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Periodontics · patient case question

Which defect offers the best prognosis for regenerative therapy?

Patient case: Implants, Peri-implantitis, and a Regeneration Question

Patient: 59-year-old male

Chief Complaint: Review of two implants placed four years ago, and assessment of a defect on tooth #6.

Background: Former smoker. History of treated periodontitis. Irregular maintenance attendance.

Medications: None

Vital Signs: BP 130/82 mmHg · HR 74 bpm · RR 16 · T 98.4°F

Findings: Implant at site #19: 6 mm probing depth with bleeding and suppuration, 2 mm of radiographic crestal bone loss. Tooth #6 has a NARROW three-walled intrabony defect on its MESIAL surface, 6 mm deep, with the tooth firm and vital. Posterior mandibular ridge is being assessed for a further implant.

  1. A narrow three-walled intrabony defect on the mesial of a canine
  2. A Class III furcation involvement of a mandibular molar
  3. A horizontal bone loss defect in the posterior mandible
  4. A wide one-walled defect on the distal of a molar
Show answer and explanation

Correct answer: A. A narrow three-walled intrabony defect on the mesial of a canine

  • A. CORRECT. NARROW THREE-WALLED intrabony defects give the most predictable regenerative outcome. The reasons are geometric and biological: three surrounding bony walls provide space maintenance and containment for the graft, a large surface area of vascular bone supplying progenitor cells, and mechanical protection for the clot. Narrow, deep defects — with a small angle between the root and the bony wall — regenerate better than wide shallow ones. A single-rooted anterior tooth adds good access.
  • B. A Class III (through-and-through) furcation has a very poor regenerative prognosis. Only Class II furcations, particularly mandibular buccal ones, respond predictably.
  • C. HORIZONTAL bone loss cannot be regenerated at all. There is no defect to contain a graft — this is the fundamental limitation of regenerative periodontal therapy.
  • D. A one-walled defect has almost no containment, minimal cellular contribution and no clot protection. These are usually managed by resective therapy instead.

Note: The hierarchy: three-wall > two-wall > one-wall, and narrow > wide, and deep > shallow. Mandibular Class II furcations respond; Class III does not.

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