My kids are kids. If they had their ways, they'd go to bed whenever they wanted, never get a bath, only eat chicken nuggets and pasta, and they'd never brush their teeth. Sometimes the only way I can get them to do something is to make it fun, and thankfully the Avengers toothbrush makes it a little easier to call brushing "fun". My kids love it. It's easy to hold and use. It isn't oversized in their hands or mouths. It keeps their teeth clean and I encourage them to keep using it.
Or else Hulk smash.