With winter months being relatively quiet in a large animal veterinary practice, we look for maintenance things to do while we wait for the chaos of spring to settle over us. Many equine veterinarians like to focus on dental work during quiet times, and I have to admit, cold, snowy weather makes me think of horse teeth.
Horses are similar to us in that they have two sets of teeth, a baby set (called deciduous or milk teeth) and an adult set. Adult teeth in horses come in gradually and a horse usually has all his adult teeth by the age of five, although this varies on the individual and, interestingly, sometimes by breed. Horses have 24 baby teeth, which then are replaced by 36 to 40 adult teeth.
Starting from the front, an adult horse has 12 incisors — six on the top and six on the bottom. These are used for cutting grass and for biting and nipping during fights to establish dominance. Behind the incisors, in each quadrant of the mouth (upper left, upper right, lower left, lower right) there may or may not be a canine tooth. Male horses more frequently have canine teeth, but females can have them, too. A horse may have all four canine teeth, just a few, or none at all, hence the number of adult teeth being 36 to 40.
Between where the canine tooth is located and the back premolars and molars there is a large empty space of gum line called the interdental space. This is where the bit lies in the horse’s mouth when it is ridden.
Behind the interdental space begins the line of serious teeth for serious grinding. Each adult horse has three premolars followed by three molars in each quadrant, giving a total of 12 of each kind. Many horses will have an extra premolar at the start of the line. This is called a wolf tooth and is considered a vestigial premolar. It is usually very small and serves no purpose except in some cases when it interferes with the bit. For this reason, wolf teeth are often removed.
You can estimate the age of a horse based on his teeth, but the key word is estimate. Due to the individuality of when a horse’s adult teeth erupt and differences in wear and tear, horse dental age estimation is more of an art than a science. It also has its seedy side when, historically, unscrupulous horse traders would excessively file a horse’s teeth down to change its apparent age.
Horses’ adult teeth grow continuously over the course of their lives. The root of the tooth is very large, much larger than the part of the tooth you can actually see. This tooth design is necessary due to the fact that horses are grazing animals and are constantly grinding coarse roughage that creates a lot of wear and tear on the back teeth.
Constant tooth growth also frequently creates instances of uneven wear, causing the development of sharp points in the horse’s mouth. This can lead to cheek or tongue ulcers, infection, and weight loss. For this reason, horses should have their teeth checked by a veterinarian at least once a year. Usually, a horse requires some filing down of sharp edges that have developed. Using a procedure called floating, a veterinarian will use a long hand-held rasp (called a float) or a mechanized file to wear down the sharp edges of the teeth.
If you’re not supposed to look a gift horse in the mouth, then what about cows, sheep, and goats? We’ll talk about them next week.
Dr. Anna O'Brien