Acrylic shrinkage

[trianglej]

When using Lucitone HIPA or GC Natur-cryl for the Pour Technique or using either for relines, I have been finding that my acrylic has been shrinking away from my models during curing to where I see a definite gap.
GC instructions tell me that excessive liquid (monomer) will cause shrinkage but I measure precisely.
Any other thoughts out there?
Please dial back the criticism about Pouring Dentures, I've read them before.

 

[Doris A]

I'm not going to criticize you for pouring dentures and relines because you have already answered your own question. Inject them and your problem will be eliminated.

 

[bigj1972]

All acrylics "shrink" during polymerization. Just the way it is. Just like composites.
Which is why Ivocap was promoted as a solution..

There are ways to mitigate it, but I wouldn't worry too much about it. Just follow IFU, and it'll be fine.

 

[Cleo]

With relines I have my techs let it start to set just a little before pressing. Just enough to hold its shape a little. It is really easy if it is too runny to press uneven and push excess out and be short material. Easy to do, but easy to rush.

 

[Flipperlady]

There have been many conversations and arguments about acrylic shrinkage, manufacturers make product sheets that discuss such. There really isn't a quick way to get quality, I used the Lucitone pour acrylic in the past and it was a nightmare, the few minutes I thought I was saving was erased with make over and just not using it anymore. You can follow the directions exactly then call Dentsply/Sirona and let them know what you think I suppose.
As for Naturecryl, the microwaveable is the way to go.

 

[bigj1972]

Any material must be mastered to get the most from it. With pour their are pros and cons just like the rest. Definitely a steeper learning curve with pour.

But I wouldn't touch the old generations of pours like Lucitone FasPor or Millennium. Just runny repair acrylic.

 

[kytoothdude]

It's my understanding that dental stone expands to compensate for acrylic shrinkage.

 

[JKraver]

It's my understanding that dental stone expands to compensate for acrylic shrinkage.

Your understanding is incorrect, Diekeen is deigned with a high expansion so crowns will fit better because they will be loose. That is probably where you got that idea.

 

[Tylen]

I don’t have any problem with shrinkage when pour. Try pressure pot at room temperature over night if you can. It takes around 2 hour to completely cure in cold weather, around 1 hour in hot weather. You can to do some experiments depends on your mix ratio and acrylic brands.
Flasks exposure to heat (hot or warm water) will cause shrinkage from my experience.