61. 下列何者不是頭頸部放線治療的併發症(complication)或後遺症(sequela)? (A)放射線齲齒 (radiation caries) (B)牙周膿瘍 (periodontal abscess) (C)口乾症 (xerostomia) (D)放射線性骨壞死 (osteoradionecrosis)