e.max Press - printed wax questions...

[Edward123]

I have two simple questions...

1. Does the .75 gram rule work with printed wax material? It may be my imagination, but the printed wax we are outsourcing seems heavier, ie. greater specific gravity than inlay wax. Using the .75 grams of wax per one e.max ingot seems to leave a bigger button which leads me to believe that it's heavier and thus would allow for more weight or more patterns than inlay wax. Has anyone else observed this and whats the printed wax per ingot formula you are using to compensate?

2. Old argument... This has to do with Press-Vest liquid/water ratio and setting expansion and printed wax. We are doing slow burnouts with a high (70%) liquid/water ratio and get loose fits. I regret having to ask this one but... shouldn't a high liquid to water mix yield tighter fits and a low (60%) liquid/water ratio give looser fits? Is this a printed wax material issue or did I just forget how to invest for fit altogether?

Thanks to all for the help!

 

[2thm8kr]

2. More special liquid in the ratio equals more expansion.

 

[Edward123]

2. More special liquid in the ratio equals more expansion.

Yes, that has always been the rule... but it seems to be creating looser fits with printed wax. Shouldn't higher expansion create tighter fits on crowns?

 

[Mohammad Khair]

the more water ratio the more tight crowns you get, that's why we use 100% water when we cast a post and core( no fitting fight),
reduce liquid and increase water to get tighter fit.

 

[Mohammad Khair]

more expansion means more loose crowns.

 

[rkm rdt]

Adjust the cement spacer settings in your cad design software.

 

[Edward123]

more expansion means more loose crowns.

If more expansion means loose crowns... would it hold true that more expansion means tighter inlays?

 

[Mohammad Khair]

If more expansion means loose crowns... would it hold true that more expansion means tighter inlays?

yes 100% correct statement.
i thought you were talking about crowns not inlays.

we will have a big problem if we had a bridge with one retainer as a crown and the other retainer as an inlay

 

[Edward123]

yes 100% correct statement.
i thought you were talking about crowns not inlays.

Thanks Mohammad. I was referring to crowns but threw inlays in as a validation comparison. The answer I got from IVOCLAR technical was the opposite. They said more liquid to water ratio = more setting expansion = tighter crowns for e.max. They explained that ceramic vs glass creates a different situation than casting precious alloys.

 

[Mohammad Khair]

well, it is really does not matter what material you cast or press into investment mold.

it is regarding the investment material control,the dental companies in general stop producing the gypsum bonded investment material and stop also producing silica bonded investment material long time ago.
99.99 of the investment martial in the dental world is a phosphate bonded investment,
for pressing technique and for casting technique.
the expansion control for such a material is related to its liquid concentration.

the more liquid the more expansion for all dental investment material.

more expansion means the cast or the pressed object will be bigger in size,
bigger in size means loose crown or tighter post or inlay.

this expansion is made to compensate the shrinkage of a hot molten material, when the said molten material is start to harden.

so all the dental investment is acting the same, and so does any molded molten material
the difference is only in range of expansion, size of the particles and hardness of the materials.

now a dental technician can have a little control of this process by controlling the liquid to water ratio.
adding more liquid means bigger pressed object or/and bigger cast object and vise versa.

 

[2thm8kr]

I don't have a specific ratio answer for you.
This is how I work out my liquid/water to powder ratios:

Make a master die out of something other than stone, epoxy, pmma, etc.
Something that doesn't erode easily.
Fabricate your pattern out of desired material. Use manufacturer's recommendation for liquid/powder ratio. Cast or press and then check the fit on the master die. Incrementally increase or decrease the special liquid by 1cc as needed to increase or decrease expansion until you get the fit that you want. Write it down for each material you make the patterns from.

My ratios are different for wax vs. pattern resin. I don't use printed patterns so I won't be if much use regarding that.

I'll add that, denser alloys require more expansion that less dense alloys(high noble vs. base) regardless of the material used to make the patterns. I assume it is the same for ceramic density as well. (emax vs. empress or other)

 

[Mohammad Khair]

Thanks Mohammad. I was referring to crowns but threw inlays in as a validation comparison. The answer I got from IVOCLAR technical was the opposite. They said more liquid to water ratio = more setting expansion = tighter crowns for e.max. They explained that ceramic vs glass creates a different situation than casting precious alloys.

your welcome anytime Edward

 

[Edward123]

well, it is really does not matter what material you cast or press into investment mold.


the more liquid the more expansion for all dental investment material.

more expansion means the cast or the pressed object will be bigger in size,
bigger in size means loose crown or tighter post or inlay.

adding more liquid means bigger pressed object or/and bigger cast object and vise versa.

I agree with you on fit but this is how I see it...

"more expansion means the cast or the pressed object will be bigger in size,
bigger in size means loose crown or tighter post or inlay."

Theoretically speaking, If the investment expands, it will expand in all directions therefore creating a thinner object in all directions. Thus the interior of a crown will be larger giving to more internal space rendering a looser fit but the the exterior will be smaller, which is of little consequence.

But if that were true, wouldn't it make sense that an inlay would also have a looser fit due to the additional expansion pressing inwards and making it smaller?

I am guessing you may agree?

 

[Gru]

I agree with you on fit but this is how I see it...

"more expansion means the cast or the pressed object will be bigger in size,
bigger in size means loose crown or tighter post or inlay."

Theoretically speaking, If the investment expands, it will expand in all directions therefore creating a thinner object in all directions. Thus the interior of a crown will be larger giving to more internal space rendering a looser fit but the the exterior will be smaller, which is of little consequence.

But if that were true, wouldn't it make sense that an inlay would also have a looser fit due to the additional expansion pressing inwards and making it smaller?

I am guessing you may agree?

It does not make a thinner pattern in all directions. The exterior is also larger.

No, the expansion is for the entire ring from the center outward (i.e. more liquid= higher expansion). Higher expansion does not increase the expansion into the pattern area, it's an overall outward expansion. So if the space left for a burned out crown is larger, the space of a burned out pattern of any shape is also larger. This ratio change is demonstrated well by looking at the pressvest speed empress esthetic crown vs. inlay ratios. Inlays have a lower expansion ratio in order to fit the die.