teeth will have a 0% / 37.5% / 75% / 100% chance to interrupt an opponent and put them into hit recovery if it deals between 0-6.25% / 6.25% - 12.5% / 12.5% - 25% / 25%+ of an enemy's max HP per hit.
if an opponent has 3500 HP you need at least 1287 damage on teeth to reach that 37.5% chance to hitstun your opponent, below that it won't interrupt them.
teeth can trigger claw block, avoid or evade all of which can interrupt your opponent. It cannot be blocked by shields nor trigger a non-claw block animation.
if your opponent is under the effects of a stun debuff, like the one provided by smite or mind blast, then teeth will have a 100% chance to hitstun regardless of damage dealt.

and as FHR thresholds are based on damage dealt after reductions, while normally most people can't reduce magic damage, if they're using a safety shield or energy shield, it can increase the damage needed to FHR them

This post was edited by Goomshill on Feb 13 2018 06:22pm

very well xplained.. and nice info. thank you