1. Department of Periodontology, School of Dentistry, Kyungpook National University, Daegu, Korea
2. Jin-Woo Park, Department of Periodontology, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-Gu, Daegu 41940, Korea.
3. Department of Materials Science and Engineering, Korea University, Seoul, Korea
4. School of Dentistry, Kyungpook National University, Daegu, Korea