Acrylic curing questio was asked...

[labdude]

... a while back in a phone conversation.
I'll try to answer that question here.
Anyone who has taken a class on appliance fabrication has furthered their knowledge no doubt. The various books and VHS and cd tutorials are excellent as well.
One thing I have found over the years is that, while they teach you to make a specific appliance, the method start to finish is sometimes not the most productive. Meaning that there is more than one way to skin that cat.
I have tried many methods and do not approve of any that compromise quality of the out come.
That being said here's a few so called "secrets".
Keep in mind, most ideas I use have come from hiring and working with many indiviuals that worked in the larger labs. Some of those labs are the ones that offer the training.

Simple of it....Bionators and Splints etc. can be layed up or "shot" or salt and peppered. It only requires a little practice. Some of the instructional classes etc. have you mixing a large wad of acrylic and placing on the work models. This is costly in materials and mostly your time spent grinding all that excess material. Not to mention placing a picture.
The question about curing acrylic, as in rubbery acrylic against the tissue bearing surface, while the rest of the appliance is set. This is nothing more than uncured acrylic. A little more time is all that is needed.
Do this, leave it in the pressure pot, go do something else productive.

My method is to have metal work (rpe's etc) things without acrylic, soaking in warm water to dissolve flux, while I lay up acrylic.
By the time I have the pressure pot loaded, I leave it and go finish up the metal work. This allows the appliances in the pressure pot to cure completely.
Then I work on the acrylic. Here are a couple of pictures of the pressure pot. I don't submerge appliances. I do apply a thin coat of clear powder to prevent slumping of the acrylic. There is a small amount of water under the plate in the bottom of the pot. KISS.
Mike.

 

[rs promotions]

Is there any advantages or disadvantages to submerging them in water?
I think it was retainerdesigner that said he submerges his. I'm guessing it's just a matter of preference.

Ron

 

[labdude]

I only have to think of what it would be like to submerge 15 or so cases. Messy. I have enough to pick up for around here.
The picture of the full pot is of 15 appliances. Doing 3 at a time allows you to stack and keep working on more. Sometimes just 1 or 2 at a time. Depends on wether it's a single color or pattern. The rainbow I did while you were here, I just do 1 more single color at the same time.
Thing is, curing underwater can be more time consuming, you want to make 50 or 100 dollars an hour???
Again , keeping the highest quality in the finished product is foremost.
I don't find a difference in the finished product using either method. Just a difference in the bottom line, and the time it gives me to do other appliances.
Mike.

 

[rs promotions]

What is the maximum amount of time from finishing shooting the acrylic to starting the pressure curing. If your doing 15 at a time your shooting acrylic pretty fast.

Ron

 

[labdude]

I only shoot a maximum of 3 at a time. Those 3 would be of a solid single color, maybe 1 with a picture. Those 3 go into the pot and go under pressure.
Then I do the next 3.
The time it takes me to do another 3 allows for the first 3 to cure to a point where there is no danger of incorperating porosity into the acrylic when I open the pot for the next 3.
If you open a pot to soon, appliances inside will have porosity.
The time it takes to shoot 3 or 2 or 1 obviously will vary on your ability.
Again, the rainbow I did while you were here, only allows me enough time for 1 more solid color before it has to go under pressure.
I will try to remember to time myself, I have no clue as to how many minutes I take for shooting a batch before they need to be under pressure.
I'll post back here with that time limit. Time limit being, a safetime for which to wait to put a appliance under pressure.
Shoot an appliance and put it straight into the pot, no problem.
Wait to long to put it in the pot, you get porosity.
Also, if you open the pot to soon while doing batches of 3, you'll get porosity.
Mike.

 

[rs promotions]

So you're saying the ones in the bottom have been pressurized a few times?

Thanks
Ron

 

[labdude]

Exactly.
They just stay there till ther are totally cured. I remove the cases after I finish my metal work. That's when I go over and open the pot. I like to remove them 1 at a time from the open pot, as the glue removes easier. I place the models on the counter behind meand the appliances over by the handpiece.
That is the reason for the timing schedule I have. (internal clock for me, been at it so long)
The first ones in aren't bothered by the changes in pressure because they have been under pressure and low heat, long enough.
Mike.

 

[rs promotions]

Ok Now it makes sense. Sorry if I was slow getting it, just couldn't figure out how you were getting 15 in there if you shoot 1 to 3 at a time.

Thanks
Ron

 

[RetainerDesigner]

Do you pre-soak the models?
I set mine in a small amount of water while I bend the wires for the other, when I am done bending wire's I just start shooting acrylic on the ones that have been in the water the longest. I believe this is called the capillary method. Where there is just enough water to touch the bottom of he cast. The Orthodontists I first trained under used to completely submerge the cast for a few minutes before shooting acrylic. What about the attached wires you ask? He didnt attach the wires, he would place the wires as he shot the acrylic. He also did not submerge the model in the pressure pot. It worked for him, I didnt learn about the capillary method and submerging the model for curing until Lab school. Of course his office uses plaster to pour up the models instead of stone, and they make real thick stone patties on the back, makes for about a 30 min soak. THe other offices that use stone to pour up the models, takes about 2 min to soak completely all the way through. using the capillary method.
I worked for a ortho lab while I was in lab school that would only submerge the model for curing if it was a repair. I dont know why, he had his reasons. He also didnt have a single handpiece in his lab. He finished all appliances on the lathe start to finish. That was a neat learning experience, I have seemed to adopt many of his method into my methods....of madness!

 

[labdude]

Hi Ron,
No problem. Ask away.
Mike.

 

[labdude]

Cade,
Those are nice methods. Just not the ones used by the larger labs.
Thing is, the quality of the finished product. I must be strong, clean, accurate etc.
I have on an emergency occassion, placed wires with no tacking in place. Really slow, but o.k. for a quick emergency when you don't want to fire up a torch or wait for the glue gun to heat.
Time, it's all about YOUR time.
I share my methods here with the hope that some will try them. My methods come from experience with production labs, as well as small labs.
Combine the 2 and you won't be spending time doing needless things.

Oh yeah, you asked about how I moisten models, or not.

Here's exactly how it happens here. In batches of 10 to 30.

All wires are bent. Setting on tray next to their model. I do wax relief of undercuts where needed, and a THIN coat of wax where a wire is to be placed.I take the entire tray over to the sink and hold each model under flowing warm water for a second or 2. Never soaked before, dry models.
I go back to my chair and apply separator.(from OSE) Then I tack glue the wires to the models. Then any springs exp. screws etc. that need to be waxed, I do that next.
Now its over to the acrylic station. I place all colors need in easy reach, line up which cases I want to lay up first. I do the toughest first.(patterns, Bionators,etc.)
Lay up 3, they go in the pot. 1 cup of water under the plate first however. I don't want it to touch the models, to messy.
Then I continue in this way till they are all done.
Then I go finish my metal work while they cure completely.

You do this type of batch flow, your time spent making an appliance can come down to 20 minutes, start to finish. I average 20 to 30 minutes per case UNIT wiht this method.

Bottom line, is the bottom line. You want to make 50 or 100 dolars per hour, while produceing the same quality???
Choice is yours, no harm in trying it guys,
Mike.