Applied Dentistry for Veterinary
Technicians
Occlusion and Malocclusion
Occlusion
• Orthodontics studies the way in which the teeth
meet each other (occlude).
• Occlusion is defined as the normal position of the
teeth when the jaws are closed.
• In normal occlusion, the length and width of the
jaws and the position of the teeth in the
respective jaws are in harmony
• The development of the occlusion is determined
primarily by genetic factors.
• The shape of the head affects the positioning of
the teeth.
Mesocephalic Breeds
Well proportioned skull width and maxillary length;
Dalmations, Labs & German shepherds.
Dolichocephalic
Narrow skull and long maxilla;
Sight hounds and Siamese cats.
Brachycephalic Breeds
Wide skull with a short maxilla;
Boxers, Bulldogs & Persian cats
Normal “Scissor” Occlusion
• In dogs, each lower canine tooth occludes in the
interdental space between the upper third incisor and
the upper canine tooth. In other words, the lower canine
tooth occludes in front of the upper canine.
– No incisor or canine tooth surface should touch.
– The upper fourth premolar tooth overlaps the lower first
molar, which together, constitute the carnassial teeth
(shearing teeth).
• In cats, normal occlusion is also a scissor occlusion with
the upper incisors and canines slightly overlapping the
lower incisors and canines slightly overlapping the lower
incisors and canines.
– The upper fourth premolar and lower molar are the feline
carnassial (shearing teeth).
Normal scissors occlusion in a dog:
Rostral view of incisors and canine teeth
Normal Scissors Occlusion:
Lateral view of a dog skull. Premolar cusps interdigitate toward the
opposing interdental space.
Malocclusion
• Malocclusion is an abnormality in the position of
the teeth. It can occur in any of the three head
shapes, but is more common in brachycephalic
breeds.
• It is more common in dogs but also occurs in cats.
• Skeletal malocclusion results from jaw length
and/or width discrepancy (usually inherited).
• Dental malocclusion results from tooth
malpositioning.
• Four classes of malocclusions (Class I, II, III, and
IV).
Mandibular Prognathism
• “Underbite” or “Undershot jaw”
• Lower jaw is of normal length but the upper jaw
is too short.
• These dogs will lose some of their self-cleaning
ability and trap plaque and debris.
• Maxillary incisors can traumatize the mandible.
• Normally seen in brachycephalic breeds such as
Bulldogs, Pekingese, Boston terriers, Pugs, and
Persian cats.
Mandibular Prognathism
Mandible is
Longer than
The maxilla
Mandibular Prognathism
Mandibular Brachygnathism
• “Overshot jaw,” “Overbite,” “Parrot mouth”
• Not as common as mandibular prognathism.
• Mandible is shorter than normal and dog has an
“overbite.”
• Lack of self-cleaning ability and can create painful
hard palate abrasion holes.
• Not an accepted standard in any breed.
• Often occurs in German Shepherd Dogs,
Rottweilers, Collies, Standard Poodles and
Dachshunds.
Upper jaw longer than
the lower jaw.
Mandible is longer
than the maxilla.
Wry Mouth
• Each upper and lower right and left quadrant of the mouth
is independent of the other, resulting in uneven growth
which produces a wry occlusion (wry bite).
• In its mildest form, a one-sided prognathic or brachygnathic
bite forms. In more severe cases, a crooked head and bite
develop with a deviated midline.
• In some cases one side of the head may be smaller and the
nose turned slightly to one side.
• A triangular opening (open bite) will also appear in the
incisor area where the affected incisors do not meet. In
severe cases, the tongue protrudes from the open bite.
Wry Mouth: One quadrant develops unevenly
from the other quadrants
Anterior Crossbite
• Also called “Reverse Scissor.”
• Most common malocclusion in veterinary dentistry.
• Upper incisor teeth are caudal to the lower. May affect
one, several, or all of the incisors.
• Thought to occur secondary to retained deciduous
incisors. Can also be caused by tug-of-war games.
• Most common in medium and large breed dogs.
• May be a skeletal or dental malocclusion.
• Treatment consists of orthodontic movement or
extraction of the abnormal teeth.
Anterior Crossbite
Posterior Crossbite
• Mandible is wider than the maxilla in the
carnassial tooth area (area where the upper
fourth premolar tooth overlaps the lower first
premolar).
• Occurs occasionally in boxers, collies, and
other dolichocephalic (long muzzled) breeds.
• More frequent professional prophylaxis will be
needed for these pets.
Posterior Crossbite
• Notice the upper fourth
premolar tooth is
positioned
in an abnormal position
inside the lower first molar
tooth. This
condition is referred to as
"posterior crossbite". This
condition did
not require treatment as
the pet had a comfortable
and functional
occlusion (bite).
Retained Deciduous Teeth
• This is the most common dental problem seen in
small animal practice.
• Mandibular canines, upper canines, and incisors.
• Interfere with normal eruption pathway of
permanent teeth and are a reservoir for debris.
• Extraction is almost always necessary.
• Most common in small breed dogs.
• Note: All permanent incisors are positioned lingual
to the deciduous teeth (babies in front). Permanent
canine teeth will lie rostral to the deciduous teeth
and appear whiter than the baby tooth (babies
toward the back).
Retained Deciduous Teeth
Polydontia
• Supernumerary teeth should not be confused with
retained deciduous teeth.
• Radiographs aid in differentiation.
• Occurs in about 10% of dogs and rarely in cats.
• Commonly, the mandibular premolars and maxillary
incisors are affected.
• Occasionally the extra teeth will erupt in an abnormal
angle or be impacted.
• Unless extra tooth causes crowding, no treatment is
necessary.
• If crowding is present, periodontal disease may result
and spread to adjacent teeth. (Extraction necessary)
Supernumerary Teeth
Oligodontia
• Also called hypodontia
• One or more teeth (usually incisors or premolars)
do not form in the dental arcade.
• Many breeds are affected.
• In order to determine if tooth is unerrupted or
hypodontia, an x-ray can be taken.
• If permanent tooth is absent, a baby tooth will
often remain in the arch for months to years.
• No treatment; usually does not cause any
problems.