1. Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
2. Department of Public Health and Infectious Diseases, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, Sweden
3. Division of Preventive Dentistry Periodontology and Implant Biology, Aristotle University of Thessaloniki, Thessaloniki Greece
4. Department of Public Health and Infectious Diseases, Sapienza University, Rome, Italy