Advances in Dental Research, Vol 3, 219-233, Copyright © 1989 by International & American Associations for Dental Research
Macroscopic and scanning electron microscopic appearance and hardness values of developmental defects in human permanent tooth enamel
G. W. Suckling, D. G. Nelson and M. J. Patel
Defects present in 12 human permanent teeth were classified on the basis of
their macroscopic appearance as hypoplasia (three teeth), diffuse opacities
(three teeth), white demarcated opacities (one tooth but two defects), or
yellow demarcated opacities (five teeth but six defects). The hardness
values and SEM appearance of the defective enamel were determined after the
teeth were sectioned through the lesion(s) and were distinctive for each
type of defect. The thin enamel of the hypoplastic lesions was either
opaque (with reduced hardness values) or translucent (with near-normal
hardness values and sometimes a change in prism orientation external to an
incremental line). The enamel of the diffuse and demarcated opacities was
of normal thickness. The changes in the macroscopic and SEM appearance, and
the reduced hardness values of the diffuse patchy opacities, were
restricted to the outer 150 microns of the enamel. The demarcated opacities
varied in position and depth, and in places had a clearly marked boundary
with the adjacent normal enamel. Hardness values were related to color
change, with yellow lesions being softer than white. Although prism
direction was normal within demarcated opacities, prism outlines were less
distinct. The findings suggest that temporary and permanent dysfunction of
ameloblasts can occur in both secretory and maturation phases, influencing
the final appearance of the lesion.
