1. School of Dentistry, Chung Shan Medical University, Taichung City 402, Taiwan
2. School of Dentistry, China Medical University, Taichung City 404, Taiwan
3. Department of Dentistry, China Medical University and Hospital, Taichung City 404, Taiwan
4. Department of Stomatology, Chung Shan Medical University Hospital, Taichung City 402, Taiwan
5. Institute of Oral Science, Chung Shan Medical University, Taichung City 402, Taiwan