Porosity!

Mona Lobsey

Mona Lobsey

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I am assuming press, what material? I have been told to never do 3 units unless they are lower mandibular, and small.

It's Emax. You can do 3 United bridges up to the second premolars. And I never had any breakage. Just keep the thickness not less than 0.8, big connectors and light occlusion..
 
Mona Lobsey

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Looking at the photo I see investment down in the "porosities" an this tells me it is not true Porosity. As Gru wrote it is some sort of investment breakdown. To help avoid this I would look at the following.

1. Investment: check your powder and liquid - make sure they are not expired, and there are no crystals/debris in the bottom of the investment bottle or measuring vial. Follow the manufacturer's directions precisely for mixing ratios/total liquid; mixing, setting, and burnout times.

2. Debubblizer: if you are using it, use one that is not soap based and dry all liquid from the restoration and sprue base/ring system as this extra liquid will mix with the investment and weaken it at the surface of the restoration. This will cause investment to break off and mix with the press material.

3. Wax pattern/Sprueing: NO SHARP CORNERS! Make sure the sprue attachment point to both the base and restoration are smooth and slightly flared and there are no really fine anatomy that will break during the pressing process. These very fine corners will break and become mixed into your press material.

4. If you are using a CAD/CAM process and either milling or, in particular, printing your patterns, many of these materials have a high resin content. These resins tend to expand quickly before melting and crack or breakdown the investment, which then again gets mixed with your press materials. If using a printed pattern, I always recommend a two stage burnout from room temperature. This will soften the material more slowly and it will prevent the rapid expansion that is so damaging.

I hope these tips help!

Thank you Patrick for the valuable informations! Will you please tell me what do you mean by two stage burnout?
 
Mona Lobsey

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Thank you all for the valuable informations! :)
 
CatamountRob

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Thank you Patrick for the valuable informations! Will you please tell me what do you mean by two stage burnout?
Two-stage burnout simply means to put a ring in a cold oven, raise it to some temperature and hold it at that for a length of time before raising it to the final temp.
 
Gru

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Thank you Patrick for the valuable informations! Will you please tell me what do you mean by two stage burnout?

As CRob said, raise the temp from room temp to the lowest temp at which the wax/resin melt and pour out of the investment. Hold the amount of time it takes to complete this on a large ring, then raise it to proper burnout temp and hold the recommended time per normal.
 
Patrick Coon

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Thank you Patrick for the valuable informations! Will you please tell me what do you mean by two stage burnout?

Here is our two stage burnout program for IPS PressVest Investment (NOT PressVest Speed):

Start at room Temp and raise 5C/41F per minute to 250C/482F and hold for 30 minutes. THen raise 5C/41F per minute to 850C/1562F and hold 45 minutes for 100gr ring and 1 hour for 200gr rings. If placing more than one ring in at a time, increase the hold at high temp by 1o minute per 100gr ring and 15 minutes per 200gr ring. So if you are placing three (3) 200gr rings in at the same time your hold time at the top temperature would be 1.5 hours (This is the earliest time to press your first ring).
 

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Mona Lobsey

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Here is our two stage burnout program for IPS PressVest Investment (NOT PressVest Speed):

Start at room Temp and raise 5C/41F per minute to 250C/482F and hold for 30 minutes. THen raise 5C/41F per minute to 850C/1562F and hold 45 minutes for 100gr ring and 1 hour for 200gr rings. If placing more than one ring in at a time, increase the hold at high temp by 1o minute per 100gr ring and 15 minutes per 200gr ring. So if you are placing three (3) 200gr rings in at the same time your hold time at the top temperature would be 1.5 hours (This is the earliest time to press your first ring).

Thank you Patrick! I'm using Bego investment so I wonder if that program would be Ok with Bego?
 
PearlZ

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alien_worms_creatures_by_klauskaos.jpg
 
Patrick Coon

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Thank you Patrick! I'm using Bego investment so I wonder if that program would be Ok with Bego?


It will probably be fine, but I would check their instructions for use to make sure. The only thing to be sure of is to use our high temperature, and make sure you heat soak at the top temperature longer as Bego is a denser investment than the PressVest and needs to heat soak longer to make sure the entire ring is hot all the way through.
 

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