[1] Univ Palermo, Dept Sci Hlth Promot & Mother & Child Care G DAle, Palermo, Italy
[2] Univ Sassari, Sch Dent, Dept Surg Microsurg & Med Sci, I-07100 Sassari, Italy
[3] Univ Sassari, Dept Biomed Sci, Epidemiol & Biostat Lab, Unit Hyg, IT-07100 Sassari, Italy
[4] WHO, Collaborating Ctr Epidemiol & Community Dent Mila, Milan, Italy