In order to diagnose any oral problem, a comprehensive examination of the horse’s mouth needs to be done under sedation using a bright head torch and angled mirror or an oroscope. This allows assessment of all the teeth and the surrounding soft tissues for evidence of disease. Equine upper cheek teeth are unique in that they have structures called infundibulae in the centre of them. These are enamel cup like structures within the tooth which add strength. The smaller dark areas seen on the flat part of the horse’s teeth are the pulp horns, under which lie the sensitive, living part of the tooth. The lower teeth have pulp horns, but only rarely have infundibulae.
Caries is described as the destruction of tooth tissue (‘tooth decay’). Very often, these will be noticed at a routine dental examination and the horse will not be exhibiting any symptoms at all. Although we cannot definitively say why caries occur, it appears bacteria, pH, oral environment and tooth structure all play a part. Caries can be classified as either infundibular caries when the infundibulum is affected, or peripheral caries like lesions (PCLL) when the tissue on the sides of the teeth become eroded. Limited time spent eating, together with high sugar diets, is often implicated in peripheral caries like lesions.
The infundibulae are blind ending, cup like structures of enamel which are normally filled with cementum. We know that cementum often fails to completely fill the infundibulae, leaving a cavity. This cavity can then become packed with food as the horse chews. Over time, this food can become rotten and ultimately start to decay the tooth causing caries. Infundibular caries are often detected in horses over 12 years of age. These caries can be graded according to how severe the decay is and whether they affect the surrounding enamel or just the cementum of the infundibula. Early or mild caries can be monitored at routine dental examinations and then treated when appropriate. Ultimately caries can extend such that the tooth becomes weakened and then fractures.
Once identified using a mirror or oroscope, the food material is initially picked out and the depth of the pocket of decay measured. If the pocket is deep or extensive, the infundibula may be suitable for restoration to reduce the risk of the tooth the fracturing. If horse is over the age of 20 years old, the risk of fracture is reduced as the infundiblum becomes shallower when the tooth grows out with advancing age.
In order to restore the tooth, the horse is radiographed to check for any obvious signs of infection surrounding the tooth root. If there is infection surrounding the tooth, then tooth restoration may not be suitable. After radiographs are assessed, the infundibulum can be cleaned out and is often much larger than first thought. This is a time-consuming task and the horse needs to be well sedated to allow careful and precise working. Once it is cleaned, the tooth is filled in much the same way as a human tooth is when you visit the dentist. The filling material is then ‘cured’ and the horse can return to normal life – although avoiding toffee is still a good idea! We would usually advise a 6 monthly check up to ensure the filling is still in place.
Peripheral caries like lesions (PCLL)
These are often identified on the sides of the lower, back cheek teeth. Horses fed high carbohydrate diets with limited time spent chewing are at risk of these problems. Interestingly, if these triggers are avoided, you may be able to prevent new caries forming. If these are identified, we often advise increased time spent chewing and ensuring the horse has a more fibrous, lower carbohydrate feed intake.
Occasionally, we will diagnose PCLL adjacent to diastemata (gaps between the teeth). These diastemata can allow food to become trapped between the teeth and the resulting rotten food material can then cause decay on the surrounding tooth tissue. Often resolving the diastemata can prevent worsening of the caries like lesions.
In summary, if you are concerned about your horse’s dental health, please do discuss this with your vet and undertake routine dental examinations to identify and monitor any problems.