Shaping the future of animal health
Dentistry & Oral health

Malocclusion

Cause

photo7.jpg
Photo 7 - Labrador with brachygnatic
mandible / retrognathia inferior : the
mandible is shortened, the mandible is
shorta compared tot the maxilla.

  • Jaw length or width discrepancy (skeletal malocclusion) 
  • Tooth malpositioning (dental malocclusion) 
  • Combination of both

Skeletal malocclusions are most likely to be inherited (polygenic mechanism) unless a developmental influence (e.g. trauma, hormonal disease) can be reliably identified. 
Pure dental malocclusion, unless known to have a breed or family predisposition (e.g. lance teeth in Shetland Sheepdog), should have the benefit of a doubt and not be considered inherited.

Definitions

photo8.jpg
Photo 8 - Crowding of teeth in the
maxilla in a boxer Premolar teeth
are rotated.

The terms brachygnathia, prognathia, retrognathia should always be used with reference to either upper or lower jaw (i.e. should be prefixed by mandibular ..., maxillary ... as appropriate)


Brachygnathia: shortened jaw (Photo 7)
E.g. mandibular brachygnathism: shortened lower jaw
A shortened jaw is evidenced by rotation and crowding of teeth(Photo 8)

Prognathia: lengthened jaw
E.g. mandibular prognathism: lengthened lower jaw
A lengthened jaw is evidenced by abnormally large interdental spaces

Retrognathia: jaw short as compared to other jaw
E.g. mandibular retrognathism: lower jaw short as compared to upper jaw

 

Consequences of Malocclusion

photo9.jpg
Photo 9 - Damage of the palatal
mucosa as a consequence or
retrognathia inferior.

Malocclusions may cause pain and discomfort to the animal and may be the direct cause of severe oral pathology. (Photo 9)
It is essential to diagnose malocclusions early in life. The aim of treatment is always to make the animal comfortable with a functional bite; esthetic considerations should be of no importance in veterinary medicine.

Some common Malocclusions

photo10.jpg
Photo 10 - Anterior crossbite : note
premolar occlusion. Upper P2 occludes
with lower P3. This case is a skeletal
malocclusion.

Rostral (Anterior) Crossbite

reverse scissor occlusion of one or more incisors (Photo 10) 

  • less commonly caused by dental malocclusion (if only the incisors are in abnormal position)
  • most often this is a skeletal malocclusion (maxillary brachygnathism, mandibular prognathism)
  • very common malocclusion !

Caudal (Posterior) Crossbite

upper premolar/molar occludes lingually to the lower 

  • rare malocclusion, seen most often in narrow, long-nosed breeds.

 

Mesio-occlusion and disto-occlusion of premolar teeth

  • most often in combination with incisor malocclusion
  • common malocclusion
  • often the consequence of a skeletal malocclusion

Lingual displacement of mandibular canine teeth, Upright canine teeth

  • the mandibular canine teeth impinge on the hard palate. (Photo 11)
  • Cause : 
    - a skeletal abnormality (narrow mandible, micrognathia)
    - a dental abnormality (linguoversion or linguoposition of canine teeth, which may be caused by retained deciduous canines). 
  • common, painful condition

photo11.jpg
Photo 11 - Lingual displacement of
lower canine tooth. The crown tip of
the canine tooth is impinging on
the palate.

Rostroversion of upper canine teeth

  • also known as lance teeth, tusk teeth 
  • breed predisposition : Shetland Sheepdog (but can occur in other breeds such as the Italian Greyhound)