I think Kaprow was trying to say that depending on your view of the world anything can be art, but not just that. When he went into the details of what he saw while he brushed his teeth I think he wants to point out to not only look for art in unlikely places but to pay attention to the smallest of details which can contribute a lot to your art. Also perhaps when viewing others artwork to pay attention to the small details of their work to really try to see everything that they saw when they created it.
I think this concept relates to our class and and how it might help our art, because most if not all of the class is not used to considering time when we create art, just like Kaprow had never considered brushing his teeth as art. Along with that, brushing your teeth is something someone does everyday (hopefully) and the actions you do while brushing your teeth are a repeated gesture. This does give an interesting new side to our first project and what can be considered for it.