Why do you say that? Is it more difficult to obtain a work permit through dentistry than through other career paths?
While US work visas are not guaranteed and immigration laws are subject to change, obtaining a graduate degree from an American university seems to be one of the more reliable pathways to immigration. It’s certainly much easier to enter the US labor market with an American degree than without one.
But yes, if going to college in the US would be catastrophic (e.g. financially) in case you can’t finish your education or you can’t get a permanent work permit here, it would be prudent to re-consider your college plans.