pour, inject ,press or ,denture

[kcdt]

I always perform the whole deal in HC resin, or n my case microwave. I've never tried laminating two materials like HC and CC, but if it holds up the way most repairs and relines do, I'd pass on trying it for a new appliance.
For those interested, processing to a microwave base with microwave resin works really well. If you prepare the material right, you can't even see a finish line.

 

[altlab]

Success system Need help-intermittent problem

Q? on problem follows set-up:
I spent about 7 years in dentures and am now getting back into it.


Greetings.I use the Dentsply Success System with a twist- I use their Fas-Por+ that can be poured or injected. I inject all dentures. Cures in 15 minutes in a 50c(ish) pressure pot @30psi. Really -15 minutes period.Great for relines. I usually let it cool for 10 minutes or so but the temps are so low it cools fast. I actually go about 45c -low is not critical but over 50c you will percolate the monomer. I often use the same acrylic to pour partials and stayplates and in a pinch pour a denture - looks the same.

I use DVA APS seperator (2-3 coats) as recommended by one of you fine people. After about a 100 test samples with a variety of products including Ivoclar's this gave the best final surface. Ice cube trays make good stone samples.

Result: Generally excellent. Signifigantly harder(denser) than the press pack Luc.199 I used to use.Excellent color/vein pattern. Teeth stay put much better than press pack and fuse better.Bites are dead on and after checking remount a number of times and finding it always perfect, I have stopped remounting (of course check the tuberosity/retromolar area for acrylic interference by hand).I NEVER adjust the bite on the teeth when I inject.I can't imagine press packing again.

Typical sequence:Mix, wait to gel 4 min,press 2 min., cure 15 min.,10 min cool.Total max process/cool time: 31 min. ,devest and finish normally.

Q? Intermittent problem: For no apparent reason I will sometimes get an odd bubble (that can be anywhere) with a strange gooey center of what appears to be uncured or contaminated acrylic. They are simple to repair using the same acrylic but it would be nice to know if the collective brain has experienced this. It is not coming from the model - Still happens when I use silicone models.I suspect exotherm and am going to lower the water temp.Just for fun I put a digital thermometer in a blob of curing acrylic and it went over 100c(212F)!The advantages to the system are sooo profound that it is worth putting up with this mystery.s on the bubble?

 

[harry1]

Ditto, have been using Success for a while, easy to install and not locked into a single acrylic, use whatever I preffer.

Once and a while, have had the odd bubble, tends to be in bulky sections, usally lower the temp slightly, other than that works well.

 

[altlab]

Update to Success bubble Q?

Thanks Mr. Harry1 for the reply.I also strongly suspect an exotherm culprit exascerbated by cure temp and thickness.

I finally got through to a tech rep at Dentsply. Friendly but completely baffled. No answer to the question of why we are curing the denture at 52C when the denture is creating its own exotherm of 100C+. Said I may expect a call from some of their scientists higher up the food chain. I will pass on their thoughts.

I did find on an industrial website that methacryl. monomer tends to gas at 80C at room pressure. Tends to make me think the 30psi sure is just to control monomer percolation (lower boiling point)and has less to do with bubble supression under pressure as if it were a cold cure repair that was never subjected to mechanical pressure. After 2 minutes in the press the material is fairly hard anyway. Will be conducting some cure temp experiments.

I had a hard time getting the rep to understand the true pressure being used was not the pressure indicated on the press's air guage. Since a previous commenter was sharing their pressure choices, here is how to determine the real pressure for this or any system: PI(3.14) X radius of the cylinder (2") X squared (2) X the air pressure being used. Example, at 90 psi: 3.14X 2 X 2 X 90psi = 1130.4 PSI...So tell me how a bubble could form at this pressure! Even 75 psi air still gives you 942 psi net. Imagine the pressure on just one steam engine cylinder (12") at 250psi....(9420 psi). Of course when the material starts to harden neither air or other mechanical pressure will have an effect anymore.

Back in my old press-pack days I recall still getting an occaisional bubble in spite of a screw hand press that is capable of 4,000-10,000 psi although this was exerted mostly on the flask edges and not the contents. There must be great potential energy in monomer. I can't believe after 35 years I still don't know all there is to know about methylmethacrylate. I didn't even know I wanted to know.To be continued. Are quotes the thing to do here? If so here is my favorite lab related quote for the next time you are thinking "free remake", "When a poor man gives a rich man a present the Devil laughs." B. Cellini

 

[CShof]

I'm definitely no math genius and it may be arbitrary but you sure your equation is correct? Shouldn't you take the air pressure and divide it by area of the circular piece that moves down your cylinder to get actual pressure?

I'll admit I'm more of a car guy than anything else so I related it to brake master cylinder pressure and I know the formula for that.
C = pedal ratio
D= pounds of foot pressure
E = area of master cylinder
F = pounds of output pressure from master cylinder
C x D / E = F

The area of a circle with a 2 inch radius would be pi * r^2 or 12.57, you sure you used the radius and not the diameter? With no pedal ratio on an injection unit and using your 90 psi the formula would read.
C = 1
D = 90
E = 12.57
90(psi) / 12.57(pi) = 7.16 psi.

If the diameter was 2 inches and the radius was 1 inch then it would come out to 28.6 psi.

Lord knows as longs as it been since I've taken a math class I could be one that's wrong here but I'm just trying to learn about injection units and how they work and I am truly curious as to how much pressure they actually put out. Maybe someone smarter than me can double check.

 

[JohnWilson]

After that last two posts I will just scream utilizing my best impression of someone with tourettes.....


IVOCAP, IVOCAP errrrrrrrrrrrrrAHHHHHHH

I
VO
CAP!!!

My newest bestest old friend!

 

[araucaria]

OMG! My brain's hurting. This may affect my mojo.
I think I better go check out my steam engine before it's too late.

 

[Clear Precision Dental]

After that last two posts I will just scream utilizing my best impression of someone with tourettes.....


IVOCAP, IVOCAP errrrrrrrrrrrrrAHHHHHHH

I
VO
CAP!!!

My newest bestest old friend!

Agreed. Attach, filp the lever on the injector, watch it climb to the green zone. Done. Process. No brainer.

 

[altlab]

Mr. CSHOF with appreciation a reply on air cylinder pressure computation

Thanks for the commemnt Mr. CSHOF.
I certainly could have gone into more detail that would have been clearer and the truth is you are not exactly right or wrong on all points but your final pressure computations would not be correct as per the further provenance I submit below. If your force calculations were correct the force at the injection site would by about 3 bags of sugar (harmless) but I would not reccomend a test with your hand or it would likely punch a hole right through it. Please bear with me a few paragraphs.

Disclaimers: As per another commenter warning of exploding brain syndrome from this kind of article,If anyone is susceptible please avert your eyes now or you will go gronk!

Also for anyone and especially the helpful and concerned Mr. CSHOF: If you think my my goal here is to put on "airs" (pun intended) remember I have allowed myself to be abused by dentists for 36 years so I can't be all that smart.

Mr. CSHOF,
The comparison of liquid and gaseous working fluids requiring single or multiple cylinders such as a master and slave or working piston and air reservoir are a bit of apples and oranges unless the equipment is exactly mechanically the same piece-by-piece for both devices you are comparing.For instance, dental presses do not have a master cylinder with its own diameter,pressure and working rod diameter, not to mention the "reservoir" is pressurized only by your foot or an assist and limited to its working design.

Although both air and oil are fluids in the exact sense, oil is basically uncompressable as a (ambient)liquid and a slave to the master cylinder initial pressure (no pun intended but it is a good one...) and the final working connection is going to be a composite of the master and slave as well as the rod size and is not directly applicable to air (at ambient a gas not a liquid) cylinders where the working fluid is very compressable. I used the steam rough comparison (adding unnecesary complexity) because although ambient temp. water is like oil in not being hardly compressable, when it turns to steam it is compressable and force computations are done basically as air.

Of course if you overheat your brake fluid and it turns to a spongy gas or you use liquid oxygen instead of gaseous air the roles then reverse...I'm sorry I brought it up, let's not go there!

Anyhow following is an article from google (EHOW) I reprint because coincidentally the diameter/pressure #s are close and I shouldn't requote myself. This article is for air but in a general sense any fluid as you can read at the end.

One thing to mention where you were not wrong... and that is for the most precise result the size of the rod IS a small but real factor depending on the size of the rod (usually a small percentage but not nercessarily if the rod is the size of the piston)... but neverless a real factor that I did not mention for simplicity but from this article you can see you have a valid point.

Unrelated: I have gotten some more Dentsply feedback but more is expected shortly as well as the results of a few more experiments.

Thanks Mr. CSHOF for the reply. See if you can guess what hydraulic mischief the attached photos are. Here is the article for provenance:

How to Calculate Pneumatic Cylinder Force ( eHow.com )
Read more: How to Calculate Pneumatic Cylinder Force | eHow.com How to Calculate Pneumatic Cylinder Force | eHow.com
G.K. Bayne is a freelance writer for various websites, specializing in back-to-basics instructional articles on computers and electrical equipment. Bayne began her writing career in 1975 and studied history at the University of Tennessee. By G.K. Bayne, eHow Contributor

Pneumatic cylinders are used widespread in industry for repetitive motion in the manipulation of objects. Whether that object is being pushed or pulled, that cylinder must have enough force in order to efficiently move the object. All air pressure is measured in pounds per square inch (PSI),and by following a basic process you can calculate the total force that a pneumatic cylinder can deliver.

Instructions
1.
o 1
Measure the size of the air cylinder to calculate the total area that the air will be pushing against to create the force. All pneumatic cylinders are classified by the diameter of the cylinder and the length of the stroke. The most important measurement we need in calculating force is the diameter of the cylinder.
o 2
Find the total area in the pneumatic cylinder if the diameter is 4 inches. To find the area of a round circle for any object, the formula is A= (pi) x (Rsquared). Where A is equal to area, pi is equal to 3.1416 and Rsquared is the radius of the circle squared.
o 3
Calculate the area of the 4-inch diameter circle by first multiplying the radius times itself. This would equal 2 inches as the radius, times itself or 2 X 2 is equal to 4. Next multiply pi (3.1416) times the 4 and the answer is 12.5664 square inches. So the total area of the air cylinder is equal to 12.5664 inches^2, read as inches squared.
o 4
Find the total force from the air cylinder if the air pressure is equal to 100 PSI. Since PSI is equal to pounds per square inch, all we need to do is multiply the total area in square inches of the pneumatic cylinder times the air pressure in PSI. The total force delivered from the 4-inch diameter air cylinder with 100 PSI of air pressure would equal 12.5664 inches^2 times 100 PSI, which is equal to 1,256.4 pounds of force.
o 5
Understand that the 1,256.4 pounds of force would be on the push stroke only and not on the retraction end of the cylinder. The diameter of the push rod must be subtracted from the overall area, as the connection of the push rod interferes with the force measurement.
o 6
Find the area of the push rod for the retraction force measurement if the push rod is 2 inches in diameter. Using the formula from Step 3, the area of the push rod would be A = (3.1416) times 1^2, which is equal to 3.1416 square inches. Subtract 3.1416 from 12.5664 and the resultant area on the retraction stroke of the pneumatic cylinder would be equal to 9.4248 square inches. If the air pressure remains the same, at 100PSI, then the force would be equal to 942.48 pounds of force.
Tips & Warnings
• Any size cylinder can be calculated using the formula above. This includes hydraulic cylinders, as well. You only need to know the total pressure that the hydraulic system will deliver to the cylinder.


Read more: How to Calculate Pneumatic Cylinder Force | eHow.com How to Calculate Pneumatic Cylinder Force | eHow.com

See photo attachments if you wish. See if you can guess what hydraulic mischief the attached photos are.

 

[araucaria]

Wow, now that was an interesting presentation. You'd be a good physics/technology teacher. To be dedicated to making a difficult subject easier for others to understand and for free, in your own time, and for no reward is great. Thanks for the input.
Here's some extra questions for you to have a look into if you don't mind - with injection of acrylic in the lab we have several factors which may affect control.
1. when we have several injections to carry out (eg success system) the first injection will have fresher acrylic than the last. 2. Also the size and thickness of each mould inside the flasks will be different. The spruing patterns are likely to be different according to the shape and size of the enclosed moulds. 4. The ambient temperature in labs will vary due to the seasons and daily weather conditions, affecting the temperature of the equipment, materials, and rates of reaaction for the mixed resin.
So, on a warm day with warm equipment and materials, and a bunch of jobs to inject it's quite likely that the technician will be using his/her own personal experiences to determine how to proceed and not to refer to any scientifically produced manual for guidance. The pressure that will rapidly increase the rate of reaction during the injection will need to be taking into accout the final pressure needed to ensure a complete injection. The scientific data will help with rationalising when problems occur or when there's a potential for problems.
Scientifically produced data that supports the spruing sizes and patterns would be useful where there's a chance to improve the control of procedures.
Then we have different materials, eg autopolymerising resin, heatcured resin, and thermoforming resins (such as valplast) and they'll behave differently. Also, is there a benefit to having venting channels or sink-heads? And how would these affect the processes. Thanks in advance for having a look into these questions. I'm sure there's a load more questions out there from experienced techs who're looking for explanations to peculiar issues involving day-to-day procedures.

 

[altlab]

Reply to aracuria

Aracuria,
I think I would be well suited to being a teacher since they work long hours, are pooly paid and they have obstreperous clientell who know everything! I appreciate your appreciation. I wish there were more practical uses for this research. Achieving greatness as a methacrylate wizard just doesen't have that cache' you want. Reminds me of the man who named his new dog "Greatness" -because it was thrust upon him.If you find any of these answers before I do please let me know.

Since my serious research on methylmethacryate is just getting serious I will be of little immediate help for your extremely logical and linear supplemental questions. You make me realize just how under-researched this material is.I AM going to keep a copy of them and if I stumble accross answers I will certianly post you. I strongly suspect we are getting some bad curing temp info and if I didn't mention it before Dentsply said the tech sheet info for Faspor+ cure is incorrect and 52C is too high and go back to 40C. I had already done this and it is a dramatic improvement but I have got to do some more experiments incrementally to see the absolute low temp range. It IS time consumeing doing tests and only changing one variable at a time. I am even going to see if I an develop a cycle with a slightly chilled flask ramping up to 40C or so since the cure cycle is a bell curve with most of the polymerization/exotherm at the beginning.

Weekends for experiment activity...very slow. I am making molds to produce a consistent thickness acrylic wafer(s) to get around the thick/thin variable. Once I have figures for an average thin/thick there should be a mean temp. or cycle that works. I am also building an 80psi curing tank (mine blows at 30PSI). Just to see if it affects the density. Incidentally pre-vacuum degassing of the liquidus momomer/polymer mix before injection makes no difference. e a special machine for that too.

I am just gobsmocked as to how little usuable basic info there is on the internet on this material since its uses are so narrow. Also trying to get basic info from a well-meaning but superficial tech-rep is not much help either...although Denstsply powers-that-be promises to get back to me on this soon...we'll see. Contrary to appearances I don't really like being their beta-tester...I thought I was paying for that!

Only one thing to mention perhaps of help on your Q's: The Valplast family of materials are only phase-change pellet materials (melts,cools) and there is no other chemical reaction similar to methacryl. where the chemicals combine to make polymer chains and the excess monomer is leached out. I do know that the material used is acetal and nylon and was invented by the same person who invented the boomerang as we find out at repair or adjustment time. Having said this general industry by and large uses phase-change materials for most plastic products since it is so simple to heat and extrude (or blow-mold) and they don't expect you to repair the items. I don't offer the product because of the repair problems and in view of the fact the local clientell's favorite words are "free redo" coupled with the fact they could not take an accurate impression of their bottoms with both hands if their life depended on it.
Thanks and I will report back as I get educated.
Your Socrates quote: You may not have heard about it but Socrates' ascetic lifestyle resulted in him having continuing bouts of constipation. One day one of his pupils offered him a herbal remedy in the form of some local fern fronds -with great success. From this we get one of his greatest quotes: "With fronds like these, who needs enemas?"

 

[harry1]

"With fronds like these, who needs enemas?"

LOL!, my mojo for a Monday has just gone vertical!

 

[Smilestyler]

Okay, I'm not reading those last long posts, but the question was asked about using both materials in the same denture. I recently did a check up on a case that I relined last year with ivocap. The original denture base was made with probase hot and then relined using sr ivocap. Same usp shade was used but the two acrylics did not color match perfectly. Not a real issue. The one interesting thing that I found was the plaque accumulation was zero on the probase but on the ivocap there was significant plaque build. The only thing I can explain that might cause the difference is that ivocap is a high impact material and from years ago in school I recall rubber characteristics in high impact acrylic give it the resiliency to prevent breakage thereby changing the density, and therefore create less hygienic surfaces. If this is true than all acrylic that is 'high impact' will have this issue. I'm my opinion it can not be argued the more accurate fit of the ivocap regardless of the acrylic characteristics.