That is interesting thanks.
Seems to me that if the board could have made the case that teeth whitening can be damaging to the teeth or gums if done improperly they might have made the case that it was dentistry.
They still get to make that argument when the case goes back down to the lower courts. The point is that if the elected state legislature had said that only dentists could do teeth whitening, that decision couldn't be challenged at all in federal court. Because the decision was made by dentists trying to exclude competitors, they don't get the immunity that the state would have had, and have to justify their decision to a court and jury.