Well both, stuff between the teeth that the brush doesn't get (I guess that's why you'd floss after brushing, but also with foam in your mouth?), and also just food microparticles that would go away when rinsing after brushing generally.

I suppose it helps to floss before brushing (as recommended) but for me personally the stray particle isn't something I've worried about. In my mind, the added benefit of retaining the fluoride longer outweighs the downsides of microparticles of food.

> I suppose it helps to floss before brushing (as recommended)

Wellp, that's something I've never heard before. Even at the dentist, when she does a cleaning, flossing comes last.

Honestly, the timing of flossing is the least important thing about it, considering most people are averse to even doing it. The payoff with flossing before brushing is that any gunk that gets brought out and left over after rinsing gets scrubbed away during brushing.

https://www.healthline.com/health/dental-and-oral-health/flo...

If you have food microparticles that would go away, then rinse them out, then wash your teeth again and keep that foam in.