Bma Illustrated Medical Dictionary

cross-matchingA procedure to deter-

mine compatibility between the blood

of a person requiring a blood transfusion

and that of a donor. Red blood cells from

one person are combined with serum

from the other. Clumping of red blood

cells indicates the presence of antibodies,

showing the blood is not compatible.

croupA common condition in infants

and young children in which narrowing

and inflammation of the airways causes

hoarseness, stridor (a grunting noise

during breathing), and a barking cough.

Croup may be caused by a viral or bac-

terial infection that affects the larynx,

epiglottis (see epiglottitis), or trachea.

Other causes include diphtheria, allergy,

spasm caused by deficient calciumin the

blood, and inhalation of a foreign body.

Most cases are due to a viral infection

and are mild.

Humidifying the air can help to make

breathing easier. Nebulized cortico-

steroid drugs(see nebulizer) and oxygen

may be prescribed. Infections are treat-

ed with antibiotic drugs.

crowding, dentalSee overcrowding,

dental.

crown, dentalAn artificial replacement

for the crown of a tooththat has be-

come decayed, discoloured, or broken.

A porcelain crown is usually used on

front teeth, but back teeth require the

greater strength of a crown made from

gold or porcelain fused to metal.

A crown may be fitted by filing the nat-

ural tooth to form a peg and cementing

the crown over the top. If the tooth is

crisisA term for a turning point in the

course of a disease (either the onset of

recovery or deterioration), or for a dis-

tressing and difficult episode in life.

crisis interventionThe provision of

immediate advice or help by a variety of

agencies such as social services depart-

ments to people with acute personal or

sociomedical problems.

criticalA term used to mean seriously ill

or to describe a crucial state of illness

from which a patient may not recover.

Crohn’s diseaseA chronic inflamma-

tory disease affecting the gastrointestinal

tract. In young people, Crohn’s disease

usually affects the ileum, causing spasms

of abdominal pain, diarrhoea, loss of

appetite, anaemia, weight loss, and mal-

absorption. In elderly people, the rectum

is more often affected, causing rectal

bleeding.In both groups, the disease

may also affect the anus, the colon and,

rarely, the mouth, oesophagus, stom-

ach, and duodenum.

Complications include obstructions in

the intestine; chronic abscesses; inter-

nal fistulas (abnormal passageways)

between intestinal loops; and external

fistulas from the intestine to the skin of

the abdomin skin or around the anus.

Complications in other parts of the

body may include inflammation of the

eye, severe arthritisin various joints,

ankylosing spondylitis, and skin disor-

ders (including eczema).

Investigatory procedures may include

sigmoidoscopy and X-rays using barium

(see barium X-ray examinations). Colon-

oscopy and biopsymay help distinguish

the disease from ulcerative colitis.

Sulfasalazineand related drugs, and

corticosteroid drugsmay be prescribed.

A high-vitamin, low-fibre diet may be

beneficial. Acute attacks may require hos-

pital treatment, and many patients need

surgery. The symptoms fluctuate over

many years, eventually subsiding in some

patients. If the disease is localized, a

person may remain in normal health.

crossbiteA type of malocclusion in

which some or all of the lower front

teeth overlap the upper front teeth.

cross-eyeA type of strabismus(squint)

in which one or both eyes turns inwards

relative to the other.

CRISIS CROWN, DENTAL

C

Peg of the

original tooth

Natural tooth

CROWN, DENTAL

Crown