What celebrities are most linked to endorsements of toothpastes,
mouthwash, mints and other oral care products?  What are the most
recent campaigns with the most current celebrities in this category?

I dunno, but if you haven't checked out this site... do so, it's amazingly funny:

http://www.japander.com/

skermit-ga

Florence Henderson did a commercial for Polident in 1997.

Arthur O'Connell played a druggist in a series of toothpaste
commercials (it might have been Crest) before his death in 1981.

Al Hodge, who starred in the early TV series, Captain Video, later
played a dentist who advised his patients to chew Dentyne in a
mid-1950's commercial.

I'm sure there are others.

Phred22