We feed our cats meat, cooked whole chickens, bones… A natural alternative really is real food. A previous lovely beast came to us with tartar, she liked raw fish. We fed her on pieces of raw mackerel a couple of times a week, bones included. She also liked a dried organic food (Pascoes, here in the uk), which was flat and easy to crunch. After only 3 months, her teeth were free of tartar and her coat was great.
The bengals we now have (or whom we serve) each have slightly different tastes, but the boy will happily eat any raw meat, which in itself helps cleaning. The girl doesn’t like meat, but will happily demolish cooked (roast) chicken bones. Great for cleaning and for calcium. They have that once a week or so. It is safe to give cats bones, but not dogs. The cat’s gut is designed for a totally carnivorous diet – see them eat whole birds, voles etc – so I would strongly recommend introducing something natural rather than relying on dried foods.