1. Department of Oral Physiology, School of Dentistry & Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea.
2. Research and Development Division, Hugel Inc., Chuncheon 24206, Korea.
3. Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea.