Yorkies are notorious for bad teeth. I only feed my Bijou dry food and I brush her teeth every night. Yes, I said every night!
She is used to it because we have done it so long. After I brush mine I hop in the bed and brush hers. I also give her teeth cleaning treats from time to time but there's no substitute for brushing. Imagine if we didn't brush our teeth every day. Yuk. Anyway, it only takes 5 min max and it makes a huge difference in your babies health. And they have good breath!