(excess teeth) may be present in a young child. The
excess teeth are called supernumerary
(extra) teeth. Hyperdontia is more common with permanent
teeth but can also occur with primary teeth. Hyperdontia
can usually be diagnosed after radiographic assessment.
Delayed tooth loss or eruption may be a sign of hyperdontia.
Numerous hereditary syndromes include
congenitally missing teeth as a characteristic. One
or several teeth may be missing (hypodontia), or all
the teeth may be missing (anodontia) (e.g., in individuals
with ectodermal dysplasias). Ectodermal dysplasia
involves defects in two or more tissues derived from
the ectoderm — skin, hair, teeth, nails, and
sweat glands. Dental management of hypodontia or anodontia
often involves the use of fixed and removable prostheses
to replace the missing teeth to enhance oral function
||Fig 10. Hypoplasia
A disruption during tooth development
may affect the enamel. Generally such a disruption
is referred to as hypoplasia
(insufficient and/or irregular quantity of enamel).
Tetracycline can cause enamel hypoplasia when taken
during pregnancy or by an infant or young child during
tooth development. Tetracycline should not be used
during pregnancy or by children ages 8 and under.
In addition, Vitamin D deficiency during
tooth development and calcification results in enamel
hypoplasia. The enamel is poorly calcified and may
fail to form at all in some areas. In the dentin,
areas of uncalcified dentin may result.
(hypomineralization of the enamel) is a type of hypoplasia
caused by ingesting excessive quantities of fluoride
during tooth development. Mild fluorosis causes the
teeth to have a white, spotted, or lacy appearance.
Severe fluorosis results in the enamel being markedly
hypomineralized; the enamel may be brown in color
and has a propensity to break and excessively wear.