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