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Prosthodontics & Occlusion · patient case question

The supra-erupted mandibular left posterior segment presents which principal problem for rehabilitation?

Patient case: Failing anterior bridge and a collapsed posterior bite

Patient: Female, 68 years old

Chief complaint: “My front bridge is loose, and my temporary cap fell off while I was eating.”

History: Hyperlipidaemia, depression. Medications: atorvastatin, citalopram.

Findings: Anterior fixed partial denture is mobile as a unit. An existing metal-ceramic crown on tooth #14 shows a grey band at the gingival margin. Diagnostic casts show the mandibular left posterior segment supra-erupted into the opposing edentulous space. A new all-ceramic crown is being tried in on tooth #30.

  1. An increased vertical dimension of occlusion
  2. Increased risk of caries in the supra-erupted teeth
  3. Reduced retention of a future partial denture clasp
  4. Loss of interocclusal restorative space, with a collapsed occlusal plane
Show answer and explanation

Correct answer: D. Loss of interocclusal restorative space, with a collapsed occlusal plane

  • A. Supra-eruption does not increase the vertical dimension of occlusion, which is set by the remaining posterior contacts. What changes is the occlusal PLANE, which becomes irregular.
  • B. Supra-erupted teeth do carry caries and periodontal risk from the exposed root surface, but that is a secondary consequence rather than the principal obstacle to rehabilitation.
  • C. Clasp retention concerns the abutment on the OPPOSITE side of the arch and is not the governing problem.
  • D. CORRECT. A tooth without an opponent erupts, carrying its alveolar bone with it. The consequences are a DISTURBED OCCLUSAL PLANE and, critically, LOSS OF THE INTEROCCLUSAL SPACE needed to restore the opposing arch. There is simply nowhere to put a prosthesis. The options for recovering space are enameloplasty for minor discrepancies, elective endodontics with crown shortening for moderate ones, orthodontic intrusion, segmental osteotomy, or extraction.

Note: Prevention is far easier than correction. Replace or otherwise manage an opposing space promptly — by the time a segment has dropped 3 to 4 mm, recovering space costs endodontics or surgery.

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