1. Department of Periodontics, College of Dentistry, University of Baghdad, Bab Al Mudam, Baghdad P.O. Box 1417, Iraq
2. Medical Laboratory Department, College of Health and Medical Technology, Sulaimani Polytechnic University, Sulaymaniyah P.O. Box 70-236, Iraq
3. Department of Periodontics, College of Dentistry, University of Sulaimani, Sulaymaniyah 46001, Iraq
4. Academic Unit of Restorative Dentistry, School of Clinical Dentistry, Claremont Crescent, Sheffield S10 2TA, UK