The posterior extent and effectiveness of the posterior palatal seal is determined primarily by:

Correct answer: B. The resilience (displaceability) of the soft tissue in that region

• A. The maxillary tuberosity is a support and stability landmark; it does not determine the depth of the posterior palatal seal.
• B. CORRECT. The posterior palatal seal is carved into the cast to a depth governed by TISSUE RESILIENCE — how far the soft tissue at the vibrating line can be displaced without discomfort. Displaceability is assessed clinically with a blunt instrument, and the seal is deepest where the tissue is most compressible (typically the pterygomaxillary notch region) and shallowest where the tissue is firm and thin, such as over the midline raphe. Correct carving produces intimate contact that maintains a peripheral seal and prevents air from breaking retention.
• C. The labial vestibule governs the anterior border extension and has no relationship to the posterior seal.
• D. The uvula is a soft palate structure, posterior to the seal region. The relevant landmark is the VIBRATING LINE (demonstrated by having the patient say 'ah'), not the uvula itself.

Note: Over-carving causes tissue soreness and hyperplasia; under-carving causes loss of the seal and a dropping denture. Remember to provide relief over a MIDLINE RAPHE or torus, where thin tissue over bone cannot be compressed.