1. College of Dentistry King Saud bin Abdulaziz University for Health Sciences Riyadh Saudi Arabia
2. Birmingham Community Healthcare NHS Foundation Trust Birmingham UK
3. Periodontal Research Group University of Birmingham Birmingham UK
4. Department of Oral Surgery, The School of Dentistry University of Birmingham Birmingham UK
5. Health Policy and Health Services Research Boston University Henry M. Goldman School of Dental Medicine Boston Massachusetts USA
6. Department of Epidemiology Boston University School of Public Health Boston Massachusetts USA