Prosthodontics & Occlusion · patient case question
Which statement about the posterior palatal seal is FALSE?
Patient case: New Dentures That Never Felt Right
Patient: 71-year-old female
Chief Complaint: “These dentures make my face look collapsed and I whistle when I talk.”
Background: Maxillary complete denture and mandibular RPD made three years ago elsewhere. Chronic dry mouth.
Medications: Amitriptyline, oxybutynin, atenolol
Vital Signs: BP 134/78 mmHg · HR 68 bpm · RR 16 · T 98.4°F
Findings: Reduced lower facial height with deep nasolabial folds and angular cheilitis. The maxillary denture drops on wide opening. The posterior border ends short of the vibrating line. Mucosa is dry and tacky; the mirror sticks to the buccal mucosa.
Show answer and explanation
Correct answer: C. It should cover the entire soft palate
- A. This IS true. The seal is placed at or just posterior to the VIBRATING LINE, the junction between the movable and non-movable soft palate.
- B. This IS true, and it is the principal purpose. Acrylic resin shrinks on polymerisation, lifting the posterior border away from the tissue; the seal is the compensating displacement that preserves the peripheral seal.
- C. CORRECT — this is the FALSE statement. The posterior palatal seal is a NARROW BAND of controlled tissue displacement, roughly 1–2 mm wide anteroposteriorly and up to about 1.5 mm deep at its centre, located at the junction of the hard and soft palate. Extending it across the whole soft palate would produce gagging, tissue trauma and instability — the soft palate MOVES during swallowing and speech, and a denture cannot be seated on moving tissue.
- D. This IS true. Asking the patient to say 'Ah' vigorously demonstrates the vibrating line; the Valsalva manoeuvre with the nose held is the other standard method.
Note: The seal ends laterally in the HAMULAR NOTCHES on each side, between the pterygoid hamulus and the maxillary tuberosity. This patient's denture ends SHORT of the vibrating line, which explains why it drops on wide opening — the peripheral seal is incomplete.
Practice Prosthodontics & Occlusion questions Prosthodontics & Occlusion study notes