Leo Tjäderhane1, Marília A Buzalaf2, Tuula Salo3. 1. Institute of Dentistry, University of Oulu, Oulu University Hospital, Oulu, Finland; Institute of Dentistry, University of Turku, Turku, Finland; Nordic Institute of Dental Materials (NIOM), Oslo, Norway. Electronic address: leo.tjaderhane@oulu.fi. 2. Discipline of Biochemistry, Department of Biological Sciences, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil. 3. Institute of Dentistry, University of Oulu, Oulu University Hospital, Oulu, Finland; Institute of Dentistry, University of Helsinki, Helsinki, Finland.