dentureAn appliance that replaces miss-
ing natural teeth. It consists of a metal
and/or acrylicbase mounted with porce-
lain or acrylic teeth. The artificial teeth
are matched to be similar to the origi-
nal teeth. Denture baseplates, created
from impressions taken from the upper
and lower gums, fit the mouth accurately.
deodorantA substance that removes un-
pleasant odours, especially body odours.
deoxyribonucleic acidSee DNA; nu-
cleic acids.
dependencePsychological or physical
reliance on persons or drugs. An infant is
naturally dependent on parents, but, as
he or she grows, dependence normally
wanes. Alcohol and drugs may induce a
state of physical or emotional depen-
dence in users. A person who has a
dependency may develop physical symp-
toms or emotional distress if deprived
of the drug. (See also alcohol depen-
dence; drug dependence.)
depersonalizationA state of feeling
unreal, in which there is a sense of
detachment from self and surroundings.
Depersonalization is often accompa-
nied by derealization. It is rarely serious
and usually comes on suddenly and may
last for moments or for hours. Deper-
sonalization most often occurs in people
with anxiety disorders. Other causes in-
clude drugs and temporal lobe epilepsy.
depilatoryA chemical hair remover, such
as barium sulphide, used in the form of
a cream or paste for cosmetic reasons
and to treat hirsutism.
depot injectionAn intramuscular in-
jection of a drug that gives a slow,
steady release of its active chemicals
into the bloodstream. Release of the
drug is slowed by the inclusion of sub-
stances such as oil or wax. The release
of the active drug can be made to last
for hours, days, or weeks.
A depot injection is useful for patients
who may not take their medication cor-
rectly. It also prevents the necessity of
giving a series of injections over a short
period. Hormonal contraceptives (see
contraception, hormonal methods of),
corticosteroid drugs, and antipsychotic
drugsmay be given by depot injection.
Side effects may arise due to the uneven
release of the drug into the bloodstream.depressionFeelings of sadness, hope-
lessness, and a loss of interest in life,
combined with a sense of reduced emo-
tional well-being. Symptoms vary with the
severity of the depression. It may cause
loss of appetite, difficulty in sleeping,
tiredness, loss of interest in social
activities, concentration problems,and,
sometimes, anxiety. The severely depres-
sed may have thoughts of suicideand
feelings of worthlessness. Hallucinations
or delusionsmay occur in extreme cases.
Often, there is no single obvious cause.
It may be triggered by physical illnesses
(such as a viral infection), hormonal
disorders (such as hypothyroidism), or
hormonal changes after childbirth (see
postnatal depression). Some drugs, such
asoral contraceptives, may contribute.
Inheritance may play a part. Some peo-
ple become depressed in winter (see
seasonal affective disorder syndrome).
Aside from these causes, social and
psychological factors may play a part.
Treatment usually includes a form of
psychological treatment, such as cogni-
tive–behavioural therapyor counselling
and/or antidepressant drugs. Antidepres-
sant drugs are usually effective over a
period of time. ECT(electroconvulsive
therapy) is infrequently used for treat-
ing severely depressed people who have
not responded to other treatments.
derealizationFeeling that the world
has become unreal. It usually occurs
together with depersonalizationand may
be caused by fatigue, hallucinogenic
drugs, or disordered brain function.
dermabrasionRemoval of the surface
layer of the skin by high-speed sanding
to improve the appearance of scars,
such as from acne, or to remove tattoos.
dermatitisInflammation of the skin,
sometimes due to an allergy. Dermatitis
is the same as eczema,and the terms
can be used interchangeably.
Seborrhoeic dermatitis is a red, scaly,
itchy rash that develops on the face,
scalp, chest, and back. The rash often
develops during times of stress and is
probably caused by an excess growth of
yeast on the skin. Corticosteroid drugs
and/or drugs that kill microorganisms
may help. Contact dermatitis results from
a reaction to some substance that comesDENTURE DERMATITISD