The Equine Mouth

The equine mouth is enclosed on the front and sides by the lips and cheeks, above by the hard and soft palate, and below by the tongue and the muscles of the floor of the mouth. Four pairs of salivary glands drain into the mouth.

The horse’s mouth is remarkably well-adapted to a life of continuous grazing.  The lips are designed to grasp and hold vegetation, while the sharp incisor teeth cut the vegetation.  The rough surfaces of the cheek teeth (the premolars and molars) grind down plant material and separate the energy portion of the material from the fiber.

Signs of Mouth Problems

A horse with a painful mouth will change his eating behavior.  Eating slowly is common but often owners do not notice the change.  Many horses with pain on one side of the mouth will tilt their heads and chew on the other side.  A horse with a tender mouth eats selectively, dropping feed that is too coarse.  With a very sensitive mouth, the horse may stop eating altogether.  Weight loss occurs rapidly once a horse stops eating.  A horse with a painful mouth often won’t drink water either.

A young horse with a painful mouth may object to bridle training, throw his head, and bleed from the mouth after being ridden with a snaffle bit.  Blood may be found in the feed box.

Quidding means spitting out or dropping feed after it has been shifted back and forth from one side of the mouth to the other.  This is a sign of painful chewing or the inability to chew properly. Some horses avoid chewing by bolting their feed.  Improper chewing results in feed not being properly ground and therefore not adequately digested.  Accordingly, horses with chronic mouth pain lose weight and are prone to colic and constipation.  This syndrome tends to occur in older horses.  It also increases the frequency of choking and large colon impactions.

Common causes of painful chewing include:

• Lacerations of the cheeks, gums, and tongue caused by sharp points on cheek teeth or by dental caps and other teething problems.
• Infected and abscessed teeth.
• Mouth infections such as stomatitis.

Drooling is an important sign of mouth infection.  The saliva is tenacious, is stained brown, and has a strong odor. Drooling can also indicate paralysis of the swallowing mechanism.

A clear salivary discharge indicates the inability to swallow saliva, caused by a blockage or paralysis of the swallowing mechanism.  Drooling saliva also occurs when the horse is being given tranquilizers.  A peculiar type of slobbering is caused by the mycotoxin of a fungus present in contaminated legume hay.  It disappears when the hay is removed.

Lolling is a condition in which the tongue is paralyzed and hangs limply from the mouth between the incisors or protrudes from the side of the mouth through the interdental space.  Tongue paralysis occurs with botulism (forage poisoning), encephalitis, meningitis, rabies, and lead poisoning.  Yellow star thistle, Russian knapweed, and ergot poisoning also cause tongue paralysis. 

Swelling of the face and discharge from one nostril indicate a maxillary sinusitis caused by the infected root of an upper molar.

How to Examine the Equine Mouth

Most mouth disorders will become evident by careful examination of the lips, teeth, palate, throat, and soft tissues of the face and neck.  Many horses can be examined with minimal restraint.  However, a horse with a painful mouth may resist examination and require restraint or tranquilization.  Because of this, it may be prudent to have the owner of the horse open the its mouth for investigators to inspect.  Another option is to have a veterinarian or equine dentist inspect the horse’s mouth for you.

To examine the lips, gums, and incisor teeth, raise the horse’s upper lip with one hand while drawing down the lower lip with the other.  Healthy gums are firm.  In nonpigmented areas the color is pink.  Pale gums are a sign or ill health (possibly parasites or anemia).  Bluish-grey gums (cyanosis) indicate low oxygen levels in the blood caused by respiratory or circulatory failure.  Yellow gums indicate jaundice.

The state of the circulation can be assessed by capillary refill time – how long it takes the gums to pink up after they have been pressed firmly with a finger.  The area you pressed will turn shite.  When you take your finger away a pink color should return to the blanched area within two seconds.  A delay in capillary refill of three seconds or longer indicates dehydration or shock.

Before opening the horse’s mouth to complete the examination, handle him about the head until he relaxes.  Then insert the fingers of one hand through the interdental space between the incisors and cheek teeth, grasp the tongue and pull it out.  The horse will automatically open his mouth and keep it open as long as you maintain a firm hold on the tongue.  With the mouth open, you will be able to see the molars, tongue, and palate.  Because the soft palate is dropped when the mouth is open, you will not be able to see the nasopharynx (the area of the pharynx that is about the soft palate).  This area will need to be examined by a veterinarian using nasopharyngeal endoscopy.  

Problems in the Mouth

Lacerations of the Mouth, Lips, and Tongue

The soft tissues of the mouth are common sites for cuts.  Most are caused by neglected teeth; others by nails, wire fences, or foreign bodies.  Tongue lacerations are usually associated with rough handling and harsh bits.  Minor cuts heal rapidly.

Treatment for most lacerations includes: bleeding can be controlled by applying pressure to the cut with a clean gauze or a piece of linen.  Sutures may be required when the laceration is large, ragged or deep; when bleeding resumes after pressure is removed; when the tongue is badly cut; or when lip lacerations involve the borders of the mouth.

A horse with a moth injury should be switched to a soft diet, such as chopped wet hay or soaked pellets, until he is fully healed.  Extensive wounds may require cross-tying and feeding through a nasogastric tube.

Foreign Bodies in the Mouth

Foreign bodies in the mouth may include foxtail weeds, bearded barley, wire, wood splinters, and wood sticks or corncobs lodged in the dental arch.  Small plant awns, burrs, and splinters can become embedded on the surface of the tongue.  Owing to the natural curiosity of horses, porcupine quills can become imbedded in the face nose, lips, oral cavity, and skin.

Suspect a foreign body if the horse shakes its head, refuses to eat, and drools.  When a foreign body has be present for some time, there will be an offensive mouth odor.

Treatment for foreign bodies in the mouth can be as simple as locating and removing the object or more complex involving a veterinarian and sedation for the horse.

Stomatitis (Sore Mouth)

A horse with stomatitis drools, refuses to eat, drinks more water than usual, is mouth-shy, and has an offensive mouth odor.  The mucous membranes are reddened, swollen, tender, and often have blisters or a tenacious exudate.

Specific causes of stomatitis include infected teeth foreign bodies in the mouth, equine viral infectious diseases, photosensitivity reactions, prolonged use of antibiotics, blister beetle poisoning, and alkaloid plant toxicity.

Vesicular stomatitis is a common contagious viral disease that produces blister-like vesicles on the mucous membranes of the lips and tongue, and on the coronary bands of the feet.

Growths in the Mouth

Tumors in the mouth are not common.  Growths that ulcerate and exude a bad odor are usually malignant.  Squamous cell carcinoma is the most common type.  It is found most often on the lips, tongue, and gums.  Other malignant tumors include fibrosarcoma, melanoma, and lymphoma.

Benign tumors that occur in and around the mouth include sarcoids, a papillomas, lampas, cysts, neoplasms or dental origin, and granulomas.

Papillomas (warts) are caused by a virus that is different from the one that causes warts on the skins.  Warts in the mouth disappear spontaneously.

Lampas is a swelling of the hard palate just behind the front teeth.  It occurs, and then the permanent incisors erupt at 3 to 4 years of age.  This hard mass forms a ridge that can project below the level of the upper teeth and cause eating problems.  Although scraping the palate with a sharp knife and rubbing salt into the wound have traditionally be used to treat this problem, they are not effective.  Feed the horse a soft, moist ration to encourage eating.  The lampas will disappear spontaneously.

A ranula (honey cyst) is a smooth, rounded salivary gland swelling in the floor of the mouth on one side of the tongue.  When a needle is put into the cyst, a thick, mucus-like, honey-colored material runs out.  This often brings about a cure without surgery.  This procedure should only be done by a veterinarian with the horse under sedation.

The Teeth

The horse has 24 deciduous (temporary or milk) teeth and 44 permanent (adult) teeth in a male or 40 permanent teeth in a female.  The variation is because male horses have four canine teeth.  Some mares can also have canines.

The top surface or crown of the tooth is covered by a hard coating of enamel.  Enamel is impervious to bacteria and acids.  Beneath the enamel is a soften material called dentin, and beneath the dentin is the pulp or center of the tooth.  The pulp contains blood vessels and nerves.  If the tooth cracks exposing the pulp, the tooth decays rapidly and the root dies.

The root of each tooth is covered by a substance called cementum that attaches the tooth to the periodontal membrane and thus to the bony socket of the tooth.  The tooth is weakest and most susceptible to periodontal disease and tooth decay at this juncture with the periodontal membrane.

Te teeth of horses are very long, with up to 4 inches embedded in the bone of the upper and lower jaws.  The teeth of horses erupt continually throughout life at about the same rate as they are worn down by grinding.  As each tooth emerges, it is ground and shaped by the opposing tooth.

The nature of the horse’s diet and intestinal tract requires that all food must be thoroughly ground between the premolars and molars before being swallowed.  If the food is not adequately ground, the horse will not receive the full nutritional benefit and will lose weight and body condition.

In the process of grinding, the horse moves his jaws both up and down and from side to side.  In a normal horse, the dental arcades (the rows of molars and premolars) of the upper and lower jaws are not in exact alignment along the sides, as they are in people.  The arcade of the upper jaw overlaps that of the lower jaw along the sides by about 30 degrees.  The effect of the circular grinding action, plus the overlapping arcades, creates uneven tooth wear – specifically, the development of sharp enamel points on the tongue side of the lower jaw and cheek side of the upper jaw.  You can test this by sliding your fingers along the spaces between the cheeks and the teeth, feeling for points on the premolars and molars on the upper arcade.  When these points are prominent, they interfere with roper chewing and become a source of irritation to the soft tissues of the mouth.

The enamel points should be removed regularly by filing with a long handled rasp.  This filing, called floating the teeth, should be limited to the points of the teeth and should not involve the enamel on the grinding surfaces.

Deciduous Teeth

Foals are born toothless but begin to acquire teeth within the first week of life.  The first to appear are the central incisors.  There are two in the upper jaw and two in the lower jaw.

All three premolars erupt at two weeks of age.  The second incisors appear at 1 month and the third incisors at 6 to 9 months.  At about 9 months of age, a foal has a complete set of 24 deciduous teeth.

Permanent Teeth

The first permanent molars appear at 9 to 12 months of age.  The second erupt at two years.  At 2.5 years, the central deciduous incisors are expelled and replaced by permanent incisors.  Also at this time, the first and second premolars make their appearance. The first premolars, commonly called wolf-teeth, are usually found only in the upper jaw; if they are present in the lower jaw, they are quire small and needle-like

At three years of age, the third premolars erupt (although the lower ones may erupt six months earlier).  At 3.5 years, the lateral incisors and the third molars are present. At 4.5 years, the horse has his corner incisors, fourth premolars, and canine teeth.  The canine teeth are usually present by then in the males, but are absent or rudimentary in the mare.

By 5 years of age, the horse has a complete set or 40 to 44 permanent teeth.

Aging a Horse by Its Teeth

The age at which the permanent teeth erupt is quite constant.  In summary, the central incisors erupt at 2.5 years, the lateral incisors erupt at 3.5 years, and the corner incisors erupt at 4.5 years.  This sequence, along with the presence or absence of canine teeth in the male, can be used to accurately determine the age of a horse up to 5 years.

With experience, it is possible to determine a horse’s age up to 30 years with reasonable accuracy by looking at the dental cups, changes in the shape of the teeth and jaws, and the appearance of Galvayne’s groove.

Dental cups are hollow depressions present in new teeth.  As a consequence of bacterial action on retained food particles, these hollows become dark-stained.  As the edges of the cups wear down through age and use, the depressions become shallower and eventually disappear, leaving a white surface with a small, dark central pit called a dental star.  The order in which the dental cups disappear from the incisor teeth can be used to age the horse.

Disappearance of the cups and changes in the shape of the teeth follow a generally predictable pattern.  The lower incisors also wear about three years faster than the upper incisors.

• 6 years – The lower central incisors are worn smooth with shallow cups in the lower lateral incisors.
• 7 years – the lower lateral incisors are also worn smooth.  The lower central and lateral incisors begin to assume a more oval appearance.
• 8 years – The lower corner incisors are now worn smooth.
• 9 years – The upper central incisors are smooth, with shallow cups in the upper lateral incisors.
• 10 years – The upper lateral incisors are now worn smooth. The central and lateral incisors appear somewhat oval.
• 11 years – The cups af all incisors are worn smooth.  Thus at 11 years of age, a horse is “smooth-mouthed” (referring to the incisors).
• 15 years – The lower incisors appear shorter than the upper incisors when viewed from the front.  All teeth show a distinct dark round dental star in their centers.
• 21 years – The angle of the jaw is distinctly oblique.  There is considerable space between the teeth.  The lower incisors may be worn nearly to the gums.

Galvayne’s groove can be used to judge the age of horses from 10 to 30 years.  This is a groove on the surface of only the two upper corner incisors.  It first appears at the gum line at 10 years of age.  It works its way downward year by year as the tooth continues to wear.  At 15 years, the line is present the full length of the tooth.  It then begins to recede from the gums, so that at 25 years, it is present in the lower half of the   tooth and is completely gone by age 30.

As the horse advances in age, there is a tendency for the incisors to protrude outward against the lips, creating a jaw and tooth angle that is more oblique. In addition, the gums shrink or recede. The teeth thus appear longer and more exposed when viewed from a side, giving rise to the expression, “Getting long in the tooth”.

Taking Care of Equine Teeth

Routine dental care can add ten years to your horse’s life and increase the efficiency of his feed, thereby improving his performance.  Your horse’s teeth are continually growing and changing.  The foods horses eat – hay, grass, and grains – contain silica, a very abrasive substance that causes the tooth surface to wear down.  This wear does not occur evenly, which causes the sharp points that can cut and ulcerate the cheeks.

It is important to check your horse’s teeth regularly.  In addition, your horse should have a dental veterinary examination every six months until two years of age, and then annually.  With a little simple observation of the horse, how he eats, his weight and condition, and the smell of his breath, you can determine if a veterinarian’s dental examination is needed more often.  A thorough oral exam requires the use of a full-mouth speculum and is usually done with the horse under mild sedation.

Dental practitioners are formally schooled in the art of equine dentistry, their main work is to equilibrate and balance the teeth of the horse by cutting, burring, and filing the sharp points of the tooth crown. Often the veterinarian can work together with a dental technician to the benefit of the horse.

Dental examinations are particularly important in young horses, as their teeth wear faster and form extremely sharp enamel ridges.  In addition, young horses may have problems associated with caps or impacted adult teeth.  Most dental problems can be treated successfully if they are identified before tooth disease and abnormal wear patterns become fixed and irreversible.  A dental chart similar to one a dentist for humans uses shows what alterations have been made to the horse’s teeth. 

Older horses may have loose teeth.  However, they do not always fall out by themselves because the teeth are so tightly packed together.  The teeth of old horses should be examined every three months, and any loose teeth should be removed to relieve discomfort and prevent dental infection.

Floating the Teeth

Floating (rasping or filing) the teeth is done routinely once a year after a horse reaches 18 months of age. The purpose of floating is to control the sharp edges and point present on the cheek side of the upper premolars and molars and on the tongue side of the lower premolars and molars. Floating is also used to correct minor abnormalities of wear such as lowering a tooth that has grown too long.

The filing is done with a long-handled rasp and carbide-chip blade. The procedure is not painful to the horse and can generally be performed with minimal restraint. These points should be removed with a few strokes of the rasp.

The same results can also be obtained using power tools. These enable the dental procedures to be done more quickly, which increases the horses comfort level and enables the practitioner to correct more significant problems. However, a greater skill level is necessary to prevent damage to the horse’s mouth.

Other Dental Procedures

Most dental procedures are not painful. Because the sensitive structures of the teeth are located deep in the tooth.  Accordingly, teeth can be filed, chiseled, or cut to a desired length using special dental instruments under physical restraint or sedation.  Tranquilization is needed for some cutting procedures that produce a loud noise when the tooth is snapped, since this could startle the horse.

Dental caps and wolf teeth can be removed with bone cutters, dental elevators, and forceps. Badly infected teeth or split teeth can sometimes be removed with long-handled forceps.

When the root is embedded in bone or the extraction is otherwise complicated, the dental procedure is usually done under a general anesthetic. Some teeth, because of their location, cannot be extracted through the mouth and will need to be repulsed. Repulsion involves making an incision in the skin overlying the tooth, drilling a hole in the bone to the base of the tooth, and then driving the tooth out from its socket with a dental punch and a mallet. This procedure is not without some danger of damaging an adjacent tooth or fracturing the jaw.

Special Problems of Miniature Horses

Miniature horses have increased popularity for horse lovers everywhere. These small horses are often less than 28 inches high at the withers in height and have presented unique problems in equine dentistry. These dental issues include teeth that do not erupt through the gums (maleruptions), teeth that do not align properly (malocclusion), and teeth that do not develop normally (malformation).

The miniature horse perhaps benefits most from dental examinations at an early age, as a prophylactic measure, to address the potential hazards of malocclusions, maleruptions, and malformations as early as possible. Early oral intervention will prolong miniature horses’ life by increasing the efficiency by which he chews, processes, and metabolizes feed.

Dental Problems

Teething Problems

The teething process in horses occurs over a long period of time. It generally begins at about 9-12 months of age and is completed by 5 years of age. During that time, many things can go wrong.

Dental Caps

Dental caps are deciduous cheek teeth that remain attached to the chewing surfaces of the permanent teeth after they have erupted. These caps are extremely sharp and may cut the cheek or tongue and interfere with eating. Occasionally, a cap becomes partially detached and rotates out to the side, where it damages the cheek and deforms the face.

Treatment: Dental caps, whether loose or not, should be removed once the adult teeth have emerged from the gum line.

Retained Incisors

Retained deciduous incisors are similar to dental caps except that the retained incisors are in front of the permanent incisors.

Treatment: In most cases, the deciduous teeth are loose and can be removed with dental forceps. If this is not possible, extraction is necessary to ensure a correct bite.

Supernumerary Teeth

This uncommon problem is due to splitting of the tooth bud. When that happens, the horse may grow one or two extra teeth (incisors or cheek teeth). Rarely a horse will have an entire extra row of teeth. Dental crowding can result in tooth overgrowth and gaps between teeth that result in gum infection and tooth decay.

Treatment: Extra teeth that injure the gums of cheeks can be filed or trimmed with dental cutters. Occasionally, extraction will be necessary. A loose supernumerary tooth should be removed.

Absent Teeth

Absent teeth are fairly common. They occur when a tooth bud fails to develop normally.

Treatment: Unless there is a problem with a horse’s bite, no treatment is necessary.

Impacted Teeth

Impacted teeth tend to occur in horses with a foreshortened upper or lower jaw. These horses have insufficient room for the teeth to erupt normally. This forces the tooth to remain in the jaw bone, creating inflammation and even swelling of the bone. Some cases are associated with dental caps.

Treatment: If an impacted tooth becomes infected, it should be extracted. Treating retained dental caps will prevent some cases.

Wolf Teeth

Wolf teeth are vestiges of the first premolars and are very rare in the lower jaw. In the upper jaw, wolf teeth are common and are the only remnant of the first premolar, which sometimes does not exist at all.

If a horse has wolf teeth, they are almost always removed. Delay in the eruption and displacement of the wolf teeth by the second premolars can cause abnormal alignment, with sharp points lacerating the lining of the cheeks and tongue. Even wolf teeth that do not erupt often need to be removed, because they have short roots that enable them to move easily and this is irritating to the horse’s mouth.

Treatment: Wolf teeth may interfere with th bit, irritate the horse’s mouth, and be a handicap in training, which is why some owners ask for them to be removed. Extraction is best done at 18 to 24 months of age.

Canine Teeth

Canine teeth, (sometimes called tusks) are large curved teeth found in the interdental spaces of male horses. In females, they are either missing or are very small. Canine teeth are often confused with wolf teeth. When the canine teeth erupt between 4 and 5 years of age, the gum surrounding the tooth can become sensitive to the bit. A canine tooth that fails to erupt may cause a cyst in the gum.

Treatment: Canine teeth that become long and sharp interfere with the bridle and should be rasped down.

Hooks

Long sharp points may develop on the first cheek tooth, the second premolars, and the last lower molar. This may be due to a preexisting malocclusion problem. The long sharp points can lacerate the gums and cause pain on chewing.

Treatment: Small hooks can be filed. Large hooks are also removed using power equipment. The horse should be adequately restrained or tranquilized for the procedure.

Split or Broken Teeth

A fractured tooth may be of no consequence, especially when the fracture does not extend below the gum line. However, if the tooth is broken very short or is lost, the opposing tooth will not be ground down and may become long enough to interfere with chewing.

Treatment: The unopposed tooth should be rasped every four months to prevent mouth injury. If damage to the broken or split tooth involves the root or surrounding bone, the tooth should be removed.

Malocclusion (Incorrect Bite)

The bite is determined by seeing how the upper and lower incisors meet in front. If a horse has a normal bite, the incisor teeth will meet edge to edge. An incorrect bite is one in which the incisors meet some other alignment. This results in malocclusion.

Most congenital malocclusion problems are apparent during the first weeks of life. Severe malocclusion may lead to mouth infections, poor chewing, and impaired digestion. This can compromise growth and development.

Treatment involves periodically rasping the teeth to remove points and hooks in an attempt to maintain a normal alignment. Placing the horse on hard feed, such as pellets or unprocessed grain, may prolong the need for repeated treatments. Because malocclusions have a hereditary basis, horses with such deformities should not be bred.

Overshot Jaw (Parrot Mouth)

This is the most common malocclusion. In a horse with this deformity, the lower jaw is shorter than the upper jaw. In consequence, the upper incisors overhang the lower ones. Because the upper incisors are unopposed, they grow long like rabbit teeth.

When the malocclusion is restricted to the front teeth, it may not cause a problem. However, if the molars are also out of alignment, they will not be ground down and will form hooks and sharp points. These hooks may interfere with the bit and cause considerable pain.

If detected at an early age (less than 6 months), parrot mouth can be treated by applying wire tension bands from the upper incisors to the first maxillary cheek in an attempt to slow the rate of growth of the upper jaw. These braces can be left in place for several months, but should be carefully monitored for adverse effects, such as infection, impaction, and ulceration.

Undershot Jaw

This is the reverse of an overshot jaw – the lower jaw in longer than the upper, and the lower incisors project beyond the uppers like a Bulldog. It is less common than parrot mouth. The horse have trouble grazing or “nipping” grass.

Shear Mouth

In normal horses, the upper arcade is always wider than the lower arcade. In a horse with shear mouth, this discrepancy is exaggerated. This produces long, extremely sharp shearing edges on the cheek teeth. An acquired type of shear mouth occurs in old horses who develop age-related changes involving the shape of the mandible.

Abnormal Wear Patterns

Abnormal chewing patterns can produce abnormalities of tooth wear. It has also been suggested that in susceptible horses, some teeth may be innately softer than others and therefore do not offer equal resistance to wear and use. Regardless of the cause, these abnormalities tend to get worse with time. In the early stages, they cause subtle performance problems such as interfering with the bit. As the problem worsens, the horse develops painful chewing, quidding, and weight loss. Whole grain may be seen in the feces.

Wave Mouth

This usually occurs in ponies and older horses and results in abnormal undulating surface to the teeth when viewed from the side. The crests and troughs created by the wave pattern allow some teeth to become too long; others opposing them are ground down to the gum line. Mouth and gum injuries are common.

Treatment: Mild cases may respond to floating the teeth at frequent intervals. In more severe cases, an attempt should be made to even the arcades by rasping, using motorized equipment.

Step Mouth

In horses with this disorder, there is an abrupt change in the height of adjacent premolars and molars. In many cases, a lost tooth leaves a space that permits an opposing tooth to grow out without meeting resistance. A retained dental cap is another cause of step mouth.

Treatment: Treatment involves rasping the elongated molars, using motorized equipment, at six-month intervals.

Smooth Mouth

This is caused by equal wear of both the enamel and dentin and produces an absolutely smooth surface on the cheek teeth instead of the normal rough grinding surface. In young horses, it is caused by a defect in the composition and structure of the teeth. In very old horses, it occurs when the teeth are worn down to the roots.

Then the cheek teeth are worn absolutely smooth, the horse cannot grind his feed.  These horses experience significant weight loss and suffer from digestive ailments such as colic, constipation, and malabsorption. Whole grain may be seen in the feces.

Treatment: Young horses who have been improperly floated may, with time, reestablish normal grinding surfaces. In all other cases, there is no effective treatment except to feed soft mashes, chapped wet hay, or pelleted food.

Periodontal Disease

The periodontium consists of the gingiva (gum), the alveolar bone (the socket in which the tooth sits), the periodontal ligament (which anchors the tooth in the socket), and the cementum (the outer layer of the tooth). Horses do not develop cavities in the crowns of their teeth as people do. Instead, dental infection begins near the root of the tooth at the junction of the cementum and the periodontal membrane.

Periodontal disease in horses is an inflammation of the tissue and structures around the tooth. It may be painful and is probably the most common cause of premature tooth loss in adult horses. Periodontal disease predominantly affects the cheek teeth, rarely the incisors. The gums may be involved in the process but are seldom a predisposing cause.

The primary cause of periodontal disease in the horse is the misalignment, or malocclusion, of the cheek teeth. This may be a result of the aging of the horse, improper alignment of cheek teeth caused by genetics, or normal wearing down of teeth. These predisposing factors may cause abnormal chewing of feed, abnormal wear of teeth surfaces, malocclusion of the teeth, and gaps between the teeth where food may be trapped. 

With normal chewing, the horse’s mouth is fairly self-cleaning; feed does not accumulate on or around the teeth. When trapped feed packs down between the teeth, it starts to decompose and undergoes bacterial fermentation. The gum will recede and form a pocket. The pocket continues to ferment, and the infection progresses toward the tooth root.  If this process is not checked, it will continue until the periodontal ligament is destroyed and the tooth will loosen in the socket. Abscesses may occur as a result of periodontal disease.

Signs of periodontal disease may include some or none of these: bad breath, losing weight, dropping feed (quidding), performance problems, or the horse just not seeming “right.” A thorough oral exam by a veterinarian is necessary to detect periodontal disease. The cheek teeth, where most periodontal disease occurs, are not easily viewed without specialized equipment.

Treatment: The cause or causes of the periodontal disease must be addressed. Restoring the normal flat contour of the molars is a key step, as is removing impacted feed material from between the teeth. These treatments alone often restore the cheek arcade to normal function, thus eliminating the periodontal disease.

Sometimes an oral rinse of 0.1 percent chlorhexidine solution may be used to control bacterial growth after the entrapped forage is removed. If a tooth appears to be beyond help and the periodontal disease has progressed over a long period of time, the tooth may have to be extracted. This will require frequent check-ups to prevent overgrowth of the opposing tooth.

Antibiotics are seldom required. If antibiotics are indicated, periodontal pockets can be filled with a special antibiotic polymer such as the gel doxycycline (Doxirobe). The polymer prevents the pocket from filling back up with impacted feed material and the antibiotic is slowly released.

There are high-pressure irrigation systems available that use a baking soda and disinfectant slurry. These machines, similar to those used in human and small animal dentistry, also contain high- and low-speed drills, air , and water delivery, sonic scaler, and suction.

Abscessed Tooth

Abscessed teeth are caused by periodontal disease. A special situation involves the cheek teeth in the upper jaw. The roots of these teeth (primarily the first molars) are embedded in the maxillary sinuses. Consequently, root infections of these teeth commonly cause bacterial sinusitis and a purulent, foul-smelling, persistent discharge through one nostril. A fistula may develop between the oral and nasal cavities.

Treatment: it is necessary to extract the tooth and cure the infection. Antibiotics may be given at the discretion of the veterinarian.