I don't think a disproportionate amount of people want to study dentistry. Maybe in certain schools with more kids from certain backgrounds you'll get lots of dentist hopefuls, but surely also lots of doctors too?
To me, the mouth is just another part of the body and is not that much more gross than other bits.
I have noticed that the trend is, aspiring doctors are worshipped as selfless do-gooders admired for wanting to help people, while dentists are seen as just in it for the money.
Upon discovering my ambition to be a dentist, the first thing people actually say to me is "oh, good money". I know what they are thinking of me. It's quite funny actually. For me there's actually this weird kind of allure to going into a demonised profession (obviously not my main motivation).