Green’s Dictionary of Slang

gnashers n.

the teeth.

1932		(con. WWI) L. Mann Flesh in Armour 253: Monsieur Vanet walked about next day with his jaw swollen [...] his tormentors asked him ‘How’s the gnashers today, m’sieur’.
2001		K. Sampson Outlaws (ms.) 6: They always do tend to look a bit on the wet side to be fair, ratter’s gnashers. He’s got very wet teeth.
2002		(ref. 1940s) B. Morrison Things My Mother Never Told Me 211: It’s not that he expects any thanks, but it’s a bind shoving decent work at rotten gnashers.
2005		Observer Life 8 May 49: You lift the bones to your gnashers and chew away at the crusty bits.
2013		K. Sampson Killing Pool 18: He hits me with the stale yellow gnashers again and gives a funny bow .