1. Center for Research in Epidemiology, Economics and Oral Public Health (CIEESPO), Faculty of Dentistry, Universidad de La Frontera, Temuco 4811230, Chile
2. Melbourne Dental School, The University of Melbourne, Parkville, VIC 3010, Australia
3. Faculty of Dentistry, University of Puthisastra, Phnom Penh 12211, Cambodia