1. School for Dental Hygiene; University of Applied Sciences Utrecht; Utrecht The Netherlands
2. Dentist; Hoevelaken The Netherlands
3. Department of Periodontology; Academic Centre for Dentistry Amsterdam (ACTA); University of Amsterdam and Vrije Universiteit Amsterdam; Amsterdam The Netherlands
4. Department of Preventive Dentistry; Academic Centre for Dentistry Amsterdam (ACTA); University of Amsterdam and Vrije Universiteit Amsterdam; Amsterdam The Netherlands
5. Division of Clinical Methods and Public Health; Academic Medical Centre (AMC); University of Amsterdam; Amsterdam The Netherlands