Any tooth with no opposing tooth to wear away the enamel will form a taller edge relative to the area where there is wear. When this over-eruption involves the front (rostral), back (caudal), or the whole tooth, it is called a hook. Hooks occur on the corner incisors and are most common on the upper corner incisor, either on one or both sides. They are easily seen here and, therefore, cause concern with horse owners because they look like they block the movement of the jaw. This belief is invalid because hooks form when there is no movement in the area. The following points help to explain.

First, all horses’ teeth continually erupt and are worn down when chewing against the opposing teeth. The unopposed eruption of the cheek teeth edge is how points occur and is the reason for floating the teeth. Unlike the hooks of the corner incisors, points become razor sharp when stropped by the tongue and consequently, cause pain to the soft tissues that contact the points. The corner incisor hooks do not cause pain to any soft tissue.

Second, imagine a boat moored to a wood piling. The boat moves from wind and small waves, eventually creating a notch in the wood. Does the wood prevent the boat from moving? No, because the movement causes the notch. The same is true for the corner incisor hooks. The hook develops because nothing touches it; therefore, it cannot limit the jaw’s movement.

Third, according to electron microscopy evaluation, the enamel of the incisors is softer than the enamel of the cheek teeth. When there is no opposition to incisors, as in parrot or sow-mouthed horses, the incisors never over-erupt into the palate because the movement of the tongue wears away the incisors. Further, it is the tongue’s movement that shapes the incisors, creating the visual of a “smile,” “frown,” “slant,” or “V.”

In 2002, I had lunch with Dr Paddy Dixon of the veterinary school in Edinburgh, Scotland. He told me then that the veterinary profession in the United Kingdom was moving away from incisor reductions (filing the incisors). Three months later, Dr Lowder of the Georgia Vet School echoed this. The AAEP no longer advises filing the incisors. Yet, there are dentists and other para-practitioners of horses who erroneously believe that the corner incisor hooks prevent jaw movement and that these need filing to “balance” the jaw and allow movement. There is no science behind this, and as I told Dr Dixon in 2002, removing the sharp points of the cheek teeth allows for better tongue and jaw movement. With freedom of pain, the incisor issues resolve on their own.

In my practice, I do not file the incisors as a routine procedure. However, if a client insists, I will file off the corner incisor hooks because this does not harm the horse. If left alone, they usually go away by themselves. In fact, in the tradition of aging horses by looking at the incisors, corner incisor hooks often form at seven and eleven years. Although inaccurate, the “7-year hooks” and “11-year hooks” form around these times.

The images here show that only one pull of a float blade is enough to remove the soft enamel corner incisor hook. The horse could easily do this themselves if the opposing tooth touched the hook, but it doesn’t, so removing it is not necessary for the jaw’s function.

If you have time, look at the side (lateral) views in the section called “Aging Horses By The Teeth.” (Left side, Right side) Notice the relaxed space between the incisors in most of the horses. Also, notice that many have the hook.

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