New Dentures That Never Felt Right

Correct answer: A. Bilateral balanced occlusion — simultaneous contact on both sides in centric and in excursions

• A. CORRECT. BILATERAL BALANCED OCCLUSION is the scheme for complete dentures, and the reason is mechanical rather than biological. A complete denture is a free-floating prosthesis retained by a peripheral seal. If contact occurs on one side only during an excursion, the base tips and the seal breaks on the other side. Simultaneous contact bilaterally — and anteriorly and posteriorly — keeps both bases seated. Centric relation is used as the reference position because there is no reproducible tooth-determined position in an edentulous patient.
• B. Mutually protected occlusion with canine guidance is the scheme for the NATURAL dentition, where the periodontal ligament and the roots resist lateral load. Applied to a complete denture, canine guidance would tip the base off the ridge on every lateral movement.
• C. Posterior disclusion is the defining feature of a mutually protected scheme and is precisely what a complete denture cannot tolerate.
• D. Group function is likewise a natural-dentition scheme, appropriate where canine guidance is not achievable.

Note: ⚑ FLAG. The recall keyed 'centric relation with mutually protected occlusion only.' Centric relation IS correct as the reference position, but the excursive scheme for complete dentures is BILATERAL BALANCED, not mutually protected. Note the exception: an implant-retained or implant-supported prosthesis is stable enough to use canine guidance.

Correct answer: D. By measuring the interocclusal rest space, using phonetics such as repeating the letter 'M' to establish rest position

• A. The 'S' sound establishes the CLOSEST SPEAKING SPACE, about 1–1.5 mm, which is used to check that the VDO is not EXCESSIVE. It is a valid technique but tests the opposite error.
• B. Condylar position on radiograph does not measure vertical dimension.
• C. Deep nasolabial folds, a reduced lower facial height and angular cheilitis are clinical CLUES that raise the suspicion, but they are subjective and cannot quantify the loss.
• D. CORRECT. The patient repeats a sound that returns the mandible to PHYSIOLOGIC REST POSITION — the classic one is the letter 'M', as in 'Emma', after which the mandible settles at rest with the lips lightly together. The vertical dimension at rest (VDR) is measured between two marked points, and the OCCLUSAL vertical dimension (VDO) is measured with the teeth in contact. The difference is the INTEROCCLUSAL REST SPACE or freeway space, normally 2–4 mm. A freeway space substantially greater than this indicates lost VDO — which is exactly this patient's picture.

Note: The two phonetic tests are worth keeping straight: 'M' → rest position → measures freeway space → detects INSUFFICIENT VDO. 'S' → closest speaking space → detects EXCESSIVE VDO (teeth click during speech). Note that this patient's THREE anticholinergic medications explain the xerostomia, which itself worsens denture retention.

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.

Correct answer: A. The infraorbital rim

• A. CORRECT — this is the exception. The INFRAORBITAL RIM is part of the orbital margin, high on the facial skeleton and nowhere near the denture-bearing area or the depth of the buccal vestibule. It has no relationship to the flange.
• B. The CORONOID PROCESS DOES interfere. It moves forward and medially as the mouth opens, encroaching on the distobuccal flange in the tuberosity region. This is exactly why a patient reports the denture dislodging on wide opening or on lateral movement.
• C. The zygomatic process of the maxilla DOES limit the flange. It descends into the vestibule above the first molar region and must be relieved, or the denture rocks and the tissue over it ulcerates.
• D. The buccal frenum DOES interfere. It is a fold of mucosa that must be notched into the flange, and it moves with the orbicularis oris and buccinator — its position is recorded during border moulding.

Note: Border moulding for the maxillary denture: pull the cheek out, down and inward and ask the patient to open wide and move the mandible side to side — the last movement records the coronoid limit specifically.

Correct answer: D. Increase salty foods to stimulate salivary flow

• A. This IS good advice. Frequent sips of plain water are the simplest and most reliable measure.
• B. This IS good advice. Sugar-FREE gum, particularly with xylitol, mechanically stimulates residual salivary flow and xylitol additionally reduces cariogenic bacteria.
• C. This IS good advice. A humidifier reduces overnight mucosal drying, which is when symptoms are usually worst, especially in a mouth-breather.
• D. CORRECT — this is what should NOT be advised. Salty foods IRRITATE already dry, atrophic mucosa and cause burning and discomfort. Spicy, acidic, very dry and salty foods, alcohol and alcohol-containing mouthwashes, caffeine and tobacco should all be avoided in xerostomia.

Note: Complete the picture for this patient: identify and, with her physician, review the causative drugs — amitriptyline and oxybutynin are both strongly anticholinergic. Add saliva substitutes, prescription-strength fluoride (5000 ppm) because caries risk is high, and consider pilocarpine or cevimeline where residual gland function exists.