1. Department of Preventive and Community Dentistry, College of Dentistry University of Iowa Iowa City Iowa USA
2. Department of Community Dentistry Rawal Institute of Health Sciences Islamabad Pakistan
3. Department of Epidemiology, College of Public Health University of Iowa Iowa City Iowa USA
4. Division of Biostatistics and Computational Biology, Iowa Institute for Oral Health Research University of Iowa Iowa City Iowa USA
5. Department of Biostatistics, College of Public Health University of Iowa Iowa City Iowa USA
6. Department of Operative Dentistry, College of Dentistry University of Iowa Iowa City Iowa USA