As scarce as hens' teeth and Few

Few and as scarce as hens' teeth are semantically related. In some cases you can use "Few" instead an adjective phrase "As scarce as hens' teeth".

Few adjective - A quantifier that can be used with count nouns and is often preceded by `a'; a small but indefinite number.

As scarce as hens' teeth and few are semantically related. You can use "As scarce as hens' teeth" instead an adjective "Few".