1. Faculty of Dentistry, King Abdulaziz University, Jeddah 21589, Saudi Arabia
2. Faculty of Dentistry, Ain Shams University, Cairo 11566, Egypt
3. Departments of Medicine and Epidemiology & Public Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA
4. Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21201, USA