> Over bite and Under bite
Over bite or parrot mouth is a common cause of hooks, ramps, and other cheek teeth malocclusions due to misalignment of the whole jaw.
It prevents freedom of movement of the jaw effecting feeding and riding. Due to the misalignment there's no contact between the upper and lower incisors, first premolars or last molars. Incisors may have to be reduced during dental treatment. This condition is hereditary but can be managed by routine dentistry.
Under bite or sow mouth is fairly rare in horses, this is when the lower incisors protrude in front of the uppers. It causes the same sort of problems as over bite and can corrected if found early in life.