Denosumab and a Split Molar: Weighing MRONJ Risk
A 74-year-old woman is referred for management of tooth 36. The tooth has a necrotic pulp, a 6 mm periapical radiolucency and a split of the mesial cusp; it is symptomatic on chewing. Her medical history includes postmenopausal osteoporosis treated with denosumab 60 mg subcutaneously every six months for the past four years; the most recent injection was eight weeks ago. She also takes calcium and vitamin D and has well-controlled hypothyroidism. She has never had radiotherapy to the head and neck and has no history of malignancy. She has no other teeth with periapical disease, and her periodontal condition is stable with 3 mm pockets. She asks whether the tooth can be saved and whether the injection will cause 'my jawbone to die'.
1. How would you estimate and explain her risk of medication-related osteonecrosis of the jaw (MRONJ)?
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Estimate: low but not zero. Denosumab is an antiresorptive, and MRONJ risk in osteoporosis dosing is in the order of 0.01–0.1%, far below the risk seen with oncology dosing. Risk rises with duration of therapy (over about four years), with concomitant corticosteroids, diabetes, smoking, and with invasive procedures. She has none of those additional factors and no relevant malignancy or radiotherapy history, so she falls into a low-risk group - but low is not the same as none.
Explain in plain language: 'The injection slows the cells that break down bone. In a small number of people, after a tooth is removed, the bone can be slow to heal and a small piece of bone may stay exposed. Most people heal normally. Your risk is small because you are on the osteoporosis dose and have no other risk factors, but it is not zero, and we will plan the extraction to reduce it.'
Avoid jargon such as 'dead bone' and avoid guaranteeing that nothing will happen.
2. Should the tooth be root-treated or extracted, and what is your view on a drug holiday?
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Extraction is the more defensible choice here. The tooth has a necrotic pulp, a periapical lesion and a split mesial cusp. Root canal treatment would remove the infection but would not restore the fractured cusp; the tooth would still need cuspal coverage and would remain at high risk of further fracture. The split cusp also suggests the fracture may extend subgingivally, which worsens the restorative prognosis.
If the tooth were restorable and the patient strongly preferred to keep it, root canal treatment plus a cuspal-coverage restoration would be a legitimate alternative, with the caveat that failure would eventually require extraction anyway. That conversation should be documented.
Drug holiday: generally not recommended for denosumab. Unlike bisphosphonates, denosumab is not incorporated into bone; its effect wanes over months after the last dose, and interrupting therapy causes rebound bone loss and, in some patients, vertebral fractures. The decision to alter therapy belongs to the physician managing her osteoporosis. The practical approach is to proceed with the extraction and inform the physician, rather than to stop or delay the drug. CTX testing has not been validated as a risk predictor and should not be used to gate treatment.
3. Outline your operative protocol and follow-up.
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Pre-operative
- Informed consent covering MRONJ risk, alternatives (including no treatment and root canal treatment), and the plan if healing is delayed.
- Optimise oral hygiene; chlorhexidine rinse before and after.
- Consider timing the extraction shortly before the next scheduled denosumab dose (i.e., near the end of the dosing interval), in consultation with the physician.
Operative
- Local anaesthesia; atraumatic technique - periotome, careful luxation, avoid prolonged bone trauma.
- Remove sharp bony edges, smooth the socket, and aim for primary soft-tissue closure.
- Avoid unnecessary curettage and avoid placing a membrane or graft in an infected socket.
- Antibiotics only if there is spreading infection or another specific indication, not routinely.
Follow-up
- Review at 1–2 weeks for soft tissue, then at 8 weeks for mucosal healing.
- If bone remains exposed beyond 8 weeks with no healing, this meets the definition of MRONJ: stage it, manage conservatively with hygiene, chlorhexidine and symptom control, and refer to oral and maxillofacial surgery if needed. Avoid further elective surgery in the region.
- Report the event to the physician and, where applicable, to the relevant pharmacovigilance programme.