Horses' teeth are often used to estimate the animal's age, hence the sayings "long in the tooth", "straight from the horse's mouth" and "Don't look a gift horse in the mouth".
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At five years of age a horse has between 36 and 44 teeth. All horses have
Additionally, a horse may have:
A horse's incisors, premolars, and molars, once fully developed, continue to erupt as the grinding surface is worn down through chewing. A young adult horse will have teeth which are 4.5-5 inches long, but the majority of the crown remaining below the gumline in the dental socket. The rest of the tooth will slowly emerge from the jaw, erupting about 1/8" each year, as the horse ages. When the animal reaches old age, the crowns of the teeth are very short and the teeth are often lost altogether. Very old horses, if lacking molars, may need to have their fodder ground up and soaked in water to create a soft mush for them to eat in order to obtain adequate nutrition. Commercially prepared hay pellets and Hay cubes can be moistened for this purpose. Beet pulp may also be a suitable feed.
Contrary to popular belief, the bit of a bridle is not held between the horse's teeth, but lies in the "interdental space." This space lacks teeth, providing an area for the bit to rest without forcing the jaws open, and occurs between the cheek teeth and the incisors (or canines, should the horse have them).
However, if the bridle is adjusted so that the bit rests too low, or (more commonly) too high, it may push against the teeth and cause discomfort.
Sometimes, a "bit seat" is filed in the first cheek tooth. A veterinarian rounds the surface, so that, when the bit is pulled, the flesh of the cheek is not pushed into the sharp edge of the tooth. Although this practice is disputed, and most agree that an extreme bit seat can indeed be harmful, many veterinarians believe it makes riding more comfortable for the horse.
It is possible to age a horse using signs of the tooth eruption and wear. However, this is not an exact science, and become increasingly difficult after the horse is "aged." Horses are individuals, and two horses of the same age may have different wear patterns.
There are 24 deciduous teeth (also known as milk, temporary, or baby teeth). These come out in pairs, and are pushed out later by the permanent teeth. The number of permanent teeth may vary, depending on whether the horse has wolf teeth or canines. Most mares have 36, and most male horses have 40.
| Type of tooth | Number | Deciduous | Permanent |
|---|---|---|---|
| Incisor | First (central) | birth to 8 days | 2.5 yrs |
| Incisor | Second (intermediate) | 4.5–6 weeks | 3.5-4 yrs |
| Incisor | Third (corner) | 6–9 months | 4.5-5 yrs |
| Canine | Absent | 3.5-5 yrs, some around 6 yrs (if ever) | |
| Premolar | First (wolf) | Absent | 6 months to 3 years (if ever) |
| Premolar | Second | birth to 2 weeks | 2-3 yrs |
| Premolar | Third | birth to 2 weeks | 2.5-3 yrs |
| Premolar | Fourth | birth to 2 weeks | 3-4 yrs |
| Molar | First | Absent | 9–12 months |
| Molar | Second | Absent | 2 yrs |
| Molar | Third | Absent | 3-4 yrs |
By age five, all permanent teeth have usually erupted. The horse is then said to have a "full" mouth.
However, individual horses vary, and some breeds and types of horse are known to have differing eruption timelines. These include:
After five years, the age of a horse can only be conjectured by study of the wear patterns on the incisors, shape, the angle at which the incisors meet, and other factors. The wear of teeth may also be affected by diet, natural abnormalities, and cribbing.
Like humans, horses can develop a variety of dental problems, some which may be very serious and require surgery. To head off any potential issues an annual exam is recommended and especially if the horse exhibits any signs of feeding problems. Abnormal teeth not only affect the horse's comfort while chewing,but may also manifest themselves as disobediences or other performance issues while the animal is ridden. Tooth issues may have an impact on how the horse uses its entire body. Treatment can be performed by an equine veterinarian, ideally one that specializes in horse's teeth check their animals' teeth regularly. In some nations, non-veterinarian specialists in equine dentistry may also perform equine tooth care services.
Many dental problems in horses are related to the fact that their teeth erupt continuously throughout their life. Horses are evolved to graze nearly continuously, often on rough forage in semi-arid climates. Their teeth are designed to wear against the tooth above or below as the horse chews, thus preventing excess growth. The upper jaw is wider than the lower one. Sharp edges occur on the outside of the upper molars and the inside of the lower molars, as they are unopposed by an opposite grinding surface.
There are many times when tooth wear is not even, and the horse may develop sharp edges on their teeth that reduce chewing efficiency of the teeth, interfere with jaw motion, and in extreme cases can cut the tongue or cheek, making eating and riding painful.
In the wild, natural foodstuffs may have allowed teeth to wear more evenly. Because many modern horses often graze on lusher, softer forage than their ancestors, and are also frequently fed grain or other concentrated feed, it is possible some natural wear may be reduced in the domestic horse. On the other hand, this same uneven wear in the wild may have at times contributed to a shorter lifespan. Modern wild horses live an estimated 20 years at most, while a domesticated horse, depending on breed and management, quite often lives 25 to 30 years. Thus, because domesticated animals also live longer, they may simply have more time to develop dental issues that their wild forebears never faced.
Sharp enamel points usually develop on the outside of the upper cheekteeth (grinders) and the inside of the lower cheekteeth . "Hooks" also commonly occur on the front of the first upper cheekteeth (second upper premolars/#106/206), or at the posterior end of the last lower molars (distal #311/411).
A step mouth occurs when one cheek tooth grows longer than the others in that jaw. This is usually because the tooth opposing that particular one, located in the opposite jaw, was missing or broken, and therefore could not wear down its opponent.
A wave mouth occurs when at least two of the cheek teeth are higher than the others, so that, when viewed from the side, the grinding surfaces produce a wave-like pattern rather than a straight line. This can lead to periodontal disease and excessive wear of some of the teeth, eventually leading to some discomfort or trouble with mastication.
A shear mouth occurs when the grinding surfaces of the cheek teeth are severely sloped on each individual tooth (so the inner side of the teeth are much higher or lower than the outer side of the teeth). This may result in an angle at 60-75 degrees, opposed to the normal 15-degree angle seen on most horses. Again, the chewing motion is severely affected.
Horses may also experience an overbite/brachygnathism (parrot mouth), or an underbite/prognathism (sow mouth, monkey mouth). These may affect how the incisors wear. In severe cases, the horse's ability to graze may be affected. Horses also sometimes suffer from equine malocclusion where there is a misalignment between their upper and lower jaws.
The curvature of the incisors may also vary from the normal, straight bite. The curvature may be dorsal or ventral . These curvatures may be the result of an incisor malocclusion (e.g. ventral=overbite/dorsal=underbite). The curvature may also be diagonal, stemming from a wear pattern,offset incisors, or pain in the cheek teeth (rather than the incisors), which causes the horse to chew in one direction over the other.
Other common problems include abscessed, loose, infected, or cracked teeth, retained deciduous teeth, and plaque build up. Wolf teeth may also cause problems, and are many times removed, as are retained caps.
Additionally, many problems under saddle can be tooth-related, such as:
For many performance-related problems, it is often best to check the teeth to rule out that factor.
To help prevent dental problems, it is recommended to get a horse's teeth checked by a veterinarian or equine dental technician every 6 months. However, regular checks may be needed more often for individuals, especially if the horse is very young or very old. Additionally, the horse's teeth should be checked if it is having major performance problems or showing any of the above signs of a dental problem.
Many horses require floating (or rasping) of teeth once every 12 months, although this, too, is variable and dependent on the individual horse. In young horses, twenty four teeth are deciduous or "caps". These are the first three premolars of each arcade (not including wolf teeth) and all incisors. Caps are pushed out by the new permanent teeth, starting late in a horse's two year old year. Caps will eventually shed on their own, but may cause discomfort when still loose, requiring extraction. The first four or five years of a horse's life are when the most growth-related changes occur and hence frequent checkups may prevent problems from developing. Equine teeth get harder as the horse gets older and may not have rapid changes during the prime adult years of life, but as horses become aged, particularly from the late teens on, additional changes in incisor angle and other molar growth patterns often necessitate frequent care. Once a horse is in its late 20s or early 30s, molar loss becomes a concern. Floating involves a veterinarian wearing down the surface of the teeth, usually to remove sharp points or to balance out the mouth. However, the veterinarian must be careful not to take off too much of the surface, or there will not be enough roughened area on the tooth to allow it to properly tear apart food. Additionally, too much work on a tooth can cause thermal damage (which could lead to having to extract the tooth), or expose the sensitive interior of the tooth (pulp). A person without a veterinary degree who performs this service is called a horse floater or equine dental technician.[3]
The common folk saying "don't look a gift horse in the mouth" is taken from the era when gifting horses was common. The teeth of a horse are a good indication of the age of the animal, and it was considered rude to inspect the teeth of a gifted animal as you would one that you were purchasing. The saying is used in reference to being an ungrateful gift receiver.[4]