1. Institute of Dentistry, University of Oulu, Aapistie 3, SF-90220 Oulu, Finland
2. Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, SF-20520 Turku, Finland
3. Department of Dentistry, The University of Adelaide, G.P.O. Box 498, Adelaide, South Australia 5001