For how long after head and neck radiotherapy does the risk of OSTEORADIONECROSIS persist?

Correct answer: C. For the patient's lifetime

• A. Two years is a common but incorrect assumption; extractions performed years after radiotherapy still precipitate ORN.
• B. Six months corresponds only to the acute mucositis and xerostomia phase. The bony risk long outlasts the soft tissue recovery.
• C. CORRECT. The risk of osteoradionecrosis is LIFELONG and, if anything, increases with time. Radiation produces a permanently HYPOXIC, HYPOVASCULAR and HYPOCELLULAR bone as endarteritis obliterans progressively narrows the vessels — an irreversible change that does not recover. The mandible is at far greater risk than the maxilla because of its dense cortex and single-vessel end-arterial supply. Risk rises sharply above roughly 60 Gy.
• D. Seven years is arbitrary; no such expiry exists.

Note: This is why PRE-radiation dental clearance is critical: extract any tooth of questionable prognosis at least 14-21 days BEFORE radiotherapy begins to allow mucosal healing. Afterwards, aim to avoid extractions in the radiated field entirely — restore, endodontically treat and decoronate rather than extract, maintain scrupulous prevention with daily fluoride trays, and consult the oncologist regarding hyperbaric oxygen if surgery is unavoidable.