Pour the Dental Model

After the stone is thoroughly mixed and air bubbles removed, you are ready to begin filling the impression.

  1. Fill the tooth depressions: Rest the impression tray against the vibrator’s edge. Place a small amount of stone on one of the distal ends of the arch. Allow the vibration to carry the material slowly across the impression, watching closely to ensure that the stone fills each depression with no air bubbles.
  2. Fill the impression body: When the tooth depressions have filled, add stone in larger amounts to a level slightly above the impression walls. Continue to vibrate to ensure complete coverage.
  3. Build the base: Place the remaining stone onto the work surface or plastic square, forming a mound slightly wider than the impression. If needed, make a second mix of gypsum and water for the base.
  4. Invert the tray: Place it on top of the base, smoothing the sides up onto the stone in the impression. Take care not to lock the edge of the tray into the stone.
  5. Let it set: Stone mixtures take from 30 minutes to one hour to completely set up and obtain maximum strength.
  6. Separate the model: After the stone is set and is cool to the touch, carefully separate the impression tray from the stone. Surface damage may occur if the cast remains attached to the impression material as it dehydrates.

Trim the Dental Model

The dental model is now ready for trimming. Factors that influence criteria for proper trimming include the following:

Keep the proportion of the base approximately half the thickness of the anatomic portion of the model. Be sure the base and occlusal plane are parallel to each other. The cast should extend slightly past the retromolar pad of the mandibular and the hamular notch of the maxillary.