From the anatomy and physiology of the mouth and teeth, and
because the humans domesticated the horse, we can already imagine
that problems can and will occur. Because the teeth continues
to erupt for most of the horse's lives, "overgrowth"
where a tooth doesn't meet another tooth in occlusion and wear
down, can become a problem. The wear will be uneven, and the
formation of so called hooks and ramps will take place.
Hooks,
very sloping molar tables and high ridges of enamel can prevent
side movement of the jaws and make it difficult for the horse
to move its jaw normally from side to side.
Here
are a few conditions of the molars:
(see also the
photos section for more illustrations)
Sharp
enamel ridges and overgrowths
The chewing cycle discussed in the physiology
section influences how good the
horse wears down his enamel ridges on his own. The shorter the
side stroke is (often diet related), the sharper the points
and steeper the angles of the molar tables. The "indoor"
diet pointed out affects the lateral side movement of the jaw,
combined with the fact that the upper jaw is broader than the
lower jaw is, (and also the anatomy of the tooth itself), will
create razor sharp rows of enamel points especially on the outside
of the upper molar rows and the inside of the lower. The pain
can cause a number of symptoms, and the high points and rows
can physically prevent the jaw from moving sideways to chew
properly.
Long
teeth
If
a horse has lost a tooth, or a tooth has been extracted for
some reason, the opposite tooth that was in occlusion, has nothing
to wear against. The result is a long tooth. This needs to be
reduced regularly so that the horse doesn't develop any secondary
problems with chewing and oral health. It can get long and sharp
enough to penetrate the gum where the opposite tooth used to
sit, and there can also be problems with the side movement of
the jaw.
Wolf
teeth
The wolf teeth can cause the horse discomfort
with a bit in the mouth and are usually removed. The tooth and
its surroundings can be sensitive, and having lips pulled into
a sharp wolf tooth is not a pleasant experience for the horse
either. Unerrupted wolf teeth can get inflammed and also get
in the way for the bit as they are usually a little dislocated
from its usual location.
Rooth
slivers, caps (retained decidious premolars) & tooth impactions
Eruption
of permanent teeth and shedding of decidious teeth can cause
discomfort and pathological conditions. Caps can cause chewing
problems, anorexia, infection and abnormal wear pattern (step).
The caps should not be removed too early as this might damage
the permanent premolar underneath, and it is also important
to avoid putting too much pressure on this during extraction
of the caps. Milk
teeth caps or root slivers from these can get stuck in the gums
and can cause infection and also dislocate or damage the new
permanent tooth trying to get in. This usually affects the pm4
which is the last of the permanent molar to erupt, and the gap
it is coming out in is usually quite narrow and can easily be
blocked by a stuck milk tooth cap. The problem usually manifests
itself a couple of years later, so a root abscess on the pm4
is usually seen in 6-7 year old horses because of what happened
when they were shedding a couple of years earlier. If a decidious
tooth doesn't shed like it should, problems can occur. Often
the permanent teeth will be a little dislocated towards the
palate, and can cause problems later. When the row of molars
isn't straight, there will be a pouch gathering feed particles
and bacteria and periodontal disease can follow. Tooth impaction
also occur in instances where a decidious cap is retained. There
will be pressure to the permanent tooth, root abscesses with
the formation of drainage canals from the jaw.
Root
abscesses and sinusitis
Anatomically
there is a very close connection between the large sinus (maxillary)
of the upper jaw and the roots of the molars. Secondary sinusitis
from molar problems such as dental impactions, infection, disease
in the teeth sockets (aloveolus), fractures and periodontal
disease is seen every now and then. The symptoms can vary from
mild to quite severe, with or without swelling. You might see
a mild pus like nasal discharge, usually from just one nostril,
or you can see blood mixed discharge, notice foul smell, the
horse might have difficulties chewing or doesn't want to eat
at all. An opening draining puss (a fistula) can develop both
on the upper jaw and the lower jaw.
Fractured
teeth
Molar fractures can give infection and/or
pain.
Loose
teeth
Loose
teeth can get uncomfortable for the horse and easily gather
food and bacteria and will get infected.
Supernumerary
(too many teeth)
Too many teeth will cause a rows of molars
to be too long, there will be alignment problems and the development
of hooks and ramps. TO many teeth can be caused by traumatical
split of a tooth bud, or it can be congenital.
Missing
teeth
Teeth
can be missing from old age, fractures, periodontal disease,
malformation, congenital reasons etc. A big problem a missing
tooth can cause is feed packing into the empty socket if it
is still open, and this will easily get infected, but also another
problem is overgrowth of the opposite tooth as this will have
nothing to wear down against, so every year it will get 2-3
mm longer than the other teeth in the mouth. Eventually, depending
on what age the tooth was lost/extracted, the opposite tooth
will reach the gum where the missing tooth used to be, and the
horse will start chewing on the gum in this spot. This can cause
injuries, infections and can be very painful to the horse. With
a gap in the row, the other molars will also start to move and
the row of teeth becomes shorter than normal. Again, this will
lead to overrowhts and abnormal wear.
Step
mouth
A
step is the result of an overgrowth within a molar table, caused
by lack of occlusion. See illustration above.
Hooks
and ramps
As
mentioned before, the horse teeth erupts constantly all the
horse's life, and wears down against the opposing tooth. If
the rows of molars (or incisors for that matter) are not aligned
properly (for example in a horse with an overjet or underjet)
a part of the tooth will not be in occlusion and will not wear
down. Hooks and ramps will develop in the front or back of both
the upper and the lower rows of molars. The difference between
a hook and a ramp is that a hook is much steaper and more pointy
than a ramp which protrudes more gradually. The
hooks and ramps can prevent jaw movement and chewing, and it
can also prevent the horse from lowering its head and collect
itself properly (horses need to slide their lower jaw forwards
to be able to bend the head down). Seriously long hooks can
pierce through the gums and cause serious infections and bleeding.
Irregularities like hooks and ramps should be corrected.
Waves
When
the
whole molar row becomes uneven . It often occurs secondary to
other conditions such as caps, missing teeth, big hooks and
ramps, and old age where some of the teeth are running out of
enamel. See illustration above. The result can be problems with
the normal movement of the jaw and thereby chewing the food
properly.
Accentuated
transverse ridges
If
the molar rows aren't properly aligned, points of sharp enamel
will develop, and make a ridged appearance of the molars. If
aligned properly, the points would meet and wear each other
down. The reason for the misalignment can be anatomically, or
it can be secondary to other problems in the mouth, preventing
the normal anatomy and function of the jaws. An example of this
is if a horse has large hooks in the upper front, and the lower
jaw is prevented to slide into a normal porsition. See illustrations
below.
Shear
mouth
You
call the condition shear mouth when the angle of the occlusal
surfaces is extremely steap. Restriction in movement of the
jaws, abnormal chewing pattern and anatomical factors plays
a role in the development of this wear pattern.
This illustration shows normal wear on the left side, shear
mouth on the right side.
