STRAIGHT FROM THE HORSE’S MOUTH: MAXIMIZING YOUR HORSE’S PERFORMANCE THROUGH DENTAL CARE

Dr. Honor Ame Walesby, DVM, MS, DACVS
Assistant Professor, Equine Surgery
Equine Health Studies Program
School of Veterinary Medicine
Louisiana State University
Baton Rouge, LA 70803

The horse has evolved as a grazing animal. As a result the teeth have adapted in both form and function for the sole purpose of gathering and processing forage. The basic horse tooth is a composite of three substances, dentin, cementum, and enamel. Each substance is unique in its composition, hardness, function, and wear characteristics. For example, enamel is the hardest substance in the body and is recognized as the hard shiny finish on the surface of the tooth as it is observed within the mouth. Enamel forms a folded ribbon within the tooth, which produces the sharp ridges necessary for grinding forage. Dentin is found throughout the tooth and is responsible for tooth repair and maintenance. Cementum is found throughout the tooth, and functions primarily to fill in the spaces between the enamel and dentin.
The primary diet of the horse has historically been forage. In their natural state, horses are continuous grazers; spending up to 22 hours per day grazing. Forages are high in digestible and non-digestible plant fibers. In order to utilize forage as a nutrient source, the horse must thoroughly grind the forage with the cheek teeth (premolars and molars). Grinding reduces forage to small particles and increases the exposed surface area. Small particle size allows the forage to pass easily though the intestine. Increasing the surface area exposes the ground forage to enzymes and bacteria optimizing digestion and absorption. It is critical that forage be properly prepared before it passes into the intestine. Large forage particles will collect in either the esophagus or the intestine causing obstructions such as choke or large bowel impactions (colic). Improperly prepared forage is not accessible to digestive enzymes and therefore passes through the intestine into the feces without being utilized by the horse.
The horse needs teeth to procure and process forage for survival. Therefore, it stands to reason that disease of the teeth, gums, tongue, and associated structures of the mouth can severely impact the health and survival of the horse. Unfortunately, the influence of human kind has negatively impacted the health of the horse tooth with husbandry, management, and feeding practices. Continuous grazing results in continuous, balanced tooth wear. The introduction of hay and grain to the horse’s diet has affected not only the wear rate, but also the wear pattern of the teeth resulting in dental problems. High carbohydrate diets result in elevtaed levels of bacteria and lactic acid causing inflammation of the gums and dental decay. Stall confinement has produced behavior characteristics in the horse, such as cribbing and wood chewing, that accelerate tooth wear and loss. Selective breeding without regard to dentition has produced severe congenital and heritable dental defects that influence the health of the affected individuals.
Dental problems manifest themselves in a variety of ways. Many horses may not show noticeable signs of dental problems because they adapt to pain and discomfort. Others will show obvious signs of pain and irritation. Noticeable signs of dental problems in the horse include, but are not limited to, the following list: 1) excessive loss of feed from the mouth; 2) difficulty chewing with or without exaggerated tongue movement; 3) holding the head to the side while chewing; 4) excessive salivation when chewing; 5) slow deliberate chewing of grain/slow to finish eating; 6) preferentially eating hay before grain; 7) large particles of grain and hay within the feces; 8) weight loss or poor body condition; 9) foul odor from the mouth and/or nostrils; 10) bleeding from the mouth and/or gums; 11) discharge from the nostrils; 12) swelling of the face or jaw; 13) change in performance habits; 14) head shaking/tossing/throwing, bit chewing, tongue rolling; 15) fighting the bit or resisting the bridle; 16) failure to stop, turn, or respond to rider aids; 17) bucking, rearing, bolting, or refusing to perform; 18) carrying head excessively high or low; and 19) backing up at a rapid rate when unprompted. Dental problems often go undetected. As a result, the problem progresses until the health and performance of the animal is adversely affected before intervention and treatment is implemented. The bridle and bit place pressure on the cheeks, gums, tongue, and teeth. This pressure causes pain when dental disease is present. Consequently, performance becomes limited as the horse modifies its behavior to avoid the pain.
Recognizing dental problems and their affect upon a horse’s health and performance requires a basic knowledge of anatomy and physiology. The horse’s teeth and the associated structures of the mouth are dynamic. Horses have two sets of incisor teeth and two sets of premolar cheek teeth during their lifetime. The first deciduous incisors erupt during the first week of life with a complete set of deciduous incisors being in place by 6 to 8 months of age. All of the premolars are present at birth or within the first two weeks of life. The deciduous incisors are shed and replaced with permanent teeth beginning at 2½ years of age with the last incisor being shed at 4½ years of age. The deciduous premolars are shed and replaced with permanent teeth beginning at 2 years and 8 months of age and ending at 3 years and 10 months of age. Other teeth in the mouth such as the canine teeth, also called the “tusks” or “bridle teeth”, and the molars do not have deciduous precursors. These teeth erupt as permanent teeth during the first five years of a horse’s life. The horse has a full complement of permanent teeth by 5 years of age. The adult male horse will have as many as 40 permanent teeth and the adult female will have as many as 36 to 40 permanent teeth (females do not generally have canine teeth). Thus, during the first five years of life, the horse’s mouth is undergoing remarkable change and development.
Once in place, the permanent teeth wear and change in response to dietary, environmental, and physiological influences. The permanent teeth continue to lengthen through out the lifetime of the horse. The rate at which the teeth lengthen is directly related to the rate of wear. If teeth are not worn because the diet is high in soft or processed feeds and low in forage, then the teeth will become long and wear unevenly causing dental disease. If the teeth wear excessively, then the teeth will lengthen at a faster rate resulting in uneven tooth wear and premature tooth loss. The horse’s lower jaw is narrower than the upper jaw. The difference in widths influences the contact points between the upper and lower cheek teeth (premolars and molars). The inside portion of the upper teeth contacts the outside portion of the lower teeth resulting in wear. The disparity in jaw width and the location of the contact points, combined with the elliptical chewing pattern, produce sharp enamel points on the outside of the upper teeth and the inside of the lower teeth. These points become sharper and longer with time due to continuous tooth lengthening. The enamel points irritate the cheek and tongue resulting in lacerations, ulcerations, and generalized discomfort and pain.
Performance problems and dental disease are intimately related. The young horse is being asked to accept a bit, a rider, and a rider’s aids during a period of extraordinary dental maturation and change. Twenty-four teeth will be shed and replaced during this time, with the potential for 12 to 16 teeth to be erupting simultaneously. A young horse will erupt up to four wolf teeth by the time it is six months of age. The wolf teeth sit just ahead of the cheek teeth. When pressure is applied to the bit with the reins, especially with a gag or an over-check bit, not only will the bit exert a direct force upon the wolf teeth, but it will also draw the fleshy portion of the cheek against the sharp wolf teeth. The result is discomfort and pain, which teaches the horse to resist the bit and avoid the rider’s aids. Young horses shedding deciduous premolars, also known as “caps”, are unable to close their mouths completely because the cap is elevated above the gum line as it is being pushed up and off of the permanent tooth below. The inability to completely close the mouth interferes with the horse’s ability to grind its food, resulting in excessive loss of foodstuffs from the mouth and difficulty maintaining condition. If the caps do not dislodge, they become impacted on the permanent teeth below, food then becomes entrapped and pressure builds. Pain and bone swelling develop, interfering with the horse’s comfort, ability to concentrate, and willingness to perform. The cheek teeth of the young horse are soft and form sharp enamel points quickly. The pressure exerted through the bit and bridle force the soft tissues of the cheek and tongue against the sharp points causing pain. Therefore, the young horse begins to associate the rider’s aids with pain and discomfort and rapidly becomes frustrated. Head tossing, bucking, and the unwillingness to perform ensue. The horse develops a negative association with the rider and the damage to future performance is done.
Dental disease causes performance problems in the mature horse too. The horse has a full complement of permanent teeth by 5 years of age and is considered mature from a dental standpoint. Once in place, the permanent teeth wear and change. Sharp enamel points develop on the outsides of the upper and the inside of the lower cheek teeth. The enamel points can lacerate the tongue and cheeks as the bit and bridle press against the soft tissues of the mouth. Head shaking, head tossing, and holding the head too high or too low result as the horse tries to avoid the pain. Vigorous training or application of aids to overcome the “behavior problems” can result in more severe problems, such as bolting, bucking, backing at high speed, and falling over. Uneven wear can result in long hooks projecting from the front portion of the first cheek tooth. The hooks not only can lacerate the cheek, gum, and tongue, but it can also drive the bit downward as pressure from the rein is applied. This downward movement places excessive force on the tongue and gum resulting in ulceration, laceration, and bone spur formation. The choice of bit and noseband can add to the discomfort and injury. For example, a bit with a high port will drive into the wolf teeth and the roof of the mouth causing irritation and ulceration; as will a snaffle bit with straight cannons. A snaffle bit with large diameter cannons will force a larger portion of the cheeks and associated soft tissues against the enamel points of the cheek teeth. A tight noseband will place constant pressure on the outside of the cheeks, forcing the tissue against the enamel points of the cheek teeth. The constant application of pain sends a negative signal to the horse. The horse becomes confused and tries to escape the discomfort associated with the rider’s aids. The end result is a poor performer with potential for dangerous behavioral problems.
Most major dental problems and dental related behavioral problems of the horse are preventable with proper general maintenance. However, it is important to realize that most major problems do not occur overnight, but rather stem from misalignment of the teeth and uneven tooth wear. Most dental problems are minor at the onset, but without attention and maintenance through the years become greater and greater in proportion and eventually rob the horse of years of service. Regular dental examinations are needed to detect dental disease early, before it negatively influences the horse’s comfort level and performance. Enamel points and uneven tooth wear occur in every horse, but with regular floating (filling of the teeth) these problems can be managed. Wolf teeth should be extracted early in a horse’s life, before training begins, thus preventing a negative experience for the young horse. The goal with dental care is prevention. Pain destroys trust, confidence, and the willingness to please; sharp teeth, sharp bits, and ill-fitting tack cause pain. Pain can be prevented and performance optimized with a regular, comprehensive dental care program.

Recommended Schedule of Dental Care

Late Yearling: Float premolars and first molars
Extract wolf teeth
Install a bit seat on premolars

Two-year-old: Float premolars and molars
Maintain bit seat
Extract wolf teeth if still present
Remove retained caps if present
Check incisor eruption
Extract retained incisors if present
Three-year-old: Float premolars and molars
Maintain bit seat
Remove retained caps if present
Check incisor eruption
Extract retained incisors if present

Four-year-old: Float premolars and molars
Maintain bit seat
Remove retained caps if still present
Monitor eruption of male canine teeth

Adult: Routine floating and dental examinations twice annually
Maintain bit seat on all performance horses
Maintain balanced tooth wear
Maintain incisor length
Maintain occlusion of upper and lower cheek teeth