles, as if anything did fail it's just one part.

Did someone really try and send out a full arch STML/UTML case? that's a bit nutty....


But we do full arch STML/Changs cases all the time, just not a full arch connected case.

 

[CoolHandLuke]

most ive done was a 7u cubex2, two years on and no remake yet.

 

[DanM]

Ah, now i understand.


Yeah we would never mill a connect full arch on STML either. Actually, we tend to break em up into groups or even better singles, as if anything did fail it's just one part.

Did someone really try and send out a full arch STML/UTML case? that's a bit nutty....


But we do full arch STML/Changs cases all the time, just not a full arch connected case.

Found it...
http://dentallabnetwork.com/forums/threads/hybrid-bar-zirconia-fractured.24022/#post-219343

 

[user name]

i don't think the consideration not to do that with anterior materials is based on strength, but rather two other factors both related to each other - translucency, and translucency.

the greyness of the implant will come through in an anterior zirconia more.

and theres too much translucency to use the anterior zirconia without a proper opaque zirconia frame or otherwize anodized ti / gold coloured np bar.

Changs opaque white. Works wonders.

 

[CoolHandLuke]

i aint said it was an impossible hurdle, only that it wouldn't be an immediate consideration due to those colour factors.

its more work to block it with crazy cements and opaquers than it is to make a white frame in the first place, and add porcelain.

 

[user name]

i aint said it was an impossible hurdle, only that it wouldn't be an immediate consideration due to those colour factors.

its more work to block it with crazy cements and opaquers than it is to make a white frame in the first place, and add porcelain.

Disagree. Theres a small learning curve for Changs opaque, but then its quick and works wonders.

 

[grantoz]

What you guys have to remember is just because you have only been doing zi full arch cases for a few years the rest of the world has been doing them for 10-12 years. if there was going to be a problem in the mouth it would have surfaced by now, zirkonzahn would have been in all kinds of pain as would armin girbach just to name a few. The whole oh no the sky is falling attitude towards Zi restorations has been long documented by muppets who want to be the 1st to tell you i told you it would fail. Procera has been making zi bridges for close to 17 years i have been doing ZZ full archcases in prettau and traditional Zi for 12 years and im talking hundreds of them with 1 failure,it was due to an inaccurate impression. If you are trying to justify using super trans for full arches because they all are the same strength after time as normal Zi ,because of better aesthetics you are going to been in all kinds of trouble. ZirkonZahn have prettau anterior 650-700mpa which was the 1st of these super trans to come out they show degradation studies that show they have no degradation on their Zi and guess what .They only recommend it for single teeth and small anterior bridges because of its strength.