This is the first in a series of dentistry guides that will help you understand the terms used to describe your horse’s teeth. Since this is the first guide, we'll start with some basic dental anatomy concepts before moving on to the definitions of hooks and points.
Horses erupt two sets of teeth in their lifetime, just like we do: deciduous (baby) teeth, and permanent (adult) teeth. For right now, we’ll just be talking about the permanent set of teeth, since this is what we are usually “floating.” The permanent teeth erupt continuously over the lifetime of the adult horse, and are worn down by the natural chewing action of the opposing teeth. This type of tooth is referred to as hypsodont, as opposed to our brachydont teeth, which stop growing after they erupt out of the gumline. Many herbivores who grind tough, fibrous matter as their main diet have hyspodont teeth. Floating is the use of specialized rasps to shape the teeth of the horse and correct many of the abnormalities that develop. This can be done because the tooth is going to continue to erupt, at least until a very advanced age.
The teeth of the normal horse are not perfectly aligned within their mouth. The upper teeth are set wider and more forward than the lower teeth. This causes natural “overhangs,” or portions of the teeth where there is less wear, even during normal chewing. A hook is a sharp edge that forms at an overhang in the front or back of the mouth. They typically form at the front of the first upper cheek tooth, and the back of the last lower cheek tooth. The term cheek teeth refers to the combination of premolars and molars in the adult horse. The term arcade refers to a line of cheek teeth, either upper or lower, and can be used interchangeably (upper left cheek teeth = upper left arcade).
The first diagram below shows the left side of a horse’s mouth, where the nose is to the left and the ears are to the right. The upper teeth are shifted very slightly forward (left) compared to the lower teeth. In the second diagram, you can see how this leads to the development of hooks at the front of the upper arcade and the back of the lower arcade, as opposing teeth wear each other down.
Hooks developing on
first upper cheek tooth and
last lower cheek tooth
Depending on the exact conformation of your horse’s mouth, they will be more or less likely to form hooks. Horses with parrot-mouth (overbite) have extreme hooks, and horses with monkey-mouth (underbite) often have hooks in the opposite positions on the arcades. Front hooks are much more accessible to dentists than back ones, so I rarely see significant front hooks on horses that have had routine dentistry performed. However, back hooks are a common finding in horses that have had “quick floats” over the years, and can be difficult to address once they become advanced. Some back hooks are so tall that they impale the upper gumline, and it becomes very difficult to open the mouth wide enough to rasp them down. In that situation, they will need to be removed with manual cutters or powerfloat attachments.
Points are sharp edges that typically form on the outside (cheek side) of the upper arcade, and the inside (tongue side) of the lower arcade. This is because the normal conformation of the horse’s mouth has the upper teeth set wider than the lower teeth. The first diagram below shows a cross-section of the horse’s mouth as if you were looking into it at the level of the bit/bars. The horse’s right teeth are to the left, and the horse’s left teeth are to the right. You can see that the upper teeth have a slight overhang on the outside, and the lower teeth have a shelf on the inside. The second diagram shows the typical pattern of points that develop due to this offset.
Points developing on the outside of the upper cheek teeth and the inside of the lower cheek teeth
Again, depending on how narrow your horse’s jaw is, the tendency to form points will be more or less significant. It is easier for dentists to address the outer points on the upper teeth; you do not need to open the horse’s mouth very wide to float these, and most horses tolerate it fairly well without sedation. However, the inside points on the lower teeth are more difficult to access. Some horses I examine for the first time have very well-floated upper teeth and absolute daggers on the inside of the lower teeth.
What problems do hooks and points cause?
Hooks and points are sharp; anyone who does dental exams will have cut their hands more times that we’d care for. Your horse’s mouth can also be cut by these sharp edges. Back hooks can lacerate the upper gumline behind the last tooth. Points on the edges of the cheek teeth can lacerate the cheeks and the tongue. These problems may worsen under saddle, when a bit puts pressure on the cheek and jaw, bringing sharp points into contact with soft tissues. Hooks and points can also limit the mobility of the jaw, which causes general discomfort and TMJ pain. By limiting the range of motion of the jaw, they further reduce the portion of the teeth involved in active grinding. This leads to the formation of even larger hooks and points, and a vicious cycle develops. You can see in the second and fourth diagrams (above), that if the hooks and points become long enough, they will physically obstruct the forward/back and right/left motion of the jaw during a normal chewing motion.
Routine examination and floating can address small hooks and points before they become problems. The examination and the float must address the back and inside of the mouth, not just the parts of the mouth that are easy to see and feel. The use of a speculum is a must, and some horses will require sedation.
Next dentistry topic: steps and waves.