Definition:
- Multiple authors have defined ORN
- Marx 1983- greater than 1cm for longer than 6 months
- Harris 1992 (easiest definition)- exposed and necrotic bone associated with ulcerated or necrotic soft tissue that persists longer than 3 months in an area that been previously irradiated
Aetiology:
- Radiation injury to bone
- Rare if less than 60 gray given
- Lower if hyperfractionation
- IMRT may reduce it
- Addition of chemo potentially increases risk
- Brachytherapy highest risk
Epidemiology:
- Varies from 2.6-22%
- Mainly mandible- especially mylohyoid ridge
- Thought that inferior alveolar artery affected by the radiotherapy
Presentation:
- Mild asymptotic disease
- Progressive pain
- Supparation
- Exposed bone
- Fracture
Changing concepts:
- Before 1980s it was thought that infection was the key precipitant
- In 1980s Marx suggested the 3 Hs
- 2004 onwards Delanian theory
Marx '3 H' concept:
- Hypovascularity
- Hypoxia
- Hypocellularity
Delanian theory:
- Proposed fibroatrophic theory
- Radiation produces free radicals
- This injures endothelial cells
Classification:
- Multiple authors have proposed methods of classification including Marx and Notani
- Notani most commonly used as simple and can guide treatment
Notani classification:
- Applicable to ORN in the mandible only
- Combination of clinical examination and OPG
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