1. Department of Cariology, Karolinska Institutet, School of Dentistry, Box 4064, 141 04 Huddinge, Sweden
2. Specialized Caries Research Center, College of Dentistry, The University of Iowa, Iowa City, Iowa 52242
3. Department of Oral Radiology, Karolinska Institutet, School of Dentistry, Box 4064, 141 04 Huddinge, Sweden