Bma Illustrated Medical Dictionary

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 synthesis.)

Rocky Mountain spotted feverA

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-

amphenicolor tetracycline.

rodOne of the 2 specialized types of

nerve cell within the retinaof 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 ulcerA common name for basal

cell carcinoma.

rofecoxiba type of COX-2 inhibitor drug

used to relieve the pain and inflamma-

tion of osteoarthritisand 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-playingThe 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 treatmentA 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, periodontitismay occur.

Treated teeth may turn grey but their

appearance can be restored by bonding

(see bonding, dental), fitting an artificial

crown (see crown, dental), or by bleach-

ing (see bleaching, dental).

Rorschach testA 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.)

rosaceaA chronicskindisorder in which

the nose and cheeks are abnormally red.

The cause is usually unknown, but in

some cases it results from overuse of cor-

ticosteroidcreams. 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 rhinophyma. Treatment includes

oral tetracyclineor topical metronidazole.

Rosacea tends to recur for 5–10 years

before disappearing.

ROOT-CANAL TREATMENT

ROCKY MOUNTAIN SPOTTED FEVER ROSACEA

R

Root

Enamel

Gum Crown

Bone

Area to be

removed

Decay

Nerve

Pulp

Blood

vessels

Repaired

tooth surface

Filling

Filled pulp

cavity

Filled root

canal

BEFORE TREATMENT AFTER TREATMENT