Year by Year, Tooth by Tooth

Year by Year, Tooth by Tooth

There are many elements in a horse's mouth that must remain within a normal range in order for that mouth to function properly and stay healthy.

Photo: Adam Spradling/The Horse

It makes little difference if you are new to horse ownership or a seasoned professional, you probably aren't as familiar as you would like to be with the expanding field of equine dentistry. Horse owners have many questions about proper dental care for their equine charges. "My horse is only three years old. He doesn't need his teeth looked at...does he?" "How often should my broodmares be examined?" "What about my daughter's 4-H mount?" "My dressage horse is suddenly hanging on his right rein, but my vet just floated his teeth six months ago. What's wrong?" "My 25-year-old Appy is having trouble eating. She slobbers and drops wads of hay. Could it be her teeth?"

The answers to the above questions will vary with each individual horse and each individual circumstance. There are, however, some general tendencies based on a horse's age, gender, career, overall health, and dental health that provide guidelines from which to make recommendations.

When Does Dental Care First Need to be Addressed?

That one has an easy answer: At birth! At least a cursory visual and digital inspection of the foal's mouth should be performed by your veterinarian during the "well-baby" examination the day of, or the day after, his birth. In addition to the rest of the physical examination, your veterinarian will check to make sure that the foal does not have a severe overbite or underbite that could make nursing difficult and predispose him to other dental abnormalities as he matures. It's also important to make sure that the foal's palate is normal so that he can swallow without difficulty.

In the first two weeks of life, your foal will erupt 16 deciduous (baby) teeth! That's why it's important to know early on whether the foal has a malocclusion (bite misalignment) such as an overbite or underbite. Their deciduous premolars are all in use within the first few weeks of life and can soon start to wear abnormally if they do not meet properly. For example, if the foal has an overbite, not only do the incisors not match up, often the foal's premolars don't match up at the front and back since the entire lower jaw is too short. The portion of the tooth that overhangs won't have a tooth surface to grind against as the rest of the tooth wears. These hook-shaped overgrowths that result can prevent the lower jaw from growing to the length of the upper jaw.

While there are orthodontic devices and surgical remedies to correct truly severe overbites and underbites, they are expensive, difficult to maintain, and have variable rates of success. It is far easier to let Mother Nature do the best job she can by keeping the teeth free of hooks and ramps that prevent normal jaw growth. This is easily accomplished by periodic filing of the overgrown portion of the involved teeth. In many cases, this is all that is necessary to correct a mild to moderate overbite or underbite.

During the first year of life, in addition to 12 deciduous premolars, the youngster also erupts two more sets of deciduous incisors, for a total of 12. All 24 baby teeth are in place by the age of about nine months. At this age, most horses will also erupt two wolf teeth and the first permanent molar set (two on top and two on the bottom) erupts behind the baby premolars.

Get the Point? How Sharp Points Develop

This illustration shows in cross section that the horse's lower jaw is narrower than his upper jaw. His upper teeth overhang the lower teeth. Correspondingly, the lower teeth are positioned slightly to the inside of the upper teeth. As a horse moves his jaw through a roughly triangular chewing pattern, he might not use the entire occlusal surface during the grinding stroke. This causes the outside edges of the upper teeth and the insides edges of the lower teeth to become sharp. The hard enamel in those areas is not being worn away as fast as the rest of the surface, leaving very sharp points of enamel against the cheeks and tongue.

Mary DeLorey, DVM

By the time the foal is a yearling, he has erupted 24 to 30 teeth! If there have been no problems detected previously, it is strongly recommended that a skilled veterinary professional perform a complete dental exam on every horse no later than 12-18 months of age. At that time, all of the deciduous teeth have been "in wear" long enough that their edges are always very sharp. 

Many owners do not realize that even very young horses need comprehensive dental attention, ideally every six to eight months. Deciduous teeth are softer than permanent teeth and develop sharp edges much faster. It is not uncommon for yearlings to have ulcers or lacerations on their cheeks and tongues from these razor-sharp points. The wolf teeth, which become sharp and can cause pain when the horse is bitted, are best removed when the horse is a yearling. This is a good time to make the young horse comfortable and ensure that the stage is set for the next phase of dental development.

Young Working Horse Dental Care

Two to 3 1/2 years of age is the next pivotal time in equine dental development. During this time is the largest turnover of deciduous to permanent teeth. He will lose two sets of deciduous incisors and two sets of premolars, all to be replaced by permanent teeth. He will have already erupted his second set of permanent molars and the third set might be getting ready to erupt by 3 1/2 years of age. That's up to 24 permanent teeth in 1 1/2 years! If certain baby teeth wait too long to fall out, they are termed "retained." The longer the baby teeth take to "shed," the longer it takes for the permanent ones to replace them and become useful for mastication (chewing).

While it is detrimental to remove baby teeth before the permanent ones are ready to move into place, it's also potentially troublesome to leave old baby teeth in place for too long. If pairs of deciduous teeth shed asynchronously (at different times), the corresponding permanent teeth will erupt asynchronously. This situation is undesirable since it sets up uneven chewing surfaces in the mouth that the horse will have difficulty overcoming on his own. Incisors can also be affected by imbalances caused by pairs of teeth that erupt too early or too late. Therefore, the attention of a skilled veterinary professional (usually every six to eight months until maturity) can be very important in promptly correcting imbalances and preparing the mouth for normal adult development.

By the age of 4 1/2 to five years, a young horse should have shed or be very close to shedding the last deciduous teeth and all permanent teeth should be erupted. It's very possible that a horse might have retained a set of baby incisors or even a set of baby premolars at this age. These probably should be removed. Brand new permanent teeth get very sharp very quickly as the horse begins to use them in earnest, and they need to be smoothed.

A Note on Canine Teeth

Geldings and stallions might have four canine teeth that are just breaking through the gumline at age five. These are noticeable teeth visible in the space between the incisors and the cheek teeth. Some horses experience discomfort associated with the eruption of these teeth, which might explain fussy behavior that appears suddenly during this time. This is the time to make any small adjustments to keep the mouth in balance as the last permanent teeth come into wear.

By six years of age, the only teeth not fully erupted might be the canines in geldings and stallions. As these teeth reach significant size, they can become like small daggers protruding from the gums. While they might not interfere directly with the bit or any chewing surfaces, their sharp edges can be quite painful as they contact the tongue and lips during eating and bitting. It is common practice to reduce the height of these teeth and round the tops so that they are non-irritating. They serve no useful purpose in domestic horses, so shortening them is not detrimental. Occasionally, a mare will have canine teeth. They are usually much smaller than their male counterparts' canines, but they should be addressed similarly.

Teeth For Life: Hypsodont Teeth

Unlike dogs, cats, and humans, horses have hypsodont (long) teeth that slowly wear away during their lives. That's okay for horses, since they have about four inches of tooth crown below the surface of the gums hidden in the bone of the jaws. As the grinding of their coarse diet wears away a little bit of tooth surface, more erupts into the mouth to take its place. On average, a horse's teeth will wear and a new crown will replace it at a rate of about 0.11-0.16 inches (3-4 mm) per year. That translates to enough tooth to last about 25 years under ideal circumstances. For horses, ideal circumstances include reproduction according to the forces of natural selection, exposure to a diet of mainly soft grasses, but including coarser varieties, grains, broad leaf plants and the fine sand-like silicates that accompany these plants, and most importantly, exposure to these forages 24 hours a day, every day. This environment helps ensure that a horse will wear his teeth evenly and maintain good dental health. Since most modern equines don't live under such ideal circumstances, modern equine dentistry is evolving to make up for the imbalances.

Mary DeLorey, DVM

How About Mature Horses' Teeth?

Once your horse has reached the age of six, all of his permanent teeth are in position and in use. If your horse has had periodic, comprehensive dental care up to this time and has no severe malocclusions or dental disease, he's well poised for lifelong good dental health. He should receive maintenance care, including smoothing of sharp edges, minor rebalancing, and troubleshooting, every eight to 12 months. Horses which are in demanding competition or have heightened sensitivity or pre-existing dental abnormalities might need attention more frequently, perhaps every six months, to maintain dental health and comfort. Each horse is an individual with unique needs. A veterinarian skilled in equine dentistry can work with you to determine a schedule most appropriate for your horse.

Horses over the age of 16 which have had regular, skilled dental maintenance might require little more than a well-cared-for younger horse. In general, however, there are some things that need periodic monitoring.

In the older horse, the crown that has been slowly erupting out of the jaw over his entire life is running out. This inevitably brings with it the tendency toward gum disease and the possibility of fractured teeth, diseased roots, and loose teeth. There are many different ways to approach these problems, and more work is being done to understand the best management options.

Often, early gum disease can be treated with topical gels or flushing therapies. Loose teeth (recognized early) can be shortened and rested so that the opposing tooth is not continuously grinding against it. Some of these might re-establish their firm connections. Other loose, damaged, or diseased teeth are best removed. Then regular maintenance becomes even more important because the surrounding teeth might migrate into the space created by tooth extraction. Again, a horse which has had regular, skilled dental care during his youth and middle age is much less likely to develop significant problems in his golden years.

What About Horses You Buy?

What do you do if you've just purchased a 5-year-old dressage prospect, or a 10-year-old barrel horse, or a 15-year-old pony hunter and you don't know what level of dental attention this new horse has received during his previous owner's care? The sooner you arrange for a veterinary professional skilled in equine dentistry to perform a comprehensive examination, the better. Many horses have never had their teeth examined by the age of five, 10, or even 15! Just because the horse has been "floated" does not necessarily mean that he has ever had a comprehensive exam and correction.

There is a jungle of abnormalities that can develop even by the age of five that "floating" won't address. "Waves," "steps," and "ramps" develop when some of the teeth in an arcade remain too tall and cause the opposing teeth to become overworn, giving a roller-coaster appearance to the line of teeth as you sight from front to back. "Hooks" on the upper first cheek tooth or lower last cheek tooth can overhang the opposing tooth and impede jaw movement or can dig into the opposing gums. Incisors can develop abnormalities of wear and meet at a diagonal or curve instead of a straight line, making balanced functioning of the jaws impossible.

Of course, the longer these abnormalities go unaddressed, the more severe and the more difficult to correct they become.

A veterinary professional experienced in equine dentistry is also acutely aware of the importance of more subtle issues. There are integral concepts, such as incisor length and angle, interocclusal space (the distance between the chewing surfaces of the cheek teeth when the jaws are closed and centered), occlusal angles (the angles at which the chewing surfaces of the cheek teeth meet), lateral excursion (the distance the lower jaw must be moved to the side before the cheek teeth contact, forcing the incisors apart), and quality and degree of premolar and molar contact that should be addressed in every horse.

5 Dental Care Tips

  • Dental care should start at birth with at least a cursory visual and digital inspection of the foal's mouth during the veterinarian's "well-baby" examination.
  • A skilled veterinary professional should perform a complete dental exam by the time the horse is 12-18 months old.
  • By 4 1/2 to five years, a young horse should have shed or be very close to shedding the last deciduous teeth and all permanent teeth should be erupted.
  • Mature horses should get maintenance care, including smoothing of sharp edges, minor rebalancing, and troubleshooting, every eight to 12 months.
  • Older horses have a tendency toward gum disease, the possibility of fractured teeth, diseased roots, and loose teeth.

There are many elements in a horse's mouth that must remain within a normal range in order for that mouth to function properly and stay healthy. Advances in equine health care are impressive, and more information is available on an almost daily basis. Horses and their owners are benefiting from this wealth of knowledge so that horses are living longer and more active lives. It isn't uncommon for horses to live into their late 30s. But nature only gave the horse enough tooth to last an average of 25 years. If we want our equine partners to remain healthy and happy that long, or even a decade longer, it is only logical that we do everything within our power to ensure that they are able to eat (and work) comfortably and effectively.

A skilled equine dental practitioner can prevent most abnormalities from becoming problems, thereby maximizing the useful life of each tooth. Modern equine dentistry combines thorough knowledge of anatomy and biomechanics, current research, and clinical findings with the most advanced equipment and the safest drugs to optimize your horse's dental health for a lifetime. Comprehensive dental care delivered regularly by a specially skilled veterinary professional might be one of the most beneficial health care services you can provide your horse.

At right is the normal tooth wear pattern of a horse that has had skilled annual dental care and only needs correction of a few sharp points. Without proper care, the problems below can result. Normal teeth

This 13-year-old gelding has a large hook on his second premolar and wave mouth (unevenly worn arcade, or row of teeth).

Large hook, wave mouth
This older horse is missing two teeth in his lower jaw, has wave mouth, and is packing food in between and around his teeth at the gum line (commonly caused by tooth imbalances that have pushed teeth apart, weakening their attachments and leaving a small gap). Missing teeth, wave mouth
This horse presented with sharp points on the outer edges of his teeth, and excessive transverse ridges (uneven wear of an individual tooth, vs. wave mouth's uneven wear of an entire arcade). Sharp points, transverse ridges
This 4-year-old has an overly tall first molar, excessive transverse ridges, a newly erupted fourth premolar, and sharp points. Tall first molar, transverse ridges, sharp points

This horse has a diagonal bite with an offset jaw, which can be improved by evening the longer teeth in the upper and lower jaws.

--Text and photos courtesy Mary DeLorey, DVM

Diagonal bite with offset jaw

Glossary: Dentistry Terms

Arcade--A row of teeth; i.e., there are four arcades of cheek teeth and two arcades of incisors.
Cap--Horseman's term for a baby tooth as it sits in place on the permanent tooth ready to erupt.
Cheek teeth--A general term used to indicate all the grinding teeth, the premolars and molars.
Crown--The portion of the tooth that gradually erupts into the mouth and is used for grinding; not the root.
Deciduous teeth--"Baby" teeth. They are replaced by permanent teeth.
Eruption--The movement of the tooth crown out from the bone of the jaw through the gum into the mouth.
Incisors--Front teeth, just inside the lips, used to grasp, nip, and pull grass.
"In wear"--The point in time when opposing teeth have reached sufficient height above the gumline to grind against one another.
Malocclusion--Abnormal contact between opposing teeth.
Mastication--The act of chewing or grinding food.
Molars--Second three sets of large cheek teeth, top and bottom jaws, used for grinding. There are no deciduous molars, they erupt as permanent teeth.
Permanent teeth--"Adult" teeth. They are intended to remain for the horse's life.
Premolars--First three sets of large cheek teeth, top and bottom jaws, used for grinding. There is a full deciduous set followed by a full permanent set.
Occlusion--The contact points of opposing teeth; occlusal surface refers to the chewing or biting surfaces.
Shedding caps--The loss of expired baby teeth as the new permanent teeth erupt to take their place.

About the Author

Mary DeLorey, DVM

Mary S. DeLorey, DVM earned her veterinary degree from University of Missouri in 1992. Since 2000, she has devoted her entire professional energies to equine dentistry. Her practice, Northwest Equine Dentistry, Inc. serves the states of Washington and Idaho and is based near Seattle. Dr. DeLorey has traveled internationally to instruct veterinarians in equine dentistry techniques and speaks to horse owners nationwide. She trail rides and raises sport ponies from her ranch in Eastern Washington when she's not on the road.

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