1. Department of Periodontics; School of Dental Medicine; University of Pennsylvania; Philadelphia PA USA
2. Department of Periodontics, Endodontics and Dental Hygiene; Center for Oral Health and Systemic Disease; University of Louisville School of Dentistry; Louisville KY USA
3. Health Care Research Center; Procter & Gamble Company; Mason OH USA
4. Institute of Medical Microbiology and Hygiene; Philipps University Marburg; Marburg Germany