Tooth decay in toddler

Hi mummies, i realised my 1yo has decay on her tooth. Brought her to a dentist alr and the dentist mentioned that no treatment is required, just frequent brushing (without toothpaste) will do. But after a month, the decay got worse and starting to have holes on that tooth, what should i do? Any mummies is experiencing/experienced the same problem? Please advise a worried mom here 😭