Hey Meggs,
F-1 visa is totally dependant upon your country's US consulate's visa official! It depends on all the documents and admissions proof that you provide at the consulate.
Even if you were given the F-1 visa, there is a chance that you may not be allowed into the country at the point-of-inspection at the airport or seaport (however you enter the US)...
The USCIS (formerly INS) official will inspect you and will require you to furnish any evidence that you have no intention of staying in the US after the studies are completed. (Now you need to be photographed and fingerprinted!) This may be done with a job offer letter from your home country saying that you will be "fired" if you don't return... any family commitments at home, financial commitments with your business at home etc.. As long as you can prove to the Officer at the point of entry that you are only coming into the US to study and then leave, they won't suspect you of a possible visa fraud.
However, I have also heard from some of my Latin American, Middle Eastern or Indian colleagues that sometimes there is an over generalisation that a person of certain nationality or ethnicity is more suspect than other students and hence the student will carry a bigger burden of proof (of non-immigrant entry)! Unfair? I agree... However, we don't make rules around here! So beware!
Visa processes will take longer nowadays due to many factors. This is totally independant of the Dental School admissions. Just make sure your School officials know where you are with each step of the way and don't take it too personally. Everyone goes through this now!
Good luck Meggs!
Cheerio
2ed.
