1. Hunan Key Laboratory of Oral Health Research, Hunan Xiangya Stomatological Hospital, Central South University, Changsha, Hunan 410000, P.R. China
2. Department of Endocrinology and Metabolism, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
3. Department of Urban Palliative Home Care, Grey Nuns Community Hospital, Edmonton, AB T5J3E4, Canada
4. Department of Stomatology, Changsha Central Hospital, Changsha, Hunan 410018, P.R. China