from the Vet Corner Archives
Part of Horse Previews Magazine website. Posted on 03/02/2000; 2:00:00PM.
Veterinary Corner 03/00: A New Approach To Equine Dentistry
by Katherine Burnett, DVM
Edgecliff Equine Hospital
S. 1322 Park Road, Spokane, WA 99212 * 509/924-6069
The field of equine dentistry has undergone dramatic transformation in recent years. The days of a quick float just using a few tools are disappearing and are being replaced by skilled practitioners with special training and sophisticated instrumentation. We now know that much more than a simple float is needed in many cases to preserve the dental health, digestive health and comfort of our horses.
Why the recent excitement over equine dental care? Actually, many of the "advanced" techniques being used today are a revival of theories and practices developed decades ago. Comprehensive dental care was heavily emphasized when horses were depended upon as work horses. It appears that this interest waned when they became pleasure animals. In recent years, clients and veterinarians have become more interested in prevention of disease, rather than just the fire engine approach to treating disease once it once it occurs. It is now understood that dentistry is an integral part of preventive care in the horse, jut as it is in humans and pets - maybe even more so, since horses eat the coarsest feeds and are also ridden with bits that are placed in their mouths. Additionally, newer sedatives have made restraint much safer and easier. Modern medicine has also helped veterinarians develop instrumentation that is more precise, easier to use, and gentle to oral tissue. Performance horse dentistry is a growing field, helping sport horses perform better.
Advancement in equine dentistry has been further fueled from the positive reinforcement that practitioners and horse people have received by observing the remarkable benefits to their horses firsthand. Good dental care helps horses live longer, more comfortable lives. Horses who have comfortable mouths work better in the bridle, so many frustrating performance problems can be eliminated. Most importantly, comprehensive dental care is essential to digestive health, preventing many types of colic, choke and chronic weight loss.
Many question the need for prophylactic and even restorative dental care, since wild horses have survived for centuries without it. The answer is easily understood when one examines the domestic horse's diet. Wild horses graze 24 hours per day on coarse grass. Domestic horses derive the majority of their ration from hays and grains. The teeth of the horse are designed to tear and grind these grasses, and they wear down quickly. Each back (cheek) tooth in the young horse has a very long reserve "root," so that it can erupt continuously throughout the horse's life, replacing worn tooth. The upper jaw is 30 percent winder than the lower jaw, and the horse chews from side to side. Wild grasses are coarse enough that the horse must make a large side-to-side movement when chewing. Domestic horses usually eat hay and grain or soft grasses, which require smaller side-to-side motion. As a result, the outer portion of the upper cheek teeth and the inner portion of the lower cheek teeth, are not worn adequately. Sharp "points" develop, which make bitting and chewing uncomfortable.
This lack of coarse forage also seems to affect the shedding times of baby (deciduous) teeth. Retained cheek teeth, called "cap," can cause uneven growth of the permanent tooth underlying them. This usually occurs in the second and third year, and is very common. The typical result of these retained teeth is an uneven surface developing along the surface of several cheek teeth in a row, a condition called wave mouth or step mouth. Both conditions are a very common and potentially serious cause of performance and digestive problems.
The incisors (front teeth) get very little wear in the domestic horse. Like the cheek teeth, they continually erupt, and were meant to be worn down by grazing coarse forages. The result of this lack of forage is that the incisors are not worn down enough, and they overgrow. In the normal mouth the cheek teeth are held apart by 2 to 3 millimeters when the mouth is closed and the incisors are touching. The surface of the cheek teeth are sloped from side to side, so as the horse chews from side to side, the upper cheek teeth slide up and down the lower cheek teeth. This grinds the feed. If the front teeth are overgrown, the mouth is impaled too far open, and the cheek teeth do not have enough contact time to grind feed efficiently. Eventually the surfaces of the cheek will loose their normal angle as well, and then the mouth is a real mess.
Inefficient chewing is detrimental, sometimes even fatal, in the horse. The normal stem fiber length in the stool of the horse with proper dentition should not exceed 1/2 to 3/4 inches in length. There are places in the equine large intestine where the diameter of the bowel decreases dramatically, and the bowel makes an 180 degree turn at the same time. If the fiber length of the stool is too long, then as chewed feed "funnels" through this area, it forms a clog, leading to an impaction. This slows the transit time of feed through the bowel. When feed slows down it starts to ferment, and can cause the pain of colic. This could also be a contributing factor in some cases of "twisted intestine" that can be fatal. Excessive fermentation can also lead to systemic bacterial infections and other illnesses.
Choke is a fairly common digestive problem that can be caused by poor dentition. Improperly chewed hay is swallowed in a ball and gets lodged in the esophagus. Many horses who choke sustain permanent damage to the esophageal muscle and will have repeated bouts for life. Some develop aspiration pneumonia and may die. I have observed that most horses prone to choke have dental malocclusions, that when corrected, result in less frequent choke episodes.
Most underweight horses can reach their desired weight if they are fed an adequate diet combined with proper dental care. Incisor overgrowth is a common cause of weight loss. All horses over the age of nine should have their incisor length and the distance between their cheek teeth evaluated. If necessary, the incisors should be reduced in length. This is a procedure that can be done under mild sedation at the farm. Any malocclusions of the cheek teeth, such as wave or step mouth, should be assessed and corrected if possible. This will help the horse chew better, which in turn will prevent gum disease and tooth loss. This author has seen tremendous weight gain in a short period of time in even very old horses, after restorative dental care. Of course, other medical problems could be present as well, and might be ruled out with blood work and other diagnostic tests.
The economic benefits of comprehensive equine dentistry are incredible. While it is more costly than dentistry of the past, you get what you pay for. Reduction of overgrown teeth and sharp points and hooks requires special instrumentation, much of it motorized. Not all veterinarians are equipped to provide this care, so you may have to pay a larger travel fee to get a practitioner to your door. The results are worth it. Feed efficiency can be increased dramatically, especially in the older horse or the hard keeper. I continually see cases where feeds can be reduced dramatically after preventative and restorative dental care.
Research has shown that the healthiest diets (aside from pasture) for adult horses are mostly based on roughages that are not excessively high in carbohydrates and proteins, and contain as few concentrates (grains) as possible. These diets lead to lower incidences of colic. Horses who have proper dental care maintain their weight better on food that is less rich. Less money is spent on expensive foods such as grains, and less money is spent on veterinary bills for digestive ailments.
A thorough dental examination should be performed on any recently acquired horse. Any horse with fiber lengths over 3/4 inches in the stool should also be examined, as should any horse that is dropping feed, eating slowly, or not working well on the bit. All horses should have a thorough dental examination and float at least once per year, even if none of the above signs are present (remember, the idea is to prevent problems before they start). These procedures are best performed under light sedation, after the mouth is rinsed with water and opened gently with a speculum. A dental problem should always be suspected in cases of weight loss, colic or choke. Some horses need examinations more than once per year, and this should be determined on a case-by-case basis.
by Katherine Burnett, DVM