Their teeth need to be brushed 3-4 times a week minimum, but if there is already tartar build up, they will probably need dentals under anesthesia. It's so common in small dogs and some need dentals 1-2 times a year, especially if the home care isn't good.
Ellie had 9 adult teeth pulled. I didn't know that you should really make a habit of brushing before then. Live and learn.
She has a pretty healthy mouth now.