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Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.926.1 Osteoradionecrosis ofthejaws (Figures6.1–6.6)• Clinically exposed bone of more than 3 months’ duration is a definition. Other definitions have been described. Some include the size of the bone exposure and may require presence of the exposed bone over a longer period.• Most commonly seen in the mandible, especially posteriorly.• Pain is not a constant feature.• Infection is often secondary but may also be a contributing factor.• Contributing factors include trauma, including teeth extractions.Radiological features• Osteoradionecrosis (ORN) is a clinical diagnosis and can be present with minimal or negative radiological findings.• Common postradiotherapy changes (Figure 6.6) which do not in themselves indicate the presence of ORN include: ◦Widening of periodontal ligament spaces, sometimes irregular. There may be sclerotic thickening of the lamina dura. ◦Sclerotic change. The sclerotic bone may occasionally demonstrate a slightly ground‐glass architecture. ◦Not infrequently, extractions have been performed peri‐radiotherapy. In these cases, delayed or non‐healing tooth sockets may be demonstrated.• Multidetector computed tomography (MDCT) may show rel-evant soft tissue changes but cone beam computed tomogra-phy (CBCT) may be sufficient. 2D radiography is not optimal. MDCT is recommended if there is secondary infection with soft tissue involvement. ◦The involved bone often primarily demonstrates ill‐defined lucent focus/foci. Early changes may be limited to the cortices. ◦The affected region is often largely sclerotic, resembling chronic osteomyelitis, with or without lucent foci. However, postradiotherapy sclerotic bone changes are often seen in the absence of ORN. ◦Sequestra may or may not be present. ◦Periosteal new bone formation is not a feature, usually not seen. May be present if secondarily infected. ◦Delayed or non‐healing postextraction tooth sockets may be present but this is another common postradiotherapy finding. ◦Occasionally, there may be pathological fracture.• Magnetic resonance imaging (MRI) features can be similar to osteomyelitis. ◦Decreased T1 signal and increased T2 and short T1 inversion recovery (STIR) signal related to marrow oedema. Gadolinium contrast enhancement of the marrow. ◦Sequestra demonstrate low T1, T2 and STIR signal.Differential diagnosisKey radiological differencesMalignant lesionsMalignant bony destruction can resemble the lucencies seen with ORN. Differentiation of postradiotherapy irregular periodontal ligament space from that related to a malignant lesion can also be difficult. MDCT and MRI may demonstrate a soft tissue mass related to the malignancy.Chronic osteomyelitisCan be difficult to differentiate radio-logically. Periosteal response is not usually seen with ORN unless there has been secondary infection.CHAPTER 6Osteoradionecrosis andOsteonecrosis oftheJaws Osteoradionecrosis andOsteonecrosis oftheJaws 93Lingual corticalsequestrumWidened periodontal ligament spaceswith slightly thickened lamina dura, apostradiotherapy feature. This featuredoes not specifically relate to ORN(a)(b)Figure6.1 ORN of the left body of the mandible with lingual cortical sequestrum: axial MDCT images (a,b).Sequestrum. Note is made of the difficulty in definitively identifying the sequestrum on the panoramic radiograph. Sequestra within the jaws cannot be excluded with intraoral and panoramic radiography (a) (b)Figure6.2 ORN with sequestrum of the left body of the mandible: cropped panoramic radiograph (a) and corrected coronal MDCT image (b). 94 Atlas of Oral and Maxillofacial RadiologyLucent lesion with effacement of the anterior cortex. Note the absence of sequestra Focal abnormal T1hypointensityFocal abnormal T2 hyperintensity (d)(e)(a) (b)Enhancement Corticaleffacement (c) Figure6.3 ORN of the left mandibular condyle: axial T2 (a), T1 (b) and postgadolinium corrected sagittal (c) MRI images and axial (d) and corrected sagittal (e) CBCT images.Buccal cortical sequestra.No evidence of new boneformation (a) (b)Figure6.4 ORN at the 48 socket with buccal cortical sequestrum: axial (a) and coronal (b) MDCT images. Osteoradionecrosis andOsteonecrosis oftheJaws 95Sequestra are well demonstrated onMDCT but not appreciated on thepanoramic radiograph. Sequestra within jaws also cannot be excludedwith intraoral radiography (a) (b)Figure6.5 ORN with sequestra at the anterior maxilla: cropped panoramic radiograph (a) and axial MDCT image (b).No evidence of new bone formationWidened periodontalligament spaces and also sclerotic changeof the body of the mandible typically seen post radiotherapy, unrelated to ORNFigure6.6 Lack of new bone formation within anterior tooth sockets several months post extraction related to radiotherapy. No clinical or radiological evidence of ORN: axial MDCT image. 96 Atlas of Oral and Maxillofacial Radiology6.2 Osteonecrosis ofthejaws (Figure6.7)• Synonyms: ONJ, medication-related osteonecrosis of the jaws, MRONJ, bisphosphonate-related ONJ, BRONJ.• Exposed necrotic bone. Some definitions require that this bony exposure persists for at least 8 weeks.• Related to antiresorptive and antiangiogenic drugs. BRONJ is presently most common. Other potential causes include long‐term steroid therapy.• Trauma is a significant contributing factor, including dentoalveolar surgical procedures and irritation from dentures.• Most commonly seen in the posterior mandible.• May be secondarily infected.Radiological features• MDCT has the advantage of demonstrating relevant soft tissue changes but CBCT may be sufficient. This is insufficiently examined with 2D radiography. MDCT is recommended if there is secondary infection with soft tissue involvement.• Osteonecrosis is a clinical diagnosis and can be present without significant radiological findings.• Radiological appearances are similar to ORN. However, the commonly seen postradiotherapy appearance of widened periodontal ligament spaces, thickened lamina dura and sclerotic changes in the irradiated bone is usually not seen (see section6.1).• Air/gas may be seen in cases where there is secondary infection.Sequestrum, notclearly demonstratedon the panoramic radiograph. Osteonecrosis of the jaw can be clinically present without the presence of sequestra Presence of gasrelated to thesecondary infection (a) (b)Figure6.7 Secondarily infected right mandibular osteonecrosis of the jaw related to bisphosphonate therapy, with presence of a sequestrum: panoramic radiograph (a) and axial MDCT image (b).