1. Operative Dentistry Department, Faculty of Dentistry, Ain Shams University, Cairo, Egypt
2. Restorative Dentistry Department, Faculty of Dentistry, The British University in Egypt, Cairo, Egypt
3. Dental Biomaterial Department, Faculty of Dentistry, Ain Shams University, Cairo, Egypt
4. Dental Materials Unit, Center for Dental and Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, University of Zurich, Zürich, Switzerland