Braces.

"But we just hold our heads up high; 
On orthodontists' chairs we lie, 
For they're the ones who control the rate 
At which our crooked teeth turn straight. 

In mirror dreamily we gaze, 
And eagerly we count the days 
Till we'll display our brand-new bite 
With teeth now back to gleaming white"

...continued by me

The glorious day finally arrives,

The orthodontist controls our lives

We see the old, gross metal in a pile

Take the mirror and see our new smile :)