1. Department of Cariology, Endodontology, and Periodontology, University Leipzig, Leipzig, Germany.
2. Department of Nephrology and Rheumatology, University Medical Center Goettingen, Goettingen, Germany.
3. Department of Preventive Dentistry, Periodontology, and Cariology; University Medical Center Goettingen.
4. Clinical Research Organization, Hamm, Germany.