I would leave out saying what you want to do after dental school, besides saying you want to help others etc. You practically mention every option a person has with a dental degree; specialize, general, teach, research. It wont really mean anything saying you want to do it all. Also, keep it positive, don't say you were disappointed with people giving free dental care, spin the experience and focus on the good things. Just state your volunteer experience and keep it unique, anyone can talk about that other stuff.