Critical Reviews in Oral Biology & Medicine, Vol 11, 481-495, Copyright © 2000 by International & American Associations for Dental Research
The chemistry of enamel caries
C. Robinson, R. C. Shore, S. J. Brookes, S. Strafford, S. R. Wood and J. Kirkham
University of Leeds, Leeds Dental Institute, Division of Oral Biology, United Kingdom. orl6cr@oralbio.novell.Leeds.ac.uk
The chemical changes which occur during the process of carious destruction
of enamel are complex due to a number of factors. First, substituted
hydroxyapatite, the main component of dental enamel, can behave in a very
complex manner during dissolution. This is due not only to its ability to
accept substituent ions but also to the wide range of calcium phosphate
species which can form following dissolution. In addition, the composition,
i.e., the extent of substitution, changes throughout enamel in the
direction of carious attack, i.e., from surface to interior. Both surface
and positively birefringent zones of the lesion clearly illustrate that
carious destruction is not simple dissolution. Selective dissolution of
soluble minerals occurs, and there is the probability of reprecipitation.
The role of fluoride here is crucial in that not only does it protect
enamel per se but also its presence in solution means that rather insoluble
fluoridated species can form very easily, encouraging redeposition. The
role of organic material clearly needs further investigation, but there is
the real possibility of both inhibition of repair and facilitation of
redeposition. For the future, delivering fluoride deep into the lesion
would appear to offer the prospect of improved repair. This would entail a
delivery vehicle which solved the problem of fluoride uptake by apatite at
the tooth surface. Elucidation of the role of organic material may also
reveal putative mechanisms for encouraging repair and/or protecting the
enamel mineral.
