Advances in Dental Research, Vol 9, 244-254, Copyright © 1995 by International & American Associations for Dental Research
The role of microbiology in models of dental caries
P. D. Marsh
Department of Microbial Pathogenicity, Centre for Applied Microbiology and Research, Salisbury, England.
Models of dental caries (laboratory, animal, and human in situ models) vary
markedly in their microbiological complexity. Laboratory models range from
mono-cultures of cariogenic species providing an acidic challenge to
enamel, to the development of diverse mixed cultures growing on a
habitat-simulating medium in an artificial mouth or chemostat. The latter
systems are of value in determining either mechanisms of action or
cause-and-effect relationships--e.g., between dietary components or
antimicrobial agents and the microflora. Laboratory models have also shown
that the sensitivity of oral bacteria to inhibitors is markedly reduced
when growing in biofilms such as dental plaque. Animal models have proved
unequivocally that caries is an infectious and transmissible disease. Their
use has enabled comparisons to be made of (a) the cariogenic potential of
different bacterial species, (b) the role of the diet, and (c) the effects
of potential anti-caries agents. It has been claimed that no
caries-protective agent currently in use has failed a rodent test. In situ
human models have been designed to permit the development of "natural"
plaque on standardized enamel surfaces freely exposed to the human oral
environment. The microflora that develops on unadulterated surfaces is
similar in composition to that found at comparable sites on vital teeth.
Demineralization can be accelerated by the inoculation of additional
cariogenic bacteria coupled with either intra- or extra-oral sucrose
rinses. The increased realism associated with the transition from
laboratory to human in situ models is countered by a reduced ability to
control or manipulate the system for experimental purposes. Thus a
hierarchy of tests is needed for the study of anti-caries agents, each
requiring a varying degree of microbiological complexity.
