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Tufts OpenCourseware
Author: David M. Hern, D.M.D.

Guidelines for Marking the Posterior Limit and Placing the Posterior Palatal Seal

The following is a laboratory technique only. Clinically the posterior limit and the posterior palatal seal are determined intra-orally using vision, palpitation and patient response.

  1. Locate the left and right hamular notches and draw U-shaped outlines into each which extend 3mm buccal to the mid-point of each hamular notch.
  2. Draw a small line perpendicular to the mid-palatal suture line ad the midline, posteriorly on the palate, 4mm. from the inside of the land area.
  3. From the distal line of the left hamular notch “U” draw a gracefully curving line medially to the mid-palatal line. Repeat this procedure on the right side.
  4. The following illustration shows the curved line which will determine the anterior aspect of the pot dam. From the anterior line of the left hamular notch "U" it will curve anteriorly over the area of the minor palatine glands, curve posteriorly to the area which is approximately 3mm to the left of the mid-palatial suture. The line will continue across the mid-palatal suture creating a thin isthmus over this landmark. The line continues identically on the right side.
  5. Using a #8 round burr, at either high or low speed, and the discoid carving instrument, relieve the master cast along the entire length of the distal aspect of the post damn line from the end of one hammular notch "U" to the other. When using the burr, rest the shank of the burr on the surface of the cast so as not to cut too deeply into it. Create a channel 1 1/2 to 2mm. deep from the edge of one hamular notch "U" to the other. Using the cleiod carving instrument, square the posterior aspect of this channel.
  6. Using the cleoid carver and a laboratory knife scrape the posterior palatal seal (post dam) into the master cast. This relief should extend from the depth created posteriorly to the anterior outline of the post dam where it comes to a feather edge.