There is a playschool song about teeth brushing... I think these are the words (off the top of my head). I think it's on the playschool favourites album. DS loves it.

Brush, brush, brush,
You mustn't rush, rush, rush,
When you clean your teeth
In the morning

Paste, paste, paste,
For a peppermint taste, taste, taste,
When you clean your teeth
In the morning

You can munch, munch, munch
On your lunch, lunch, lunch
You can crunch, crunch, crunch
All day long

You can bite, bite, bite
With all your might, might, might
It's alright, right, right
Your teeth are strong

So...
Up and down with your...

Brush, brush, brush,
You mustn't rush, rush, rush,
When you clean your teeth
In the morning (and last thing at night)