Equine teeth are ingeniously designed to function well through many years of hard use. As the grinding surfaces wear down, the teeth continuously emerge from the gums at a rate of about an eighth of an inch per year.
Given that the average equine tooth is about two to 3½ inches long, this provides years of “reserve,” ready to emerge from the gums. But as a horse reaches his late teens and 20s, he starts to deplete his tooth reserve, which makes him more prone to conditions ranging from periodontal disease to tooth loss, and less able to benefit from the usual solutions for bite problems. And all of this can affect a horse’s overall well-being: Poor dental health can lead to malnutrition or even serious infections.
That’s why dental care is a cornerstone of managing an older horse’s health. Annual dental exams are important for horses of all ages, of course, but when a horse enters his later years, they become increasingly critical. In fact, says Jim Latham, DVM, of Pagosa Springs, Colorado, some horses need even more frequent dental checks. “Not tending to the teeth of an older horse, or even being aware of what to look for, can lead to a situation where problems compound and extend far beyond the mouth,” he says.
One of the dental conditions seen most often in older horses is periodontal disease---inflammation of the ligaments, gums and other tissues that hold the teeth firmly in place. “We see this very commonly in older horses,” says Latham. In fact, studies have shown that 60 percent of horses over the age of 15 have identifiable periodontal disease.
The natural eruption of equine teeth, combined with a change in shape as they emerge from the gums, contributes to the development of periodontal disease, explains Latham. Equine teeth taper and become progressively narrower at the gum line as they erupt. This causes a gap to develop at the gum line---a space called a diastema---where feed can collect. Trapped food irritates the gums and harbors bacteria that can cause infection and inflammation.
Any disruption of the mouth’s function from bite problems (malocclusions) or loose or missing teeth increases the risk of periodontal disease, says Latham: “The movement of food through the mouth is a very orderly process. A bolus of food [goes] from the front of the mouth to the cheek teeth, where it is transferred from side to side and mixed with saliva as the horse chews. When the process is disrupted, feed can get trapped in a diastema or packed into hollows on biting surfaces of the upper cheek teeth called infundibular recesses. And there it sits to stagnate and cause inflammation and infection.”
Left unchecked, the infections can spread deep into the gums to the periodontal ligament and even to the root of the tooth. If bacteria invade the pulp chamber of the tooth, a painful root abscess may result. All of these factors can cause teeth to become loose and eventually fall out. “It’s not a given that a very old horse’s teeth will fall out,” says Latham. “But a combination of wear and disease can certainly make that happen.”
To treat periodontal disease, a veterinarian will carefully remove food trapped between teeth or in an infundibular recess manually, with a probe and possibly also a high-pressure stream of antiseptic solution. If deeper pockets have formed in the gums around each tooth, your veterinarian may x-ray the tooth roots and look for inflammation and then pack any pockets with an antibiotic gel that is slowly absorbed. The gel treats infection while keeping the pockets clear of food long enough for the gums to heal and close up again. A horse with advanced periodontal disease may also be given systemic antibiotics. And, since tall or dominant teeth may cause additional wearing and forceful trapping of food into an opposing, cupped-out, decayed or worn tooth, your veterinarian may slightly reduce the dominant tooth.
With aggressive treatment, periodontal deterioration can be reversed enough to “tighten” teeth loosened by the inflammation. But in some cases, extractions are necessary. “We try to keep the teeth in as long as we can, because having a missing tooth creates new problems to manage,” says Latham.
As a caretaker of a horse with periodontal disease, you’ll have some new responsibilities: To keep food from packing between teeth again, your veterinarian may instruct you on how to flush your horse’s mouth daily---the equivalent of flossing or using a Water-pik. It may also be necessary to change the horse’s diet to include forages that aren’t likely to become trapped in spaces between teeth.
When the bite’s not right
Malocclusions occur in horses of all ages, but they have more consequences and are harder to correct in a geriatric horse. Common bite abnormalities include:
• Hooks, sharp protrusions on the front (rostral) or rear (caudal) teeth, develop when an overbite, underbite or other dental deformity causes an imperfect meeting of the top and bottom arcades.
• Ramps are upward-sloping surfaces on premolars.
• Step mouth occurs when a premolar or molar is missing and the opposing tooth grows unchecked into that space.
• An abnormal wear pattern of the cheek teeth known as wave mouth gives the grinding surfaces an undulating appearance from front to back. A tooth higher than the rest of the arcade may be opposite a cupped-out, worn tooth.
• In shear mouth, the cheek teeth grinding surfaces are worn at a sharp angle (45 degrees or more) as opposed to the normal 15 degrees.
All these bite abnormalities make it harder for a horse to properly chew food, which can lead to weight loss and even choke. Malocclusions can also create sores inside the horse’s cheeks that, in addition to being painful, can lead to infections an older horse may have trouble fighting off.
“Cushing’s syndrome, in particular, can lower a horse’s immune function,” says Latham. “So in an older horse with Cushing’s, all infections are more likely to become chronic. That goes for periodontal disease as well as lesions within the mouth.”
Malocclusions in older horses are treated as they would be in younger ones---with careful reshaping of the teeth through floating---but in a much more conservative manner. “In a younger horse, the teeth erupt quickly and you’ve got more reserve tooth,” says Latham. “You do a bit of work, wait for more tooth to erupt, then come back and do a bit more. Over time, you work the mouth back into a more normal conformation. The trouble with older horses is there’s not a lot left to work with. All you can do sometimes is make the horse as comfortable as possible, even if his bite is far from ideal.”
With equine dental problems, as with so many other things, the best approach is proactive. In other words, says Latham, take care of a horse’s tooth problems before his age makes it more difficult. “The main key to having a healthy geriatric mouth is taking care of it before it gets geriatric. Hooks, waves and ramps are all easier to correct when the horse is younger and the teeth are emerging more quickly.”
Dental problems that are left to linger for years will compound, Latham says. “If you have any abnormal forces in the mouth, they will change the way a horse chews, and that changes the forces on the teeth and how they erupt. Over time, all of this will lead to bigger problems such as periodontal disease.” Many of the dental problems of geriatric horses, he says, are simply problems that were left unaddressed when the horse was younger.
A word about weight loss
Tooth troubles can cause a horse to lose weight, but that doesn’t mean that dental problems will necessarily lead to poor condition. “The fact that a horse is old and has bad teeth is not, in itself, a reason for that horse to be thin,” says Jim Latham, DVM. “If there are no other underlying conditions, a horse with bad teeth can still be fed in a manner that allows him to take in enough calories to maintain a healthy body weight. It becomes a matter of commitment to feeding the horse appropriately to the condition of his mouth. The horse may need to be fed soaked senior feeds or hay cubes. He may need vitamin and mineral supplements. Managing a geriatric mouth isn’t just managing the teeth, but the diet.”
Malalignments that cause bite problems
Some jaw malalignments are present at birth while others develop over time, but all can complicate dental care as a horse ages.
• In an overbite (parrot mouth, brachygnathism) the upper incisors overlap the lower incisors.
• An underbite (monkey mouth, sow mouth, prognathism) is a deformity in which the lower incisors extend beyond the upper incisors.
• Retained baby teeth or abnormal chewing can lead to ventral curvature (smile), which occurs when the outer corner lower incisors grow longer than the opposing teeth above, or dorsal curvature (frown), which results when the outer corner upper incisors grow longer than the opposing teeth below.
• A diagonal bite (tilted bite) may result from pain in the cheek teeth that causes a horse to grind feed primarily in one direction.,