ROCKY MOUNTAIN SPOTTED FEVER
ROSACEA
ROOT-CANAL TREATMENT
cells, DNA carries the instructions and
RNA helps decode them. In some
viruses
the instructions are held by RNA instead.
(See also
nucleic acids; protein s^mthesis.)
Rocky Mountain spotted fever A
rare, infectious disease causing fever
and a rash with spots that spread over
the body, darken, enlarge, and bleed.
The disease occurs in North and South
America and is caused by a
rickettsia
transmitted from small mammals by
tick
bites. Treatment is with
chlor-
amphenicol
or
tetracycline.
rod One of the 2 specialized types of
nerve cell within the
retina
of the eye that
convert light energy into nerve impulses.
The rods are very sensitive and can res-
pond to very dim light. (See also
cone.)
rodent ulcer A common name for
basal
cell carcinoma.
rofecoxib a type of
COX-2 inhibitor drug
used to relieve the pain and inflamma-
tion of
osteoarthritis
and
rheumatoid
arthritis.
Gastrointestinal side effects are
less likely than with other
nonsteroidal
anti-inflammatory drugs
(NSAIDs), but
mouth ulcers, sleep disturbance, and
muscle cramps may occur.
role-playing The acting out of a role
(the pattern of behaviour expected in a
given situation). The phrase "sick role"
describes the type of passive behaviour
expected and allowed of a patient; peo-
ple with social or emotional problems
may unconsciously adopt this role to
gain sympathy and understanding.
root-canal treatm ent A dental proce-
dure performed to save a tooth in which
the pulp (see
pulp
,
dental)
has died or
become untreatably diseased, usually
as the result of extensive dental
caries.
The pulp is removed through a hole
drilled in the crown. An antibiotic paste
and a temporary filling are packed in. A
few days later, the filling is removed and
the canals are checked for infection.
When no infection is detected the cavity
is filled and the roots are sealed with
cement. If the cavity is not filled com-
pletely,
periodontitis
may occur.
Treated teeth may turn grey but their
appearance can be restored by bonding
(see
bondingr
, dental),
fitting an artificial
crown (see
crown
,
dental),
or by bleach-
ing (see
bleaching, dental).
Rorschach test A psychological test
based on a person's responses to a set of
ink-blot pictures. The test is now rarely
used. (See also
personality tests.)
rosacea A chronic
skin
disorder in which
the nose and cheeks are abnormally red.
The cause is usually unknown, but in
some cases it results from overuse of
cor-
ticosteroid
creams. The disorder is most
common among middle-aged women.
Rosacea may develop into permanent
redness of the skin, sometimes with acne-
like pustules. In elderly men, it may
lead to
rhinoph^mia.
Treatment includes
oral
tetracycline
or topical
metronidazole.
Rosacea tends to recur for 5-10 years
before disappearing.
494
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