Charles T. McCauley, DVM, Diplomate ABVP and ACVS
Assistant Professor, Equine Surgery
Equine Health Studies Program, School of Veterinary Medicine
Louisiana State University, Baton Rouge, LA 70803
Domestication has significantly improved the quality of life and prolonged the average
life expectancy of horses. Improved nutrition, housing, preventive health care and parasite
control programs have resulted in a large population of geriatric horses, sometimes living into
their thirties and forties. Highly processed grain diets, confinement, minimal exposure to
continuous grazing, feeding from elevated troughs, and minimizing exposure to environmental
abrasive substances have as a consequence affected the way in which the horse’s teeth erupt and
wear. With the increasing age of the horse population, comprehensive dental care is becoming
more important. Up to 10% of equine veterinary practice time in the US involves dental related
conditions. Horse’s teeth are long and primarily composed of reserve crown that is buried deep
below the gum line (gingiva) within the upper (maxilla) and lower (mandible) bones of the jaw.
Unlike humans, the crown erupts continuously as the horse ages until it is exhausted and only
shallow roots remain to hold the tooth in the bone. Throughout the horse’s lifetime, the
continuously erupting crown of each tooth is worn away at a rate of 2 – 4 mm per year by the
opposing tooth. Once the reserve crown is exhausted, the horse is unable to chew properly and as
it has been said, “horses do not die of old age, they simply run out of teeth”.
Although we associate dental disease with obvious clinical signs, more often than not
dental problems develop slowly without outward symptoms. Frequently there are no obvious
external signs until the disease has progressed to complications such as infection of the gingiva,
tooth roots, bone or sinus. When signs of dental disease are present it may be manifested by any
of the following signs:
• Quidding – dropping partially chewed, saliva soaked food
• Halitosis – bad breath
• Weight loss, poor body condition, or failure to gain weight
• Head shaking, bitting problems, resistance to the bit, and abnormal head carriage
• Excessive salivation
• Reluctant or slow eating or chewing
• Food pouching
• Oral pain
• Changes in fecal consistency – ranging form dry hard fecal balls to diarrhea and often
comprised of undigested long fibrous material
• Other behavioral/training issues
Many times poor dentition is mistaken for behavioral or training problems that appear not
to be correctable. Lack of appropriate dental care can lead to early attrition and tooth loss,
making it difficult for older horses to maintain their body weight and can also lead to systemic
manifestations of dental disease such as choke (esophageal obstruction) or colic.
Adult horses have 36 to 44 permanent teeth. These teeth include 6 upper and 6 lower
incisors. There are normally 3 or 4 premolars and 3 molar teeth in the upper and lower jaw,
which are collectively known as the cheek teeth (Figure 1). The first premolars, if present, are
usually poorly developed or vestigial and are termed “wolf teeth”. These teeth are frequently
removed by veterinarians due to the perception that failure to remove wolf teeth will result in
problems with the bit. The remaining premolars and molars are used primarily for grinding the
fibrous feed material typical of the horse’s diet. It is important to remember that the upper jaw is
wider than the lower jaw. To accommodate this, the occlusive or grinding surface of the cheek
teeth is slanted approximately 15-degrees.
Figure 1 – Equine skull demonstrating normal upper and lower canine, premolar and
molar teeth. I = incisor, PM = premolar and M = molar.
The only way to accurately identify abnormalities in the dentition of a horse is by
complete and thorough oral and dental examinations. A proper dental examination is performed
with the horse adequately restrained in a stock and usually sedated. The dental examination
typically begins with a discussion of any history of abnormal behaviors. This may give clues to
an existing problem that needs to be addressed. In addition, it is important for the person
performing the examination to have an understanding of the horse’s use. The number, position
and alignment of the incisors are evaluated first. Supernumerary (too many) incisors and fracture
or missing incisors are not uncommon and should be noted. Malocclusion of cheek teeth such as
hooks or steps can prohibit normal front-to-back and side-to-side movement during eating and
chewing. Side-to-side movement or lateral excursion of the lower jaw in relation to the upper jaw
is necessary for the normal chewing and grinding motion of the horse and should be evaluated.
While the upper jaw is held in a fixed position, the lower jaw is moved laterally. A normal lateral
excursion is roughly the width of 1½ teeth. In addition, due to the normal angle of the cheek
teeth, as lateral movement continues and the grinding surfaces of the cheek teeth come into
contact, the incisors should separate approximately 2 – 6 mm. Also necessary for normal
chewing, the incisors must be flat and level from one side to the other. Locking of the jaw,
decreased lateral excursion and failure of the incisors to separate are all indication of
abnormalities of the cheek teeth.
Examination of the cheek teeth is facilitated by use of a full mouth speculum, dental
mirror and bright light source. This should include examination of the soft tissues including the
inside of the cheek and tongue for the presence of ulcerations, lacerations or erosions. Each
cheek tooth in both the upper and lower dental arcades should be examined for evidence of
abnormal location, presence of sharp enamel points and abnormal overgrowths, fractures, spaces
between the teeth (diastema) and areas of decay. Suspicious areas should be further investigated
using a dental probe and the tooth should be assessed for looseness.
Foals, Juveniles and Young Adults
It is a misconception that young horses do not need regularly scheduled dental
examination and care. Sharp enamel points begin to develop almost immediately after eruption
of the cheek teeth. At a minimum, foals should be examined at birth and again at weaning for
evidence of congenital abnormalities such as overbite or parrot mouth (Figure 2) and
developmental abnormalities such as poor incisor alignment and errant cheek tooth eruption.
Figure 2 – Parrot mouth in a young foal.
Tumors of dental origin and those affecting the bones of the jaw are also commonly diagnosed at
this age. Eruption of the permanent teeth begins at approximately 1 year of age and continues
until the horse is 4 – 5 years old. As the premolars erupt, they cause resorption of the deciduous
root and push the remaining deciduous crown up above the gum line. This premolar cap is
usually lost shortly after the molar tooth erupts through the gum. In some instances, this cap can
be retained and have sharp spicules of enamel that may penetrate the gum when pressure is
applied by the opposing premolar resulting in pain. Affected horses are often presented to
veterinarians for examination due to excessive dropping of feed or behavioral problems.
Removal of retained caps results in almost immediate resolution of oral pain. In addition to
retained premolar caps, asynchronous eruption of premolar and molar teeth can result in
malocclusions that can affect the horse’s ability to adequately grind feed. This problem is easily
recognized and corrected on a routine oral examination. Finally, there is evidence to suggest the
enamel of horses up to 6 – 7 years of age is softer than that of older horses. Because of this,
sharp enamel points may reform earlier after routine dental care in young horses. For these
reasons, it is recommended that young horses form birth to 7 years of age undergo a dental
examination approximately every 6 months.
Mature horses between the ages of 7 – 15 years of age with normal dentition typically
require only annual examinations and routine care. The most common abnormality observed in
this group of horses is the development of sharp enamel points on the outer surface of the upper
check teeth and the inner surface of the lower cheek teeth (Figure 3).
Figure 3 – Sharp enamel points affecting the outer margin of the upper cheek teeth.
If left untreated, these enamel points may continue to lengthen, causing painful ulcers or
lacerations of the cheek and tongue (Figure 4). Another common abnormality of the adult horse
is the development of hooks on the first upper premolar and last lower molar. These hooks
develop as a result of abnormal alignment of the mandibular and maxillary cheek teeth. Hooks
may restrict the normal front to back movement of the lower incisors in relation to the upper
incisors with change in head position. This is especially important when horses are expected to
bend at the neck and poll. Hooks affecting the last lower molar are more difficult to treat due to
the depth of the teeth in the mouth, minimal working space and close proximity of the bone and
surrounding soft tissues. Minor oral trauma frequently accompanies reduction of these hooks.
Other malocclusions result in steps or waves. A wave is a series of overgrown teeth
opposed by a corresponding series of over worn teeth. Although there are several techniques for
the correction of steps or waves, these abnormalities may not be correctable in a single dental
treatment due to the potential for invasion of the pulp chamber if excessive tooth is removed.
Therefore, additional treatment at a more frequent interval (often every 4 – 6 months until the
malocclusion is corrected) may be necessary.
Figure 4 – Traumatic ulcer (bold arrow) secondary to sharp enamel points and a large
premolar hook (thin arrow).
Although geriatric horses may suffer from any of the malocclusions previously described
for adult horses, the most severe dental abnormality in these horses is periodontal disease. As the
cheek teeth erupt, there is a natural tapering of the tooth from the occlusal surface to the root. In
young horses, all 6 cheek teeth are packed tightly together with no normal space between the
teeth. As the tooth erupts and the occlusal surface is worn, this tapering results in formation of
spaces known as diastema between the teeth. Food and other debris can become trapped in these
spaces and undergo fermentation. This food packing and bacterial fermentation has a negative
effect on the natural defenses in the mouth and infection of the gingiva occurs. With time, this
infection migrates along the tooth eventually affecting the surrounding bony and soft tissue
attachments of the tooth to the jaw (Figure 5). Periodontal disease may eventually lead to
infection of the tooth root, tooth root abscesses and premature tooth loss. Although there are
usually no obvious outward clinical signs, this is a painful condition that eventually will lead to
difficulty chewing, weight loss and potentially other more serious health problems such as
secondary infection of the sinuses and colic.
Figure 5 – Example of severe bone and tooth loss secondary to periodontal disease in
a geriatric horse. Compare the bone surrounding the teeth of this specimen to that in Figure 1.
Treatment of periodontal disease is much more difficult than prevention. Prevention
involves routine dental examination and maintenance as previously discussed. Treatment
involves removal of all packed feed material and debris, instillation of an antibiotic gel and
covering the affected area with dental impression material to prevent further mechanical trauma.
A more advanced treatment for periodontal disease is flushing and disinfection using the Equine
Dental System by Pacific Equine Dental Institute (P.E.D.I.). This technique utilizes high pressure
air abrasion and flushing with sodium bicarbonate (baking soda) and disinfection. If periodontal
disease is severe enough, removal of the affected tooth may be the only viable treatment.
As horses age, eruption begins to slow and the availability of reserve crown begins to
decrease. Older horses with significant malocclusion must be treated carefully. Severe steps or
waves may be present; however, aggressive treatment especially removing excess crown to bring
the teeth into more normal occlusion may result in removal of too much remaining crown, thus
permanently affecting the horse’s ability to grind feed. Essentially any sharp enamel structure(s)
should be corrected by removal of a minimum of remaining crown. Because formation of these
points is dependent on continued eruption and wear, they are usually slow to reform if they recur
at all. Finally, older horses’ teeth will expire and either fall out or become cupped. This condition
is not correctable and these horses must be managed through dietary modification.
Systemic Manifestations of Dental Disease
Besides the obvious oral manifestations of dental disease in horse, there are several
disease processes that can be directly related to disease of the teeth and surrounding structures.
Because the last 4 maxillary cheek teeth are embedded in the sinus, infection that travels along
the tooth may invade the sinus and surrounding bones. This condition is usually recognized by
malodorous discharge draining from a single nostril on the side of the affected tooth. As fluid
builds up in the sinus there can be swelling of the face directly over the involved tooth and
distortion of the facial bones. Eventually a draining tract may open on the face. Radiographs of
the head in these patients will often demonstrate fluid in the sinus and destruction of the bone
supporting the tooth and its root. In these cases, surgery is often necessary to remove the affected
tooth and drain the sinus. These diseased teeth can sometimes be removed in the standing,
heavily sedated patient, but frequently require general anesthesia and opening of a bone flap into
the sinus. On many occasions, a small enamel fragment or diseased bone that is not identified at
the time of tooth removal may require additional surgery for complete removal.
Abdominal distress or colic is another condition that is highly associated with pre-
existing dental abnormalities. Malocclusion of the cheek teeth will prohibit effective grinding of
fibrous material. This, in addition to other environmental factors such as failure of the horse to
drink adequate water and poor quality hay, may lead to impaction of the large colon, ileum, or
In older horses, tooth loss commonly leads to esophageal obstruction (choke) because of
inadequate mastication (chewing). This condition is also difficult to treat and can lead to
esophageal damage and rupture. In addition, if the horse aspirates a large amount of saliva and
feed material severe sometimes fatal pneumonia can develop.
Although not completely, each of these conditions to a large degree is preventable by
regular dental examination and care.
The importance of comprehensive routine dental care cannot be overemphasized. Many
painful and potentially debilitating dental conditions are preventable if appropriate dental care is
provided. Not only can the horse be saved form painful conditions affecting the mouth, but the
occurrence of potentially performance limiting and life threatening conditions that are expensive
to treat and require extended periods of time off may be significantly decreased.
Does Your Horse Have a Dental Problem?
The LSU Equine Clinic is now offering a regular comprehensive equine dental service
for routine and advanced procedures. This service will be provided each Thursday. Please
contact the LSU Equine Clinic (225-578-9500) for more information or to schedule an