Title:
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Laboratory studies into the development and control of extrinsic chlorhexidine stain
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Extrinsic staining of teeth is a common aesthetic problem for which toothpaste
manufacturers strive to produce effective products to chemically and/or physically control
the problem. Clinical studies proving efficacy are rare and reliance on tests in vitro are
more common. The aim of these studies was to develop two in vitro models which could
be used to screen and compare agents and formulations for dietary stain control.
The first model utilised immobilised hydroxyapatite (RA) with tea as the chromogen.
Using residual tea optical density to assess extrinsic staining proved unreliable. Tea
extraction and direct measurement from wells however was shown to be reliable in
demonstrating the efficacy of known active chemical agents and differentiating between
toothpastes. The second model used roughened Perspex to simultaneously assess
toothpastes and their ingredients for chemical and or mechanical stain removal. In line
with the RA model, results differentiated between toothpastes and other agents for
chemical stain removal. Chemical/mechanical stain removal in the model also showed
differences for toothpastes, abrasives and detergents but abrasivity levels did not show the
expected linear correlation: the toothbrush itself appeared to be the dominant factor in the
model. The final experiment attempted to determine whether chromogen/pellicle
interaction was specific or non-specific. Results showed no evidence of specificity indeed
data suggested that chromogens may merely be absorbed into the pellicle and held
physically rather than by chemical interactions. Since some of the data from both models
was consistent with other published laboratory and clinical studies it is cautiously
concluded that the models may prove rapid, simple and useful screening methods for anti-staining
agents and products. Only the availability of more clinical data to support claims
for numerous products, however, will allow the models to be retrospectively validated.
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