If movies showed you everything, they'd last forever -- so they trust their audience to fill in the gaps. You never see Bruce Wayne brushing his teeth, but you don't wonder why Batman never knocks out evildoers with his rotten breath -- you just assume that happened off-screen. (Also, you know he'll punch you if you don't floss.)
Vigilantes' oral hygiene isn't the only thing left to the viewers' imaginations. There are many episodes that you never witnessed, yet you know had to happen some time or another. Things like, for example, these.