Prosthodontics & Occlusion · patient case question
What is the PRIMARY stress-bearing area of the mandible for a complete denture?
Patient case: A resorbed ridge and a sore denture
Patient: Male, 68 years old
Chief Complaint: “My lower denture has never been comfortable and the roof of my mouth is sore.”
Background: Edentulous for twenty-two years. Current dentures are eight years old; the lower was relined chairside with a self-curing acrylic three years ago. He wears both day and night.
Vital Signs: BP 138/82 mmHg · HR 74 bpm
Findings: Severely resorbed mandibular ridge. Diffuse erythema of the denture-bearing palatal mucosa conforming exactly to the outline of the upper denture. The mandibular arch appears wide relative to the maxilla, and the posterior teeth meet edge to edge.
Show answer and explanation
Correct answer: A. The buccal shelf
- A. CORRECT. The BUCCAL SHELF is bounded by the external oblique ridge buccally, the crest of the residual ridge lingually, the buccal frenum anteriorly and the retromolar pad posteriorly. Two properties make it the primary stress-bearing area: it is covered by DENSE CORTICAL bone, and it lies at RIGHT ANGLES to the direction of vertical occlusal force. The slopes of the residual ridge are usually named alongside it.
- B. The retromolar pad is a SECONDARY stress-bearing area, and its more important role is as a posterior LIMITING structure — the denture must cover its anterior two-thirds to achieve the posterior seal. It is also the landmark for the occlusal plane and for setting the second molar.
- C. The mylohyoid ridge is a RELIEF area: sharp, covered by thin mucosa, and a classic source of lingual soreness. It is relieved, never loaded.
- D. The CREST of the mandibular residual ridge is cancellous, it is the site of ongoing resorption, and it tolerates load poorly — it is relieved rather than loaded. This is the option most candidates take.
Note: ⚠️ The recall author chose ‘alveolar ridge’ and doubted it. The examinable answer for the mandible is the BUCCAL SHELF. Keep the maxillary counterpart separate: there the primary stress-bearing areas are the HORIZONTAL HARD PALATE and the posterior ridge slopes, with relief over the incisive papilla, the midpalatine raphe or torus, and the crest of a flabby anterior ridge.
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