What is the ruling on studying medicine in general, and pediatric dentistry in particular, at a mixed-gender university, given that the female student does not yet wear the niqab?

Studying medicine is good and beneficial. It is one of the communal obligations (fard kifaya) where, if some individuals fulfill it, the obligation is lifted from others. It transforms into a righteous deed through intention. As for studying in mixed-gender environments, the original ruling is prohibition due to the presence of objectionable matters, unless no other non-mixed university is available, in which case it becomes permissible, provided one adheres to Islamic guidelines.