Borax works great for not just bad breath, but in a toothpaste too. I make it with approx 1tsp coconut oil organic, 1tsp borax, mix till all blend nicely, ok maybe still feel some grainy texture here and there. also add drops of teatree oil at first, but actually prefer adding a drop or two when putting on a toothbrush, right before brushing. Once all brushed nicely, I then pull the oily content as in “oil pulling”, then spit out after 2mins.
Adding borax makes substantial difference in how my gums feel afterwards.