1. Dental Implant Center, Affiliated Hospital of Qingdao University, Qingdao, P.R. China.
2. School of Stomatology, Qingdao University, Qingdao, Shandong, P.R. China.
3. Department of Stomatology, Laoshan Branch of No. 401 Hospital of the Chinese Navy, Qingdao, Shandong, P.R. China.
4. Department of Chemistry and Biochemistry, Georgia Southern University, Savannah, Georgia.