As a horse ages, there is an ongoing wear and tear process that slowly, but steadily, erodes the animal's ability to be as productive and athletic as he was during earlier years. Nowhere is this more evident than with his teeth.
The bad news is that, in the past, little attention was paid to equine dental work and often horses ended their lives in misery, with a set of worn-out teeth that were unable to properly masticate (chew) hay or grain. The result, in many cases, was continuous pain and, quite often, malnutrition. Horses can literally starve to death because of teeth that can no longer do their job.
The good news is that attitudes and approaches have changed. More and more horse owners have become aware that good dental care is a key component in keeping a horse fit and productive and ensuring that he is able to consume adequate nutrition even in his later years.
Because there has been a change in attitude and focus of horse owners, increasing numbers of veterinarians are making dental care a key part of their practices, and others are concentrating solely on equine dental work as a specialty practice.
Two veterinarians in the latter category are our sources for this article. They are Mary DeLorey, DVM, of the Seattle, Wash., area, and Jack Easley, DVM, MS, Dipl. ABVP, of Shelbyville, Ky. Both have spoken at American Association of Equine Practitioners (AAEP) functions concerning equine dental care, and both have authored dentistry papers and articles. Easley is co-author of the first and second editions of Equine Dentistry (Elsevier). The information attributed to them comes from these sources as well as personal interviews.
The Horse's Mouth
Before we launch into a discussion of dental problems in the older horse, we must understand what we are dealing with inside the horse's mouth. This is key because, as DeLorey says, what happens from a dental care point of view when the horse is young very, often determines what the quality of his dental health will be when he is older.
There are between 36 and 44 teeth to deal with in the adult horse. Why the disparity in numbers? One reason is that mares don't usually develop canine teeth, while males usually have four of them. Then, there's the matter of wolf teeth. Some horses might have up to four, while others might have none.
During his lifetime, a horse will have two sets of teeth. The first set consists of deciduous or baby teeth, and the second set involves permanent teeth. The equine teeth are classed as hypsodont. Simply put, this means that the teeth are constantly erupting as the grinding action wears away the crown surface.
To further simplify, the tooth can be likened to a piece of chalk. As one writes on the blackboard, the chalk is worn away and, after a time, it becomes so short as to become pretty much useless. It is much the same with hypsodont teeth. They erupt into the mouth throughout the horse's life as the chewing surfaces are gradually worn down through the grinding of food. Because they are not replenished in total length, the time comes when only stubs remain, and the older horse might have difficulty masticating his food.
When a foal is born, she normally has no teeth. However, that condition lasts for only a few days. Within the first weeks of her life, the foal will develop four incisors--two in the upper jaw and two in the lower. These are the central incisors. The second or intermediate set will erupt within the first couple weeks, and the final set, the corner incisors, will arrive at about six months of age.
A few weeks after birth, the foal also will erupt three cheek teeth or premolars in each dental arcade (side of the jaw), which translates into six uppers and six lowers. Thus, a full set of baby teeth totals 24--six upper and six lower incisors, and six upper and six lower premolars.
Ultimately all of these baby teeth loosen and are replaced by permanent teeth.
"There's a lot going on inside a horse's mouth between the time he's six months old with a full set of baby teeth, and when he's four to 4½ years old," says Easley. "By that time, all of the baby teeth have been replaced with permanent teeth, plus there are 12 additional molars."
The baby teeth have short roots and are designed to be pushed clear by the erupting permanent teeth. When all goes well, that is exactly what happens, and the horse's lifestyle is not interrupted. However, it is not a perfect world inside a horse's mouth; myriad problems can arise. A baby tooth might break or become wedged into place in such a manner that it can't be shed. The list goes on.
Enter an equine dental practitioner. Because of these potential problems, Easley says, a young horse's teeth should be examined at least every six months. Problems eliminated at that early stage of life can have a positive influence on the horse's dental health as she matures and ages.
The way in which horses are fed throughout a lifetime also can have an influence on dental health. It often has been stated that the horse's digestive system is designed to handle small amounts of forage consumed frequently during a 24-hour period. However, that often is not the case in regimented circumstances where horses are fed a larger quantity less frequently. In addition, an equine diet very often features processed feed that produces a different form of chewing than when grass or hay are involved.
When a horse chews hay, Easley says, a big, wide chew is involved. This assists in producing even wear on the teeth doing the grinding. When grain is masticated, the chewing motion involves limited lateral movement of the jaws, which can translate into uneven wear, and even malocclusions (poor alignment) of the teeth.
Easley offers this comparison between horses and humans: The difference between a horse eating hay and processed feed, he says, is much like the difference between a human eating shredded wheat and peanuts. When a human eats shredded wheat, nearly all of the teeth in the mouth are involved in what he describes as "a big wide chew." The same would be true of a horse eating hay. When a human eats peanuts, a "tight, little chew" is involved. Much the same is true when a horse eats processed feed or grain.
DeLorey, in the March 2007 issue of The Horse (page 73, or www.TheHorse.com/ViewArticle.aspx?ID=9222), described what occurs when a horse has normal dental occlusion, or proper meeting of upper and lower grinding surfaces, as well as the problems that arise when there is malocclusion.
The horse's cheek teeth are designed to crush, mash, grind, and masticate coarse forages such as grasses and hay. The surfaces of these molars have wavy edges that are made up of tough enamel and slightly less hard dentine and cementum. Because of this difference in density, certain areas of the teeth wear faster than others, leaving ridges on the chewing surfaces. These "transverse ridges," which lie in a crosswise fashion, are normal and they help the horse grind the forages efficiently.
There should be two transverse ridges with a shallow trough between them in each tooth, and the ridges should be uniform in size throughout the mouth. One or more teeth can wear at an accelerated rate if opposing teeth do not meet properly. A tooth or part of a tooth can overgrow if it does not have an opposing surface to grind against. "If even one tooth is too short or too tall, the rest of the system compensates to accommodate the primary abnormality," she says.
But, DeLorey cautions, if these malocclusions are not dealt with during the animal's developing years, they can have serious repercussions when the horse is at an advanced age. The equine dental practitioner's job is to level the playing field, so to speak, so that the teeth meet evenly to wear normally and provide maximum grinding surface.
There is no magic time when age-related equine dental problems begin to appear. Some horses have an "old" mouth at age 15, says DeLorey, while others might not reach that state until their late 20s. Generally speaking, she says, equine dental practitioners expect to see age-related problems when the horse reaches 17 to 18 years of age. One of the prime problems in the older horse is periodontal (gum) disease (see April issue, page 59, or www.TheHorse.com/ViewArticle.aspx?ID=9284).
The type and severity of age-related dental problems, DeLorey says, often are determined by the type of dental care the horse has had during its lifetime. If malocculusions and other problems have been dealt with all along the way, the senior horse might face only a gradual wearing out of the tooth.
At maturity, the hypsodont tooth is four inches or more in length. By the time the horse reaches old age--into his 20s and beyond--the length of the tooth might have been reduced to less than an inch. The tooth, DeLorey explains, has been wearing away at the rate of about three to four millimeters per year. What this means, generally speaking, is that the four inches of tooth present at maturity should service the horse's chewing needs for at least 20 to 25 years.
However, if the teeth have been compromised due to untreated malocclusions and other problems, the stage is set for periodontal disease and problems that can hasten the demise of good dental health.
"Once a horse has reached the age of six years," DeLorey says, "all of his permanent teeth are in position and in use. If the horse has had periodic, comprehensive dental care up to this time and has no severe malocclusions or dental disease, he's well-poised for lifelong dental health. He should receive maintenance care, including smoothing of sharp edges, minor rebalancing, and troubleshooting every eight to 12 months. Horses involved in demanding disciplines might need dental care more frequently."
Actually, DeLorey says, older horses--those 16 years of age or older--might require no more care than a younger horse, providing that they have had the advantage of regular dental care along the way. However, she added, close monitoring of the older horse's dental health is important.
"In the older horse," she says, "the crown that has been slowly erupting out of the jaw over his entire life is running out. This progression brings with it the tendency toward periodontal disease, and the increased possibility of fractured teeth, diseased roots, and loose teeth."
At this stage of life, she says, the tooth at the gum line is shrinking in circumference. If the mouth structure adjusts to this change, DeLorey adds, this might not pose problems. However, if gaps develop that can become impacted with food, the threat of periodontal disease is heightened.
When periodontal disease does strike, DeLorey states, veterinarians can often successfully treat the disease with focused cleaning and local use of special antibiotics and protective materials.
Many other tooth problems in the older horse also can be solved with ongoing dental care. For example, she says, loose teeth, recognized early, can be shortened and rested so that the opposing tooth is not constantly grinding against it. By doing this, there is the chance that the loose tooth can re-establish a firm connection. In other cases, she says, loose, damaged, or diseased teeth are best removed.
DeLorey says horses are "incredibly stoic," especially as they relate to pain involving teeth and gums. They will endure the pain and continue eating, she says, until the pain becomes too severe or until physical forces make it impossible to do so. She maintains the owner has an obligation to prevent this kind of suffering.
DeLorey says, "One of the most important concepts that horse owners can embrace from all this is that prevention is the absolute key to equine dental health. The idea that a horse doesn't need dental attention until he is in his or her middle age must disappear. The tendency to abnormally wear the teeth is usually present very early in life. Minor abnormalities detected at the age of one to five years can usually be easily corrected and need never become an issue. If the same problems are left undiagnosed until that horse is older, much more aggressive techniques are required to correct the situation."
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.