1. Endodontic Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia;
2. Endodontic Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt;
3. Department of Spectroscopy, National Research Center, Cairo, Egypt;
4. Department of Operative Dentistry, Biomaterials Division, King Abdulaziz University, Jeddah, Saudi Arabia;
5. Faculty of Oral and Dental Medicine, Biomaterials Division, Tanta University, Tanta, Egypt;
6. UCL Eastman Dental Institute, United Kingdom of Great Britain and Northern Ireland