Periodontal disease in the horse is similar to dental issues in other domesticated animals and in humans. The disease begins when bacteria in the mouth proliferate around the teeth and gums, most commonly due to the trapping of food between or around the teeth and the formation of plaque. The body’s defences are overwhelmed by bacteria which attack the gingiva or gums, leading to inflammation and gingivitis.
As the gum becomes more inflamed it swells and begins to bleed, allowing bacteria to enter the bloodstream and thus placing all of the vital organs at risk of infection. As the disease progresses the attachment between the gum, the teeth and the jaw is lost. At this point periodontal disease can be stopped but cannot reversed. If the disease process continues it will lead to the loss of periodontal attachment around the tooth, which becomes loose and must be extracted. This can have life long consequences for the horse, who relies on healthy teeth to gain adequate nutrition from feed.
As a herbivore, the horse has teeth designed to grab and grind forage (grasses). To do this efficiently there are some important differences in the anatomy of their teeth compared to ourselves and other domesticated animals such as dogs. The teeth of the horse are are constantly worn away by the actions of chewing and grinding. To combat this wear and tear, horses have two sets of teeth during their life. The horse possesses extra tooth or reserve crown below the gumline in the jaw and this grows out (erupts) at a similar rate to the rate at which tooth is worn away. There is enough of this reserve crown to last the average horse well into their twenties, and often their thirties.
This system of tooth being worn away and replaced must remain in balance or problems will quickly occur. Just like people, horses can experience severe dental pain and pain is the most common reason the system become imbalanced; in response to pain the horse will alter the way it eats and chews, which rapidly affects the wear patterns of the teeth. Dental pain in the horse has a number of sources. The maxillary branch of the infraorbital nerve innervates the teeth of the upper jaw, while the mandibular branch of the trigeminal nerve innervates the teeth of the lower jaw, leading to severe pain caused by sensation to these nerves.
Horses also experience pain due to oral ulcers, impacted teeth, feed packing into the diastema — the spaces between the teeth — fractured teeth, unopposed teeth erupting into soft tissues and tooth root infections causing abscesses.
Horses evolved to graze with their heads down at ground level, eating grasses for many hours a day. Altering their diet and their living conditions can mean we also alter the way their teeth wear. Feeding of hard feeds, grains, chaff and pelleted feeds alters their normal grazing patterns and forces shorter feeding times. It also often forces them to eat with their head up. These management changes can all affect the dentition of the horse.
Horses have another important anatomical difference from people. Seen from the front, their upper jaw is wider than the lower jaw. This means that the outer surface of the upper teeth, closest to the cheeks, and the inner surface of the lower cheek teeth, closest to the tongue, are both unopposed. Through the continual process of eruption the edges, or cingulae, of these teeth grow but are not worn away but form razor sharp points along the arc of teeth.
When the horse eats it is forced to bring its cheeks into contact with these points. Unlike us, the horse does not chew in a simple up or down or side to side motion but in a complicated four part cycle, so these sharp points act on the horse’s cheeks and tongue like a saw, causing ulceration, cuts and, if bacterial infection occurs, abscesses. Fortunately, these cingulae, or sharp points, are formed of enamel, meaning these points can be removed relatively easily, providing relief for the horse and, usually, a return to a normal chewing cycle.
The early signs of periodontal disease in horses can be difficult to spot. More advanced signs are easier, but once disease is advanced it cannot be reversed so it is important that horse owners make themselves aware of the normal signs of healthy dentition and carefully note any changes from the norm. Call the hospital if you see signs that your horse is experiencing discomfort, is not eating normally or has sharp points on the upper and lower teeth.
The most effective way to prevent equine periodontal disease is to have the teeth of your horses checked annually.
How is equine periodontal disease diagnosed?
Dental disease is primarily diagnosed by visual exam. It is important that a thorough examination is made of a horse’s mouth as there are many other conditions that commonly occur in the mouth, many of which cannot be diagnosed without visualisation.
Treatment is aimed at assisting the body’s natural defence systems by removing excessive bacterial growth and maintaining a balance of the bacterial population in the mouth. How this is achieved depends on the location and severity of the disease, as well as other factors such as the age of the horse and any other health conditions they may have.
Our dental care is based on an oral examination, then a dental rasp to grind the apposing surfaces of their sharp hooks and ramps. In a few rare cases, mostly in old horses, ‘wave formations’ — where the upper or lower arcade has lost a tooth and because of the continual dental growth, the apposing tooth has grown down to the point of preventing chewing — we will usually anaesthetise and then use gigli wire to saw through the offending lower portion, and trephine out the upper portion.
We will remove plaque and where food is trapped in the spaces between teeth remove the offending material to prevent bacterial population, followed by an antibacterial solution to kill any remaining bacteria. This treatment is practical only for incisor teeth. For cheek teeth the space where the food is packed may need to be widened to allow the food to fall out before it is overrun by bacteria. Patients may also need to be on systemic antibiotic therapy, and x-rays may be required to assess the structures below the gum.