I still want to know: How many dentists _are_ there in Poland?
Starting with the same density, (190k / 319M) * 38M, we would get 22.5k dentists in Poland. We know there are slightly fewer physicians per capita in Poland though. So let's take 22.5k * (2.2 / 2.5) and we get roughly 20k dentists in Poland.
1. https://en.wikipedia.org/wiki/Dentistry_in_the_United_States
2. http://data.worldbank.org/indicator/SH.MED.PHYS.ZS
3. https://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&...
Edit: Off by a factor of 2. Darn!
Source: http://stat.gov.pl/en/topics/health/health/health-and-health..., though you have to dig through a bit to find the figure.