The singular term "sweet tooth" is a phrase that everyone knows, referring to a liking or preference for sweet foods or candies.
While reading The Blind Assassin, I encountered this sentence:
“Young girls have such sweet tooths.” (p. 234)The knee-jerk response is that it must be wrong, that it should read "sweet teeth," but then the latter sounds equally awkward.
The "sweet tooth" is either a single item in one's mouth, or a condition or perception in one's senses, so one person can't have plural "sweet teeth," which conveys the wrong implication that the teeth themselves are sweet. To my ear, "sweet tooths" does in fact sound more appropriate.
But "tooths" is not offered as a plural of "tooth" in Random House or in the OED. (Though, curiously, "teeths" can sometimes be used).
Perhaps there's a copy editor out there somewhere with a reference book of usage that can clarify this matter...