We brush our teeth and use floss, but sometimes a big person has to help. Sometimes they might have a hair or piece of food stuck in their mouth and want it out, but no one should be sticking toys or other things into their mouth (or eyes or ears – just to keep it general) “just for fun”.
Before taking a trip to the dentist or doctor’s office explain that they will be looking and touching inside their mouth but it is OK because mommy or daddy is there and because it’s the doctor’s job to check their throat/teeth/tongue/ears/eyes etc.