Adjuvant chemo-therapy Article Cross-Sectional Studies Epidemiology Female Head and Neck Neoplasms Head and neck neoplasms Humans Male Middle Aged Osteoradionecrosis Prevalence Radiotherapy Retrospective Studies Risk Factors Time Factors adult aged bone necrosis cancer radiotherapy cross-sectional study female head and neck cancer head and neck tumor human major clinical study male middle aged mouth cavity oral mucositis