DENTAL MATERIALS
Figure 4 The (Nε)- (ε) and log(Nε) - log(ε) plots which give the fractal dimension for Filtek Ultimate
fractal dimension are plotted, where the coulour
codes are given in Fig. 3 c. The fractal dimension
results from the slope of log(Nε) - log(ε) plot (Fig. 4
a, b,) as being 1.6532 with a error r2=0,9989, i.e. a
good accuracy of the results.
The values of fractal dimension for Filtek Supreme
XT and Filtek Ultimate, as a average of all 20
samples evaluation are given in Table 2. Higher
value of fractal dimension for Filtek Ultimate was
obtained when compared to Filtek Supreme XT.
Fractal analysis is used for objectively analyzing
complexity and heterogeneity, as well as some
other measures of binary digital images: to
measure difficult to describe geometrical forms
where the details of design are as important as
gross morphology (13-16). It is suitable for images
of biological cells and other biological structures,
including branching structures and textures, as
well as for known fractals (17). Patterns can be
easily extracted from many types of images and
converted to binary digital images that can be
analyzed (18-21).
Two different commercial composite resins were
evaluated in the present study. Filtek Supreme
XT is a nano-filled composite, having nonagglomerated nanoparticles and clusters of
agglomerated zirconia/silica. In Filtek Ultimate
Universal Restorative (10) the resin system is
slightly modified from the original Filtek Supreme
resin. The resin contains bis-GMA, UDMA,
TEGDMA, and bis-EMA (6) resins. To moderate
the shrinkage, PEGDMA has been substituted for
a portion of the TEGDMA resin in Filtek Supreme
XT restorative. The fillers are a combination of
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non-agglomerated/non-aggregated 20 nm silica
filler, non-agglomerated/non-aggregated 4 to 11
nm zirconia filler, and aggregated zirconia/silica
cluster filler (comprised of 20 nm silica and 4 to 11
nm zirconia particles).
The main objective of the present study was
to observe a connection between the fractal
dimension and microstructure. As the fractal
dimension is increasing the higher are the
irregularities at the matrix-filler particles interface,
so the adhesion between those two components
becomes stronger. This fact is influenced, in the
case of the studied nanocomposites, by the
clusters particle size.It was observed that the
decreasing of the clusters dimension defines an
increased fractal dimension. Similar studies made
possible to understand the fracture behavior of
the composites, and also confirmed the good
potential of fractal analysis to explain complex
mechanisms such as those involved in the fracture
of brittle materials (14,15,18). Thus, the great
potential of such method becomes more obvious.
Conclusions
Filtek Supreme XT composite resin present a higher
SiO2 but a lower ZrO2 particle percent in volume
when compare to Filtek Ultimate composite resin.
Both SiO2 and ZrO2 cluster particle size are higher
in Filtek Supreme XT then in Filtek Ultimate. Filtek
Ultimate microstructure have an increased fractal
dimension when compared to Filtek Supreme
XT, as an expression of a better particle-matrix
adhesion surface.
STOMA.EDUJ (2015) 2 (1)