[1] Kings Coll London, Sch Dent, London, England
[2] Univ Bern, Dept Prevent Restorat & Pediat Dent, CH-3010 Bern, Switzerland
[3] Bristol Dent Sch, Bristol, Avon, England
[4] Univ Paris 07, AP HP, Rothschild Hosp, Dept Periodontol,Serv Odontol,UFR Odontol,EA 2496, Paris, France
[5] Univ Complutense Madrid, Fac Odontol, Dept Periodontol Periodont, E-28040 Madrid, Spain
[6] Univ Lyon 1, Dept Publ Hlth, EA 4129, F-69622 Villeurbanne, France
[7] Univ Lyon, Lyon, France