Chairside Guide to Pouring Models

Step 1

Disinfect non-porous impressions by immersing in disinfectant.

-

Step 2

Use the "Island" Technique. Place water in a mixing bowl first. Add the measured powder and allow gypsum particles to "wet" for approximately 15 seconds. Never place powder in the mixing bowl first.

-

Step 3

If spatulating by hand, spatulate the mix by stirring vigorously with a clean, stiff spatula, constantly wiping the material down the side of the mixing bowl until the water has wet all the powder

-

Step 4

Spatulate by hand at a rate of 120 RPM for 60 seconds until a smooth and uniform mix is achieved or mix with mechanical spatulation for 15 seconds at slow speed or use manufacturer's suggested mixing application.

-

Step 5

If using mechanical spatulation, upon removal of lid, vibrate the lid from the mixing container so all of the material flows back into the mixing vessel.

-

Step 6

Start in an area away from actual preparation. Using a small instrument, add the gypsum to the impression in small increments under vibration until the gypsum wets all sides of the impression. No water should be remaining in the impression. If water is present, the impression should be rinsed out and poured again.

-

Step 7

Allow impression to set for 2-3 minutes and then invert. The model should be left undisturbed for 45 minutes to 1 hour before removing impression.

-

Step 8

For best results, models should be allowed to dry for 24 hours.

-

The Physical Facts

Warm water = Faster set

Cold water = Slower set

Excess powder = Fast set, stronger model

Excess water = Slow set, weaker model

Additional mix time = Longer working time, lumpy mix, weaker set

Shorten mix time = Longer working time, lumpy mix, weaker set