Dental Impression Plaster

AVAILABLE IN 5, 25, AND 50LB OPTIONS IN THE DROPDOWN

USG Dental Plaster - Impression is designed for use in oral impression work where very fast set times
are needed. Fast-setting USG Dental Plaster – Impression is easy to use and offers many applications
for dental stones. Its set time can be altered by the use of accelerators or retarders. Water soluble,
USG Dental Plaster – Impression requires no organic solvents for cleanup.

MIXING INSTRUCTIONS

Use potable water at temperatures between 70 °F (21 °C) and 100 °F (38 °C). Because variations
in slurry (USG Dental Plaster - Impression and water mixture) temperature produce variations in
set time, it is important to keep both the USG Dental Plaster - Impression and water in a stable
temperature environment prior to use. The higher the temperature of the slurry, the shorter the set
time. Conversely, the lower the temperature of the slurry, the longer the set time.

Weigh both the USG Dental Plaster - Impression and the water prior to use for each mix. The water-
to-USG Dental Plaster - Impression ratio is critical because it governs the strength and the density
of the final cast.

Sift or strew USG Dental Plaster - Impression into the water slowly and evenly. Do not drop large
amounts of USG Dental Plaster - Impression directly into the water as proper soaking of the
USG Dental Plaster - Impression may not occur. USG Dental Plaster - Impression should be fully
dispersed in the water prior to mixing. Small batches require less soaking time than large batches.
See USG IG503 Plaster Mixing Procedures for specific soaking instructions.

Mixing USG Dental Plaster - Impression slurry is one of the most important steps in producing
USG Dental Plaster - Impression casts with maximum strength, absorption, hardness and other
important properties.

Mechanically mixed slurries develop uniform casts with optimal strengths. USG Dental Plaster -
Impression can be mechanically mixed through both batch and continuous processes. Proper blade
and bucket dimensions are important for obtaining the best batch mix (see USG IG503 Plaster
Mixing Procedures for details).

Longer mixing times result in higher mold strength and shorter set times.

POURING

To prevent air entrainment and provide a uniform, smooth surface, careful pouring of USG Dental
Plaster - Impression slurry is necessary. Agitation/vibration of the filled mold is a further step used
to prevent air at or near the mold surface. Whenever possible, USG Dental Plaster - Impression
slurry should be poured carefully in the deepest area so that the slurry flows evenly across the
surface of the case mold.

Pouring a large amount of slurry directly on the face of the case mold may result in slight
densification of the USG Dental Plaster - Impression mold at the point where it strikes the surface of
the case. This produces a hard spot, giving uneven absorption.

DRYING

All casts should be dried as quickly as is safely possible after manufacture so that maximum
physical properties can develop. Dry to a constant weight.

The best drying rooms or ovens provide 1) uniform and rapid circulation (minimum of 15-30 fps
(4.6-9.1 mps)) of air with no “dead spots” having little or no air movement, 2) equal temperatures
throughout the entire area, and 3) provisions for exhausting a portion of the air while replacing
it with fresh air. High humidity surrounding the drying room or oven inhibits drying efficiency
because the air pulled into the room is incapable of picking up much moisture from the molds.

The maximum temperature at which USG Dental Plaster - Impression molds are safe from calcination
is 120 °F (49 °C). With substantial free water in the mold, a higher drying temperature can be used
without difficulty. As drying progresses, the temperature must be reduced to prevent calcination.
Before removing molds from the dryer, the temperature should approach that of the area around
the dryer to prevent thermal shock. See IG502 Drying Plaster Casts for additional information.

STORAGE AND USE

When properly used, USG Dental Plaster - Impression is safe to handle and easy to work with.
Keep indoors at temperatures between 65 °F – 75 °F (18 °C – 24 °C) and 45% – 55% RH. Do not
stack more than two pallets high. Keep from drafts. Rotate stock. USG Dental Plaster - Impression
should be used within six months of the manufacturing date located on the package. Always follow
handling and use directions and safety warnings on the package.

SDS