Thanks to everyone, I'm going to try giving her some charcoal biscuits, and regularly brushing her teeth! I've tried dog toothpaste on the dogs before, both my dogs like the flavor, but I've just been lazy with it.
She doesn't have any rotted teeth, as we often look in her mouth (we have since she was a puppy to get her used to being handled by people and the vet), but does anyone know how often dogs should have their teeth professionally cleaned? Marta is almost 3, and she has never had her teeth cleaned by the vet- I just feed her dry food and give her greenies once and a while.
Does anyone know if a professional teeth cleaning can be done without anesthesia? I've had to take my cat in the past for a cleaning, and she had to be put under, but Marta is very good at the vet's office and tolerant of all kinds of handling. Thanks for the advice!