1. Department of Primary Dental Care, Division of Dental Hygiene University of Minnesota School of Dentistry Minneapolis Minnesota USA
2. Biostatistical Design and Analysis Center, Clinical and Translational Science Institute University of Minnesota Minneapolis Minnesota USA
3. Department of Primary Dental Care University of Minnesota School of Dentistry Minneapolis Minnesota USA
4. Dental Hygiene Program, Department of Primary Dental Care University of Minnesota School of Dentistry Minneapolis Minnesota USA