After brushing, I still think and feel that my mouth is "unclean" if I don't use floss afterwards. My teeth have barely room to breathe in between, so not even a toothpick can penetrate to remove food debris and bacteria. So I need to floss my teeth especially to remove minuscule food particles stuck in between my teeth and gums.
But I don't use just any floss--I juse Oral-B Essential Floss. I have used this product for several years already. I have tried other brands in between, especially when this brand is sold out, but I still go back to buying it. One of the primary reasons that I like Oral-B Essential Floss is the size of the floss. Other brands get stuck in between my teeth. I have a hard time pulling it down in between the teeth and removing it. Unlike Oral-B, their floss is small and smooth because it is waxed, so it easily slides down in between my teeth. Yet, it effectively removes particles that were left after brushing. And I believe, the bacteria are effectively removed, too. (Whatever is left is killed by my mouthwash.)
Additionally, Oral-B is mint flavored, so my mouth really feels fresh afterwards. My gums also feel good with the touch of the gentle mint on the floss. So for healthy teeth and gums, flossing with Oral-B Essential Floss is a must for me.