bare (one's) teeth
To display an angry, violent, and/or threatening reaction to or against something or someone, as does a dog or wolf when threatened. I will bare my teeth to anyone who tries to take away my land. We seemed to be getting along just fine, but she suddenly bared her teeth when I brought up religion.
bare your ˈteeth
show your teeth in a fierce and threatening way: The dog bared its teeth and growled.