|
The importance of regular oral examinations and floating
is difficult to overstate. Minor problems, which could evolve
into significant dental abnormalities, can be detected and
corrected. Additionally, performance problems caused by
soft tissue paid from contact with sharp teeth can be eliminated.
The horse has evolved from the eocene period as a three
toed 26 inch tall mammal with low crowned brachyodont teeth
(similar to humans), into a 60 to 72 inch 1100 lb. animal
with greatly increased demands on the digestive system.
A doubling of the height requires an eight-fold increase
in food intake. The teeth have lengthened and have reserve
crowns that continually erupt throughout the life of the
horse. The head has lengthened and deepened to accommodate
these changes. The teeth are worn off at the chewing (occlusal)
surface by the grit, silica, and coarseness of the material
being chewed.
Dental Function
Horses select food with their sensitive upper and lower
lips. The lips are drawn back as the incisors (front teeth)
grasp food. The tongue moves food into the mouth where the
molars grind food into small particles. The free ranging
horse prefers grasses and legumes but will eat shrubs, woody
plants and even roots. Unlike the cow, the horse cannot
regurgitate food and chew it again. If mastication of food
is incomplete, incomplete digestion and absorption of nutrients
can occur as well as the occasional case of colic. The 24
cheek teeth (molars) are arranged in four rows or arcades
of six teeth. The first cheek teeth begin just behind the
commissure (corner) of the mouth and continue rearwards
to the front corner of the eye. The maxillary or upper molar
arcades are wider apart than the mandibular or lower arcades
of molars. The anisognathic (unequal) arrangement couples
with side to side chewing causes the occlusal or chewing
surface to become tilted with the inner edge of the lower
teeth taller that the outer edge. The inner edge of the
upper teeth is shorter than the outer edge. The taller edges
of the teeth (inner on lower arcades, outer on upper arcades)
develop sharp tooth points that are removed when the teeth
are floated.
Horses confined to stalls with free access to hay will exhibit
feeding patterns similar to free ranging horses and usually
eat 10 to 12 hours per day in sessions lasting 30 to 180
minutes. In contrast, confined horses with limited access
to hay will eat their grain and spend the rest of their
time in boredom, i.e. standing, lying down, searching for
food, chewing wood, etc.
The horse chews by moving the mandible (jaw) in a side to
side oval pattern. The jaw is opened, moved to the side
then closed. The extent of the lateral movement or range
of motion of the mandible is influenced by the consistency
and nature of the food being eaten. Horses eating grain
or pellets have limited lateral movement of the jaw compared
to horses eating forage. The decreased motion influences
molar wear resulting in more problems with sharp points
on the molars.
Signs of Dental Disease
Included with these notes is a sheet listing signs associated
with dental disorders. The tendency of a horse to show signs
of oral pain is highly variable. Horses with major abnormalities
may act normally, while minor problems may cause persistent
training difficulties. Signs are usually related to soft
tissue pain from contact with sharp edges or points on teeth.
Performance problems include head tilt, inflexibility, protruding
tongue and nosing out to name a few.
Oral Examination
A complete oral examination is a vital part of routine dentistry
as well as a part of lameness, insurance or prepurchase
examination. Identification of dental, ocular, neurological
or musculo-skeletal abnormalities can be detected early.
Floating
Historically, floating or removal of sharp enamel points
was performed to facilitate mastication of food. In recent
years, floating has evolved to accommodate the demands of
performance. Although technique varies with each practitioner,
the goal is to remove sharp points and edges from molars
preventing soft tissue damage. Floating should also prevent
soft tissue damage when soft tissue is trapped between teeth
and bit or bridle.
Proper shaping of the upper first and second cheek teeth
prevents cheek injury between the bit and attached leather
and these teeth. Shaping the lower first cheek teeth stops
soft tissue pinching as the bit moves back and forth in
the mouth. The last upper and lower molars frequently cause
performance problems. The inside of the lower molars presses
against the side of the tongue. Smoothing last two lower
molars is essential in preventing tongue irritation and
aiding in keeping the tongue quiet in the mouth. The large
masseter muscle covers the last two upper molars. The muscle
traps the cheek and maintains a constant pressure pushing
the mucosa into the points creating the ulcers. Smoothing
these teeth aids frequently results in smoother transitions
and turns.
A simple way to check if the cheek is sore is to gently
push with the heel of the hand into the masseter muscle
about three inches below and just in front of the eye. The
horse will flinch and jerk the head upward if this area
is tender or inflamed.
Occlusion
Occlusion simply means contact. Proper incisor and molar
contact are necessary for grinding of forage. At rest, the
mandible is directly below the maxilla. To observe this,
raise the horse's nose to eye level and open the lips; the
lower incisors should be directly under the upper incisors.
The contact surface between these teeth should appear as
a straight line, parallel to the ground. When the mandible
is pushed to the side, the incisors remain touching until
the upper and lower molar arcades touch each other. Because
the molars are angled, when the molar arcades meet, the
incisors separate. The drawing represents the relationship
between the incisors and molars. If the incisors have an
abnormal shape or are too long (from lack of wear during
several years) the molars cannot grind food properly. An
oral examination will identify incisor abnormalities and
treatment needed. How far the mandible moves before the
molars touch is determined how molar contact is maintained
when grinding food. Remember the horse chews backward from
the manner that a practitioner checks occlusion. The horse
moves the mandible to the side, closes the mouth, the molars
touch and grind food and as the mandible returns to the
resting position when the incisors touch and the molars
separate. An oral examination will assess the occlusion
of both the incisors and molars. Molars are checked to determine
if occlusion is uniform end to end and there is no interference
from bumps, ramped up or tall teeth or hook formation on
either end of the arcades.
Age Related Dental Problems
Foals are born with the first three (deciduous or temporary)
premolars erupted. (Premolars are molars that have temporary
or deciduous teeth, three molars erupt into wear by age
four, and all are called "cheek" teeth.) The temporary
incisors are all erupted into position by 9 months of age.
Foals are checked at or close to birth to determine if any
congenital abnormalities exist. Deciduous teeth are soft
and can develop sharp edges quickly. From age 2 to 4 months
to about 18 months, these teeth should be checked every
4 to 6 months and floated if needed. Floating can be done
without a speculum, requiring only three to four strokes
of a float per molar arcade to correct. Permanent premolars
begin and are in wear from age two years and six months
to age four years. An eruption timetable is included with
these notes. The eruption of permanent teeth and deciduous
teeth (cap) removal can vary two to three months. The permanent
molars (last three check teeth) are also developing and
erupting. The first molar erupts at one year of age. The
last molar erupts into position at age three. Eruption "bumps"
begin forming on the bottom of the mandible about age two.
These bumps are the developing roots of the permanent third
and fourth premolars. The bone of the mandible is remodeling
and expanding to allow for the tooth elongation. The bone
over these roots is quite thin and the roots can be damaged
easily.
Check two-year old horses every six months or more frequently
during eruption to remove caps. Loose caps cause pain with
mastication. Caps can be retained and may need to be removed
to prevent uneven eruption of permanent teeth. Examination
and floating every six months after premolar cap removal
will identify abnormal incisor or molar wear abnormal occlusion
and maintain a pain-free mouth. Horses with a mature mouth
(over five years of age) should be examined at least every
year. See the sheet listing abnormalities. Performance horses
may need floating every six months, depending upon how sensitive
they are to oral problems. Some horses become quite reactive
to just one sharp point after they have been pain free for
several months.
Horses over 15 years need yearly examinations to evaluate
occlusion and the development of other age-related problems.
These problems include worn out teeth, gingivitis and subsequent
periodontal disease, wave and step mouth. Identification
of these problems will enable your veterinarian to maintain
your horse's teeth and health for many years. (Contributed
by Dr. Larry A. Lawrence, Department of Animal and Poultry
Sciences)
Back
to Treatments and Therapies
|
