I have it straight from Ken Schlotfeldt that he means the airbrush cleaning brushes you commonly see sold on E-bay and even by airbrush dealers. These have very stiff plastic bristles. He hates them. Some airbrushes depend on smooth metal to metal seals that could be compromized by fine scratches. And, they could definitely scratch soft teflon seals. They are for sure not something you would use on your teeth. The interdental brushes are soft and aren't going to damage anything.
Don