Iyāt conveys strong sunlight or radiance. Mentioning lithāt shows that the poet’s picture of a smile includes the coloring surrounding the teeth, not only their surfaces. Usiffa suggests dusting with a fine powder, while tukdam negates a more forceful crushing or rubbing action.
This is a poetic color description rather than a literal medical claim. The main contrast is between brilliant whiteness and natural darkness around the gums, expressed through the imagery of finely applied antimony.