Do the Crest or other company White Strips for the teeth have to have a Hechsher? If not, are there any ingredients I have to be aware of to avoid? Or is it not considered edible and therefore is okay no matter what ingredients it contains?
If the white strips are flavored it is highly recommended that they should have some hechsher. Even though it is not the normal hecher you would rely upon for food products.
Y:D 98 Pishchey Teshuvah 1