Press packing question

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Acrylicwookie

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I am just curious how tight you guys clamp the flasks into the flask holders for curing? We use the typical flask/press as seen in the pic I posted (just a pic I grabbed from net) I was taught to tighten it as tight as I can get it. However, the more I think about it due to some issues I've been having, I think I'm clamping too tight.

I final pack to 3k and let it sit for a while under that load until I have no more flash. Then I put them into the flask press and let sit for 20-30 minutes and then into the bath overnight. When I get in in the morning, there is occasionally some very thin flash that is curly.

So, I'm thinking maybe, just maybe, I'm not getting the flash when I'm packing because the brass is cold. But when it heats up it possibly becomes softer which causes it to be more malleable than normal? Also, the flask press doesn't exert it's pressure evenly over the flask either - unlike our press pack does. The curing press is just a bar that goes over the middle. So I'm wondering if it is pushing down more as it heats up causing the flash?

The issue that caused me to think this over is I've been having some fit issues lately...but they are sporadic. The flash issue is sporadic as well. I'm wondering if flasks have a usage life and if so, maybe we have a couple that are needing to be recycled? I recently had an upper that was just ridiculously loose. The bite rim was nice and snug so I know my final model was good - I'm just wondering if the flask was pushed in further than normal causing the model to push into the acrylic causing the intaglio surface to be bigger?

Like I said, I think I'm clamping too tight...but I don't really have the urge to experiment and screw up a denture! lol. Any input would be greatly appreciated! (and the Ivo system is not an option to fix things right now ;) lol
 

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A

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Just to be clear how tight I make the curing press, I was taught to do it until the bottom plate with the springs under them is flush against the bottom so you cannot see the springs. I usually have to turn the press on it's side and press the allen key against the countertop for leverage to get it tight enough.
 
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Old School Dentures

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I'm unclear exactly what the issue is are you getting porosity? I don't let my cases sit 20-30 min before putting into press. We trial pack then do final pack then right in to the clamp then water bath. You can make clamp too tight, I use the bench to gain leverage as you do but you don't need crazy amounts of pressure, just make sure they are tight with reasonable pressure. As long as your cases don't have porosity I don't see and issue with a little flash outside the flask at the end of the water cycle. That just tells me your clamping a little too tight


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No porosity - I was referring to being scared to end up with porosity if I experimented with a looser clamp. The main issue I had that got me to thinking about possibly clamping too hard is I had an upper come out with ridiculous mobility in the patients mouth. I checked using the bite rim and it fit snug/perfectly to patient arch and so I started wondering if I was deforming the flask by too much pressure which would push the model deeper into the acrylic causing the flash and the poor fit.
 
kcdt

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Just to be clear how tight I make the curing press, I was taught to do it until the bottom plate with the springs under them is flush against the bottom so you cannot see the springs. I usually have to turn the press on it's side and press the allen key against the countertop for leverage to get it tight enough.
I see two issues. The thin flashing means you haven't trial packed enough times.
That will open your pin.
Second issue is the flask clamp. This type has springs in the bottom that counteract resin expansion.
You're supposed to wind them down, then back off a quarter turn to load the springs.
When you overtighten, the springs are completely compressed and useless. That can also open the bite
 
kcdt

kcdt

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A couple more thoughts: if you're not having issues with excessive VDO opening or porosity, I wouldn't chase my tale. Most likely your fit issue is unrelated.

My other is that bench cure is never an issue. In fact, it's helpful. There's a study that pushes bench set as long as six hours, that regardless of flask closure clamping method ( they tested two),the bench set produced superior results.
 
kcdt

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No porosity - I was referring to being scared to end up with porosity if I experimented with a looser clamp. The main issue I had that got me to thinking about possibly clamping too hard is I had an upper come out with ridiculous mobility in the patients mouth. I checked using the bite rim and it fit snug/perfectly to patient arch and so I started wondering if I was deforming the flask by too much pressure which would push the model deeper into the acrylic causing the flash and the poor fit.
Also the fit issue could be tissue rebound. That wouldn't show up at record base procedures because the fit isn't intimate.
If the tissue was swollen or mobile, then a better fit would lead to sudden loosening because the tissue is improving.
In something like that, I'd go with a round of tissue conditioner for a week or so, then hard reline.

I'm speaking in broad generalties here.
Most processing methods will produce adequate fit on a good model.
That's not where I'd focus if you really need to go down the rabbit hole.
 
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slotboom.f

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1-1,5 k is more than enough pressure. The plaster inside is also sensitive to pressure and since i guess you do not use class4 for this this could be an issue when using 3k pressure.
Really, it is not needed. If acrylic is too hard when pressed curly flash may also occur. And when uppers come out with ridiculous mobility there are just a few things you should check:
Rimlength (maybe too long at frenuli)
Torus palatinus which prevents correct seating .
Flabby ridges. ( too much pressure when making impressions)
And of course the articulation since it was snug during fit but in function doing strange things.



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Thanks for the responses! I always like picking other peoples brains - specially in the press packing group since it is truly an art in and of itself. I am leaning more towards the tissue rebound due to poor fitting current dentures. I usually don't have my patients withhold wearing their dentures prior to final impressions....something I will most likely start doing - if I can get compliance. I did the tissue conditioner and will do the reline - just frustrating needing to do all that with a new case. I have read about bench curing and will continue to do that and will definitely let the springs do their thing from now on.
 
JKraver

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I have read about bench curing and will continue to do that and will definitely let the springs do their thing from now on.
Springs are metal, they get soft over time. I don't know how old your equipment is but have seen my share of 40+ year old flasks/compress.
 
denturist-student

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Thanks for the responses! I always like picking other peoples brains - specially in the press packing group since it is truly an art in and of itself. I am leaning more towards the tissue rebound due to poor fitting current dentures. I usually don't have my patients withhold wearing their dentures prior to final impressions....something I will most likely start doing - if I can get compliance. I did the tissue conditioner and will do the reline - just frustrating needing to do all that with a new case. I have read about bench curing and will continue to do that and will definitely let the springs do their thing from now on.
I usually place the tissue conditioner in the old denture to tighten it up a bit and allow the tissues to reach optimum state that way....Problem is some patients will turn a temporary thing into a permanent thing. But I will do that from the getgo....if I can....
 
denturist-student

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1-1,5 k is more than enough pressure. The plaster inside is also sensitive to pressure and since i guess you do not use class4 for this this could be an issue when using 3k pressure.
Really, it is not needed. If acrylic is too hard when pressed curly flash may also occur. And when uppers come out with ridiculous mobility there are just a few things you should check:
Rimlength (maybe too long at frenuli)
Torus palatinus which prevents correct seating .
Flabby ridges. ( too much pressure when making impressions)
And of course the articulation since it was snug during fit but in function doing strange things.



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Thanks for the tip...I was using 3K for my pressing and holding for 30 minutes but will change and see if any difference in fit.....
 
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nickate

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I final pack @4500psi using Coe-Bilt Pneumatic press and insert into the Kerr Equa-Lock compresses. The 4 springs on the corners get the job done even after 40+ years. OP- you are chasing the wrong dog....
 
droberts

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The old Kerr Equa Lock were awesome. I believe I sold 18 of them when I switched over
to the Ivocap. Although, I dont believe you need to final press pack at 4500.
 
denturist-student

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A couple more thoughts: if you're not having issues with excessive VDO opening or porosity, I wouldn't chase my tale. Most likely your fit issue is unrelated.

My other is that bench cure is never an issue. In fact, it's helpful. There's a study that pushes bench set as long as six hours, that regardless of flask closure clamping method ( they tested two),the bench set produced superior results.
I usually bench cure and boil for an hour and a half....But lately I have been slow curing for 8 hours and it seems the fit is much better now...at least on the last three cases....seems reducing the press pressure and long slow cure seem to produce better results....agree about tissue rebound and then if there are medications involved, and weight loss it all contributes to an ill fit and that lands squarely in our lap.
 
kcdt

kcdt

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Thanks for the responses! I always like picking other peoples brains - specially in the press packing group since it is truly an art in and of itself. I am leaning more towards the tissue rebound due to poor fitting current dentures. I usually don't have my patients withhold wearing their dentures prior to final impressions....something I will most likely start doing - if I can get compliance. I did the tissue conditioner and will do the reline - just frustrating needing to do all that with a new case. I have read about bench curing and will continue to do that and will definitely let the springs do their thing from now on.
If you examine and diagnose before you start, you can tissue condition to get a better impression.
It's all about WHEN you want to deal with it.
 
kcdt

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Springs are metal, they get soft over time. I don't know how old your equipment is but have seen my share of 40+ year old flasks/compress.
TBH, I don't think the issue lies there. I brought it up only because he mentioned it and I try to be thorough.
Most technicians don't even realize that those springs are engineered for cause, so they just crank it home and never load them at all.
But it not something I'd lose sleep over
 
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The old Kerr Equa Lock were awesome. I believe I sold 18 of them when I switched over
to the Ivocap. Although, I dont believe you need to final press pack at 4500.

I think I bought 18 of them years ago.... lol. I recently sold 15 compresses and a compress opener on ebay which leaves me with about 40 compresses and 2 compress openers. No Popeye arms or skinned knuckles.
 
denturist-student

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If you examine and diagnose before you start, you can tissue condition to get a better impression.
It's all about WHEN you want to deal with it.
I usually never reline without a week or so of tissue conditioning....only in exceptional circumstances. I will use either TEMPO or COE comfort...Saving the Hydrocast for functional impressions.
 
kcdt

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I usually never reline without a week or so of tissue conditioning....only in exceptional circumstances. I will use either TEMPO or COE comfort...Saving the Hydrocast for functional impressions.
I think it's wise to assume any denture wearer will present with abused tissue when they show up at clinic.
 
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