122
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
The paranasal sinuses are normally air filled. They appear to increase in internal
volume as the horse ages due to the continual eruption of the cheek teeth. When
sinusitis develops as a result of maxillary cheek tooth abnormalities, it can appear as
fluid lines or in more chronic cases, soft tissue accumulation. The thin shelf of bone
termed interdental bone is present between the reserve crown portions of adjacent
teeth. This bone should be wedge-shaped tapering towards the occlusal surface of
the teeth. When chronic periodontal disease exists, particularly in the older horse,
the interdental bone can become blunted as a result of osseous resorption.
Other Diagnostic Imaging
Ultrasound is a powerful and readily available tool for the equine practitioner. It is
however limited by two major impediments when discussing dental disease.
Ultrasound waves are unable to penetrate bone and dental tissue and are completely
reflected by gas. Both are common in the oral cavity. Ultrasound is however useful
for the evaluation of the overlying soft tissues and the temporomandibular joints
(TMJ).
Ultrasound is also a cross sectional imaging modality that occurs in real time.
Currently, high quality, high frequency systems are available in practice dramatically
improving image quality. It is however very important to realize that the diagnostic
utility of ultrasound is highly operator dependent and an in-depth knowledge of the
topographical anatomy is paramount in making accurate diagnoses.
Computed tomography (CT) is anatomic cross sectional imaging that uses x-rays and
x-ray attenuation to create the image. In the skull where there is high subject
contrast (gas, soft tissue, bone and enamel) computed tomography is ideal. The
principles of radiology and the search for radiographic findings compatible with a
given disease are applied to the images obtained in CT. The benefit of CT is that the
images are cross sectional eliminating superimposition of the contralateral dental
arcade or the bones of the skull as a complicating factor.
At most institutions, computed tomography requires that the horse is placed under
general anesthesia and this is considered to be the major disadvantage. Currently,
standing skull CT is performed at a few sites. The disadvantage of general anesthesia
is largely offset by the additional information gained. Most modern CT scanners are
very fast and once the horse is positioned the average horse head can be scanned
within seconds to minutes. CT images have very high resolution and are generally
considered to have high sensitivity and specificity for diseases of the skull including
dental disease.
Nuclear scintigraphy is another alternate imaging modality that can be very useful in
dental disease. Scintigraphy is a functional planar image. As with radiology the
images obtained are a two dimensional representation of three dimensional anatomy
and superimposition is a problem. The benefit of scintigraphy is that the images are
created by emission of radiation from the patient and the radiation is most intense in
regions of active bone or tooth remodeling. This renders a functional image (bone
turnover = abnormality) that is very sensitive. The disadvantage of this modality is
low specificity and poor resolution complicating accurate anatomic localization of the
lesion. This technique is very sensitive but trauma, infection or areas of bone
growth will appear similar.
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