Ok. I am having an issue with acrylic "flash" around teeth after process.

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nickate

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I have tried everything-- even waxing UP TO the teeth and never having to scrape or clean them off before investing as they never had wax on them to begin with-- yet this problem persists. THERE IS NO WAX REMAINING AROUND THE CERVICALS (I know, I know-- but really. I am using a magnifier to check.)
About a .75-1mm piece of stone left around the cervical edge of the teeth after devesting. You can pop it off but the acrylic film remains-- and needs to be lightly chiseled around just rubbing over it with the back side of the chisel lightly-- VERY thin skin or film... almost seems like it could be separator.
If I pull a tooth out of the flask after painting w/ separator- the separator has not leeched past the cervical edge.
Investing with Hydrocal 105 yelow stone.
I would rather not use insulating pastes or puddies.

The rundown:
Waxing up to teeth- not going over and removing- wax never introduced on to cerv. past where waxed
NO WAX SOLVENTS APPLIED
All yellow stone investing
Tried 3 different waxes- To soften the wax--tried from 5 min all the way to 10 mins to soften the wax in boil out tank. Nope.
Pneumatic press used- 4500psi and have tried down to 3100 psi thinking maybe pushing past... Nope.
Two different separators... no way
Tried bench set 15 mins., no bench set.... un-uh
Tried fast cure, slow cure- nada
3 different brands of acrylic-- no

Not passing the job off to another tech. Hands on by me.

This is frustrating. Help me MOMMA!!!!
 
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JKraver

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What stone are you investing with?
Edit I just reread. sorry
 
JKraver

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Do you boil wax until liquid?
 
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nickate

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Do you boil wax until liquid?
I have tried as little as 5 mins (teeth come out in still hard wax base and need to be pushed back into flask) all the way to 10 mins- wax is fully liquified. No change.
 
TheLabGuy

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yellow stone - expansion rate?
Also, I thought most folks were using a putty wash around the teeth for this reason, no?
16110183_382305162134147_1924561612543361024_n.jpg
 
JKraver

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Do you flush with clean boiling water not the boil out water? Boil out additives? What separator? Are you letting the stone fully set/cool before packing? Sounds like it is one of those fluke things, stone batch maybe.
 
JMN

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Ohkay. Waiting for stone to dry... Hehehe

I went digging and found what passes for an IFU for this stuff. http://www.amcsupplies.com.au/manuals/plaster-mixing-procedures-application-en-IG503.pdf
It is not given a dental stone Type # that I could find. Anywhere. Could have missed it.
The manufacturer has basically no data to give unless you are using it in a pond or doing agriculture with it.
https://www.usg.com/content/usgcom/...ntal/hydrocal-x-21-dental-gypsum-cement1.html


So, instead of being specific, here's the basics.
If you have a skin of acrylic on the teeth, either:
a) the teeth are shifting
b) the stone is expanding too much
c) the teeth are shrinking

Hopefully C can be dispensed with immediately.

a:
Are you being certain the teeth are fully seated into the form before you start processing?
Are you ensuring that the incisal/occlusal of the teeth remains pointed down at all times after boil out and until packed?

b:
1) Are you mixing exactly as specified? Are there any specifications or instructions at all that come with it that USG doesn't put on their website? Call them and see if you can get an answer as to what the ratio is supposed to be for your application. See if they can give any clues.

2)have you tried other stones? I mean, this stuff's SDS is the only thing I can find that says it's dental stone. It's being made by the guys who make wall plaster, wallboard, and firebricks. Nothing wrong with using it for mounting plaster, but it may be causing you more headaches than getting a stone designed for this stuff instead of relabeled for it.

3) The stone may not be intended for going swimming, my chemistry is weak, but it could be a possibility

4) How long are you letting the stone set before boilout/processing? Is it getting enough time to fully harden?

5)Are the flasks being allowed to set underwater too long causing demineralization of the stone, letting the surface you initially had effectively wash away? Over 20-30 min for no reason is bad for most labstone or buffstone that I've read or played with.

Go fish
 
JMN

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I have tried everything-- even waxing UP TO the teeth and never having to scrape or clean them off before investing as they never had wax on them to begin with-- yet this problem persists. THERE IS NO WAX REMAINING AROUND THE CERVICALS (I know, I know-- but really. I am using a magnifier to check.)
About a .75-1mm piece of stone left around the cervical edge of the teeth after devesting. You can pop it off but the acrylic film remains-- and needs to be lightly chiseled around just rubbing over it with the back side of the chisel lightly-- VERY thin skin or film... almost seems like it could be separator.
If I pull a tooth out of the flask after painting w/ separator- the separator has not leeched past the cervical edge.
Investing with Hydrocal 105 yelow stone.
I would rather not use insulating pastes or puddies.

The rundown:
Waxing up to teeth- not going over and removing- wax never introduced on to cerv. past where waxed
NO WAX SOLVENTS APPLIED
All yellow stone investing
Tried 3 different waxes- To soften the wax--tried from 5 min all the way to 10 mins to soften the wax in boil out tank. Nope.
Pneumatic press used- 4500psi and have tried down to 3100 psi thinking maybe pushing past... Nope.
Two different separators... no way
Tried bench set 15 mins., no bench set.... un-uh
Tried fast cure, slow cure- nada
3 different brands of acrylic-- no

Not passing the job off to another tech. Hands on by me.

This is frustrating. Help me MOMMA!!!!
Short version: Dude, read the label next time. Buy stuff that is supposed to work, and supposed to be used, then when you have problems it's a lot easier to figure out.

Here's yer problem. The stone you are using is this with yellow colorant.

Note that the expansion is .42%.
Dental stone expansion is allowed at max .30%
That is why it doesn't have a stone type. It is outside the classifications.

https://www.usg.com/content/dam/USG...drocal-white-gypsum-cement-data-en-IG1381.pdf
--------------------------
USG Hydrocal® Brand White Gypsum Cement is a good multi-purpose product for people looking
to upgrade from a standard plaster product to one that has a higher degree of hardness and
impact resistance. USG Hydrocal White Gypsum Cement is designed for solid and hollow casting
and is ideal for giftware and lamp base applications. USG Hydrocal White Gypsum Cement is
compatible with numerous color pigments. If information for a specific use is needed, please
contact your local USG Sales Representative for further assistance.
Normal Consistency (lbs. water/100 lbs. product)
43
Hand Mix Vicat Set, Target (minutes)
20 - 30
Compressive Strength, One Hour After Set (psi)
3000
Compressive Strength, Dry (psi)
6000
Density, Wet (lbs./cu. ft.)
110.0
Density, Dry (lbs./cu. ft.)
90.0
% Maximum Expansion
0.42%
-------------------------------------
http://info.whipmix.com/topic/gypsum


upload_2017-3-22_22-48-32.png
 
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JohnWilson

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1) Have you always had this problem?
2) Is this something new?
3) What have you recently changed?

Your outline sounds perfect,

Aside from prefect waxing I use flow stone for the top when I use ivocap. When I compression pack I mix plaster and take my finger and paint the gingival embrasures and carvings with the plaster and immediately pour the top in flow stone. The plaster is much much softer and is considerably easier to divest if it doesn't pop out clean.
 
Affinity

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Why are you not using a wax solvent to clean the teeth before investing? Its the only thing I havent heard mentioned, sometimes you cant see a film of wax even with magnification.
 
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nickate

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Whoa.... I don't know where you found that JMN but thanks! My local USG rep Mr Donald Poole from USG didn't have any luck at all about 2 weeks ago when I was asking him to provide me with the mixing ratio for the Hydrocal 105.... Ye have shined a spotlight on why!
Been using it since the 80's. This problem has just started showing itself in the last 6 months...

I am anxious to give some better stuff a go! I believe I have to step up and pay some shipping charges as I always got the Hydrocal locally pretty cheap. What stone are y'all using to pour models with for dentures and what are you using to invest said dentures?
 
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nickate

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Why are you not using a wax solvent to clean the teeth before investing? Its the only thing I havent heard mentioned, sometimes you cant see a film of wax even with magnification.
The last batch I waxed from the cervical up- not bulking it on and carving back. I have tried different wax solvents... recently Patterson brand and also my long time Remove-It. They had no effect either way.
 
JMN

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Whoa.... I don't know where you found that JMN but thanks! My local USG rep Mr Donald Poole from USG didn't have any luck at all about 2 weeks ago when I was asking him to provide me with the mixing ratio for the Hydrocal 105.... Ye have shined a spotlight on why!
Been using it since the 80's. This problem has just started showing itself in the last 6 months...

I am anxious to give some better stuff a go! I believe I have to step up and pay some shipping charges as I always got the Hydrocal locally pretty cheap. What stone are y'all using to pour models with for dentures and what are you using to invest said dentures?
You are very welcome Nickate. Just typed "hydrocal 105" into a search engine and started reading. Never heard of it before.

Kulzer's Modern Materials line is trustworthy and cheaper before shipping than the prices I saw for what you've been using. I've used them since '07 and haven't seen anything I can point to the stone's fault. Mine, oh yeah!

Buffstone/labstone for models. Your choice of setting speed white plaster to invest. I think they have a 5-7 minute and 7-12 minute?
They have a special going this month if you buy 4 you get 1 I think. I don't have room for that, but if you do...

There's lots of opinions and options here for you to choose from.
 
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JKraver

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Why are you not using a wax solvent to clean the teeth before investing? Its the only thing I havent heard mentioned, sometimes you cant see a film of wax even with magnification.
Wax solvent can leave a residue, avoid it no need for it.
Edit: It also softens wax it comes into contact with, damaging the surface making it stick to stone more.
 
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JKraver

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I use microstone great for casts, but is a bit to thick to pour a top coat and if you dilute it you get water pool lines on the interface which normally isn't much of an issue but sometimes it is. I always paint my waxed up dentures with die stone anywhere there is wax showing it just works better for me.
 
JKraver

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Your choice of setting speed white plaster to invest. I think they have a 5-7 minute and 7-12 minute?
They have a special going this month if you buy 4 you get 1 I think. I don't have room for that, but if you do...

There's lots of opinions and options here for you to choose from.
I wouldn't use lab plaster to invest, it is simply not hard enough the stone could crush. You can thin coat with a good stone on teeth/wax and backfill with plaster/stone mix
 
JKraver

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We use 2/3 stone 1/3 plaster for investing.
I agree anything over 50% stone is fine in my book for compression packing. The ivobase I do 100% stone at least and normally throw some die stone in it for good measure. I do a layer of die stone on teeth and whatever I have left in the mixing bowl I add into my top cap pour.
 
Doris A

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I agree anything over 50% stone is fine in my book for compression packing. The ivobase I do 100% stone at least and normally throw some die stone in it for good measure. I do a layer of die stone on teeth and whatever I have left in the mixing bowl I add into my top cap pour.
I use all stone for ivocap as well.
 
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