Teeth types
Incisors
The function of incisors, or “nippers”, is to cut grass at ground level. This is the beginning of the horse’s digestive process.
The horse has 12 deciduous incisors (baby teeth that will be shed) and 12 permanent incisors that will replace them.
The normal horse’s upper jaw may appear to protrude further than the lower jaw, although this will only be by a couple of millimetres. When the horse lowers its head to eat, the lower jaw moves forward and the lower incisors will be in true opposition to the upper incisors.
If a horse has an upper jaw that protrudes extensively beyond the lower jaw, this condition is referred to as a parrot mouth. Alternatively, if the lower jaw extends beyond the upper jaw, this is referred to as a sow mouth or a monkey mouth.
The canines
The canine teeth can also be referred to as tushes, fangs, fighting teeth or bridle teeth. They grow in the bar areas of the horse’s mouth (the area of gum where the bit resides) and usually appear when the horse is about 4½ years old. All horses can develop these teeth, however it is less common for females to have them.
The canine teeth are of no real functional use to the horse, but if they become large or grow at an angle they will press into the tongue or the cheek and will need to be trimmed. It is believed that these teeth were used for fighting before horses were domesticated.
If the canines are slow to erupt, the bit can press on the gum over the unerupted canine tooth, which will cause the horse pain. In this case the skin over the erupting canine tooth may need to be broken to relieve the pressure and discomfort.
The pre-molars
The cheek teeth (the back six teeth) are divided into premolars and molars. The pre-molars and molars extend along the upper and lower jaws of the horse from the bars of the mouth (the area where the bit resides) to just behind the level of the eye.
The first three cheek teeth are the pre-molars. There are 12 deciduous pre-molars (teeth that will be shed) and 12 permanent pre-molars which will replace them. The deciduous teeth may come out on their own or they may need a little encouragement from your dentist. The dentist will refer to them as caps and will generally use a cap extractor to remove them. In thoroughbred racing, for example, the trainer will not want the horse distracted from his work by fiddling with the caps, and the dentist will monitor the caps and remove them as soon as they are ready.
The first pre-molars (the number 6 teeth) will usually have shed by the time the horse reaches 2½ years of age, and by the time the horse is 3½ years of age all of the deciduous pre-molars (the number 7 and 8 teeth) should have been shed.
In the picture you can see a deciduous number 6 tooth (cap) ready to be shed, with the permanent pre-molar below it. The number 7 and 8 teeth behind are deciduous pre-molars and will also be shed during the next 12 months.
In the picture you can see two caps that have been shed. Notice the “table leg” pieces on the caps; these locate the cap in place on top of the permanent tooth as it is erupting.
Molars
The three teeth behind the pre-molars are the molars. The molars differ from the pre-molars in that they do not have any deciduous teeth preceding them, and therefore they may be referred to as accessional teeth. The lower molars are narrower than the uppers, and sit about a half-tooth-width inside the edges of the uppers.
When the horse chews, the food is ground between these tables as the lower jaw moves down, out to the side, up and in again. Normal chewing consists of a circular motion several times in one direction, then a shift to chewing several times in the other direction, forming a symmetrical figure-eight pattern overall. The food is moved backwards along the molar table as the chewing process takes place.
The more a horse can chew its food, the easier it is for the digestive system to get goodness from the food. Often people will say that their horse’s teeth are fine because he is continually eating. However, it could be that the horse is needing to eat more food than is necessary because it is not chewing the food properly. This means that the digestive system cannot get the optimum benefit from the food and the horse needs to eat more to maintain its condition. The molars can only perform at their best if the surfaces of the upper and lower cheek teeth meet properly. This meeting of the teeth (occlusion) can be affected by many factors. The most common include:
- The incisors (the front teeth) being too long, so that the cheek teeth are held apart.
- A molar or pre-molar being longer than the other teeth in the arcade, and therefore preventing a good contact.
