You should be able to tell by looking at the filament past the extruder. It's easiest to run the filament in then remove it to see what the teeth are doing to it. It should have dents in it but not to the point of chewing it up. I tend to run mine a bit tight, but I don't get dust. More than likely, it's slipping due to either too light pressure on the filament or too much back pressure in the nozzle.