Toob makes a travel toothbrush. The plastic case is nonsense, throw it out, but the toothbrush heads are made of extremely light cheap plastic, and are NOT connected to the plastic casing. Replacement heads are 2 for $2.95 at EMS and, with practice, are just the right length for serious and thorough brushing.
Plus, the reusable toothpaste tube works great, and it lets you steal toothpaste from hostels and nice old ladies along the trail. I love this setup, but I don't know the grams. probably a little more than some because of the toothpaste holder, but I bet my toothbrush weight slaughters some of yours because of how cheap and light the plastic is.
Here's a link: