Horse Teeth Anatomy and Aging: Reading Your Horses Mouth

There is an old saying that you should never look a gift horse in the mouth. Terrible advice. Looking in a horse's mouth tells you more about that animal than almost anything else you can do without a veterinarian present. Teeth are the single most reliable aging tool in equine science, and understanding dental anatomy is not optional knowledge for anyone serious about horse care. Teeth problems cause more performance issues, weight loss cases, and behavioral complaints than most people would ever guess.

Quick Answer: Adult horses have 36 to 44 teeth depending on sex and the presence of wolf teeth and canines. Teeth are hypsodont, meaning they are long-crowned and erupt continuously throughout life, wearing down at a rate of 2 to 3 millimeters per year. Age can be estimated by examining incisor shape, wear patterns, the appearance and disappearance of dental cups, the angle of incidence, and Galvayne's groove. Dental care every 6 to 12 months is essential for maintaining proper health and performance.

The Basics: What is in There

An adult male horse typically has 40 to 42 teeth. An adult mare usually has 36 to 40. The difference comes down to canine teeth, which are almost always present in males and occasionally present (usually smaller) in mares. The dental formula for one side of the mouth is: 3 incisors, 1 canine (variable), 0 to 1 wolf teeth (premolar 1, variable), 3 premolars, and 3 molars. Multiply by two sides, and you get the total.

Horses have two sets of teeth in their lifetime. Deciduous (baby) teeth, called caps, begin erupting within the first week of life. The foal has a full set of 24 deciduous teeth by about 9 months. These are replaced by permanent teeth between ages 2.5 and 5 years. The premolars shed their caps in a predictable sequence that is useful for aging young horses.

Incisors

The 12 incisors (6 upper, 6 lower) are the teeth you see when you lift the lips. They are the primary tool for aging and are named by position: centrals (the middle pair), intermediates (flanking the centrals), and corners (the outermost pair). Each incisor has a crown, a root, and a long reserve crown embedded in the jawbone that gradually pushes out as the grinding surface wears away.

Incisors are used for grasping and cutting grass. Watch a horse graze and you will see it use its lips to gather grass, then bite it off with the incisors while swinging its head. The lower incisors do most of the cutting work against the upper incisors and the dental pad (a thickened area of gum on the upper jaw in front of the incisors).

Canines

Canine teeth sit in the diastema, the gap between the incisors and the premolars where the bit sits. They are vestigial fighting teeth. In wild stallions, canines are weapons used in combat with rival males. In domestic horses, they serve no practical purpose but can accumulate tartar, develop sharp edges, and occasionally interfere with the bit. Males typically have four canines that erupt between ages 4 and 5. Some mares develop small, partially erupted canines called "blind canines."

Wolf Teeth

Wolf teeth are the first premolars, and they are a source of endless confusion. They are small, shallow-rooted teeth that sit just in front of the upper (and rarely lower) premolars, right where the bit contacts the bars of the mouth. Not all horses have them. Those that do usually erupt them around 6 to 18 months of age. Because of their location and potential to cause bit discomfort, wolf teeth are commonly extracted before a horse begins training. The procedure is straightforward and usually done under standing sedation.

Do not confuse wolf teeth with canine teeth. They are completely different structures in different locations. Wolf teeth are small, peg-like, and sit far back near the cheek teeth. Canines are larger, curved, and sit in the interdental space.

Cheek Teeth (Premolars and Molars)

The 24 cheek teeth, 12 upper and 12 lower, are the grinding powerhouse. They form a continuous arcade (row) on each side with broad, ridged surfaces designed to pulverize fibrous plant material. The ridges are formed by alternating layers of enamel, dentin, and cementum, each with different hardness, creating an uneven grinding surface that works like a millstone.

Upper cheek teeth are wider than lower cheek teeth, and the upper arcades are set slightly wider apart than the lower. This means the grinding surfaces do not perfectly align. The outer (buccal) edge of the upper teeth and the inner (lingual) edge of the lower teeth do not contact the opposing teeth and develop sharp enamel points. These points are what your equine dentist is floating (filing down) during routine dental care.

Each cheek tooth is roughly 7 to 10 centimeters long at maturity, with most of that length embedded in the jawbone as reserve crown. The tooth erupts at approximately 2 to 3 mm per year to compensate for wear. Simple math tells you that a horse will run out of tooth somewhere around age 25 to 30, which is one reason very old horses often struggle to maintain weight. When the teeth are worn to smooth, rootless nubs, grinding efficiency plummets.

Aging by the Teeth: The Art and Science

Aging horses by their teeth is an imperfect science. It works reasonably well up to about age 12 to 15, after which it becomes increasingly approximate. Still, it is the best field method available when registration papers are unavailable. Here is what to look for, organized by age range.

Birth to 5 Years: Eruption Patterns

This is the most accurate period for dental aging because you are looking at discrete events rather than gradual changes.

• Birth to 1 week: Central deciduous incisors present or erupting.
• 4 to 6 weeks: Intermediate deciduous incisors erupt.
• 6 to 9 months: Corner deciduous incisors erupt.
• 2.5 years: Central permanent incisors replace deciduous centrals.
• 3.5 years: Intermediate permanent incisors replace deciduous intermediates.
• 4.5 years: Corner permanent incisors replace deciduous corners.
• 5 years: All permanent incisors are in wear. The horse has a "full mouth." Canines, if present, are fully erupted.

5 to 10 Years: Cup and Star Changes

Each incisor has a dental cup, a dark depression on the grinding surface, that gradually wears away as the tooth erupts and wears down. The cup disappears from the lower incisors first:

• 6 years: Cups gone from lower centrals.
• 7 years: Cups gone from lower intermediates.
• 8 years: Cups gone from lower corners. The mouth is now "smooth" on the bottom.
• 9 to 11 years: Cups disappear from upper incisors in the same central-to-corner sequence.

As cups wear away, the dental star appears. This is a dark line or dot on the grinding surface representing the secondary dentin covering the pulp cavity. It first appears as a faint line in front of the cup, then becomes a distinct dark spot near the center of the tooth as the cup disappears completely.

10 to 15 Years: Shape Changes

Young incisors are oval in cross-section when viewed from the grinding surface. As the tooth wears down and the reserve crown erupts, the cross-sectional shape changes:

• Oval (round): Up to about 9 years.
• Round to triangular: 10 to 15 years.
• Triangular: 15 to 20 years.
• Rectangular (biangular): 20+ years.

15+ Years: Angle and Galvayne's Groove

The angle at which upper and lower incisors meet changes with age. In young horses, the incisors meet almost vertically. With age, the angle becomes increasingly acute, creating a more slanted profile when viewed from the side. By age 20+, the incisors may project forward at a pronounced angle.

Galvayne's groove is a dark vertical groove that appears on the labial (outer) surface of the upper corner incisor. It follows a predictable pattern:

• 10 years: Groove appears at the gum line.
• 15 years: Groove extends halfway down the tooth.
• 20 years: Groove extends the full length of the tooth.
• 25 years: Groove disappears from the upper half.
• 30 years: Groove gone completely.

Galvayne's groove is not present in all horses and varies between breeds, so it is a supporting indicator rather than a standalone aging tool.

Common Dental Problems

Sharp Enamel Points

The single most common dental issue. Because the upper arcade is wider than the lower, sharp points develop on the outside (cheek side) of the upper teeth and the inside (tongue side) of the lower teeth. These points lacerate the cheeks and tongue, causing pain, head tossing, bit resistance, quidding (dropping partially chewed food), and reduced feed efficiency. Regular floating every 6 to 12 months prevents most problems.

Hooks and Ramps

When the upper and lower arcades are not perfectly aligned (which is common), the first upper cheek tooth may overgrow into a hook on its front edge, and the last lower cheek tooth may develop a ramp on its back edge. Severe hooks can dig into the opposing gum tissue. Hooks and ramps restrict the jaw's range of motion and interfere with normal chewing mechanics. Your dentist can reduce them with motorized or hand floats.

Wave Mouth and Step Mouth

Wave mouth occurs when the grinding surface of the cheek teeth arcade undulates like a wave rather than forming a flat plane. Step mouth is when one tooth is significantly taller or shorter than its neighbors, creating a step in the arcade. Both conditions impair grinding efficiency and are often the result of a missing or fractured opposing tooth, which allows the unopposed tooth to overgrow. Correction requires repeated dental work over multiple sessions.

Retained Caps

Sometimes deciduous premolars do not shed cleanly. The cap sits on top of the erupting permanent tooth, trapping feed material and causing pain, swelling, and sometimes infection. Horses between 2.5 and 4.5 years old are most commonly affected. Retained caps can cause head shaking, bit resistance, and feed avoidance. Removal is usually easy with sedation and cap extractors.

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH)

This is a relatively recently recognized condition affecting the incisors and sometimes canines of older horses (typically 15+). The teeth undergo resorption (the body breaks down the tooth structure) and hypercementosis (excessive cementum production), leading to painful, loose, infected teeth. Signs include reluctance to accept treats, sensitivity to cold water, foul breath, and gum swelling. Extraction of affected teeth is the treatment of choice, and horses do remarkably well without their incisors, adapting to grazing with their lips and gums.

The Dental Exam: What Happens

A proper equine dental exam involves sedation, a full-mouth speculum (the metal device that holds the mouth open), a bright light source, and a mirror. The veterinarian or equine dental technician examines every tooth, checks for sharp points, hooks, ramps, fractures, loose teeth, gum disease, and abnormal wear patterns. Floating is performed with manual rasps or motorized instruments to restore balanced grinding surfaces.

Young horses (2 to 5 years) need more frequent dental attention because they are shedding caps and erupting permanent teeth. This is a period of rapid change where problems can develop quickly. Performance horses in training also benefit from more frequent exams because any dental discomfort directly affects bit acceptance and performance.

Senior horses (20+) need careful monitoring for EOTRH, loose teeth, and loss of grinding surface. Dietary adjustments, including soaked feeds, chopped hay, and complete pelleted feeds, may be necessary as dental function declines.

Dental Anatomy and the Bit

The bit sits in the diastema, the toothless gap between the incisors and premolars. This space exists because horses lost their second and third premolars through evolution. The bars of the mouth, the edges of the mandible (lower jaw) in this gap, are covered only by gum tissue and periosteum. There is no muscular padding. This is why bit fit and rider hands matter so much. Heavy, constant pressure on the bars causes pain, bone remodeling, and eventually periostitis (inflammation of the periosteum covering the bone).

Wolf teeth sit right at the front edge of the cheek teeth, exactly where many bits contact. Even a perfectly fitted bit can bump against a wolf tooth during rein contact, causing sharp pain. This is why most trainers and veterinarians recommend extracting wolf teeth before starting a horse under saddle.

Frequently Asked Questions

Sources

• Dixon, Paddy M., and Dacre, Ian. "A Review of Equine Dental Disorders." The Veterinary Journal, 2005.
• Baker, Gordon J., and Easley, Jack. Equine Dentistry, 3rd Edition. Elsevier, 2011.
• American Association of Equine Practitioners. "Equine Dental Care." aaep.org
• Staszyk, Carsten, et al. "Equine Odontoclastic Tooth Resorption and Hypercementosis." Equine Veterinary Journal, 2008.

Last reviewed: June 2026