DENDRITIC ULCER
DENTAL EXAMINATION
the
central nervous system
(CNS) or be
part of the
peripheral nervous system.
Patches of demyelination are visible
on
MRI
of the brain in
multiple sclerosis
.
The cause of the demyelination is not
known. In many cases, demyelination
attacks alternate with periods of partial
or complete recovery of nerve function.
In
encephalomyelitis
, there is inflamma-
tion of nerve cells within the CNS and
sometimes areas of demyelination.
dendritic ulcer
A type of
corneal ulcer
commonly caused by infection with
her-
pes simplex
virus.
dengue
A tropical disease caused by a
virus spread by the mosquito
AEDES
aegypti.
Symptoms include fever, head-
ache, rash, and joint and muscle pains,
which often subside after about 3 days.
There is no specific treatment for dengue.
Prevention involves protection against
mosquito bites (see
insect bites
).
densitometry
An imaging technique that
uses low-dose
X-rays
to measure bone
density, as determined by the concen-
tration of calcified material. It is used to
diagnose and assess the severity of
osteoporosis
, especially in the spine and
femur, and to assess its response to
treatment. During the procedure, X-rays
are passed through the body. A computer
assesses the amount of X-rays absorbed
by the body and uses this information
to calculate the bone density.
density
The “compactness” of a subs-
tance, defined as its mass per unit
volume. In radiology, the term relates to
the amount of radiation absorbed by the
structure being X-rayed. Bone, which ab-
sorbs radiation well, appears white on
X-ray film. A lung, which contains mostly
air, absorbs little radiation and is dark
on film. The same holds true in
CT scan-
ning
and
MRI.
(See also
specfic gravity.)
dental emergencies
Injuries or disor-
ders of the teeth and gums that require
immediate treatment because of severe
pain and/or because delay could lead to
poor healing or complications. A dis-
lodged tooth can be reimplanted (see
reimplantation, dental
) successfully if it is
done without delay. A partly dislodged
tooth should be manipulated back into
the socket straight away. Other dental
emergencies include a broken tooth
(see
fracture, dental
), severe
toothache
,
which may be caused by an abscess
(see
abscess, dental),
and Vincent's dis-
ease (see
gingivitis, acute ulcerative
).
dental examination
An examination of
the mouth, gums, and teeth by a dentist
as a routine check or as part of the
assessment a person complaining of a
symptom. Routine examinations enable
tooth decay and gum disease to be
detected and treated at an early stage.
During a routine dental examination,
the dentist uses a metal instrument to
X-ray
generator
DENSITOMETRY
Foam support
for legs
X-ray detector picks
up unabsorbed
_X-rays
i\
---
u
1
Monitor displays X-ray
image of spine
164
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