1. Department of Operative Dentistry and Dental Materials, School for Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, Kapucijnenvoer 7, B-3000 Leuven, Belgium
2. Department of General Practice, Dental School, University of Texas Health Science Center at San Antonio, Texas
3. Clinical Research Facility, Dental School, University of Texas Health Science Center at San Antonio, Texas
4. Department of Oral Biology, School of Dentistry, University of Missouri-Kansas City, Missouri
5. Electron Microscopy Facility, Department of Periodontology, Dental School, University of Texas Health Science Center at San Antonio, Texas