Of what use is it in eating?—"It wets and softens the food."
What do you mean by preserve?—"To keep from injury."
What do you mean by injury?—"Hurt."
How do you preserve your teeth? See Formula.
How do very hot or very cold drinks hurt the teeth?—"They crack the enamel."
What happens if the enamel is cracked?—"The teeth decay."
Then what must you do to preserve your teeth?—"I must try to keep the enamel from being cracked or injured in any way."