Shortening the Record Base Border

The dentist then reinserts the maxillary trial denture. The patient is once again directed to blow through the obstructed nose; this will bring the marking on the palate into contact with the maxillary trial denture base.

The dentist then shortens the base to the indicated length and watches the soft palate as the patient says Aah. The movement of the soft palate should originate at the most posterior extent of the trial denture base. The dentist can further verify the border length in the mouth by palpating the soft palate with a finger or the end of the intraoral mirror handle. The hard palate should not be evident as the finger moves posteriorly.

The trial denture is then removed. The dentist should then gently palpate the mucosal tissues just anterior to the vibrating line to ascertain the degree to which they will tolerate the deliberate distortion introduced by the posterior palatal seal. This palpation should continue laterally to the pterygomaxillary area; the region immediately posterior of the tuberosities. This area is best palpated with the edge of the introral mirror.

Designing the Posterior Palatal Seal

The posterior palatal seal will ensure the posterior extent of the maxillary denture, which has a tendency to move away from the master cast during the shrinkage that accompanies the heat curing of methylmethacrylate resin, remains in contact with the palatal tissues. If this contact is not maintained, the peripheral seal of the maxillary denture will be broken and the denture will be non-retentive. To maintain that contact despite the shrinkage of the denture, the tissue surface of the posterior portion of the denture is deliberately extended slightly into displaceable glandular and areolar tissue overlying the hard palate and the pterygopalatline notches. This is accomplished by removing a discrete amount of stone in the maxillary master cast when palpation has demonstrated the patient will tolerate it without
discomfort.

Carving the Palatal Seal

While the patient is still present and the tissue consistency of the posterior palatal seal area fresh in the dentist’s memory, the posterior palatal seal should be carved into the master cast.

The shape of the posterior palatal seal will differ from patient to patient, according to the relative tautness or flaccid nature of the tissues. The groove that is carved into the master cast should be deepest in its most posterior extent (where the tissue is transitioning into the soft palate and is therefore most displaceable) and then beveled anteriorly, as guided by the findings of the intraoral palpation. The depth of the dam is typically 0.5-1.5 mm deep at its most posterior extent. Consistent with the findings from the intraoral palpation, the carving of the post-dam should continue into the tissues posterior to the tuberosities.