Bma Illustrated Medical Dictionary

disclosing agentsDyes that make the

plaquedeposits on teeth more visible

so that they can be seen and removed.

discoid lupus erythematosusA form

of the chronic autoimmune disorder

lupus erythematosus.

discoloured teethTeeth that are ab-

normally coloured or stained. Extrinsic

stains, on the tooth’s surface, are com-

mon, but are usually easily removed by

polishing. They can be prevented by

regular tooth cleaning. Smoking tobac-

co produces a brownish-black deposit.

Pigment-producing bacteria can leave a

visible line along the teeth, especially

in children. Some dyes in foodstuffs can

cause yellowing; dark brown spots may

be due to areas of thinned enamel

stained by foods. Some bacteria pro-

duce an orange-red stain. Stains may

also follow the use of drugs containing

metallic salts.

Intrinsic stains, within the tooth’s sub-

stance, are permanent. Causes include

death of the pulp or the removal of the

pulp during root-canal treatmentand

the use of the antibiotic tetracyclinein

children. Mottling of the tooth enamel

occurs if excessive amounts of fluoride

are taken during development of the

enamel (see fluorosis). Hepatitisduring

infancy may cause discoloration of the

primary teeth. The teeth of children

with congenital malformation of the bile

ductsmay be similarly affected.

Many stains can be covered or dimin-

ished with cosmetic dental procedures.

disc prolapseA common disorder of

the spine, in which an intervertebral disc

ruptures and part of its pulpy core pro-

trudes. It causes painful and at times

disabling pressure on a nerve root or,

less commonly, on the spinal cord. The

lower back is most commonly affected.

A prolapsed disc may sometimes be

caused by a sudden strenuous action,

but it usually develops gradually as a

result of degeneration of the discs with

age. If the sciatic nerve root is com-

pressed, it causes sciatica, which may be

accompanied by numbness and tin-

gling, and, eventually, weakness in the

muscles of the leg. A prolapsed disc in

the neck causes neck pain and weak-

ness in the arm and hand.

Symptoms improve with time and anal-

gesic drugs. However, in severe cases,

surgical techniques, such as decom-

pressionof the spinal canal or removal

of the protruding material and repair of

the disc, may be necessary.

disc, slippedSee disc prolapse.

diseaseIllness or abnormal functioning

of a body part or parts due to a specific

cause, such as an infection, and identi-

fiable by certain symptomsand signs.

disinfectantsSubstances that kill micro-

organisms and thus prevent infection.

The term is usually applied to strong

chemicals that are used to decontami-

nate inanimate objects, such as items

of medical equipment.

dislocation, jointComplete displace-

ment of the 2 bones in a joint so that

they are no longer in contact, usually as

a result of injury. (Displacement that

leaves the bones in partial contact is

called subluxation.) It is usually accom-

panied by tearing of the joint ligaments

and damage to the membrane that en-

cases the joint. Injury severe enough to

cause dislocation often also causes bone

to fracture. Dislocation restricts or pre-

vents the movement of the joint; it is

usually very painful. The joint looks

misshapen and swells. In some cases,

dislocation is followed by complica-

tions, for example, paralysis.

DISCLOSING AGENTS DISLOCATION, JOINT

D

Fibrous outer

coat of disc

Plane in

view below

Compressed

nerve root

Spinal

Spinal nerves

cord

Bone of

vertebra

Gelatinous core

LOCATION

DISC PROLAPSE

Protruding

core