I should have clarified that, Criss Colon, you are quite right.
Volunteer work can be arraigned through different church or NGO organizations.
La Profe1 in POP has done this and so have a lot of the good folks on this board.
Theoretically, they should get permission from the Public Health people for the medical personnel to do their work.
Also, 99.99% of the medical health professionals that come to the DR to volunteer their services are US, Canada or European graduates, not Nigeria. And there is really a world of difference. I think that there would be some hesitation on the part of local officials....
Note that the gentleman is not pursuing an advanced degree in dentistry nor is he acquiring certification to practice in the US, a process that can take up to three years...
HB