My vet sells a gel that I use instead of trying to brush their teeth or use a finger brush (I just would get bit...ouch!), you put a bit of the gel on your finger, insert between the cheek and upper teeth and rub on, do once for both sides, just the upper teeth, each day.
Or...Wysong makes a special powder for dental care that you can sprinkle on their food. Called Dentatreat, it's for both dogs and cats.
Or <G>, there are tartar control treats, including one by PetGuard that is actually certified organic...tasty, crunchy treats can help with tartar control.
Or (somebody stop me as Jim Carrey would say) there is a prescription food (by Hills I believe, I think it is Hills T/D) which is also for dental health.
that concludes my memory dump on this topic <G>,