Horses can experience a number of different dental issues over their lifetime, impacting their ability to chew and digest their feed.

Unaddressed dental issues can affect your horse’s health, condition, behaviour and performance. This is why it’s important to have your horse’s teeth checked by an experienced veterinarian or equine dentist on a regular basis.

Dental problems are the third most common medical problem seen in large animal practices in the U.S.

Unfortunately, postmortem studies show high levels of clinically significant, undiagnosed dental disorders in horses. [1] This means that many horses are not getting the dental care they need.

In this article, we will discuss some of the common dental issues facing horses as well as signs of teeth problems and their treatment.

Equine Dental Care

Equine dental publications exist from as early as 600 BC. By 330 BC, it was common practice to age horses by looking at their teeth.

Also around this period, the effects of periodontal disease were noted and treatments were recommended.

Since that time, equine dental knowledge has progressed slowly. It wasn’t until the 1600s that the technique to remove sharp overgrowths on the lateral edges of the upper cheek teeth became prevalent. [2]

To this day, published research on the prevalence of equine dental disease remains limited, but diagnostic techniques have been developed in recent years.

As a result, equine dental disease has steadily gained recognition as a widespread problem with a significant impact on the welfare of horses. [3]

Today, equine dentistry makes up a large part of veterinary practice, with up to 10% of a large animal veterinarian’s time involving dental work. [3]

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The Horse’s Teeth

To understand some of the common dental issues that horses experience, it’s important to first understand more about their teeth, in general.

Unlike us, horses have hypsodont teeth that are high-crowned. Part of the hypsodont crown remains in the jaw after eruption and a horse’s teeth continue to erupt into old age.

This is likely an adaptation to allow the horse sufficient dental material to buffer against tooth wear during a long life that requires a large intake of plant material. [4]

Horses have between 36-42 teeth altogether, depending on their sex and whether or not they develop “wolf teeth”. In the front, they have six upper and lower incisor teeth which are deep-rooted. These teeth are used to grasp and tear grass and other plants.

Cheek Teeth

Cheek teeth (molars and premolars) help to grind grasses to prepare them for moving into the digestive system. Horses have 12 premolar and 12 molar teeth divided into an upper and lower row on the left and right sides of the mouth.

These teeth erupt in a tightly packed unit, acting as a single grinding system.

Canine Teeth

Canine teeth erupt between 4-5 years of age and grow between the incisors and cheek teeth on both the upper and lower jaw.

Canines are mainly found in geldings and stallions and serve a purpose in fighting in wild horse herds. Mares occasionally grow canines but they are usually less developed.

Wolf teeth

Wolf teeth are small teeth that some horses develop between 6-18 months of age. They are found in front of the first upper cheek teeth and often fall out by the time the horse is 3 years old.

However, many times, wolf teeth are removed by veterinarians because they can interfere with the normal function of bits and also may cause pain or tissue damage. [5]

Signs of Dental Problems in Horses

Many horses do not show signs of dental problems. However, broken or irregular teeth may cause loss of appetite, weight loss, or a general loss of condition.

Other signs of equine dental problems may include:

  • Difficulty or slowness eating
  • Reluctance to drink cold water
  • Holding head to one side while eating
  • Excessive drooling
  • Blood-tinged mucus in mouth
  • Bad breath
  • Reluctance to take a bit
  • Headshaking during riding
  • Resistance to training

Extensive dental decay and infection may lead to a sinus infection and occasional discharge from one nostril. Infection may also cause swelling of the face or jaw. [6]

Though any horse can experience dental problems, older horses are more prone to developing them.

Developmental Dental Problems

As young horses grow and develop, problems such as overjet (also known as parrot mouth) and underjet may arise.


Overjet, where the top teeth protrude further than normal over the bottom teeth, is the most common oral birth defect. It can result from exposure to poisons while the mare is pregnant or it may be an inherited trait.


Underjet is less common in horses. With this condition, the bottom teeth protrude further than the top teeth. However, both overjet and underjet can lead to problems chewing food. [7]

Extra Teeth:

Extra teeth (a condition known as polyodontia) can also grow. This could be double rows of incisor teeth or extra cheek teeth. [6]

Other developmental abnormalities include upper cheek teeth that grow further forward than the lower cheek teeth. This can cause overgrowth of certain teeth and the development of periodontal disease in the abnormal spaces between displaced and normal teeth. [7]

Shedding Baby Teeth:

Shedding baby teeth can also irritate a young horse’s mouth and loose, displaced, or broken baby teeth can lead to chewing problems. [6]

Dental Caps:

Dental caps refer to the condition of baby teeth that remain attached to permanent teeth. They can be extremely sharp and may cut the cheek or tongue or interfere with eating. Dental caps need to be removed.

Abnormal Eruption of Permanent Teeth:

Abnormal eruption of permanent teeth is usually caused by trauma to the face or jaw. In cases such as these, the bud of the permanent tooth can be damaged by a fracture or possibly the repair process. Delayed eruption or impaction of cheek teeth is a common cause of bone inflammation and tooth decay. [6]

Permanent teeth can also erupt in an abnormal location due to overcrowding of teeth. [6]

Dental Caries

Just like humans, horses can also develop dental caries or cavities. Caries refer to the decay or destruction of dental tissue by bacteria found in the mouth. [8]

Oral bacteria produce acids that erode the enamel of the horse’s teeth, resulting in demineralization and increased wear on the teeth. [8][9]

There are two main types of caries in horses: peripheral and infundibular.

Peripheral Caries:

Peripheral caries occur on the sides of the cheek teeth. [9] In one study of 500 Western Australian horses, peripheral caries were found in 58.8% of the examined horses. [10]

Peripheral caries do not usually cause serious problems, but if left untreated could lead to fractures and periodontal disease.

Feeding silage and high levels of corn-based processed feeds are associated with a higher risk of peripheral cavities. Increased access to quality pasture and feeding of grass hays appear to be protective against these cavities. [10]

Infundibular Caries:

Infundibular caries develop in the infundibula or the grinding surface of the maxillary cheek teeth. [11]

In a study of 706 UK horses, 45.5% were found to have infundibular caries. Older horses were more likely to be affected. [12]

Periodontal Disease

Periodontal disease has been acknowledged in horses for centuries and was once described as the “scourge of the horse’s mouth.”

This disease causes inflammation of the structures that support a horse’s teeth including the gums, periodontal ligaments, and bone on which the tooth sits. [13]

Unlike periodontal disease in humans, equine periodontal disease is considered almost always to be a secondary disease process. Researchers believe it results from physical and mechanical disorders of tooth growth, eruption problems, or wear.

An exception is the typically minor form of the disease associated with the canine teeth. [14]

Unfortunately, studies have shown that periodontal disease in horses is common, affecting up to one-third of all horses. [15]

Two main forms of periodontal disease exist: gingivitis and periodontitis.


Gingivitis is characterized by inflammation or recession of the gums but without any loss of the tooth’s attachment apparatus. [13]

Horses with gingivitis may develop bleeding, redness, and swelling of the gums. [16] Gingivitis can lead to pocket formation, ulceration, and cemental destruction. [15]

Dental cementum is the calcified material that covers the outside of the tooth root. It provides the attachment site for the periodontal ligaments which hold the tooth to the alveolar bone within the socket.

Gingivitis always precedes periodontitis though not all cases of gingivitis will cause more severe disease. Gingivitis is reversible with proper treatment. [13]


Periodontitis, on the other hand, attacks the deeper structures that support the teeth, damaging the surrounding bone and periodontal ligament. This often results in tooth loss.

Periodontal disease is often associated with the presence of cheek teeth diastemata, which are gaps between teeth. [13]

Equine periodontal disease usually starts with food impaction, the formation of diastemata, gingival inflammation, and finally, the formation of periodontal pockets.

This process can cause detachment of the fibers that support teeth. Periodontal disease isn’t often diagnosed until it reaches an advanced stage, requiring extraction of affected teeth. [15]

Mild, temporary periodontitis is also sometimes seen around the permanent cheek teeth when they first erupt. This usually doesn’t cause a problem and resolves on its own once the teeth have fully erupted. [13]

Risk Factors

Researchers have found that when tooth decay begins, changes in the populations of oral bacteria occur as well. This results in a large number of pathogenic organisms that produce an inflammatory response and degrade tissues. [17]

Studies have revealed several other interesting factors related to periodontal disease in horses including:

  • Stallions are significantly less likely than mares and geldings to have periodontal disease; and
  • Diets high in hay increase the prevalence of peripheral tooth decay while greater access to pasture appears to be a protective factor. [2]

With softer feedstuffs, such as green grass, a wider range of mandibular motion is used and feed material is ground in a circular pattern, rather than crushed.

This results in a large amount of soft tissue contact, gingival crevicular fluid production, and saliva flow, all of which help to prevent decay and periodontal disease. [17]

When horses eat harder feeds such as hay and grain, their range of motion is reduced and decay is more likely to occur. Additionally, saliva is partly absorbed by dry feed, reducing its effectiveness in the digestive process.

Consumption time is also reduced, resulting in reduced gingival crevicular fluid and reduced saliva which can lead to more time for feed material to decay. [17]

A common sign of periodontal disease and dental decay is bad breath (halitosis). [7] Other signs include dropping feed (quidding) and difficulty eating. However, these signs can be subtle and easily overlooked sometimes. [16]

Diastema (Gaps Between Teeth)

A gap between teeth is known as a diastema. These gaps most often occur between cheek teeth but can occasionally occur in the incisors. Diastemata can be congenital or can occur for other reasons.

Researchers have found a strong association between periodontal disease and diastemata. [1][15]

There are two types of diastemata: open and valve. An open diastema has the same width at the top and the bottom, while a valve-type diastema has a narrow opening at the top and a bigger gap at gum level. [2]

An open diastema allows feed material to filter through with little to no bacterial overgrowth or periodontal disease. The valve diastema, on the other hand, collects feed material and leads to periodontal disease. [2]

Older horses are more likely to have at least one diastema, but young horses may develop them due to the following reasons: [13]

  • Dental buds that are overcrowded or displaced;
  • Dental buds that develop too far apart;
  • Insufficient angulation of the very front and very back teeth; or
  • Inadequate peripheral cementum at the interdental spaces.

Locating diastemata usually requires the use of a dental mirror or oral endoscope. Palpation of the margins between teeth may reveal interdental spaces or impacted food material. A dental pick with a long shaft or high-pressure intra-oral lavage system can be used to clean out diastemata. [13]

Treating diastemata can be difficult and no curative treatment is currently available. Some veterinarians suggest filling cleaned-out diastemata with dental impression material. This may provide a temporary seal and allow the gingival tissue a chance to heal.

Salt or diluted chlorhexidine mouthwashes can also be administered by owners and may help reduce secondary periodontal disease. [13]

Fractured Teeth

Another common dental issue in horses is the presence of fractured teeth. This tends to occur more in male horses than female horses and may be caused by trauma to the mouth. [7]

Cheek teeth fractures may also occur without trauma. These types of fractures are known as idiopathic cheek teeth fractures. They most commonly affect the maxillary (upper) cheek teeth and one study showed that 25% of these teeth had chronic dental disease before fracturing. [18]

Fractured teeth can fill with food and may cause oral pain, quidding, loss of appetite, or bitting and/or head shaking problems. They may also lead to unilateral nasal discharge and facial swelling.

Spontaneous loss or extraction of displaced or moving fragments usually resolves the pain. [18]

Disorders of Wear

Dental overgrowths can be caused by misaligned teeth, uneven tooth rows, or mechanical problems with the mastication cycle. [4] However, many disorders of wear are believed to be caused by dietary factors related to domestication.

If left untreated, these disorders can worsen, leading to cheek teeth disorders and/or widespread periodontal disease. [7]


The most common equine dental problem is an overgrowth of the outer edge of the upper cheek teeth and the inside edge of the lower cheek teeth.

This causes sharp teeth that are referred to as enamel points. These sharp points can cause tongue or cheek lacerations and problems with chewing. [7]


Hooks are overgrowths that commonly occur in the upper second premolars and the last molars when a horse has a misaligned bite (overjet or underjet). Diets of mostly hay, which is less abrasive than fresh grass, may also promote the growth of hooks. [4]

Shear Mouth:

Shear mouth is a rare condition in horses. However, it can occur when the grinding surface of the cheek teeth become severely sloped, with the inner edge of the teeth much higher or lower than the outer edge. Shear mouth severely impedes chewing and digestion and often results in weight loss.

Several different theories exist on the cause of shear mouth but some researchers believe it could be caused by a lack of floating sharp enamel overgrowths which may lead to abnormal chewing patterns. [19]

Wave Mouth:

Wave mouth is a misalignment in the teeth that looks like a wave when viewed from the side. It is also a leading cause of periodontal disease.

Wave mouth may be caused by a number of things including, improper shedding of baby teeth, genetics (especially in miniature horses), overjet or underjet, or lack of dental care over a long period of time. [6][20]

Step Mouth:

Step mouth is a similar condition that occurs when one cheek tooth grows longer than the others. This often happens when the opposite tooth is broken or missing and wear to the grinding surface becomes uneven. [6]

Like shear mouth, wave mouth and step mouth can usually be prevented by regular dental care. However, once the irregularity has become severe, dental procedures cannot completely correct the problem. [6]

Stereotypical behaviors such as cribbing and wind-sucking can also cause excessive wear on the incisor teeth. In severe cases, the incisors can be almost completely worn down. [21]

TMJ Disorder in Horses

TMJ (temporomandibular joint) disorder is not commonly diagnosed in horses due to the difficulty of diagnosis rather than the actual prevalence of the condition.

A definitive TMJ diagnosis can be achieved with intrasynovial anesthesia of the affected TMJ. [21] Imaging the TMJ is difficult but radiographs, ultrasound, scintigraphy, and computed tomography may be also useful at times. [21]

Signs associated with TMJ in horses include:

  • Decreased range of mandibular motion;
  • Preference to chew on nonaffected side (which may lead to shear mouth);
  • Joint distension and bony swelling over affected joint; and
  • Jaw muscle atrophy in chronic cases.

Aged Horses and Dental Problems

Geriatric horses suffer from the same abnormalities of wear as younger horses, though usually at a more advanced stage. Step mouth, wave mouth, and shear mouth are more common in older horses, for example.

Overgrown teeth may also be unstable leading to displacement or loss of these teeth.

The odds of developing periodontal disease and diastemata also increase after a horse has reached 15 years of age. Horses experience age-related changes in occlusal contact (bite), which can contribute to new problems such as wave mouth or diastemata or exacerbate existing dental problems. [1][20]

Smooth Mouth:

Smooth mouth is also seen in older horses. This is where the enamel and dentin wear down at the same time and causes the teeth to become inefficient at grinding.

Smooth mouth can result from over-floating as well. The horse may need to be fed soft mashes and chopped wet hay. [20]

Equine Odontoclastic Tooth Resorption and Hypercementosis:

Senior horses may develop a severe form of incisor periodontal disease known as equine odontoclastic tooth resorption and hypercementosis (EOTRH). With this disorder, resorptive lesions extend into the tooth enamel, dentin, and cementum, causing loss of the normal tooth architecture. [20]

Older animals with dental disorders tend to do well in the summer months when grass is available, but may struggle in winter when offered hay.

An alternative is to feed chopped hay or grass cubes, or complete or pelleted feeds specifically formulated for horses with dental issues. Soaking is required to prevent choke. [20]

Preventing & Treating Equine Dental Problems

The importance of regular equine dental exams by a qualified veterinarian or equine dentist cannot be overemphasized to both prevent and treat dental problems.


Dental prophylaxis (floating) is used to remove sharp edges and maintain a normal biting surface. This is often done with the use of sedatives or a simple restraint. [6]

Young horses (from about 2 1/2 to 5 years of age) need floating twice yearly while their permanent teeth are coming in and as often as needed after that. Horses that eat hay year-round will also likely need at least two yearly oral examinations and preventative care. [6]

Most equine dental work is focused on correcting occlusal issues which may cause problems with eating and behaviour.

A second important goal of equine dentistry focuses on the extraction of deciduous (baby) teeth. These teeth may erupt incorrectly as they are pushed out by permanent teeth and cause issues with behaviour, feeding, or willingness to accept a bridle and bit. [5]

Treatment of periodontal pockets will vary depending on the needs of the individual tooth. Decayed cementum can be removed with a high-speed bur. Decayed sulcular epithelium can be removed with either hand instruments or a high-speed bur. [17]


Tooth extractions are sometimes needed for decayed teeth. Extractions can often be performed on sedated horses, but others may require general anesthesia. [6]

For older horses, cardiac disease and orthopedic problems should be considered while sedating or restraining the animal during a dental examination. These horses may have increased sensitivity to commonly used sedative agents, so a lower dose may be needed.

The key to geriatric dental care is to ensure oral comfort, improve occlusal contact where possible, and maximize mastication. [21]

If your horse is dealing with any dental issues, they may need a specially formulated diet to ensure that they are able to digest and absorb the nutrients in their feed.

Our nutritionists can help you design a feeding program for any horse with tooth problems. Submit your horse’s information online for a free diet evaluation.

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