Maxillary Complete Denture Short of the Posterior Palatal Seal After Processing

Short border

The posterior border was already established on the cast with a 1.0-mm posterior palatal seal. Adding a second increment of acrylic after a deficient trial pack changes the amount and distribution of material. Heavy flask closure forces excess acrylic into the flask rather than into the border, and the processed denture can contract away from the cast. The result is a border 1.5 mm short of the vibrating line, losing the seal.

Increased vertical dimension

Overpacking and a second increment increase the bulk of acrylic between the casts. Heat-cured PMMA also undergoes polymerization shrinkage, but the flasking and packing technique is supposed to compensate for it. Here the compensation was uncontrolled, so the occlusal surfaces were pushed apart. A 2-mm increase is clinically significant and can cause rocking and soreness.

Sore spots at the hamular notches

A border that is short posteriorly may still impinge at the hamular notch if the flash or excess material was not properly trimmed. Heavy pressure during flasking can also distort the cast or the record base. The combination of an impaired seal and an increased vertical dimension produces rocking, food collection, and localized pressure.

Judgement

This is not a simple 'sore spot' adjustment. Chairside relief alone cannot restore a border seal or correct a 2-mm vertical dimension error.

Decision

A chairside adjustment alone is inadequate. The border is 1.5 mm short, the posterior palatal seal is lost, and the vertical dimension is 2 mm high. A laboratory reline can correct the tissue surface and border if the occlusion is remounted and corrected, but the existing acrylic base is already distorted. For a definitive result, a remake or a heat-cured reline with occlusal correction is preferable.

Laboratory procedure

• Obtain a new verified impression or a reline impression with the existing denture after tissue conditioning if the mucosa is inflamed.
• Pour a master cast and re-establish the posterior palatal seal, usually about 1 mm, without excessive relief under the vault.
• Mount the casts with a new interocclusal record and correct the occlusal vertical dimension on the articulator.
• If relining, process with heat-cured PMMA, using a controlled pack and flask closure; avoid a second uncontrolled increment.
• Trim and polish the border, preserving the seal and relieving the hamular notches.
• Remount and adjust occlusion after processing.

Why not simply extend the border with autopolymerizing acrylic

Adding acrylic at the chair may close the gap temporarily, but it does not correct the processed distortion or the vertical dimension. It can also create a rough, porous border that collects plaque.

Clinical records

• Verify the vibrating line and the posterior palatal seal area on the cast before processing.
• Record the occlusal vertical dimension with a stable record base and a reproducible interocclusal record.
• Check the trial denture for border extension, retention, and occlusion before processing.

Laboratory controls

• Use a controlled packing protocol: measure the acrylic, trial pack, and remove excess evenly. Do not add a second increment to 'fill' a border deficiency unless the cast and trial base are re-evaluated.
• Close the flask under controlled pressure, not heavy force. Follow the manufacturer's flasking and curing cycle.
• After processing, measure the border extension against the cast and check the occlusal vertical dimension on the articulator.
• Remount the processed denture and correct processing changes before delivery.

Quality-assurance indicator

A denture that is more than 1 mm short of the intended border or more than 1 mm off the planned vertical dimension should be treated as a processing failure requiring laboratory correction, not chairside camouflage. Document the measurements and the corrective action.