REI pill case, with a week, at least, of toothpaste, undried, about 12 gm total.
From what I see at campsites, people tend to use massively way far too much toothpaste, I brought for example I think about 3x give or take more than I needed, but I am bad at eying it out, I'd estimate I came back with 10 days leftover.
I would say that 10gm toothpaste+pill case total really makes me want to look elsewhere for weight savings, heh heh.
That's fresh, paste, not dried, no bother, works fine.
I can probably save a bit, but not much, on my toothbrush, but again, I've used short handled ones, and I'm happy to pay the multigram penalty of a longer handle.
The baking soda pluses and minuses are good info, I wasn't aware of the unbuffered abrasive part of the matter, but as a multi-use, certainly sounds like a bit of that wouldn't hurt to have along.
But whatever you do, don't bring those mini tubes, they are heavy and it's hard to get all the toothpaste out, nearly impossible I'd say, so you're always carrying a certain amount that will never get used. Much nicer just dipping the brush into the paste, easy to see how little you need that way too.
I think I'll worry about 1/2 pounds / pounds on various items before worrying about this. If I used a small ziplock and the paste (but I don't like trusting zips for liquids in general, too messy if they fail), we'd be talking here about 5, 6 grams tops for a week plus.