Of all the domesticated animals, horses seem to be most prone to development of dental abnormalities for a number of reasons.Their teeth start to protrude through the gums at or soon after birth (the deciduous or milk teeth), and up to 24 of these deciduous teeth will erupt during the first year of life. All of these teeth are replaced during the time up to 5 years of age.Consequently, there is a constant eruption and loss of deciduous teeth, overlapping with eruption of the permanent teeth during this period. Eventually up to 44 permanent teeth might be present in the horse’s mouth – half of these are in the lower jaw or mandible and the other half are in the upper jaw or maxilla.
It is easy to see that there are plenty of opportunities for things to go wrong during dental development if there is not regular care and attention paid to the mouth and its associated structures in the growing horse.
Horses are also different from many other species because their teeth are very long, and are mostly under the gum line. Their teeth continue to erupt throughout life, unlike dogs, cats and humans. Horse teeth are abraded by chewing and grinding of food materials between the surfaces of the upper and lower teeth (the occlusal surfaces of the teeth).
Thus, if there is a change to the cyclical grinding motion of the horse’s jaw due to pain for example, the grinding surfaces of the teeth can rapidly become abnormal. A cycle of pain producing an abnormal grinding motion followed by abnormal wear and more pain is then set into play which can rapidly lead to long term problems for the horse unless there are regular dental and oral examinations to detect and correct such problems early in their development.
Horse owners should ensure that their horses have oral and dental examinations, coupled with complete clinical examinations on a regular basis. These examinations should begin early, and continue for the remainder of the horse’s life.
In most situations, dental examinations are best carried out with the horse under sedation. There should be a complete visual and manual inspection of every tooth and the surrounding structures. All abnormalities and treatments should be noted in a written clinical record for future reference.
The following information provides a snapshot of some of the issues that can plague a horse’s teeth at various stages of its life.
At or soon after birth, foals will have a total of 16 teeth present – four incisors or front teeth, and 12 premolars or back teeth. At four to six weeks, four more incisors will erupt through the gum, and at approximately six to nine months the last
set of deciduous incisors will erupt.
Around the same time, wolf teeth will erupt if the horse is to have them. Wolf teeth are small teeth that are situated in front of the upper cheek teeth. These teeth are vestigial, that is, they serve no purpose and may interfere with bitting of the horse. It is advisable to remove wolf teeth while the horse is still young as these teeth will eventually fuse with the bones of the skull making extraction far more difficult as the horse gets older. Twelve months is an ideal time to check for and extract wolf teeth.
Dental problems can be congenital, that is present at birth. Examples include brachygnathism or parrot mouth (overbite) and prognathism or sow mouth (underbite). These conditions can sometimes be treated, but to do so they must be diagnosed very early on. For this reason foals should be examined soon after birth.
Twelve months is an ideal time to begin routine dental examinations and treatment as the soft cheek teeth will be wearing each other leading to formation of sharp points. Sharp points on the upper cheek teeth can lacerate the inside of the cheeks, and on the lower teeth can lacerate the sides of the tongue. This causes pain for the horse due to ulceration of the cheeks and tongue. Changes in the way the horse eats due to this pain can affect weight gains, and change the wear patterns of teeth leading to dental abnormalities.
At twelve months of age the first of the permanent cheek teeth erupts so it is a good time to ensure that normal eruption is occurring and to identify any other problems. Dental abnormalities can reduce weight gain by up to 30% which can have long lasting effects on a horse during this critical development period.
From 1 year to 6 years of age
During this period horses will shed their 24 deciduous first set of teeth and up to 44 permanent teeth will erupt through the gums.
Common problems during this period are formation of sharp enamel points and deciduous or baby teeth that fail to shed correctly (retained caps). Early development of more serious cheek teeth changes and malocclusions such as:
hooks and ramps (overgrowths of the first or last cheek teeth) waves (uneven grinding surfaces of the cheek teeth arcades)
impaction or overcrowding of teeth preventing normal eruption.
These can be identified and treated through examinations every six months.It is also important during this time to ensure all horses have a thorough oral examination and any necessary treatments before beginning their education and breaking in. Failure to do so can lead to the development of behavioural changes associated
with oral pain and the negative experiences can have lifelong consequences for both horse and handler.
From 7 years to 15 years of age
The rate of wear begins to slow slightly as the teeth erupt and the majority of horses in light work and on a mostly pasture based diet will need to be examined every 12 months.
Horses that are fed concentrates will need more frequent examinations as these dietary changes to include hard grains cause them to chew differently thus affecting the way the teeth wear.
Again in horses of this age group early detection of problems and removal of sharp enamel points is very important. Diseases that affect the periodontal ligaments, structures which support the tooth within the tooth socket or alveolus, begin to occur and early detection and treatment is the only way to prevent premature loss of affected teeth.
Early detection of periodontal disease (disease of the structures that anchor the tooth in place and the surrounding gum or gingiva) is essential to allow effective treatment. The bacteria associated with periodontal disease also enter the bloodstream and travel through the vital organs. This can lead to serious illness affecting the heart, lungs, liver and kidneys. Horses affected by infectious periodontal disease may need antibiotic therapy to help overcome this disease.
This group of horses is beginning to reach the end of their reserve crown (the part of the tooth that remains below the gum line). They may have concurrent diseases (for example Cushing’s disease or hyperadrenocorticism) and can have difficulty maintaining weight just like elderly people. So their diet, dental care, and management of other diseases must be of the highest standard to ensure longevity and quality of life.
Horses begin to lose the enamel from their cheek teeth (commonly referred to as cupping) and as a result these affected teeth are more fragile and must be treated carefully. Because the teeth lack enamel they become softer and start to wear quickly again.
Some horses that have not had early diagnosis and treatment of periodontal disease may need to have teeth extracted. Early detection could have prolonged the longevity of these teeth and with it the longevity of the horse.
This older group of horses should be seen every six months to allow for early detection of problems and to maintain good oral hygiene.