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Arizona Equine Medical and Surgical Center

~ EQUINE DENTISTRY ~

by Gayle S. Leith, D.V.M., M.S.

Routine care and examination of your horse's mouth is as critical as vaccinations and deworming. Dental abnormalities can result in weight loss to performance and training problems. Sharp teeth will cause the horse to have difficulty chewing, and this will manifest as excessive salivation or dropping hay or grain. This article will review and discuss anatomy, aging, floating and several medical problems associated with teeth.

Anatomy
The adult horse has six upper and six lower teeth called incisors (see Diagram 1 and 2). These teeth are used for grasping food. Between the incisors and molars are the canine teeth. The canine teeth in mares are small or do not erupt from the gums. These teeth do not interfere with the bit. The first tooth past the canines are the wolf teeth. The wolf teeth are also referred to as the first premolars and are commonly found only in the upper row of teeth. Occasionally the bit interferes with these teeth causing irritation of the gums. The wolf teeth are easily removed with an elevator (to pry the tooth loose) and forceps (to grasp the tooth and remove it). These teeth have very small roots, unlike the remainder of the horse's teeth. Horses usually require mild sedation to accomplish wolf tooth removal.

The next group of teeth past the canines and wolf teeth are the premolars and molars. Over half of the premolars and molars are embedded in the horse's jaw. These teeth are used for grinding. The roots of the premolars and molars communicate with the nasal sinus cavities (see Diagram 1), therefore if one of these teeth become infected, the sinus will also become infected.

There are several anatomical factors which affect how horses wear their teeth down. The first is that the upper premolars/molars are more widely separated than the lower premolars/molars. This results in the upper teeth overlapping the lower teeth near the cheeks (on the outside) and the lower teeth overlapping the upper teeth near the tongue (on the inside). Another factor is angulation. When viewed from the front, the upper teeth slope outward and the lower teeth slope inward. The third factor which affects how the horse wears its teeth is chewing - horses chew in a side to side pattern. The overlapping, angulation and chewing causes the development of sharp points on the cheek (outside) surface of the upper teeth and on the tongue (inside) surface of the lower teeth. These points need to be floated or filed down to remove the sharp edges. I will discuss floating later.

Age
It is important to know your horse's age since some dental problems may occur only during certain times in a horse's life.

Newborn foals are born with their deciduous (baby) teeth just under the gum surface or barely erupted. The first incisor is present at birth or within the first week, the second incisor erupts within four to six weeks and the third incisor does not appear until six to nine months. There are no deciduous canine or wolf teeth. The molars are present at birth or shortly thereafter.

As the foal reaches five years of age, the permanent teeth begin to erupt. As the adult teeth erupt, the baby teeth are pushed out. The baby teeth can sometimes be found in the feeder or water bucket. Often the horse swallows the deciduous teeth. If the baby tooth does not fall out and lies on top of the adult tooth, it is referred to as a "cap". "Caps" usually do not cause any problems but can be removed with dental forceps.

Horses are aged primarily through the changes in the incisors. The "cup" is a dark hole in the center of the tooth. On the lower incisors, the cups are present up to five years of age. At six years, the cup is no longer present in the first incisor. The tooth is flat and smooth. However, the second and third incisors still retain their cups. These teeth, the second and third, lose their cups at seven and eight years respectively. The next tool utilized to age the horse is the Galvayne's groove. This is a longitudinal depression on the outside surface of the upper third incisor (see Diagram 3). The Galvayne's groove appears at the gum margin at approximately nine to ten years. At fifteen years, the groove extends halfway down the outside surface of the incisor, and at twenty years the groove extends the entire length of the tooth surface. Finally, at thirty years the Galvayne's groove disappears. The shape of the incisor tooth also changes as the horse ages. When the horse is younger, the tooth is oblong, and as the horse ages, the tooth becomes more oval.

The above changes in the teeth are all useful tools in aging a horse but aging can be difficult. A horse that cribs (grasps an object with the incisor teeth, flexes the neck and swallows air) will be difficult if not impossible to age. Cribbing and wood chewing causes excessive wear of the incisor teeth.

The older horse should have routine dental care. Sharp points will lead to improper chewing. Poor chewing can lead to choke (food blockage in the esophagus, swallowing tube), impaction of food in the intestines, weight loss, or appetite loss. Older horses may develop "wave mouths" or extremely "smooth mouths". Wave mouth refers to the molars being different lengths resulting in a wavy appearance to the teeth. This will result in abnormal chewing. Smooth mouth refers to the molars being completely smooth or absent. These horses require soft feed, which can be accomplished by soaking pellets in water.

Floating
Floating is a procedure where the veterinarian utilizes a special file to smooth the enamel points on the horse's teeth. This is a painless procedure, and most horses will stand quietly to be floated. Occasionally, the horse needs mild sedation to allow floating.
Dental DiseaseOne of the main problems that the horse can develop is infection of one of the teeth. A horse can develop a defect in a tooth through fracture of the tooth or the deficit may be the result of a developmental problem. In either case, this defect allows food material into the tooth with subsequent decay and infection. The infection and decay is not limited to the tooth, but can spread to the bone and sinus surrounding the area. The most commonly affected teeth are the upper premolars and molars.

Permanent Teeth Eruption

Tooth
First incisor
Second incisor
Third incisor
Canine
Wolf tooth (first premolar)
Second premolar
Third premolar
Fourth premolar
First molar
Second molar
Third molar

Age
2 1/2 years
3 1/2 years
4 1/2 years
4 - 5 years
5 - 6 months
2 1/2 years
3 years
4 years
9 - 12 months
2 years
3 1/2 - 4 years

The typical signs include a firm swelling on the side of the face (upper tooth involvement) or if a lower tooth is involved, swelling on the bottom of the jaw. These firm swellings may be associated with a chronic draining tract of pus. If the sinus is involved, the horse may have chronic purulent nasal discharge, facial swelling over the sinus and swelling around the eye. Diagnosis can be confirmed via a thorough oral exam and high quality detailed radiography. Radiography (x-rays) is utilized to identify specific changes in the affected teeth. With dental disease, radiographs will demonstrate loss of tooth and bone. Extraction of the diseased tooth or teeth is accomplished under general anesthesia. The bone over the affected tooth is removed and the tooth is "hammered" out carefully. After the tooth is removed, the area is packed with dental acrylic. The dental acrylic is removed at a later date. The horse is maintained on antibiotics to resolve any remaining infection.

Routine dental care, either annually or every two years, should be performed on both young and older horses. Many problems can be prevented with routine care.

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