universidade de são paulo - Faculdade de Odontologia - Unesp

72
In the groups AAt/130 W, ArO 2 /70 W and Ar/50 W, this alteration in
hydrophobicity occurred due to the increase in surface energy. Under this
condition, it has been observed that polymeric surfaces submitted to plasmas tend
to return to their original hydrophobicity [18]. This could be attributed to the
movement of polar groups from the surface to the internal part of the polymer.
Although the plasma treatment with ArSF 6 /70W created hydrophobic surfaces, or
surfaces with low surface energy, after the samples had been immersed in water
the angles of contact values of this group also came close to the values of the
others, including those of the control group. In spite of this alteration in
hydrophobicity, the fluoride remained present on the surface, as demonstrated by
the XPS analysis. Robinson et al. [24] observed that the increase in the degree of
fluorination of the surfaces became more negative due to the presence of
electronegative atoms of fluoride. Moreover, it has been suggested that resins with
charged surfaces can alter the ionic interaction between the denture base and the
microorganisms [11, 16, 35]. However, no reduction in the adherence of Candida
albicans by means of plasma treatment with ArSF 6 /70W was detected in this
study.
When the denture is inserted into the oral cavity, its surface is rapidly
covered by a fine film of saliva known as the acquired pellicle [36]. This film is
capable of altering the properties of the surfaces exposed to it [4], in the same way
as the chemical characteristic of the surface of biomaterials is also capable of
influencing the formation and composition of the acquired film [4, 10, 36]. Thus,
surfaces with small differences in their chemical compositions differ with regard