Periodontal Disease - An Introduction
If you own horses then you should be familiar with the term periodontal disease, and yet chances are you haven't heard of it. This disease is the most common disease affecting horses, with around 70% of horses suffering from its effects. So what is this important disease, what are its effects and how is it diagnosed and treated? Well firstly let's explain the word periodontal, perio means around and dontal means tooth so periodontal disease is disease of the structures that support teeth; these include the gum, the bone and the periodontal ligaments. It is a disease which can affect horses of all ages, and the author has observed life threatening periodontal disease in horses as young as 18mths of age.
The periodontal ligament
The periodontal ligament plays a very important role in the horse's mouth, it is responsible for stabilising the tooth against the forces it experiences during chewing but also has the ability to detach and reattach, allowing the continuous eruption that occurs in horses teeth. It works together with the tooth itself, the gum and the bone surrounding the tooth (the alveolus) to achieve this.
How does periodontal disease occur?
Periodontal disease is the greatest challenge for both human dentists and veterinarians in the field of oral health. There is still a lot of research going on in this area but current treatments do exist and have good success when initiated early enough. This disease begins when bacteria in the mouth proliferate around the teeth and gums. There are several factors that lead to this bacterial overgrowth, two of the more common being the trapping of food between or around the teeth and the formation of plaque. In both cases the body's natural defences are overwhelmed by massive numbers of bacteria which attack the gingiva or gums leading to inflammation. This is the first step in periodontal disease, it is called gingivitis. As the gum becomes inflamed it will swell and bleed, which allows the bacteria to enter the horse's blood stream and travel around the body, so periodontal disease can affect all areas of the body not just the horse teeth. There are links between periodontal disease and heart disease, as well as links to reproductive problems such as abortion and low birth weight.
The bacteria involved in periodontal disease produce enzymes, and these enzymes feed on the structures around them (The bone, the gum and the ligament) progressively destroying them and creating room for more food to trap around the teeth. In this way untreated periodontal disease, is a self perpetuating cycle and will simply get worse until the horse is in a great deal of pain and has teeth that move when they chew. This can cause a range of secondary symptoms or problems, such as displaced teeth that damage the tongue or cheeks, loss of muscle due to changed chewing patterns, bad breath, quidding ( balling feed up in the horses cheek), a build up of calculus (a mixture of food, saliva and bacteria), weight loss etc. Because of the differences in the type of teeth that horse's have ( hypsodont teeth) developmental issues, missing teeth, changes in diet and eating patterns can lead to overgrowths on the chewing surface of teeth, these can be a key factor in the development of periodontal disease by further altering the way a horse chews and the pressure placed on teeth, in some cases driving teeth apart and creating diastema ( gaps between teeth). There are also breed predispositions to periodontal disease and conditions contributing to periodontal disease, broadly speaking many of the Pony breeds and Arabs and Quarterhorse's develop severe periodontal disease from a young age.
How is it identified?
In order to accurately diagnose and assess periodontal disease a number of steps are required.
A thorough history is useful and observing the patient eat certain feed types a can also be helpful, symptoms such as yawning, abnormal jaw movement or washing the mouth out while eating maybe observed. Any evidence of halitosis (Bad breath) would immediately identify some form of periodontal disease.
The next step is an external examination of the horses head and the administration of pain relief and sedation. Changes in the muscles of mastication (those used for chewing) may be detected; most commonly an asymmetry of the temporal muscles, this type of change indicates a chronic (long term) problem. Once the horse is sedated and the head (including the eyes, sinuses, nostrils, lips and front teeth) have been examined a speculum (Gag) is applied. In order to identify periodontal disease the mouth must be thoroughly rinsed and a bright light, a mirror and probes used to examine around teeth. Sometimes Radiographs (x Rays) will be necessary to determine the direction of treatment (I.e. how much bone is left and should the tooth be treated or extracted).
Teeth are checked for mobility (which indicates a loss of periodontal support) and examined for evidence of calculus and cavities (caries). This can only be done effectively with the horse standing very calm and still.
Once a diagnosis has been made and prognosis (likelihood of successful treatment) determined, treatment can begin.
How is periodontal disease treated?
A really important point to understand is that structures that are destroyed by periodontal disease will not repair with treatment, so early diagnosis and treatment is extremely important ( once it's gone its gone). The principles of treatment are simple, control the bacteria (thus stopping the production of enzymes and further destruction of support for the teeth, and prevent the build up of food around teeth. Depending on where in the mouth the problem occurs, the method of treatment will vary. Once a diagnosis has been made your vet will discuss treatment options. If the problem involves the incisors or canine teeth ( teeth that can be examined and managed at home between dental consultations) then provided no extractions are necessary, your vet is likely to recommend removing the trapped feed regularly, applying a product to kill the bacteria ( such as hexarinse) and keeping regular dental appointments, to assess treatment, scale calculus etc. Only products designed specifically for treatment of this condition should be used.
If the problem involves cheek teeth then it is unlikely to be possible to manage this condition at home and the horse will require treatment from your equine dental vet. There are two main conditions that occur inside horse mouths, periodontal pockets (holes in the gum next to or around teeth) and diastema (spaces between teeth). Both conditions allow food to trap and periodontal disease to occur. Diastemas are usually treated by carefully widening the space between the teeth to allow the food to pass through. Periodontal pockets are often more difficult to treat and the process is based on cleaning the pockets and getting them to bleed to stimulate the formation of new tissue to fill in the pocket. Treatment of Diastema and periodontal pockets is done around some very sensitive structures such as a large artery and the nerves of the teeth, for this reason it can only be performed in sedated horses, by veterinarians.
As mentioned above overgrowths (or malocclusions) are an important contributor to the development of periodontal disease, these need to be identified and addressed as part of any treatment, as there are many types of malocclusion it is beyond the scope of this article to cover them in more detail.
Equine odontoclastic tooth resorption and hypercementosis
There is a particular form of periodontal disease about which little is known and for which there is currently no cure, this disease Equine odontoclastic tooth resorption and hypercementosis or EOTRH occurs in Australia and requires careful management. Although there is currently no known cure, the symptoms and the horse's pain can be managed effectively thus allowing these horses a better quality of life. EOTRH basically involves a progressive irreversible destruction of teeth and there support along with the production of extra cementum (part of the tooth) as the body attempts to counter the effects of the disease. Horses suffering this condition are usually in their mid to late teens when first diagnosed and experience pain and tooth mobility as well as the development of tooth root abcesses. Xrays often show dramatic differences from a "normal" mouth. Little is known about the cause of the disease but the author feels it is related to the horse's own immune system attacking its teeth for some reason.
Take home message
Periodontal disease is something ALL horse owners need to be aware of, early diagnosis and effective treatment are critical and if these occur then the outcome should be healthy horses free from dental pain who will benefit as they age from retaining their teeth.