Frank Schwarz1, Anton Sculean2, Thomas Georg3 and Ju ̈rgen Becker1
1 Department of Oral Surgery, Heinrich Heine University, Du ̈sseldorf, Germany;
2 Department of Periodontology and Operative Dentistry, Johannes Gutenberg- University, Mainz, Germany;
3 Institute of Medical Biometrics, Epidemiology and Medical Informatics, University of Saarland, Homburg, Germany
J Clin Periodontol 2003; 30: 975–981