Oral Surgery · patient case question
Where does MRONJ most commonly occur?
Patient case: Bisphosphonates and a Diastema
Patient: 67-year-old female
Chief Complaint: “I've always hated the gap between my front teeth. Can it be closed?”
Background: Osteoporosis, on oral alendronate for four years. Tooth #8 was root treated eight years ago.
Medications: Alendronate 70 mg weekly, calcium, vitamin D
Vital Signs: BP 134/78 mmHg · HR 70 bpm · RR 16 · T 98.4°F
Findings: A 2.5 mm midline diastema between #8 and #9. Tooth #8 is root treated with an intact but discoloured crown; #9 is vital and unrestored. Periodontium is healthy with no bone loss.
Show answer and explanation
Correct answer: A. Posterior mandible
- A. CORRECT. The POSTERIOR MANDIBLE, particularly the mylohyoid ridge and lingual aspect, is the commonest site — roughly two-thirds of cases occur in the mandible. The reasons are anatomical: thin overlying mucosa over sharp bony prominences that ulcerate easily, a relatively poorer blood supply than the maxilla, and the fact that this is where extractions and denture trauma concentrate.
- B. The condyle is not a site of MRONJ; it is not exposed to the oral environment.
- C. The posterior maxilla accounts for most of the remaining third of cases — less common than the mandible but not rare.
- D. The anterior maxilla has a rich blood supply from multiple sources and is an uncommon site.
Note: Staging: Stage 0 is non-specific symptoms with no exposed bone; Stage 1 is exposed necrotic bone, asymptomatic, no infection; Stage 2 adds pain and infection; Stage 3 extends beyond the alveolus with pathological fracture, extraoral fistula or sinus involvement. Stages 1 and 2 are managed conservatively — antimicrobial rinses, antibiotics, analgesia — with surgery reserved for Stage 3 or non-responsive disease.