1. Tongji Hospital; Huazhong University of Science and Technology; Wuhan P. R. China
2. Department of Prosthodontics; School of Stomatology; Fourth Military Medical University; Xi'an P. R. China
3. Department of Mechanical; University of Maryland Baltimore County; Baltimore MD USA
4. Department of Biomedical and Neuromotor Sciences; DIBINEM, University of Bologna and IGM-CNR; Bologna Italy
5. Georgia Regents University; Augusta GA 30912-1129 USA