Affiliation: | 1. Preventive Dentistry Department, Public Dental Health, , V?rmland, Sweden;2. Public Dental Health, Norrstrand V?rmland, , Sweden;3. Department of Dental Medicine, Karolinska Institutet, , Stockholm, Sweden;4. Institute of Odontology, The Sahlgrenska Academy, University of Gothenburg, , G?teborg, Sweden |