Our veterinarian said that a lot of tartar in dogs comes from dry mouth, just like in humans. The makers of the human Biotene products (for dry mouth) are making similar natural products for dogs now under the name Oratene. I got a sample pack from her and tried it in a gel (like a toothpaste, but not technically a paste so we still brush with CET), drinking water additive and a spray. I use all 3, though the drinking water additive is an issue when you use a water system with a big tank of water. The additive causes stuff to grow in the water (probably from the aloe vera?) if you don't change the water frequently.
We brush about 4 times a week and I do believe in dental cleanings every 2 to 3 years to get the xrays and determine if there is stuff going on at the gum level that isn't detected by my eyes.