It is highly recommended that you have your horses teeth looked at by an equine dentist or vet every 6 months. Examinations should begin at birth and continue every 6 months throughout the horse's life to correct and prevent dental problems. Not having regular dental care could lead to many major problems that will not correct themselves.
↑ Example of a rostral hook
After hook was reduced in height
Rostral hooks are an overgrowth of the first premolar 1/6 or 2/6. It is the first upper tooth visible.
In most cases I have seen, if a rostral hook is present, it is very likely that a caudal hook is present (aka a "ramp").
A lot of horses with this problem tend to have an overjet or an over bite. This is usually completely correctable!
It can be caused by the height at which the horse is fed. If the horse eats off the ground, then all the teeth are in the natural position. Once the horse is fed up higher, as seen in a lot of show barns using hay feeders, the jaw/mandible shifts back, therefore the teeth grind out of occlusion causing rostral & caudal hooks.