Is it possible to be exposed to Blood borne pathogens if you share a toothbrush?

It's maybe 1% possible, if someone with a high HIV viral load (lots of HIV in their body) used the toothbrush and then you immediately used it AND you have cuts or bleeding gums, and the virus survived in the open air and got into your bloodstream.

Very very unlikely!
HIV does not live outside the human body, it dies shortly after being exposed to air. Sharing toothbrushes may carry other risks that warrant keeping your personal hygeine products "personal," but HIV transmission is of no risk.
no, hiv/ aids is only contracted through sexual intercourse and blood.
NO, absolutely not.
HIV virus dies very quickly outside the body so the chances are very low to zero
I am not a doctor, but I think you might be able to get HIV by sharing a toothbrush, simply because there could be bleeding gums or open mouth sores....
I don't think there is really an answer, but I'll keep looking.
No.