1. Department of Operative Dentistry and Periodontology, University of Mainz, Germany, and Blaues Haus Dental Center, Duesseldorf, Germany
2. Herrmann Dental Studio, Duesseldorf, Germany
3. Division of Periodontology, Catholic University of Sacro Cuore, Rome, Italy
4. Department of Periodontics, School of Dentistry, Loma Linda University, Calif