Advances in Dental Research, Vol 8, 134-143, Copyright © 1994 by International & American Associations for Dental Research
Human experimental caries models: intra-oral environmental variability
O. Fejerskov, B. Nyvad and M. J. Larsen
Department of Dental Pathology, Operative Dentistry and Endodontics, Royal Dental College, Faculty of Health Sciences, Aarhus University, Denmark.
In situ caries models serve purposes other than just being a simpler way to
obtain data than running a clinical trial. However, variation in
information obtained not only among individuals but also, in particular,
depending on different locations of the models within the oral cavity have
so far been given little attention. In the present review, the aim has been
to characterize the different designs of in situ caries models and to
describe some important factors which may vary within the oral cavity and
thus influence the outcome of the way the different in situ models are
used. Advantages and disadvantages of in vivo models vs. in situ models are
discussed. In the latter case, the distinction is made between dental
appliance models and so-called "single tooth" models. The review concludes
that in situ models differ distinctly with regard to their "biological
potential". Because of regional differences in salivary film velocity, pH,
and composition of the microflora, results obtained by the various models
are not likely to be immediately comparable. Moreover, local factors in
relation to specimen environment, such as degree of "protection" and plaque
thickness, may further add to the differences. It is suggested that these
observations are important in considerations of the relevance of
substituting clinical trials with in situ studies. Because of the
pronounced intra-oral variation in certain parameters thought to be
important for caries lesion development, we conclude that no in situ model
can, by itself, fulfill the role as the "model of choice". Finally,
although in situ models are useful adjuncts in attempts to estimate the
relative effects of new anticaries methods or compounds on caries
initiation, the selection of in situ study model design will strongly
depend on the aim and purpose of the study.
