Well, i'm not sure if this is true across the board for all dental schools, but I had a friend (who I think was helping with the admissions process while as a student) who told me that I definitely should not write about "I love teeth. I had braces as a child, etc." Maybe he was being specific to his school, I'm not sure. He also said not to write about your own dental problems and how that led you to wanting to be a dentist. (I had wanted to do these topics and he steered me away from them.) He said that the adcoms see essays about these topics all the time and get bored of them. However, that being said, I also want to add that I do think that it is possible to write a really compelling essay with the topic -- it's just probably harder to do so.
Oh! and another friend of mine (who was also a student on the med school's adcom) said to "show, not tell" and try to put in as many anecdotes as possible to describe your character (rather than saying "I am compassionate" or "I am studious," etc.).
Hope that helps!
