Download Applied Dentistry for the Veterinary Technician

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.
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In normal occlusion, teeth come together in a scissors bite.
 The
mandibular canine tooth resides in the
interdental space of the upper third incisor and the
upper canine tooth.
 The upper fourth premolar tooth overlaps the
lower first molar, which together, constitute the
carnassial teeth.
 Mandibular incisors:
Normal Occlusion
Normal scissors occlusion in a dog:
Rostral view of incisors and canine teeth
Mesocephalic Breeds
Well proportioned skull width and maxillary length;
Ex. Dalmations, Labs, German shepherd dogs.
Dolichocephalic
Narrow skull and long maxilla;
Sight hounds, collies & Siamese cats.
Brachycephalic Breeds
Wide skull with a short maxilla;
Pugs, Bulldogs & Persian cats
Normal Scissors Occlusion:
Lateral view of a dog skull. Premolars interdigitate toward the
opposing interdental space.
Review: Can You Name These Structures?
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.
 There are four classes of malocclusions.
(Class I, II, III, and IV)
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Class I- easily fixed with orthodontic correction OR not needed
Class II-IV are skeletal malocclusions due to differing jaw length
Class I: Rostral Cross-bite
 Maxillary incisors are caudal to the mandibular
incisors.
 Very common malocclusion in veterinary dentistry.
 Thought to occur secondary to retained deciduous
incisors.
 Treatment consists of orthodontic movement or
extraction of the abnormal teeth.

Treat vs. not treat?
Rostral Cross-bite
Class I: Caudal Cross-bite
 Maxillary premolars/molars are positioned lingual to
the mandibular opposing premolars/molars
 Occurs occasionally in dolichocephalic breeds.
 More frequent professional prophylaxis will be
needed for these pets.
Caudal Cross-bite
 The maxillary fourth premolar
is positioned abnormally
inside of the lower first molar
tooth.
 This condition did not require
treatment as the pet had a
comfortable and functional
occlusion (bite).
Class II: Mandibular Distoclusion
 Mandibular brachygnathism:
abnormally short mandible, normal maxilla
 Referred to as “overshot”
 Lack of self-cleaning ability and can create painful
palate abrasions.
 Not an accepted standard in any breed.
*Note: this appearance may also be
due to maxillary prognathism
(abnormally long maxilla)
Mandible is shorter than
the normal maxilla.
Class III: Mandibular Mesiocclussion
 Mandibular prognathism:
abnormally long mandible, normal length maxilla
 Referred to as “undershot”
 These dogs will lose some of their self-cleaning
ability and trap plaque and debris more easily.
 Maxillary incisors can traumatize the mandible.
 Accepted as normal in brachycephalic breeds
such as Bulldogs, Pekingese, Boston terriers, Pugs,
and Persian cats.
*Note: Could also be maxillary brachygnathism (not common)
Mandibular Prognathism
Mandible is
longer than
the maxilla.
Mandibular Prognathism
Asymmetrical Malocclusion
 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.
 A triangular opening (open bite) will also appear in
the incisor area where the affected incisors are
displaced vertically and do not meet.

In severe cases, the tongue protrudes from the open bite.
Wry Mouth: One quadrant develops unevenly
from the other quadrants
Persistent Deciduous Teeth
 Interfere with normal eruption pathway of



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permanent teeth  malocclusion
Are a reservoir for debris  dental disease
Early detection is key!
Common in small breed dogs
Extraction is almost always necessary

Referred to as Interceptive Orthodontics
*Note: deciduous teeth are numbered differently in the
Triadan system (500, 600, 700, 800)
Persistent Deciduous Teeth
 Most permanent teeth will erupt
lingual or palatal to the deciduous
teeth. (babies in front)
 Exception: Permanent maxillary canine teeth will
erupt rostral/mesial to the deciduous canine teeth.
*Why is this significant?
Persistent Deciduous Canine Teeth
Leads to abnormal
attrition
Polydontia
 Supernumerary teeth should not be confused with
retained deciduous teeth.
 Radiographs aid in differentiation.

How?
 Occurs in about 10% of dogs and rarely in cats.
 Unless extra tooth causes crowding, no treatment is
necessary.

Occasionally the extra teeth will erupt in an abnormal angle or
be impacted.
 If crowding  increased chance of periodontal
disease. (Extraction necessary)
Supernumerary Teeth
Deciduous or Permanent?
Hypodontia
 One or more teeth (usually incisors or premolars) do
not form in the dental arcade.
 Many breeds are affected.
 Unerrupted tooth or hypodontia?

How do you confirm?
 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.