Biomedical Engineering Reference
In-Depth Information
However, the milling procedure cannot normally reduce the filler particle size below 100 nm.
Thus, nanotechnology has been used as an innovative way to manufacture fillers from the controlled
growth of an initial molecule (bottom-up approach), resulting in homogeneity in shape and size (in
the range between 5 and 20 nm).
The Filtek Supreme (3MEspe, St. Paul, MN, USA) was the commercial milestone of nanotech-
nology application in operative dentistry in the beginning of this century. This composite resin was
a combination of aggregated zirconia/silica cluster filler with a primary particle size of 5-20 nm and
nanoagglomerated 20 nm silica filler in 78.5 wt%.
Over the last few years, a combination of microhybrid and nanofilled composites has been com-
mercialized. This new combination has increased the filler weight content up to 87% by filling spaces
between larger particles with smaller ones, and has retained optical and mechanical characteristics
which are known to be exclusive to nanofilled composites.
4.5
SEM AND EDS EVALUATION
SEM has been used to analyze the shape and size of the filler particles and as a qualitative method to
classify the composite resins
[7]
. Comparative SEM images of nanofilled composites are presented in
Figure 4.3
.
Morphological comparisons show that there are similar patterns between Esthet-X (Dentsply,
Caulk, Milford, USA) and Grandio (Voco, GMBH Cuxhaven, Germany). High amount of irregular
fillers are seen with additional load of small nanofillers around and/or over them occupying the empty
spaces. The same pattern was registered to both enamel and dentin shades. A completely different
pattern can be seen with Filtek Supreme XT (3MEspe, St. Paul, MN, USA) with high amount of
rounded, uniform size fillers in both enamel and dentin shades. Following the classification proposed
by Lutz and Phillips in 1983
[8]
, all evaluated composites could be classified as microhybrid, except
the Filtek Supreme XT which is an exclusive nanofilled composite in accordance to Mitra et al.
[3]
and Beun et al.
[9]
.
(A)
(B)
(C)
1
µ
m
1
µ
m
1
µ
m
P:20.000 x
AMRAY
#0000*
10.0 kV
P:20.000 x
10.0 kV
AMRAY
#0000*
P:20.000 x
10.0 kV
AMRAY
#0000*
FIGURE 4.3
SEM: (A) Nanoclusters of Filtek Supreme XT, the exclusive nanofilled composite. (B) Esthet-X filler, a
microhybrid composite with additional load of nanofillers. (C) Grandio, a high filled microhybrid composite with
additional load of nanofillers.
Source: Hörlle, Hirakata, and Mota (2008).
