[1] Zhengzhou Univ, Affiliated Canc Hosp, Dept Head Neck & Thyroid, Henan Canc Hosp, Zhengzhou, Henan, Peoples R China
[2] Cent Hosp Yingkou, Dept Oral Med, Yingkou, Liaoning, Peoples R China
[3] Dis Control & Prevent Ctr, Shenyang, Liaoning, Peoples R China
[4] Kaifeng Cent Hosp, Dept Oral Med, Kaifeng, Henan, Peoples R China