1. Department of Clinical Dentistry - Periodontics, University of Bergen, Aarstadveien 17, N-5009 Bergen, Norway;
2. Department of Biomedicine - Physiology, University of Bergen, Norway;
3. Department of Periodontology, Academic Center for Dentistry Amsterdam -ACTA-, University of Amsterdam and Vrije University, The Netherlands; and
4. Department of Clinical Dentistry—Center for Clinical Dental Research, University of Bergen, Norway