1. Department of Dental Radiology, Institute of Dentistry, PI 41 (Mannerheimintie 172), FIN-00014 University of Helsinki, Helsinki, Finland
2. Department of Prosthetic Dentistry, Institute of Dentistry, PI 41 (Mannerheimintie 172), FIN-00014 University of Helsinki, Helsinki, Finland
3. Department of Pedodontics and Orthodontics, Institute of Dentistry, PI 41 (Mannerheimintie 172), FIN-00014 University of Helsinki, Helsinki, Finland