stronger? / Emax or pfm

[mcfly]

Was wondering what is stronger in the posterior region a full monolithic Emax or a pfm crown (strength between metal and porcelain)?

 

[Gru]

e.max is stronger. The 360mpa (milled) or 400mpa (pressed) flexual strength is way above pfm porcelains (usually more or less 80mpa). No one argues that e.max is stronger than the metal understructure, but the e.max ceramic is unquestionably stronger.

 

[eyeloveteeth]

emax also because the bond strength holding the porcelain maxes out at like 85 mpa.

 

[sidesh0wb0b]

emax by far. both for bonded (if it is properly bonded) and for strength.
the weakest part of a PFM is the ceramic. full pressed or even milled emax wins hands down and looks far better to boot

 

[grantoz]

funny I don't see to many vmk's broken in 2. by the way the porcelain on your vmk when fired on its lonesome is 85mpa but when fired correctly on a well designed coping it compresses the porcelain and it becomes stronger ie about 400mpa.so over all for strength vmk is stronger and not reliant on bonding to the tooth.Think about it all those vmk's made over the last 40 -50 years if they were only 85mpa everyone one would have been broken by now.so I think its time to stop listening to flawed ivoclar marketing and poor material science.

 

[sidesh0wb0b]

funny I don't see to many vmk's broken in 2. by the way the porcelain on your vmk when fired on its lonesome is 85mpa but when fired correctly on a well designed coping it compresses the porcelain and it becomes stronger ie about 400mpa.so over all for strength vmk is stronger and not reliant on bonding to the tooth.Think about it all those vmk's made over the last 40 -50 years if they were only 85mpa everyone one would have been broken by now.so I think its time to stop listening to flawed ivoclar marketing and poor material science.

do you have any actual science to back up your claim that stacked ceramic gets anywhere near 400mpa? or any science showing ivoclar lied or has "flawed" material?

if so, please post it. would love to see these studies.

for me, the fact remains that stacked ceramic is weaker than monolithic EMax. hands down not even a comparison. my pfm fracture rate is fairly low as it is because I try to minimize shearing load points .... however my EMax fracture rate is really non existent. I've seen 3 break in the past year and a half. (a 4 unit posterior bridge, and 2 singles on feather margins...with pulls in the impression). all three were contraindicated and the client was properly informed prior to delivery.
now, I don't do nearly as many pfms so keep that in mind. probably 85% of everything I do is metal free. and even with that my remake factor for EMax monolithic is still negligible.

 

[Affinity]

I think e.max is plenty strong, and definitely stronger than PFM porcelain.. but I have had some break.. Mainly from under-preparation and limited space. If you can convince a Dr to start using E.max in the posterior inform them that you need a good shoulder and over 1mm of material in its thinnest point. If they are concerned with breakage tell them FCZ is the way to go.

Would like to hear what others have to say about posterior breakage issues. After all it is glass, and it can and will break, it all depends on the situation and pt.

 

[sidesh0wb0b]

I think e.max is plenty strong, and definitely stronger than PFM porcelain.. but I have had some break.. Mainly from under-preparation and limited space. If you can convince a Dr to start using E.max in the posterior inform them that you need a good shoulder and over 1mm of material in its thinnest point. If they are concerned with breakage tell them FCZ is the way to go.

Would like to hear what others have to say about posterior breakage issues. After all it is glass, and it can and will break, it all depends on the situation and pt.

agreed 100%. when contraindicated i have seen breaking of emax. when proper preparations and impressions are given it stands up just fine.

 

[eyeloveteeth]

stacked porcelain at least ceramco3 is about 220 Mpa - but the metal to porcelain opaque bonder is only like 85-115mpa - this is what I've heard for a long time

 

[grantoz]

There have been many studies over the years on this subject I was even taught this at college. Seriously have you not heard about how the porcelain compresses when stacked less than 1.5mm when bonded to metal .That's where the figure 1.5mm of space is needed comes from its not just for asthetics the 1.5mm of space is the maximum thickness the porcelain should be because thicker than this the porcelain goes into tension which is not good. Studies out of japan with shofu also vita did them in the early years .I cant give exact times and dates but I will still say 40-50 years of crowns been in peoples mouths show that they are definately stronger than 85mpa.Its been a long time since ive read them but 400mpa is quite conservative.There was comparison studies done between empress 1 and vmks because emp 1 was about 200mpa and this same argument was used saying how much stronger they were than vmks so if its just the porcelain strength on its own and the bonding to metal doesnt count why not just use empress 1 instead of vmks its 2 stronger go on I dare you.

 

[TheLabGuy]

Can't wait till one of you two hammer one of those into a two-by-four and throw it up on youtube

 

[grantoz]

I totally agree the only way to go is zirconia im just trying to make the point that there is so much mythology about emax out there.Have you seen the cool hammer test done by zirkonzahn?If they did it with emax you wouldn't even be able to find the bits.

 

[LA Ceramics]

LiS2 crowns are usually fractured during try in when the command," tap tap tap" is given and the crown has not yet been cemented. If it doesn't break immediately then it is sometimes riddled with stress fractures and this is usually the reason why some crowns fail a little further down the line. You must tell your docs that if they want to check the occlusion before cementation that they MUST close the patient themselves,..do not ever ask a numb patient to "just close for me gently" because they will always clench down very hard,...because they can't feel anything,..h-e-l-l-o. After this careful check is done by the genius,..I mean Doctor,..and the crown is not found to be "crazy high",.. they should cement it and do their adjustments ONLY after the bond is complete! LiS2 is a very hard substance and has good resistance to crack provocation but it's strength is very much reliant on the adhesive bond (preferably resin-type eg. rely x) Also,...NEVER NEVER should they ever adjust using a high speed(good luck with that one ha-ha)!!!! Low speed hand-piece with a sintered diamond PLEASE (footballs work good)

 

[RileyS]

Aside from the strength of e.max, it's just so much more simple to produce! Looks consistently great. Why the heck waste your day stacking?

 

[grantoz]

that's the spirit as long as its easy whats the problem?

 

[Affinity]

I have definitely gotten out of doing PFMs and almost forgot how much work goes into one.. One client only prescribes PFM for posterior, and it takes 3x as long to make it.. for maybe slightly better esthetics..

LA, Thanks for posting that. I had one Dr who would return fractured e.max and say it cracked under finger pressure putting it in the mouth... Yet theres a blue tint to the crack.. go figure..
As Donald Trump would say "YOURE FIRED!"

 

[RileyS]

that's the spirit as long as its easy whats the problem?

Ha
I did mention that "aside from its strength"
Meaning, it's good and strong; durable; rarely, if ever, breaks or chips.
So aside all the strength perks, it allows me time to say hi to the wife and kids

 

[Drizzt]

I had two molar and one 3 unit anterior bridge made with e.max breaking . I stopped using it for posteriors or bridges , zirconia for me . I sleep better at nights . There are too many variables , that we don't always have control over , (occlusion , crappy prep , dentists that don't know sh!t about what they are doing) , that I prefer doing them with zirconia .

 

[mcfly]

Thanks for all the replies ,very interesting reading all the perspectives .What would the bond strength be between a zirconia coping and porcelain layering just out of interest sake ,would it be in the same region as porcelain to PFM ?

 

[Drizzt]

Thanks for all the replies ,very interesting reading all the perspectives .What would the bond strength be between a zirconia coping and porcelain layering just out of interest sake ,would it be in the same region as porcelain to PFM ?

There is no bond between zirconia and ceramic . At least not with the ''bond'' definition . There is only mechanical retention . (The term retention might not be correct , but I can't think of anything better with my English !)