1. UCLA School of Dentistry; Section of Restorative Dentistry; 10833 Le Conte Avenue Los Angeles USA CA 90095-1668
2. Cochrane; Bahrain Branch; Box 25438 Awali Bahrain
3. Leiden University Medical Center; Department of Dermatology; PO Box 9600 B1-Q Leiden Netherlands 2300 RC
4. The University of Louisville School of Dentistry; Department of Surgical and Hospital Dentistry; 501 South Preston Street Louisville Kentucky USA 40292
5. King Hamad University Hospital; Muharraq Bahrain