Prosthodontics & Occlusion · patient case question
What is the characteristic DIRECTION of residual ridge resorption in the two jaws?
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: C. Maxilla upward and inward (centripetal); mandible downward and outward (centrifugal)
- A. The maxilla does not widen. Its ridge migrates palatally, which is why an old maxillary denture becomes progressively too large for the ridge it sits on.
- B. If both were centripetal the interarch relationship would stay proportionate, and the characteristic pseudo-prognathism would never develop.
- C. CORRECT. In the MAXILLA the labial and buccal plates are thinner, so resorption proceeds upward and INWARD and the arch becomes progressively SMALLER — CENTRIPETAL. In the MANDIBLE the lingual plate is thinner at the crest, so resorption proceeds downward and OUTWARD and the arch becomes progressively WIDER — CENTRIFUGAL. The two moving in opposite directions is why a long-term edentulous patient develops an apparent Class III, pseudo-prognathic relationship, and why the posterior teeth in such a case are often deliberately set in crossbite.
- D. This reverses both jaws and would predict a worsening Class II, which is not what is observed clinically.
Note: The mandibular ridge resorbs roughly FOUR TIMES faster than the maxillary — Atwood's classic observation — which is why the lower denture is almost always the problem. Practical consequences: set maxillary posterior teeth slightly buccal and mandibular slightly lingual to the crest as resorption advances, reline on a defined schedule, and consider two implants in the mandibular canine regions for an overdenture, which is now widely regarded as the minimum standard of care for the edentulous mandible.
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