How do I create a script that removes an entire dialog after one use? (Not just the choice)

I've been attempting to make a game where a character, sadly but surley, dies via events and what not. It has usage of dialog boxes though, and I was wondering upon how I could remove the dialog from the character after it had died officially according to the dialog boxes so the person playing couldn't go back and talk to it over and over again though their dead, and eventually break the game. Any help?