Boyd’s Bible Dictionary:
The Jewish law of retaliation permitted the deprivation of “eye for eye, tooth for tooth”
(Ex. 21:24). The principle of this law was condemned by Christ (Matt. 5:38-42). Teeth used figuratively for the inheritable quality of sin (Ezek. 18:2); “cleanness of teeth” a figure for famine (Amos 4:6); “gnashing of teeth” indicative of rage and despair (Matt. 8:12).
Strong’s Dictionary of Greek Words:
Meaning:
perhaps from the base of 2068; a "tooth"