Centers for Disease Control (CDC): Oral Health Facts and Figures.
National Institute for Dental and Craniofacial Research Data and Statistics.
World Health Organization(WHO): Global Oral Health Statistics and Reports
American Dental Association: Insights from the ADA Health Policy Institute on the current and future supply of dentists and shifting demographics within the workforce.
This is a great starting place to understand what general understanding exists about your topic for you to further explore.