Usage patterns
牙が生えるfor tusks/fangs to grow in
Even the baby wild boar has started growing small tusks.
牙を隠すto hide one's fangs (figuratively, to conceal one's aggressive or dangerous nature)
He seems calm on the surface, but he hides his fangs underneath.
Expressions
牙を剥くbare one's fangs; snarl (at) 牙を研ぐlie in wait; wait for a chance to attack