White dots on sintered Zirconia.

[Getoothachopper]

Did we ever get a definitive answer on what causes this ? (Iv'e read through the old posts). It's shown up this morning on a batch for the first time for me in two years. Every tooth perfectly round white (where the zirc touched the beads) and just below the surface .Two trays , beads were a week old (1mm) other tray two weeks . It's been a month + since I ran decontaminator material through the furnace. Zirc was all Katana pre shaded stml (from eight different discs) No pre colouring took place. I usually sinter at 1520 in my AmannGirbach ceramill therm II ,,,,,,this time I went to 1530 because there were a lot of units in there . ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Should I charge the Doctors more for these because of the beautiful custom decalcification work on some of the occlusal tips ?

 

[zero_zero]

Did we ever get a definitive answer on what causes this ?

Everyone seems to have a different theory of what's the underlying cause is...from contamination in green state to furnace contamination. When I see them starting to appear ( I use regular AlOx as sintering media) I change the sand, place a spoonful of Zr dust in the tray and run a 1600C cycle to regrow the Si layer on the heating elements...then I'm good for another 2-3 months...

 

[user name]

Cover your beads when not in use.

 

[sidesh0wb0b]

could be old or contaminated beads....though ive seen it on brand new beads as well as old beads. so i have no true answer or solution

 

[Getoothachopper]

could be old or contaminated beads....though ive seen it on brand new beads as well as old beads. so i have no true answer or solution

It's crazy that none of us know what causes this . I changed the beads ,did a decontamination of the furnace and trays with 'Purge sinter' and got an expert in to take the bad juju off the furnace .,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, I fired some zolid in there last night and they were fine .

 

[sidesh0wb0b]

It's crazy that none of us know what causes this . I changed the beads ,did a decontamination of the furnace and trays with 'Purge sinter' and got an expert in to take the bad juju off the furnace .,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, I fired some zolid in there last night and they were fine . View attachment 24778

i dont even get it on all cases/crowns....and no one ive asked has been able to give me a straight answer either.
maybe ill try a purge too. thanks

 

[2thm8kr]

It's crazy that none of us know what causes this . I changed the beads ,did a decontamination of the furnace and trays with 'Purge sinter' and got an expert in to take the bad juju off the furnace .,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, I fired some zolid in there last night and they were fine . View attachment 24778

Clearly it was the expert nixing the bad juju.

 

[CoolHandLuke]

Clearly it was the expert nixing the bad juju.

Acetylsalicylic, Phenobarb and Arsafenamin

my god, it worked!

 

[TheLabGuy]

Yeah, I've tried all kinds of things as well. I think Zero's advice is the best thing out there currently. Although I'm curious Zero, why AlOx? instead of the beads?

 

[zero_zero]

Although I'm curious Zero, why AlOx? instead of the beads?

Because I'm a cheap bastard...lol...and it works. The whole heating chamber is insulated with AlOx, the sintering dish is also made of AlOx...so I figured why not AlOx beads as well ? I couldn't find beads to try, so I did run a few tests with 250 micron Korox...haven't used Zr beads ever since... I believe that 8kg container I got will outlast the furnace by far.

 

[Tayebdental]

I get the white spots in zirconia crowns once in a while, it is not superficial but imbedded in the zirconia, which tells me it's a manufacturing issue.
Some techs use Aluminum oxide at 250 microns instead of sintering beads.

 

[sidesh0wb0b]

Because I'm a cheap bastard...lol...and it works. The whole heating chamber is insulated with AlOx, the sintering dish is also made of AlOx...so I figured why not AlOx beads as well ? I couldn't find beads to try, so I did run a few tests with 250 micron Korox...haven't used Zr beads ever since... I believe that 8kg container I got will outlast the furnace by far.

thats interesting, and probably a far cry less expensive than sintering beads! has anyone given you the stern "no" speech as far as manufacturers/suppliers?

 

[zero_zero]

has anyone given you the stern "no" speech as far as manufacturers/suppliers?

What else could one expect from a supplier ? It won't work, conducts heat differently, it should be round so the units could roll on top as they sinter...etc,etc...
My heating elements came directly from the manufacturer...I was told by uncle Hank, it wont fit and the resistance won't match. I proved them wrong and paid one third of their price...

 

[Patrick Coon]

We recommend just placing right on the tray, no beads at all.

 

[Getoothachopper]

We recommend just placing right on the tray, no beads at all.

Thanks , I will try that .

 

[sidesh0wb0b]

We recommend just placing right on the tray, no beads at all.

for your materials and your trays, i am guessing

 

[Raffi M.]

Had the same problem... you need to change the sintering beads
And i run them through a cycle just to play it safe

 

[sidesh0wb0b]

Had the same problem... you need to change the sintering beads
And i run them through a cycle just to play it safe

tried that. 3 diff types of sintering beads. same result. try again!

 

[bartholomai]

after throwing away 3 batch of sinter pearls, I crashed some white zirkonia then I have sintered it and after 3 months still no white spots

 

[NormC]

Yep, we have same issue from time to time. I saw it when we had interns (externs?) from dental assisting schools helping in the lab and realized they were not 'dusting' off the green zirconia crowns very well. I got them to use a high pressure air hose for final dusting (dry air from the dental compressor) and the white spots have not returned since. I doubt it's the beads because we had same issue with brand new beads. If it were some other type of contamination, you'd think it would affect all crowns the same, but it's sporadic. Our Aman Girrbach vendor told us sternly NOT to use compressed air to dust off the green zirconia, but we do it anyway. Yes, I could be victim of some cause and correlation fallacy but I'm sticking to my 'dust' theory. So far, compressed air dusting (and not walking under ladders) has solved our issue with those merciless white spots.