1. 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.
There are four classes of malocclusions.
(Class I, II, III, and IV)
Class I- easily fixed with orthodontic correction OR not needed
Class II-IV are skeletal malocclusions due to differing jaw length

2. 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?

3. Rostral Cross-bite

4. Class I: Caudal Cross-bite
Maxillary premolars/molars are positioned lingual to the mandibular opposing premolars/molars
Occurs occasionally in dolichocephalic breeds.
Treatment?
Extractions or more frequent professional prophylaxis will be needed for these pets.

5. 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.

6. Class II: Mandibular Distoclusion
Appears as mandibular brachygnathism-
abnormally short mandible, normal maxilla
Referred to as “overshot”
Lack of self-cleaning ability and can create painful hard palate abrasions.
Not an accepted standard in any breed.

7. Tuna the Dog

8. Class III: Mandibular Mesiocclussion
Appears as 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.

9. Mandibular Prognathism
Mandible is
longer than
the maxilla.

10. Mandibular Prognathism

11. 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.

12. Wry Mouth: One quadrant develops unevenly from the other quadrants

13. Persistent Deciduous Teeth
Interfere with normal eruption pathway of 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)

14. Persistent Deciduous Canine Teeth

16. Polydontia
Supernumerary teeth should not be confused with retained deciduous teeth.
These are extra ___________ teeth
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)

17. Supernumerary Teeth

19. Hypodontia
One or more teeth (usually incisors or premolars) do not form in the dental arcade.
Un-errupted permanent tooth or hypodontia?
How do you confirm?
If permanent tooth is absent, a deciduous tooth will often remain in the arch for months to years.
No treatment; usually does not cause any problems.