1. Department of Stomatology, The People's Hospital of Longhua, Shenzhen, Guangdong 518109, P.R. China
2. Key Laboratory of Oral Medicine, Guangzhou Institute of Oral Disease, Stomatological Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510140, P.R. China
3. Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
4. Department of General Therapy Dentistry, Stomatology Hospital of Jilin University, Changchun, Jilin 130021, P.R. China