1. Department of Preventive and Community Dentistry; College of Dentistry; University of Iowa; Iowa City IA USA
2. Department of Epidemiology; College of Public Health; University of Iowa; Iowa City IA USA
3. Department of Pediatric Dentistry; School of Dentistry; University of Alabama at Birmingham; Birmingham AL USA
4. Department of Biostatistics; School of Public Health; University of Alabama at Birmingham; Birmingham AL USA
5. Department of Epidemiology; University of Alabama at Birmingham; Birmingham AL USA
6. School of Nursing and Department of Health Behavior; School of Public Health; University of Alabama at Birmingham; Birmingham AL USA
7. Department of Biostatistics; College of Public Health; University of Iowa; Iowa City IA USA