I understand that obviously the visa is issued by the foreign country's embassy. But as far as I know you need permission to leave the country from both sides with a valid reason. I don't remember the exact date of the article, but it stated that India was losing its medical professionals (I'm not sure whether it refers to dentists or not) to foreign countries and they wanted to prevent this by making you sign a bond (linked below). At the end of the day if you do not get a visa you're not told why.
http://forbesindia.com/blog/health/india-to-doctors-please-dont-leave-or-we-will-bring-you-back/
-there was a repeat of this article later in the year around october