I brush Pixie's teeth twice a week (or so, sometimes I slack a bit) with
Denta Clean Tarter Control Toothpaste using a baby toothbrush (the finger brushes didn't work well enough for me). It's mint so it leaves her with nice fresh breath... And then every night before bed I rub a little bit of the Life for Teeth gel on her gums. Her teeth are gleaming white and there isn't a hint of tarter that I can see.
I haven't been able to brush Fudgie's teeth yet.. He still has stitches in there from his dental work so they don't want me to mess with it too much. But once I get the okay he'll be on the same routine Pixie is.
The vet gave us some Poultry flavored tooth paste to try. Can remember who made it (C.E.T. maybe), but Pixie didn't like it at all and I didn't either, it was too thick and didn't give her minty fresh breath... She actually seems to like (rather, tolerates) the mint flavor better.