How can you die when you die from an overdose of toothpaste?

Unlikely: All toothpaste is, is soap and sand. You would get very ill and nauseous before you ingest enough to kill you.

Not an issue: As mentioned above you would get nausea and upset stomache but wouldn't die. The main concern is too much flouride, but you'd still need to ingest a full tube for any significant negative outcome.

Death?: Are you allergic to toothpastes? If there is an ingredient you're highly allergic to, you can respond in an anaphylactic way, but that's highly unlikely.

Never: I entered Dental School in 1964. In all that time there have been exactly zero cases of toothpaste overdose reported in the dental literature. It's a non-issue, so please don't worry about it.