The term “imperfect
dentition” is most often used by dog breeders to refer to a deviation
from the breed standard in the number of teeth. However, the term
also refers to can any incorrect variation in the size, type, or
alignment of teeth in a dog’s mouth. Problems with dentition
tend to run in families, and most are thought to be polygenic in nature.
However, some of the problems may be influenced by external
(non-genetic) factors. Some common improper variances in dentition
are discussed below.
Missing Teeth: A
puppy has a set of 28 “milk” teeth (baby teeth). The total
teeth in an adult canine should be 42 (20
in the upper jaw and 22 in the lower). Missing
teeth are considered a fault. The teeth most likely to be absent
are premolars. However, molars and sometimes incisors may
occasionally fail to develop. The more teeth that are missing, the
less functional the bite becomes.
Retained Teeth: Normally,
the roots of the milk teeth are absorbed as adult teeth begin to form
and the milk tooth is pushed out as the new tooth emerges.
Retained baby teeth can cause a “malocclusion,” or misalignment of
the teeth. For this reason, retained milk teeth should be removed
by a veterinarian as soon as possible.
Enamel Hypoplasia: Areas
of defective enamel formation. This can be genetic, but can also
be caused by viral infections or trauma to the developing tooth.
Improper
Alignment/Malocclusion: Tooth alignment is affected by several
genetic factors including jaw structure, lip structure, number of teeth,
and retention of baby teeth. However tooth placement can in some
cases be caused by an injury to the jaw or habits such as excessive
chewing, repeated carrying or fetching of very hard objects (such as
rocks or a training dummy). A dog’s “bite” is evaluated
based on the way his teeth fit
when his upper and lower jaws are closed.
Examples are provided below.
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Scissors
Bite: The upper
incisors just overlap and touch the lower incisors. This
arrangement prevents wear on the incisors and keeps the teeth in
alignment. A scissors bite is the ideal bite for many
breeds, including the Shiloh Shepherd.
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Level
Bite: The incisors
meet edge to edge. A level bite is acceptable, but not ideal.
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Overshot Bite/Brachygnathism:
The upper jaw is longer than the lower and the upper
front incisors project beyond the lower front incisors.
Produces a “chinless” or parrot-like appearance.
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Undershot Bite/
Prognathism: The lower jaw is longer than the upper jaw,
similar (depending on the severity of the malocclusion) to the bite
of a Bulldog.
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Wry Bite/WryMouth:
When one side of the
jaw has grown longer than the other, resulting in malocclusion of
the teeth in the front of the jaw. Neither the canines nor the
incisors line up squarely in a wry mouth.
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Anterior Crossbite:
When some, but not all, of the lower incisors extend beyond the
upper incisors but all other teeth mesh properly.
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Crowded Bite: When
the teeth are overcrowded, sometimes overlapping. Dogs with
crowded bites sometimes have narrow jaws/muzzles, or retained puppy
teeth.
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Crooked Teeth: Can be
caused by crowding in a too-small or too-narrow jaw and can also be
the result of damage to the mouth.
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| Dropped
Incisors:
When the center lower incisors are shorter than normal. Sometimes
they will tip slightly outward and, when viewed in profile, may give
the appearance of a bite that is slightly undershot. Dropped
incisors tend to run in families. |
