Just relax about the essay part. There are like 30 topics so you most likely won't get one that you heard before. I got one about the correlation between DAT scores and success in dental school...There are some weird ones out there. But the main deal with the "essay" (its more like a journal) is to see if you can communicate fluently. Don't sweat it. I think you should spend some time on the questions you have to take along with you, though. Make sure those are mistake free.
Good luck.
DesiDentist