universidade de são paulo - Faculdade de Odontologia - Unesp

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Another surface modification used in the present study involved the
incorporation of fluorine in the resin surface. To the author’s knowledge, to date
this is the first study that has addressed this issue. The results have shown that the
contact angle, immediately after plasma treatment with ArSF 6 /70 W, increased
considerably compared to control group, which is in agreement with the studies of
Guruvenket et al. 21 and Rangel et al. 20 . This was probably due to the replacement
of hydrophilic species by fluorine atoms 16 . As a result, the hydrogen bonds
between water molecules and surface groups decrease, reducing the hydrophilicity
16 . X-ray photoelectron spectroscopy (XPS) was used to confirm the chemical
changes on surfaces treated with ArSF 6 /70 W. The incorporation of fluorine
occurred, as demonstrated by the presence of F(1s) peak in XPS spectra. There
was a decrease in the atomic concentrations of carbon from 75.3 at.% to 55.4
at.%, oxygen from 23.0 at.% to 14.1 at.%, and fluorine incorporation of 29.6 at.%.
In this study, the adhesion of Candida albicans was quantified using the
2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide (XTT)
reduction assay. This colorimetric method is based on metabolic activity 30 and
has been widely used for the quantification of yeasts 27,30,31 . The results revealed
that ArO 2 /70W plasma treatment significantly reduced the yeast adhesion. These
results do not agree with the data reported by Yildirim et al. 3 , who have found
higher counts of Candida albicans in plasma treated surfaces than in the
unmodified control group. One possible reason for this disagreement could be
that, in the study of Yildirim et al. 3 , different plasma parameters were used
(oxygen atmosphere at 50 or 100 W, during 15 minutes). The decrease of