1. Department of Conservative Dentistry, Division of Biomaterials and Engineering, Showa University School of Dentistry, Tokyo, Japan
2. Department of Removable Partial Prosthodontics, Graduate School, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
3. Department of Periodontology, Graduate School, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
4. Faculty of Dentistry, Oral and Craniofacial Sciences, King’s College London (KCL), London, UK