I've used tooth powder on multi-month backpacking trips, works fine. While it saves a little weight, the great thing is that repackaging it in a sort of microbottle that I bought somewhere like here ? (BPL), just a small and light quantity lasts me for months. So no resupply problems.
I admit that after using it for months at a time it feels like kind of a treat to use "real" toothpaste when the opportunity arises, but a pretty minor treat, not a big deal.