Occlusion

2 Occlusion


Occlusion is the term used to describe how the teeth contact each other (occlude with each other). Malocclusion is an abnormality in the position of the teeth. Malocclusion can result from jaw length/width discrepancies (skeletal malocclusion), from tooth malpositioning (dental malocclusion), or a combination. Malocclusion is common in the dog, but also occurs in cats. The clinical significance of malocclusion is that it may cause discomfort and sometimes pain to the affected animal. In some cases, it may be the direct cause of severe oral pathology. It is consequently important to diagnose malocclusion early in the life of the animal so that preventative measures can be taken.


The development of the occlusion is determined by both genetic and environmental factors. While the specific genetic mechanisms regulating malocclusion are unknown, a polygenic mechanism is likely and explains why not all siblings in successive generations are affected by malocclusion to the same degree, if they are affected at all. With a polygenic mechanism, the severity of clinical signs is linked to the number of defective genes.


It is known that the following are inherited:


• Jaw length

• Tooth bud position

• Tooth size.

It is also known that the development of the upper jaw, mandible and teeth is independently regulated genetically. Disharmony in the regulation of these structures results in malocclusion. Alteration of jaw growth by hormonal disorder, trauma or functional modification may also result in skeletal malocclusion. Although tooth bud position is inherited, various events during development and growth may alter the definitive tooth position.



NORMAL OCCLUSION


The shape of the head (mesocephalic, dolicocephalic, brachycephalic) affects the positioning of the teeth.



MESOCEPHALIC DOG


The mandible is shorter and less wide than the upper jaw. This means that:


• There is a scissor bite of the incisor teeth (Fig. 2.1).

• There is interdigitation of the canine teeth (Fig. 2.2).

• The incisor scissor bite and canine interdigitation form the dental interlock, which coordinates rostral growth of the upper jaw and mandible.

• There is interdigitation of the premolars (Fig. 2.3).

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Occlusion

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