universidade de são paulo - Faculdade de Odontologia - Unesp

144
colored formazan crystals, which may be measured spectrophotometrically [41]. It
has been reported that the XTT method correlates well with other quantitative
technique, such as adenosine tri-phosphate (ATP) and colony forming units
(CFU) methods [22, 42]. For the other assay, the adhered cells are fixed, stained
with the basic dye crystal violet, and quantified by counting in selected fields of
the substrate surface [1, 26-27, 30-31, 36-37]. Therefore, because cells (both
living and dead) are stained by crystal violet, this assay does not allow
differentiating between living and dead cells [43]. These differences between XTT
and crystal violet assays may help explain the results obtained in this study and
may have accounted, at least in part, for the controversial results reported by
others. Therefore, when possible, it is recommended to use more than one method
to evaluate the effect of saliva on Candida adhesion to surfaces, particularly if
they are based on different principles.
It has been reported that exposed chemical groups of the material surface
have important role in determining the selectivity of the adsorption process [44].
Hence, considering that solid surfaces differ in respect to adsorption of salivary
proteins, the pellicle composition may vary among diverse materials [44]. An
analysis of the literature reveals that a variety of materials has been used as
substrate in vitro studies that evaluate the effect of saliva on Candida adhesion [4,
12-13, 16-20, 23-31]. This variety of materials makes the comparison of results
difficult and can partially contribute to the conflicting results regarding the effect
of preconditioning with saliva on Candida adhesion.