ivocap processing errors

[twaite]

Hopefully someone can be of assistance to me

well we have a new problem something I have never seen until recently. When we go to break out the denture after processing and the last 10mm are not processed. They are soft as if the acrylic never cured.

The water is where is should be, the flask are all the way in the clamp, the sprewing is spot on. The temp is set to 100c, we boil them for 40 minutes. There was no back flow.

Today we processed two cases in the moring with no problems then this afternoon doing all the same procedures we had two cases not cure all way. in facted all 4 cases were flasked and boiled out at the same time, but the ones that failed were the ones that sat on the counter until that first two were processed. we use the rapidflask from whipmix on our second pour rather than stone. never had this issue till we cleaned out our processor a couple weeks ago,.

Is it possible for the white shields, the flask lids to stop radiating heat? That's the only thing I can think of.


Please, is there anything you can tell us.

 

[Flipperlady]

I used to know this one..... If I remember correctly it has something to do with the spruing, I'll have to think about that for awhile and will answer if someone else doesn't get to it first. it's a simple problem to fix.

 

[twaite]

really? well that would make sense, we started to make our sprues a bit larger. and if i remember correctly i did a fairly larger size sprue on the cases. althought what doesnt exactly make sense is that all 4 cases had roughly the same size sprue and yet only 2 or the 4 had processing errors.

 

[Flipperlady]

I wouldn't make the spues larger. I used the red rope wax . How far up on the palate are you spruing? I'd sprue as far back as possible, the sprue cures last. it's been awhile since i processed with ivocap but i processed hundreds and hundreds of cases. you could also call them, like i said this should be an easy fix.
PS. I'd go by the book .

 

[twaite]

im not making the sprue overly large, i seen an ivocap video a while back and they used a bur to cut out a 5-7 mm sprue so ive waxed up accordingly. i'd say that my sprue is going about 10mm up the palate. one of the two that messed up was a lower and it was sprued right to teh end of the denture. nothing too crazy as far as the spruing goes. due to the few errors we have experience we have step my step instuctions on the wall that i follow religiously.

 

[Flipperlady]

That sounds reasonable, then i would look at the little insulating balls (make sure they are all there) and check the temp. The older the unit gets the more of these kind of things start popping up. Have you ever had the big pink bubble of acrylic come out the top yet ?

 

[twaite]

weve got lots of them balls on there. can you have too many? the temp is always right at 100*C im not sure how old the unit is, but im pretty sure its fairly new within the last 5 years. what do you mean by the big pink bubble at the top? like backflow or it going through the model to the flasking lid?

 

[araucaria]

I usually go for a minimum 45 mins, the instructions only state the minimum recommended time. Also, after immersing the clamps - wait until the water is boiling again before starting your timer - the cold metal apparatus lowers the temperature of the water bath temporarily and has a greater effect if you are filling the bath with clamps. Another thing, the local altitude may affect the temperature of boiling, only slightly but worth noting.
If you're not desperate to save the residual resin then let the flasks stay in the boiling water for longer, that'll stop the problem.

 

[Flipperlady]

It's hard to have too many when they bounce all over the floor and roll under the cabinets everytime you remove the flasks ;-)
In older flasks, sometime the acrylic squeezes through the flask leaving a huge bubble of cooked acrylic on the outside and none on the inside. Good to have happen while you're out to lunch! Are you bench setting after curing before placing in cold water?

 

[denturist-student]

You might want to check the positioning of the models in the flask...

 

[droberts]

The sprue size only needs to be the diameter of the injection nozzle. I use 8 ga round rope wax. on everything. The white plates are for insulating to allow the heat to cure from the bottom of the flask as it is positioned in the compress to the top as it is processing. I would say that they either were not down far enough in the curing tank, that the balls may have been holding them up, or the placement of the cast in the flask " too far back". Which if enought time, would have stilled cured it. As for bench setting, no issue there. I can run 11 cases flasked up and injected curing 4 at a time, that should not be an issue there. I would say it was more of a time issue. As stated by another member, make sure the water is rolling completely before starting the time, 40 minutes / 4 flasks.

 

[denturist-student]

droberts I agree with all you have said...I had a fellow student who had a similar problem and it was his timing...Since then we all boiled for 45 minutes without any problems. IN Ivocap it is my learning that all of those parameters are set and cannot be done any other way. Like our instructor said it is a great system but when one screws up its big time. I may investigate the new press and cure in one shot system from Ivoclar. I think the most reliable system though is the old press pack flasks with a 9 hour at 165 and a 30-45 min finish boil. With nowadays curing tanks we can just set them and forget them...That beats babysitting them any day.

 

[droberts]

droberts I agree with all you have said...I had a fellow student who had a similar problem and it was his timing...Since then we all boiled for 45 minutes without any problems. IN Ivocap it is my learning that all of those parameters are set and cannot be done any other way. Like our instructor said it is a great system but when one screws up its big time. I may investigate the new press and cure in one shot system from Ivoclar. I think the most reliable system though is the old press pack flasks with a 9 hour at 165 and a 30-45 min finish boil. With nowadays curing tanks we can just set them and forget them...That beats babysitting them any day.

Keep in mind. The new Ivocap one shot system is nothing but a cold cure. Cures at 140 degrees. Also curing hybrids using the press pack method, not good.
Hybrids / Bars need the cooling immediately after processing. The acrylic cools faster than the bars and can occasionally cause stress fractures in the acrylic.
It can happen with Ivocap as well. From what I was told, thats why they came out with this new system, less heat.
I dont mind "baby sitting", 3 grandchildren and love them all

 

[Smilestyler]

Ivocap cures from the bottom up or anterior to posterior. It is important to keep them in for long enough of a time period and that they are fully immersed in the bath. one tip that I also found is that the spruce should not be attatched to the denture to low in the posterior areas. For example if you are doing a lower denture, try not to put your spruce 15mm ahead of the most distal area. If the acrylic must travel up, that area seems to not cure. Place the denture as low as you can in the flask and keep your spruces high.