Journal of Dental Research, Vol 72, 923-930, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Scanning microradiographic study of the kinetics of subsurface demineralization in tooth sections under constant-composition and small constant-volume conditions
X. J. Gao, J. C. Elliott and P. Anderson
Department of Child Dental Health, London Hospital Medical College, United Kingdom.
The kinetics of subsurface demineralization of tooth sections has been
studied in real-time by scanning microradiography (SMR). Demineralization
was carried out: (1) with a large volume of solution buffered to pH = 4 to
maintain a constant composition; and (2) in a small constant volume
(approximately 3 mL), buffered initially at pH = 4, so that the degree of
saturation at the tooth surface increased as the tooth dissolved. At
constant composition, the change in lesion depth, Y, with time, T, followed
a linear relation, Y = a + bT, for T > 44 +/- 5 h. Before this time, the
relation could be approximated by a linear one with different a and b
constants. At constant volume, Y = q(1-e-r(T + s)) for all T, where q, r
and s are constants. Similar relations, with different constants, were
found for the mineral loss per unit area of lesion exposed to acid. These
results showed that the process of demineralization under the rather severe
conditions used was essentially a surface-controlled process. The change of
slope at approximately 44 h and the presence of the constant s in the
exponential function were attributed to a change in kinetics after
formation of the surface layer.
