Page 760 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.1 The upper gastrointestinal tr act 735

VetBooks.ir Premature extraction of the deciduous premolar rostral to the mandibular ones with no occlusion
or partial occlusion in milder cases. The heritabil-
caps may lead to exposure of the occlusal surface of
the permanent dentition before the complete matu-
autosomal dominant with low penetration and mul-
ration of the cementum, potentially resulting in an ity of this condition is unclear, but it appears to be
increased risk of caries. tifactorial, resulting in a low heritability incidence of
Permanent supernumerary dentition can be the condition. Prognathism or sow mouth (Class 3
asymptomatic, in which case exodontia may be con- malocclusion) is a rare condition in which the inci-
traindicated. In those clinically significant cases, sive bone grows at a less rapid rate than the mandible
dental removal is indicated but can be complicated resulting in ‘underbite’.
by the impaction and overcrowding associated with
the additional teeth. Clinical presentation
The condition is diagnosed in foals by oral exami-
BRACHYGNATHIA AND PROGNATHIA nation. Grazing may be impaired where there is no
incisor occlusion (termed severe ‘overjet’) but most
Definition/overview horses compensate sufficiently for a satisfactory
A relative asymmetric growth rate between the ros- weight gain. The cosmetic appearance may be preju-
tral mandible and incisive bone resulting in an over- dicial to a show career. The occlusion of the cheek
shot (Class 2 malocclusion) (Fig. 4.28) or undershot teeth is usually not affected and normal mastication
incisive bone (Class 3 malocclusion) (Fig. 4.29). is possible. Occasionally, the deviation occurs caudal
to the interdental space and CT can be helpful to
Aetiology/pathophysiology reveal caudal malocclusions.
Brachygnathism or parrot mouth (Class 2 maloc-
clusion) is a common disorder in which the incisive Differential diagnosis
bone overgrows the rostral mandible causing a mal- Trauma to the rostral mandible and wry nose should
occlusion of the incisors. The maxillary incisors lie be considered.

4.28 4.29

Fig. 4.28 Class 2 malocclusion described as parrot Fig. 4.29 Class 3 malocclusion with the lower jaw
mouth or overbite. undershot and overgrowth of the lower incisors.
(Photo courtesy Graham Munroe)