Plain yogurt is fine for a dog.
Yucky teeth/breath is probably due to being kibble fed, and possibly eating her poo. Get her on a good nutritious diet and as EMarie posted, fresh raw knucklebones will help. Raw has enzymes that break down the tarter on the teeth, and when the dog works the bone it helps as well. Take it away, fridge it for another session. If you leave it out to dry it can splinter and cause problems with digestion. Don't buy smoked bones, they splinter as well. And marrow bones can cause runny poo, the marrow is rich, and the bones are denser, so a cracked tooth is possible(though many feed marrow bones with no problems)
The cartiledge in a knuckle bone has much nutrition, so those would be my choice over the marrow bone.