All of the hypoplastic AI subtypes are characterized by the primary
feature of deficient amount of enamel formed. The decreased amount
of enamel varies in the different subtypes and can be characterized
by enamel that is pitted, has grooves or furrows, has large areas
of missing or very thin enamel surrounded by more normal enamel,
or enamel that is very thin over the entire tooth crown. Witkop’s
clinical classification of hypoplastic AI recognizes seven subtypes
[6].
The four main AI types are shown in Table 1 and brief descriptions
of the 14 subtypes are provided. After the name of each subtype
are the letters designating mode of inheritance (e.g. AD = autosomal
dominant, AR = autosomal recessive, and X-linked). For additional
explanation of these different modes of Mendelian Inheritance see
the section on Mendelian Inheritance.
Table1 [8]
Clinical
and Hereditary Characteristics
of Four Main AI Types
|
| Type
|
Clinical
Appearance |
Enamel
Thickness |
Radiographic
Appearance
|
Inheritance |
| Hypoplastic
(Type I)
|
Crowns size varies from
small to normal, small teeth may lack proxmial contacts, color
varies from normal to opaque white – yellow brown |
Varies from thin and smooth
to normal thickness with grooves, furrows and/or pits |
Enamel has normal to slightly
reduced contrast/ thin |
Autosomal dominant, recessive,
or X-linked |
| Hypomaturation
(Type II)
|
Varies from creamy opaque
to marked yellow/brown, surface of teeth soft and rough, dental
sensitivity and open bite common |
Normal thickness with enamel
that often chips and abrades easily |
Enamel has contrast similar
to or > than dentin, unerupted crowns have normal morphology |
Autosomal dominant, recessive,
or X-linked |
| Hypocalcified
(Type III)
|
Opaque white to yellow-brown,
soft rough enamel surface, dental sensitivity and open bite
common, heavy calculus formation common |
Normal thickness with enamel
that often chips and abrades easily |
Enamel has contrast similar
to or < dentin, unerupted crowns have normal morphology |
Autosomal dominant, recessive |
Hypomaturation/
Hypoplasia/
Taurodontism
(Type IV) |
White/Yellow- Brown mottled, teeth can appear
small and lack proximal contact |
Reduced, hypomineralized areas and pits |
Enamel contrast normal to slightly > dentin,
large pulp chambers |
Autosomal dominant |
|
