1 Department of Periodontology, School of Stomatology, China Medical University, Nanjing North Street 117, Shenyang, China. Electronic address: rleezzu@163.com.
2 Department of Periodontology, School of Stomatology, China Medical University, Nanjing North Street 117, Shenyang, China. Electronic address: hywang@cmu.edu.cn.