Modeling Dentures
After the impression was created, a plaster model (or “cast”) of the mouth area was made. (11) A plaster cast aided in constructing artificial dentures by providing its positive likeness. (12) A plaster mixture was poured onto the impressions (9) until the model had a depth of about two inches. (10) The cast was then separated from the impression by first removing any overhanging plaster with a plaster knife. Then, the impression was removed from the dental cup. This was done by warming the dental tray so that the cup and impression could be parted. Note that at this point, the impression and cast are still attached, so the next step was to separate the two. (12)
A wax impression removed from its cast by warming it over a flame or by being immersed in warm water which sufficiently softened the impression for removal. (10) Removing plaster impressions from the cast was a bit trickier. A stain such as shellac was used so that it was easily identifiable which part of the plaster is the model and which is the impression. With the dental cup in hand, model and impression was separated by tapping lightly the dental cup handle, or by using an instrument to drive a wedge between impression and cast. (9)
