Of course the literal meaning of
dent is a deformation of a
solid substance. If someone accidentally rams their car into
yours, crumpling the steel a bit, you've now got a dent in your car --
and he probably does too!
But
dent is used figuratively in a number of ways. I
remember an amusing case where a woman known for her charitable work
with the poor, when interviewed about it on television, said, "Maybe we
can't save the world, but at least we can put a dent in it."
Naturally, she meant that we can't alleviate all poverty, but at least
we can take some small steps to alleviate what we can, i.e., "put a
dent in poverty" -- not "put a dent in the world", as the original
statement seemed to say.
CJ