There's two main fraternities in dentistry.
Alpha Omega: based on princples of "judaism and brotherhood", not quite sure exactly what that means, they're not overtly religious (in the way that the christian students association of LDS students association are) but pretty much everyone in the frat is jewish, they say their goal is mainly for networking with other dentists (not many social events at our school)
Psi Omega: social fraternity, lots of social events (and TONS of social events at Upenn)