1. State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology School of Stomatology The Fourth Military Medical University Xi'an Shaanxi 710032 China
2. Institute of Orthopedic Surgery Xijing Hospital The Fourth Military Medical University Xi'an Shaanxi 710032 China
3. The Dental College of Georgia Augusta University Augusta GA 30912 USA