Perhaps one of the most neglected aspects of equine health, until a problem manifests itself, is the monitoring and care of a young horse's baby teeth. After all, they are only temporary and are shed at various stages to make way for permanent teeth. Right? True, but there is more to the story. Baby teeth can have problems along the way that might affect the young horse's development and even set the stage for problems when the permanent teeth arrive.
Neglect of equine baby teeth can have the same disastrous results as neglect of human teeth in a growing child. Without good teeth, a horse can't properly masticate its food. Debilitation, loss of energy, and poor physical health follow.
Actually, a horse uses its teeth more than a human does. Many humans eat three meals a day at spaced intervals. By contrast, horses in the wild and on pasture might spend between 10 and 12 hours per day grazing. The same is true of horses in box stalls or paddocks on free-choice hay. They will eat only a little at a time, but they will eat often.
We will employ Jack Easley, DVM, MS, Dipl. ABVP, of Shelbyville, Ky., as a guide in our discussion of equine baby teeth. He is a practitioner who devotes a good deal of his time to dental care of equines and has given a number of talks and authored a number of papers on equine dentistry. Easley presented a paper to educate his fellow veterinarians on "Equine Dental Development and Anatomy" at the 1996 American Association of Equine Practitioners (AAEP) convention in Denver, Colo., and more recently has authored other treatises on the subject.
To better understand the need for proper dental care, we first have to understand something about the unique tooth structure of the horse and the way it has evolved as horses slowly changed from an animal which was only about 26 inches tall to the half-ton or heavier horse of today. Obviously, that great increase in size over time has put greater demands on the horse's digestive system and its ability to crop food from growing grasses, plants, and shrubs.
"It has been shown during the evolution of Equus caballus," says Easley, "that with an increase in size, there is a cube factor in the increase of food required. A doubling of height requires eight times the food intake. The amazing grinding system of the horse's teeth accommodates such an increase in food intake and processing."
As the equine evolved, it developed into a continuously grazing animal. As its tooth structure evolved, changes occurred in the way it masticated food. For example, the horse developed a side-to-side chewing movement, with grass and other food being ground between the upper and lower cheek teeth after being sheared by the incisors.
The type of incisors and molars developed by the horse are hypsodont (having high or deep crowns and short roots). The teeth are constantly erupting (emerging through the gums) 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, becomes so short as to be useless. It is much the same with hypsodont teeth that keep erupting throughout the horse's lifespan. Because they are not continually replenished as to length, the time comes when only stubs remain, and the older horse might have difficulty masticating its food.
Let's take a look at the teeth as they develop from infancy into equine adulthood.
Baby Tooth Development
When a foal is born, it normally has no teeth, but that lasts for only a few days. Within the first week of life, the foal will develop four incisors--two in the upper jaw and two in the lower. These are the central incisors. The second set of inci-sors--the intermediate incisors--will erupt within the first few weeks. 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 upper or lower 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.
Eventually, all of these baby (deciduous) teeth will be 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 is four to 4 1/2 years old," says Easley. "By that time, all of the baby teeth have been replaced with permanent teeth, plus there are 12 additional molars."
Because the baby teeth, also referred to as caps, are shed in the order in which they arrive, they provide a definitive yardstick for determining a young horse's age. The central upper and lower incisors are the first to go when the young horse reaches about 2 1/2 years of age; the intermediate incisors will be lost at about 3 1/2 years, and the corner incisors at about 4 1/2 years. With the premolars, the rate of shedding is about the same--the first set will be shed at about 2 1/2 years, the second set at three years, and the final premolars at about four years of age.
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, things don't always go as they should.
Sometimes a baby tooth breaks in half and becomes lodged in the gum. Sometimes baby teeth become loose but won't shed, thus trapping the erupting permanent tooth in the jawbone. When that occurs, the horse usually will develop a knot on the jawbone as the bone remodels to make way for a tooth that is supposed to be erupting through the gum, but isn't.
Because of these and other potential problems, Easley recommends that a young horse should have its mouth examined every six months. Normally, he says, the baby teeth that don't shed are easily removed. Once the baby tooth is removed, the trapped permanent tooth can erupt and the knot on the jaw will disappear as the jawbone once again remodels.
Loose, retained baby teeth can cause a great deal of discomfort, says Easley. The discomfort often is manifested by irritability on the part of the horse, bad odor from the mouth, and sometimes behavioral problems, such as head tossing and refusing to respond to the bit. The only solution when a retained baby tooth is the root of a training problem is extraction of the tooth.
Also capable of causing training problems are wolf teeth--two short-rooted teeth located adjacent to the first premolar in the upper jaw. Wolf teeth normally erupt when a horse is between 12 and 18 months of age. Easley recommends that they be removed, particularly if the horse is to be used for performance.
"Wolf teeth sit in a precarious position in the mouth," he explains. "Depending on where they are located--on the inside of the cheek teeth or the outside--they can cause difficulty with bitting. A snaffle bit can cause the cheeks to roll back against the wolf teeth in a painful and irritating fashion. The wolf teeth may also be contacted by the bit and loosened because their root structure isn't very long. This will also cause irritation to the horse. Many trainers and owners, when they start bitting a horse, routinely have wolf teeth removed, which is something I recommend. Taking them out simply eliminates a potential complication in training."
The permanent teeth that replace the baby teeth are the kind that many humans would love to own when visiting the dentist to have a cavity drilled out and filled. The exposed crown of an adult horse's permanent tooth has neither a central nervous structure nor a blood supply. Thus, when it is treated, the horse feels no pain.
The adult horse, assuming that it has had the wolf teeth removed, has six upper and six lower incisors, six upper and six lower premolars (the most forward set of cheek teeth), and six upper and six lower molars (the cheek teeth at the rear of the mouth), plus two upper and two lower canine teeth just behind the incisors. Females normally have the same complement as males, minus the canine teeth.
Easley estimates that there are dental problems with approximately 25% of today's equine population, ranging from abnormalities involving baby teeth to worn out grinders in old horses.
Regular, routine dental care is the best safeguard against tooth problems. This might involve examining and treating horses with problems every six months. At the least, it ought to encompass a routine, annual dental exam.
A foal, Easley says, should have its mouth examined by a veterinarian as part of a routine post-natal examination. "At that point," he explains, "you can detect various congenital defects. There are steps that can be taken, such as braces or the use of wires, to correct certain problems when the horse is young. If you wait until the horse is six months old, the growth spurt is already past and it is too late. One should always remember, however, that these types of problems are hereditary and, if we use such a horse for breeding, we are enlarging the malocclusion (imperfect bite alignment) gene pool."
The young horse with normal teeth should be given another thorough dental exam at 12 months of age, Easley believes. If the horse has good occlusion (bite alignment), no treatment should be necessary. However, if there are sharp points or ledges from malocclusion, they might have to be removed by floating (rasping off the sharp edges).
The next time a routine dental exam is needed, he says, is when the horse is bitted for the first time, often at 18 months of age. This is the time when wolf teeth are identified and, if they pose a problem, are removed. This also would be the time when any rough or sharp edges at the front of the first set of premolars would be rounded off. In some horses, this might have to be done every six to 12 months as the teeth continue to erupt and sharp points or edges reappear and cause irritation when contacted by the bit.
Parents of young children routinely take their youngsters to the dentist to prevent tooth problems and to solve those that have developed. Much of the same type of care is necessary for the young, growing horse with baby teeth if the teeth are to remain healthy and give way without problems to the emerging permanent teeth.
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.