cheek muscle
buccinator muscle
musculus buccinator

He smiled so broadly his cheek muscles began to ache.

She tried to close it, tried to clench her cheek muscles, and nothing happened at all.

The old man's lips and cheek muscles had gone slack with death.

She yawned again, so wide that her cheek muscles stretched.

It was quite visible, that faint tightening of the cheek muscles.

There was no such thing among his race as a raised eyebrow or the tic of a cheek muscle.

In the control room, Sparrow fought down the twitching of a cheek muscle.

She felt the blade slice through cheek muscle and rattle along teeth.

I touched his face with my fingers and he flinched back, cheek muscles tightened.

I became vaguely aware that my cheek muscles were aching.