1. Section of Periodontology and Dental Prevention Division of Oral Diseases Department of Dental Medicine Karolinska Institutet Alfred Nobels allé 8 14152 Huddinge Stockholm Sweden
2. Department of Oral and Maxillofacial Diseases University of Helsinki Helsinki University Central Hospital P.O. Box 41 (Mannerheimintie 172) 00014 Helsinki Finland
3. Functional Genomics Center Zurich ETH Zurich and University of Zurich Winterthurerstrasse 190 8057 Zurich Switzerland
4. Section of Periodontology Department of Dentistry and Oral Health Aarhus University Vennelyst Boulevard 9 8000 Aarhus C Denmark