TL;DR: Osteoradionecrosis (ORN) is one of the most serious complications of radiation therapy for head and neck cancer. It occurs when the jawbone loses its blood supply after radiation, leading to exposed bone, infection, and pain. Hyperbaric oxygen therapy (HBOT) is one of the most well-studied treatments for ORN, helping to restore blood flow and promote healing through the growth of new blood vessels. This Daffodil Month, we explain what ORN is, how HBOT works to treat it, and what Canadian patients should know about access and coverage.
Estimated reading time: 8 minutes
What Is Osteoradionecrosis?
Osteoradionecrosis (ORN) is a serious complication of radiation therapy in which the jawbone loses its blood supply and begins to break down. Osteoradionecrosis (ORN) is a condition in which bone tissue dies after exposure to radiation therapy. It most commonly affects the mandible (lower jaw), though it can also occur in other irradiated bones. ORN develops because radiation damages the small blood vessels that supply the bone with oxygen and nutrients. Over time, this progressive vascular injury leaves the bone unable to repair itself from normal wear, dental procedures, or minor trauma.
ORN is a recognised late complication of radiation therapy for head and neck cancers, including cancers of the mouth, throat, tongue, and salivary glands. It can appear months or even years after radiation treatment has ended. Estimates suggest that ORN affects between 5% and 15% of patients who receive radiation to the head and neck region, though rates vary depending on radiation dose, technique, and individual risk factors.
During Daffodil Month, the Canadian Cancer Society’s annual campaign for cancer awareness, it is important to recognise that the effects of cancer treatment can persist long after the final radiation session. ORN is one of those lasting effects, and effective treatment exists.
How Does Radiation Damage the Jaw?
To understand ORN, it helps to understand what radiation does to bone tissue at a biological level. Radiation therapy targets rapidly dividing cancer cells, but it also affects the surrounding healthy tissue. In the jaw, the key damage occurs in three areas:
- Blood vessels: Radiation causes progressive damage to the small arteries and capillaries that supply the jawbone. This process, called endarteritis obliterans, narrows and eventually closes these vessels, cutting off blood flow.
- Bone cells: Osteoblasts (bone-building cells) and osteoclasts (bone-remodelling cells) are damaged by radiation, reducing the bone’s ability to repair and regenerate.
- Connective tissue: Radiation triggers fibrosis, a thickening and scarring of the tissue surrounding the bone, which further restricts blood flow and healing capacity.
The result is bone that is hypoxic (oxygen-starved), hypocellular (depleted of living cells), and hypovascular (lacking adequate blood supply). This is sometimes called the “three H” pathology of irradiated tissue. In this compromised state, even a simple tooth extraction or minor injury can trigger bone breakdown that the body cannot repair on its own.
Recognising the Symptoms of ORN
ORN can develop gradually, and early symptoms are sometimes mistaken for dental problems or infection. Common signs include:
- Exposed bone visible through the gum tissue that does not heal within 3 months
- Persistent jaw pain or tenderness in a previously irradiated area
- Swelling, redness, or drainage from the gum or jaw
- Difficulty opening the mouth (trismus)
- Loose teeth in the irradiated area
- A foul taste or odour from the mouth
- Numbness or altered sensation in the lower lip or chin
- In severe cases, pathologic fracture of the jaw
If you have received radiation to the head or neck and are experiencing any of these symptoms, speak with your oncologist or oral surgeon. Early intervention significantly improves outcomes.
How Does HBOT Treat Osteoradionecrosis?
Hyperbaric oxygen therapy addresses the root cause of ORN: insufficient blood supply to irradiated bone. During HBOT, patients breathe 100% oxygen at pressures greater than normal atmospheric pressure inside a specialised chamber. This dramatically increases the amount of oxygen dissolved in the blood and delivered to tissues throughout the body.
The therapeutic mechanism works through several interconnected pathways:
Angiogenesis: Repeated HBOT sessions stimulate the growth of entirely new blood vessels in the irradiated tissue. Over a course of 30 to 40 pre-operative sessions, or 60 sessions for established ORN, the treated area develops a new vascular network capable of sustaining bone health and healing.
Osteoblast activation: The elevated oxygen levels support the activity of osteoblasts, the cells responsible for building new bone. Research has shown that HBOT can enhance bone formation in previously irradiated tissue.
Antimicrobial effects: The high oxygen environment inhibits the growth of anaerobic bacteria, which are commonly found in ORN wounds. This helps control infection without relying solely on antibiotics.
Reduced inflammation: HBOT modulates the inflammatory response, reducing swelling and tissue damage while promoting a healing-oriented immune response.
A 2025 systematic meta-analysis examining treatment approaches for mandibular osteoradionecrosis found that HBOT, used as part of a comprehensive treatment strategy, contributed to improved healing outcomes in patients with ORN (Treatment Approaches Meta-Analysis, 2025).
What Does the Evidence Say?
HBOT for osteoradionecrosis is one of the most well-established applications of hyperbaric medicine. The Undersea and Hyperbaric Medical Society (UHMS) lists delayed radiation injury, including ORN, as one of its 14 approved indications.
The 2023 Cochrane review of HBOT for late radiation tissue injury confirmed that hyperbaric oxygen improves healing in patients with radiation-damaged tissue, including bone (Bennett et al., Cochrane Review, 2023).
A 2025 systematic review focused specifically on late radiation tissue toxicity after head and neck cancer found that HBOT produced significant improvements in tissue healing and symptom resolution across multiple studies (Head and Neck Systematic Review, 2025).
Research has also confirmed the safety profile of HBOT in cancer survivors. A 2025 evaluation examining HBOT for managing cancer treatment complications found no evidence that hyperbaric oxygen promotes tumour growth or recurrence (Safety Evaluation, 2025).
HBOT Protocols for Osteoradionecrosis
The standard HBOT protocol for ORN depends on whether the treatment is preventive (before a dental procedure in irradiated bone) or therapeutic (treating established ORN):
| Protocol | Sessions | Pressure | Duration per Session |
|---|---|---|---|
| Pre-operative (before dental extraction) | 20-30 sessions before surgery, 10 after | 2.0-2.4 ATA | 90-120 minutes |
| Therapeutic (established ORN) | 60 sessions, with reassessment | 2.0-2.4 ATA | 90-120 minutes |
Sessions are typically delivered once daily, five days per week. The pre-operative protocol is particularly important: if you have received radiation to the jaw area and need a tooth extraction, your dentist or oral surgeon should coordinate with a hyperbaric medicine team to plan HBOT before and after the procedure.
Is HBOT Covered for ORN in Canada?
Delayed radiation injury, including osteoradionecrosis, is one of the most widely covered indications for HBOT across Canadian provinces:
- Ontario: OHIP covers all 14 UHMS-approved indications at both hospital-based programs and approved private facilities
- Alberta: Covered at hospital-based AHS clinics and CPSA-accredited private facilities
- Quebec, British Columbia, Nova Scotia, and Newfoundland: Covered at hospital-based facilities for approved indications
- Other provinces: Interprovincial referral may be available
For a complete province-by-province breakdown, visit the Canada Hyperbarics coverage guide. To find a facility near you, use the facility finder with postal code search.
Frequently Asked Questions
Can HBOT reverse osteoradionecrosis?
HBOT can promote significant healing in ORN by restoring blood supply to the affected bone. In many cases, patients experience resolution of exposed bone, pain reduction, and improved jaw function. The degree of improvement depends on the severity of the ORN, overall health, and compliance with the full treatment protocol.
I had radiation years ago. Can HBOT still help?
Yes. ORN can develop at any time after radiation, and HBOT can be effective regardless of how long ago the radiation was delivered. Patients have been successfully treated 10, 20, and even 30 or more years after their original radiation therapy.
Do I need HBOT before a tooth extraction if I had radiation to my jaw?
If you received significant radiation to the jaw area, your dentist should consult with a hyperbaric medicine specialist before performing extractions. Pre-operative HBOT (typically 20-30 sessions before the procedure and 10 after) can significantly reduce the risk of developing ORN from dental work.
How do I get a referral for HBOT for ORN?
Ask your oncologist, oral surgeon, or family doctor for a referral to a hyperbaric medicine program. The referral should include your radiation treatment history (dates, fields, total dose) and current symptoms or planned dental procedures.
This Daffodil Month, Know Your Options
Osteoradionecrosis is a challenging complication of cancer treatment, but it is not something you have to live with without options. HBOT is a well-established, evidence-based treatment that can help restore blood supply to irradiated bone and promote genuine healing.
If you or someone you know has been treated for head or neck cancer with radiation therapy, awareness of ORN and its treatment options is an important part of long-term survivorship care. This Daffodil Month, the Canadian Cancer Society reminds us that supporting cancer survivors means supporting their ongoing health needs, including the late effects of treatment.
Find a hyperbaric facility near you across Canada.
References
- Treatment Approaches in Cases of Mandibular Osteoradionecrosis: A Systematic Meta-Analysis. (2025). View in Canada Hyperbarics Research Database.
- Bennett MH, Feldmeier J, Hampson NB, et al. Hyperbaric oxygen therapy for late radiation tissue injury. Cochrane Database of Systematic Reviews. 2023. View in Canada Hyperbarics Research Database.
- Hyperbaric Oxygen Therapy for Late Radiation Tissue Toxicity/Injury After Head and Neck Cancer: A Systematic Review of the Literature. (2025). View in Canada Hyperbarics Research Database.
- Hyperbaric Oxygen Therapy for Managing Cancer Treatment Complications: A Safety Evaluation. (2025). View in Canada Hyperbarics Research Database.
This content is for informational purposes only and does not constitute medical advice. Hyperbaric oxygen therapy should only be administered by qualified healthcare professionals in accredited facilities. Consult your physician or a certified hyperbaric medicine specialist for treatment decisions. Canada Hyperbarics is an independent educational resource and is not affiliated with any specific clinic or manufacturer.