Lithium Disilicate

[TheLabGuy]

I've got a question/comment about strength.

YZ runs around 1200 Mpa, Empress Esthetic around 140 Mpa, Lithium Disilicate around 400 Mpa.

Now tell me if i'm correct, Porcelain is as only strong as the strength between the porcelain and substructure. Now on YZ, the porcelain on the YZ is only 90 Mpa. Empress Esthetic stays the same 140 Mpa. Lithium Disilicate is also the same at 400 Mpa. Making Lithium Disilicate stronger than anything on the market. Now I know the YZ substructure is stronger, but it's weak between the porcelain and YZ substructure (90 Mpa).

Please tell me your thoughts, because what I've seen from most labs and techs for that matter is that they are seriously confused about this and think Zirconium, YZ, In-Ceram is the strongest thing out there, when technically, they're factually wrong. Unless I'm wrong............maybe?

 

[Al.]

Rob, I thought the strength value of zirconia was around 900 mpa?

I press all my posteriers full contour and layer the incisal 1/3 of upper bi's. in LD.
Anything less then .8 clearance I reduce the opposing.
For strength Id put one of these up against a milled yz coping that is layered anyday, but its a different story if I press a coping in LD and then layer it. But there is really no need to layer anything more then the incisal with the LT ingots.
Ive done plenty of posterior bridges in Lithium Disilicate with no fractures to date. As long as I have plenty of room for strong connections it would take a brute to break them.

It would be intresting to see a strength test on a 4mm pressed rod of 100% LD vs a 2mm milled rod of yz with 2mm of layered porcelin built around it.

 

[labdude]

They could be factually right, or maybe wrong technically. I don't think your wrong factually, technically maybe slightly, maybe....
I don't know for sure. I have no factually correct or technically true facts on the issue, I don't think, maybe.

 

[Al.]

They could be factually right, or maybe wrong technically. I don't think your wrong factually, technically maybe slightly, maybe....
I don't know for sure. I have no factually correct or technically true facts on the issue, I don't think, maybe.

Dang, you got me plum befuddled.

 

[sixonice]

I've got a question/comment about strength.

YZ runs around 1200 Mpa, Empress Esthetic around 140 Mpa, Lithium Disilicate around 400 Mpa.

Now tell me if i'm correct, Porcelain is as only strong as the strength between the porcelain and substructure. Now on YZ, the porcelain on the YZ is only 90 Mpa. Empress Esthetic stays the same 140 Mpa. Lithium Disilicate is also the same at 400 Mpa. Making Lithium Disilicate stronger than anything on the market. Now I know the YZ substructure is stronger, but it's weak between the porcelain and YZ substructure (90 Mpa).

Please tell me your thoughts, because what I've seen from most labs and techs for that matter is that they are seriously confused about this and think Zirconium, YZ, In-Ceram is the strongest thing out there, when technically, they're factually wrong. Unless I'm wrong............maybe?

I believe you are 100% correct and I agree with you. Here is my slice: True, Zirconia substrates are super strong (900-1000mpa depending on what you read). On a layered zirconia, you are correct the weak point is the interface between the zirconia and the build up of glass (90 mpa-like you said). Failures would come in the form of delamination of the ceramic off the zirconia. Now take a Lithium Disilicate, full press at 400mpa, no interface. Both are conventionally cemented. For single units its a no-brainer-the Lithium Disilicate would be better (and MUCH more profitable for the lab!!) Its like comparing 2 bricks that have mortar in between them versus a SOLID brick with no mortar. Zirconia shines on long span anterior bridges and posterior bridges. The substructure design is aso vital in zirconia, where proper support must be adhered to to give the layering ceramic proper support.

 

[TheLabGuy]

On a layered zirconia, you are correct the weak point is the interface between the zirconia and the build up of glass (90 mpa-like you said).

Its like comparing 2 bricks that have mortar in between them versus a SOLID brick with no mortar.

Great explanation with an awesome analogy. Thanks a bunch sixonice, once again, you came threw like a champ!!!!!!

 

[sixonice]

Glad I could help Labguy! It was funny, I was trying to think up of a cool analogy that could help all you guys get a good "picture" in your mind on the differences. I just think doing single units of zirconia is too expensive doesn't matter whether you mill it in your own lab or send it out to get milled)-save it for the longer bridges.

 

[Al.]

I just think doing single units of zirconia is too expensive doesn't matter whether you mill it in your own lab or send it out to get milled)-save it for the longer bridges.

You got that right!
It seems like all the trade magazines are trying to shove $75,000 milling units down our throats like their the cats meow of dentistry.
Ive out sourced a few maryland bridges. Close to $300 for one pontic and 2 wings.

 

[AcademyDL]

Ivoclar Zircad is 900MPA and Lava claims 1100MPA.
The Zirconia strength is supposedly dependent on the brand. Due to the
differences in the Therming process that the zirconia goes through
after it has been milled. 3M is claiming to have a superior therming method to other brands. All I know is that they spend a ton of Cash on Research and Development and 3M does indeed back up their 5 year warranty.

A Friend in the business who does a ton of zirconia told me that the other companies are terrible about backing up their warranties and literally has a coffee can full of broken substructures. The company always had an excuse why they didn't have to warranty any of them. Literally hundreds of them.

There is another lesser known brand in the Magazines claiming to be stronger. ( I cant remember the brand off the top of my head )
But I have never felt any of it was an issue past a certain point 900-1100 MPA is strong enough for me ( as far as substructures go )


I have made this debate that you guys are talking about Relating to the hand stacked porcelain being the weakest link but I have had mixed success. Several Doctors are very concerned about breakage because of the years past and the claims of previous systems. Many of my clients had to remake several cases and in some cases had to remake every single unit.

I Can see that some of you are having success with your Doctors
and Id love to do more 400MPa press work. What are you sharing with them that helps make them comfortable with Lithium Disillicate?

I'm also very sincerely interested in your % success rate with the Lithium Disillicate. What are your Failure/Success Ratios?

- Justin

 

[sixonice]

Academy, Lithium Discilicate will be a very popular product in the coming years I believe. Getting doctors to change from doing single unit zirconia's should be fairly simple. I would use phrases like "The substructure is the restoration" or "Pressing a monolithic restoration (monolithic is the new buzz word for a restoration made all out of one material) offers outstanding strength (400Mpa),conventional cementability & different translucencies complement adjacent dentition".
CRA-Clinical Reseasrch Associates recently published a report on zirconia. The report was not really good unfortnately. The report classified failures as any delamination off the zirconia frame, chips, cracks, unusual wear in the overlay ceramic or pits.
The zirconia-to-ceramic interface IS the "weak link" in a PFZ. We have a 1000Mpa substructure overlayered with a soft ceramic of 80-90Mpa. I used the analogy of a porcelian to zirconia as a foundation on a home with concrete block and mortar. If that foundation cracks, it is usually at that concrete/mortar junction or in the mortar joint itself. Newer homes have a solid foundation (also called poured foundations). The solid foundations have no weak point, no interface.

 

[Pronto]

Never had a YZ substructure crack in the mouth. Never had layered porcelain delaminate from the YZ coping. We have had the same percent of fractures from excursions on incisals on YZ as PFG and that # is very LOW. IMHO when you get near 1000mpa's your splitting hairs on strength.. look at the yield strenghts of golds and np alloys-there is a broad range. They all will work if designed correctly and there is sufficient clearance. Regardless of the material used in dental restorations, there still has to be good dentistry done for it to survive. No whizbang new product is going to change that.

 

[zena]

Isn't IPS empress esthetic 160 MPa. Does anyone know of a chart on strengths of all types of crowns.

 

[sixonice]

Isn't IPS empress esthetic 160 MPa. Does anyone know of a chart on strengths of all types of crowns.

Yes, Empress Esthetic is 160 Mpa (must be bonded!) Lithium Disilicate Pressed restorations are 400 Mpa, milled Lithium Disilicate (CAD) are 360 Mpa, zirconia substructures are 900-1200 Mpa (depending on which zirconia & what your reading),feldspathic restorations are 90-100 Mpa, layering porcelains (for zirconia & alloy) range from 90-110 Mpa depending on the manufacturer, alumina substrates are 450-500 Mpa.

 

[zena]

Yes, Empress Esthetic is 160 Mpa (must be bonded!) Lithium Disilicate Pressed restorations are 400 Mpa, milled Lithium Disilicate (CAD) are 360 Mpa, zirconia substructures are 900-1200 Mpa (depending on which zirconia & what your reading),feldspathic restorations are 90-100 Mpa, layering porcelains (for zirconia & alloy) range from 90-110 Mpa depending on the manufacturer, alumina substrates are 450-500 Mpa.

awesome thanks for the info Sixonice.

 

[anne2010Ma]

Yes, Empress Esthetic is 160 Mpa (must be bonded!) Lithium Disilicate Pressed restorations are 400 Mpa, milled Lithium Disilicate (CAD) are 360 Mpa, zirconia substructures are 900-1200 Mpa (depending on which zirconia & what your reading),feldspathic restorations are 90-100 Mpa, layering porcelains (for zirconia & alloy) range from 90-110 Mpa depending on the manufacturer, alumina substrates are 450-500 Mpa.

Hi sixonice,

when you say "Lithium Disilicate Pressed restorations are 400 Mpa" is that full press without cut back and adding incisal? If it is not the same, then what is the strength for Lithium Disilicate Pressed restorations with cut back and added incisals? Also, for the above strength is there a chart on the Internet that shows this? Thanks!

Anne

 

[sixonice]

Hi sixonice,

when you say "Lithium Disilicate Pressed restorations are 400 Mpa" is that full press without cut back and adding incisal? If it is not the same, then what is the strength for Lithium Disilicate Pressed restorations with cut back and added incisals? Also, for the above strength is there a chart on the Internet that shows this? Thanks!

Anne

yes, the 400 Mpa is for a fully anatomic pressed e.max restoration. e.max that is cut-back slightly and layered with enamel, the bulk of the restoration is still lithium disilicate (at 400 Mpa). e.max ceram porcelain is about 95 Mpa (as is all or most layering ceramics). even with a slight cut back and enamelization, this is still a very strong restoration. i attached the website with just about everything you could ever want to know about lithium disilicate. Ivoclar Vivadent | The World Speaks e.max

 

[rkm rdt]

Zirconia is a substructure material and lithium disilicate is a restoring material.

 

[TheLabGuy]

Zirconia is a substructure material and lithium disilicate is a restoring material.

and bruxzir would be?

 

[doug]

and bruxzir would be?

One of the ways I'm making my Etkon scanner pay for itself.

 

[TheLabGuy]

One of the ways I'm making my Etkon scanner pay for itself.

Mr. Doug, good to see you, are you worried about the longevity or wear of full contour zirconia? I'm always hesitant to jump on board with a new product right away, hell it took Al practically screaming at me to use E.max LT and he was right so I'm not closed to new ideas totally. As you probably remember, Artglass, Dicor, etc.... I would like to see some 3-5 year independent studies, especially with wear on natural dentition before I jump in. In addition, are you layering it or stain/glazing and how is that working out for you?