Understanding the clinical and underlying pathological differences between ORN and MRONJ probably contributes to the selection of appropriate treatment for each patient.
Twenty-one percent of ORN cases resulted from tooth extraction. The most common site of ORN (82 %) was the mandibular molar region. About half of ORN cases (49 %) occurred within 2 years after RT. All patients who received tooth extraction after RT developed ORN (100 %) independently of time interval between tooth extraction and the end of RT (median interval, 37.5 months; range, 27-120 months). In contrast, only 50 % of patients who received tooth extraction before RT developed ORN. There may have been an association between the irradiation field and the site of ORN development CONCLUSIONS: ORN occurrence due to tooth extraction was 21 %. Occurrence timing of ORN did not depend on time interval between tooth extraction and the end of RT. The irradiation field is certainly related to the site of ORN; therefore, prophylactic tooth extraction should be performed in consideration of the proposed radiation field and dose.
Background This study aimed to analyze differences in necrotic changes between cortical and cancellous bone in resection margins after segmental mandibulectomy for advanced mandibular osteoradionecrosis. Methods Anteroposterior bone specimens from eleven patients who underwent segmental mandibulectomy with simultaneous free fibula flap reconstruction for advanced osteoradionecrosis were analyzed histopathologically for the presence of necrotic bone based on the presence of blood vessels within Haversian canals. Results Ten of eleven (91%) cortices near the inferior border of the mandible at the anterior margins were necrotic. All cancellous bones at the anterior margins were viable. Seven of eleven (64%) cortices near the inferior border of the mandible at the posterior margins were necrotic. Three of eleven (27%) cancellous bones at the posterior margins were necrotic. Conclusion Necrotic changes are more prevalent in cortices than in cancellous bones in mandibular osteoradionecrosis, probably due to a decrease of periosteal blood supply caused by radiotherapy.
The degree of degeneration of mandibular canal and inferior alveolar nerve may be associated with pain severity in patients with mandibular osteoradionecrosis.
When implant insertion is planned in a reconstructed mandible, the orientation of the apex of transferred fibula should be evaluated preoperatively to allow for adjustments in implant procedure because the ridge at the apex of the fibula is narrow.
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