Journal of Dental Research, Vol 65, 89-94, Copyright © 1986 by International & American Associations for Dental Research Online Journals
A theoretical analysis of the effects of plaque thickness and initial salivary sucrose concentration on diffusion of sucrose into dental plaque and its conversion to acid during salivary clearance
C. Dawes and G. H. Dibdin
A mathematical model, written in FORTRAN, has been developed to simulate
the interrelated processes of salivary sucrose clearance from the mouth,
diffusion of sucrose into dental plaque, and conversion of sucrose to acid
and glucan. Reaction of acid with enamel is not included in the model. A
total of 28 parameters can be varied by the user, and the relative
importance of the different factors affecting acid formation can be
assessed. The output of the program gives sucrose and acid concentrations
and pH at different depths within the plaque. The initial variables studied
were plaque thickness, the salivary sucrose concentration, and the duration
of exposure of the plaque to sucrose. Stephan curves typical of those
recorded in vivo were generated by the model. With any particular salivary
sucrose concentration, there was an optimum plaque thickness at which a
minimum pH was achieved at the enamel surface, with very thin or thick
plaque samples producing a smaller pH fall. With thick plaque, the minimum
pH was often not achieved at the inner surface but at some intermediate
depth, which may explain the location of early caries lesions in fissures.
The extent of the pH fall at the inner surface and the duration of the
pH-minimum region of the Stephan curve were directly related to the initial
salivary sucrose concentration and to the duration of exposure to sucrose
prior to normal salivary clearance. Simulation of a water rinse at as short
a time as two min after the beginning of normal salivary sugar clearance
showed that this procedure had only a very small effect on the shape of the
Stephan curve.(ABSTRACT TRUNCATED AT 250 WORDS)
