the never-ending struggle with the child and the toothbrush

what exactly do i have to do to get my child to brush her flippin teeth right every time????? no matter what we say or do, it never seems to get through to her. i'm so tired of yelling at her and threatening her to get it done right the 1st time. if we're lucky, she will do it right for a little while, but then falls back into the same bad habit. i can just imagine if her teeth are a problem now, at age 9, that we're gonna have serious hygene issues with her once she hits puberty. ugh! now is one of the times when i ask, "and what exactly was the reason we decided to have children?"