Biomedical Engineering Reference
In-Depth Information
FIGURE 2.1
SEM image of silica nanoclusters in Filtek™ Supreme (3M ESPE Dental
Products) after removal of resin by acetone extraction.
Image provided by J. Perdigao, University of Minnesota. Reproduced with permission.
nanoparticles only,
Figure 2.2B
shows a nanocomposite filled with a mixture of nanoclusters alone,
and
Figure. 2.2C
shows a conventional microhybrid composite (3M ESPE Filtek Z250).
In the commercial dental composite Filtek Supreme Plus nanoclusters have been used with nano-
mers to provide nanocomposites called
nanofills
in which all the primary particles throughout the
resin matrix are in the nanometer size. Currently, the Filtek Supreme Plus system from 3M ESPE is
the only commercial nanofill available
[19]
. A schematic diagram of this nanofill composite Filtek
Supreme Plus is shown in
Figure 2.3
. The use of spheroidal nanocluster fillers with a broad particle
size distribution results in high filler loading, desirable handling characteristics and excellent mechan-
ical properties. The properties of the nanofill composite will be compared with those of other dental
composites as will be shown later in this chapter.
2.3.1.2 Nanohybrid Composites
As mentioned earlier the use of unagglomerated nanomeric particles only often lead to undesirable
rheological properties in a highly filled composite. Some manufacturers have added larger particles
in the submicron and micron range or incorporated prepolymerized organic fillers to improve the
handling properties of the composites where nanomers were included. The resulting composites are
called
nanohybrids
[19]
. These materials have improved aesthetic properties compared to the tradi-
tional hybrids and microhybrids, but since polish retention is governed by the size of the largest, the
nanohybrid approach still suffer from the loss of larger particles and the potential loss of initial gloss
