1. WHO Collaborating Centre of Milan for Epidemiology and Community Dentistry, University of Milan, San Paolo Hospital, Milan, Italy
2. Department of Surgery, Microsurgery, and Medical Science, School of Dentistry, University of Sassari, Italy
3. Department of Chemistry, University of Sassari, Italy
4. Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, Sweden