1. Institute of Modern Optics, Nankai University, Nankai, Tianjin 300350, P. R. China
2. Department of Oral Pathology, Tianjin Stomatological Hospital, Hospital of Stomatology of Nankai University, Nankai, Tianjin 300041, P. R. China
3. Department of Oral Medicine, Tianjin Stomatological Hospital, Hospital of Stomatology of Nankai University, Nankai, Tianjin 300041, P. R. China
4. Department of Oral-Maxillofacial Surgery, Tianjin Stomatological Hospital, Hospital of Stomatology of Nankai University, Nankai, Tianjin 300041, P. R. China