Michal,
let's set some things straight.
When you had your dental treatment in Poland it was what? 15 years ago? 20?
At that time the problem was not so much with the dentists as with the equipment and materials they had to use. Low speed boring devices, lousy filling compunds etc.
That problem was prevalent throughout Poland's entire medical system. A good dental office outfit would have cost about as much as all the dentists in a given city made in a year. A CatScan machine would have probably cost more than the entire nation's budget for health care.
I am not encouraging you to go to Poland and see how things changed, but I do know how much better it is now, and I know it from Americans and Canadians.
Maybe their education is excellent in these sciences?
There is nothing wrong with Polish medical education. Check what Swedes, and Brits for that matter have to say about that. Students do come to Polish medical schools from the US and Canada, and none have any problems with getting their diplomas recognized, except when (strangely) they are Polish citizens.