1. Faculty of Dentistry, University of Otago, PO Box 647, Dunedin, New Zealand;
2. Discipline of Dental Public Health and Epidemiology, Department of Oral Sciences, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; and
3. Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand;