sour tooth

an eye for an eye, a tooth for a tooth

compensation for injury caused by a person, in the form of inflicting of an identical injury on that person.

clean as a hound's tooth

Very clean.

hen's tooth

Anything not naturally occurring.

leave a sour taste in one's mouth

To give one an unpleasant feeling or memory.

long in the tooth

Old; aged.

salty tooth

A liking for foods that are salty.

sour grapes

Things that somebody pretends to despise because they cannot obtain or have them.

sour note

A negative aspect to something mostly positive.