EMAX FRACTURES HELP!!!!!!!

[shearl06]

I used to hardly ever have emax fractures and now for past 2 months i have about 3 or more a week... the emax crowns are not thin so i have no clue why this keep happening! can it be the white expansion i place on the inside of the crown so that it sticks to prongs as it is firing in the oven? plz help!!

 

[amadent]

are you getting check lines, what surface are they showing on- do they run buccal to lingual, are you getting them post glaze?
have you always used " white expansion" to hold crowns in place on pegs?
are they layered or stain and glaze?
sorry for so many ?, but sometimes it helps

 

[TheLabGuy]

white expansion?...do you mean the peg putty?...If so, no. Your problem is most likely one of a couple problems, you're using a high speed carbide to finish with, or a dull diamond and pressing hard enough to create a microfracture which usually appears during the glaze cycle ( I know, a real pisser). Now it could be that you didn't do any of that and the prep wasn't designed for e.max. I've seen (although, only a couple times) where you have a thick area, then a thin area up against a thick area and the thin area always crack.

 

[amadent]

Now it could be that you didn't do any of that and the prep wasn't designed for e.max. I've seen (although, only a couple times) where you have a thick area, then a thin area up against a thick area and the thin area always crack.

had one just the other day- case was all done and then crack

 

[disturbed]

I agree with rob. its not your peg putty. move your oven recently? buy a new fan? might be cooling to quickly.

 

[Macron Dental Lab]

Check the Thermal shock of temperature ,make sure the AC vent don't hit the area were the oven is located and wait until the restoration cools down .

My two cents good luck.

 

[rkm rdt]

reusing the button?

 

[user name]

NOTIFY IVOCLAR!!! They need to know whats going on. They can help diagnose your situation to get you going straight, and help make a better product/process for us all.

 

[TheLabGuy]

I agree with rob. its not your peg putty. move your oven recently? buy a new fan? might be cooling to quickly.

Hallelujah!!!!..bout time you break that ice, now I'll get you rubbing your tummy for some zirconia too

 

[TheLabGuy]

had one just the other day- case was all done and then crack

It's rare, but I had one recently too...the DDS prepped the occlusion flat. Which looks great in an impression and also on the model, but when you start to follow the contours of the adjacent anatomy you find that the central dissectional groove is less than 0.5mm while the buccal and lingual cusps are over 2mm reduction. So then you glaze it and there she goes...a crack!!!!

 

[NicelyMKV]

I leave mine in the furnace a minute or two after the program is complete. Give it a little time to cool. I usually have them(rarely thank goodness) when a Doctor has a lot of prep reduction on the mescal for instance, and then a much thinner area adjoined to it. Thats why I like to let it slow cool to help level out the thermal cycle between varying thicknesses.

 

[Tom Moore]

I have a friend that swears by using a 6x6x2 aluminum heat sink and a large Pyrex beaker on top to cool emax. He says it cracks because it has a lot of internal stress built in when pressed and the stress will sometimes release during uneven cooling at glaze. FWIW.

 

[TheLabGuy]

Interesting Tom...after this conversation from Greg and yourself I'm going to add a few minutes to my cooling time, can't hurt.

 

[charles007]

Hmm... never heard of such, what brand of ovens are being used to have this problem, and cool time setting ? What tools are used for adjusting emax ?

Seems like eveything under the sun can go wrong with non-Ivoclar oven users and emax......

 

[user name]

Fortunately Im still batting 1000, even though Im in the Zubler clan. My first thought is the OP bought his ingots off ebay.

 

[disturbed]

I have a friend that swears by using a 6x6x2 aluminum heat sink and a large Pyrex beaker on top to cool emax. He says it cracks because it has a lot of internal stress built in when pressed and the stress will sometimes release during uneven cooling at glaze. FWIW.

sharp internal line angles can be fatal. tell your doc's to smooth and round out them sharp edges!!

 

[charles007]

The GOOD.......I'm still batting a 1000 at 3 years this month and get sharp preps every week.
THE BAD.........Now my warranty is out this month on my EP5000

 

[EJADA]

hey we all just had a thread about this about a month ago. funny thing is I had another one crack this morning. Same type of situation as last one ,and many of you have described. IE: Thin occ sharp corner. I looked at the prep and thought hope this doesn't crack. All stained, doing final glaze bake and CRACK. I really need to slow down my cooling. I just went to Dr, at 8:00am (crown due at 1:00) and said this prep doesn't work and showed him the cracked crown. I told him I could have a gold one done and here by 1:00. He called pt. and got the OK and I got to be a hero. They didn't even have to change the chair time. Probably way more info than anyone cared to hear. We just do what we do.

 

[Badgerdental]

We've definatly had issues with a sharp transition from thick to thin, the solution: slow cooling, works everytime (prior to crack occurring of course, fixing the crack is another issue). Occlussal areas can be a problem where you've tried to create your realistic anatomy you may have created thin areas that are susceptible to thermal cracks. We don't do much 'carving' anymore, more like ramps I guess, you have to communicate with your client and make sure they know what they're doing and what they're dealing with. I've found some of these guys dive in head first without learning about what they have to do in terms of prep reduction and shape.

 

[paulg100]

given that the minimum occlsual thickness should be 1mm or greater, you should never have areas that are to thin to start with.

Touch wood, have never had a single crack in 3 years yet. All i do is follow the instructions.