1. Department of Mechanical Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
2. Department of Dentistry, Taichung Hospital; Ministry of Health and Welfare; Taichung 404 Taiwan
3. Graduate Institute of Clinical Dentistry, School of Dentistry; National Taiwan University; Taipei 100 Taiwan
4. Department of Dentistry, College of Oral Medicine; Chung Shan Medical University; Taichung 403 Taiwan