दाँतों is the plural oblique of दाँत. In the direct case, masculine nouns that end in a consonant (दाँत, हाथ, घर, पहाड़, शेर, etc.) don't have a distinct plural form.
I more or less understand Zesul's answer about sing./pl. case and the relationship if it is in the oblique case; however, is there a way to determine whether to use "daant" or "daanton"? I keep getting it right, but I don't know why.
There must have been a postposition after "eyes". "Four eyes" in and of itself is translated as चार आँख. "In the four eyes", on the other hand, would be चार आँखों में.