Deads= dead back.
I speak from experience, the rewards you get from deads do not outweigh the risks. You are asking for disc trouble. You can get a good back workout with such machines like lat pull downs, T-bar rows, and pullups.
Everyone will argue, but I will send you a card someday after your surgery. I already had mine.
Oh, and i used good form and a belt, it is just a dumb excercise.