The Health Resources and Services Administration (HRSA) stewards the Area Health Resource Files, which contain county-level counts of private practice dentists. In the visualization below, dentists counts were divided by population totals from the US Census to determine relative workforce densities.
The ratio of dentists per 4,000 people was chosen to mimic the threshold used by HRSA to determine population Dental Health Professional Shortage Areas. Data are for the year 2015.