More than just an arbitrary label for naming your work, a dissertation title serves as the first summary of what your piece is all about. A good dissertation title must communicate the essence of your research project and give an accurate sense of what follows.
Publishing your dissertation as an article in an academic journal can look fabulous on your CV, particularly if you would like an academic career. If you have produced important material from your research than it can be a great help to others if you publish it. Your dissertation supervisor should be able to advise you on whether publication is appropriate for your dissertation writing.