Just to be clear, it is conjecture that the nickname was due to a dead tooth. It is not exactly clear what the nickname means. The word we translate to "tooth"

Just to be clear, it is conjecture that the nickname was due to a dead tooth. It is not exactly clear what the nickname means. The word we translate to "tooth" could also mean "thane", so it could mean something like "the blue price" or "the black prince". It has been argued that the nickname is unlikely to be because of a bad tooth, since this would have been common enough at the time not to be noteworthy. But of course there might have been some story behind which is lost to time.