Some facts about equine dentistry
- Horses’ teeth erupt at about 3mm per year
- Routine dental care requires trimming of sharp enamel edges once or twice a year depending on individual horse requirements Main points Horse teeth have a limited life span – do not let anyone shorten the tooth’s life span!
- Zebras don’t need routine dentistry so why would my horse?
- Zebras eat a varied diet, most of which requires thorough grinding before it is swallowed and very little of their diet needs to be chomped.
- Domesticated horses on the other hand, are fed commercial rations and hay, some of which is fed above the ground (for example in hay nets) leading to abnormal chewing behaviour. Horses are grazers and when their heads are down eating grass, the jaws are in their most natural positions.
Horses’ cheek teeth grow at about 3mm per year. That means that a thoroughbred or Warmblood starting out with about 100mm of tooth height will have about 33years of active tooth substance. It is therefore important to maintain as much of the tooth as possible and not over trim the teeth.
Each horse has between 36 and 40 teeth depending upon whether they have premolar 1 and canine teeth in each quadrant. Premolar 1 is often referred to as the “wolf tooth” and may engage the bit when contact is made, causing some discomfort to the animal. Is these cases the teeth are extracted. It is often not necessary to extract Premolar 1, the decision whether to extract or not is dependent on the animal’s response to the bit and contact.
The horse’s lower jaws (mandibles) are fused at the front enabling better grinding of food. They are about the same length as the upper jaws (maxilla) but they are narrower that the maxilla. The mandibular cheek teeth chewing surfaces are rectangular when viewed from front to back, while the maxillary check teeth chewing surfaces are square.
The cheek teeth have enamel, cementum and dentine on the chewing surface, and since the cementum and dentine are not as hard as enamel, they wear sooner resulting in peaks of enamel and valleys of dentine on the chewing surface. This helps the horse grind its food more efficiently.
To increase the robustness of the chewing surface of the upper cheek teeth, each of Premolars 2 to Molar 3 have what is known as an infundibulum which is an enamel lined conical structure running throughout the height of the tooth. Normally the cheek teeth infundibula are filled with cementum, but in some horses the cementum may not have been formed to fill the enamel cone or it may be defective and undergo decay. All incisors, when they are young have infundibula but they are not completely filled with cementum – these unfilled infundibula and known as cups. As the incisors wear they become shallower until there is no longer a cup and its remnant is then known as a “mark”.
During the grinding process, the upper and lower cheek teeth on one side come together to grind food between them while the upper and lower cheek teeth on the other side are apart from each other. As a result of this grinding process, the edges of the maxillary cheek teeth that face the cheeks and those of the mandibular cheek teeth that face the tongue become sharpened. These sharp edges can ulcerated the cheek mucosa and cause a lot of pain and this is exacerbated by bridle cheek straps that pull the cheek against the teeth when contact is made. In mild cases the cheek mucosa adjacent to sharp teeth becomes rough and stained by plant pigments. The sharp lower cheek teeth can cause ulceration of the tongue.
During routine trimming of equid teeth, only the sharp enamel edges must be removed. Taking away more than the sharp enamel, effectively reduces the active grinding width of the tooth.
The maxillary cheek teeth have vertical in-foldings facing the cheek, the edges of which prevent forage from traveling up between the teeth and the cheek surface. Unfortunately some teeth are over trimmed, removing these folds, which in severe cases, can lead to pouching of forage which decays causing pain and halitosis in affected horses.
Sedation of the horse by a veterinarian facilitates the examination and treatment process and also prevents the horse from having an adverse experience.
Never allow your horse to be sedated by an equine dental technician – it is illegal for technicians to inject animals or administer oral sedatives / tranquilizers.
Routine dental examination and treatment requires the placement of a dental speculum (commonly known as a “gag”) to enable thorough examination and treatment of the teeth and mouth.
A light will also be required to illuminate the mouth. A dental mirror is often used to inspect parts of the mouth and teeth that are otherwise difficult to examine.
After sedation there is likely to be unswallowed food in the mouth that must be flushed out to enable visualization of all of the teeth and prevent clogging of the trimming device.
The horse’s maxillary teeth are not in a straight line, but rather in a gentle curve from front to back, which means that the last two molars are tucked behind the rest of the teeth. A straight shanked rasp will not reach these teeth so one with an incline will be required. The chewing surfaces of the successive mandibular teeth follow a gentle arc from front to back, known as the curve of Spee, which is more pronounced in horses with a shorter face (Arabian and Welsh Pony.
The tooth examination and trimming interval is dependent on the individual horse. Some horses require treatment every 6-8 months while other need treating every 15-18 months. The required interval is determined at the second treatment.
The canine teeth are not involved in the chewing process and often accumulate plaque which becomes mineralized to calculus. The gingiva around these teeth is often inflamed and may be enlarged. The calculus must be chipped or scraped off periodically. When the calculus is removed, plaque build-up can be prevented by regular brushing of the teeth. Older horses may suffer from tooth resorption and excessive deposition of cementum on the canines and incisors (EOTRH) and in severe cases the affected teeth will need to be extracted.