Biomedical Engineering Reference
In-Depth Information
800
700
600
500
400
300
200
100
0
Esthet-X
Grandio
Supreme XT
FIGURE 4.14
Comparison of nanohardness.
Source: Rosa and Mota (2009).
Supreme XT showed the highest average microhardness when compared to Esthet-X and Venus.
However, there was no significant effect of 300,000 load cycles on the hardness. This is a completely
different behavior when compared to minifilled and microhybrid composites
[22]
. At the same time,
this gives an indication of higher clinical longevity which must be considered.
4.8.5
Nanohardness
Since the use of nanofillers started, the term “nanohardness” has been introduced. The use of a
nanoindenter with a Berkovich diamond tip with a nominal radius of 5,000 nm has been widely used.
A nanoindenter measures the hardness and elastic modulus of a material on an extremely smaller
surface scale of 50 nm
[23]
. Nanohardness results ranged from 350 to 770 MPa (
Figure 4.14
), far less
than 4,350 from enamel recorded by Machado
[23]
.
4.8.6
Wear Resistance
According to O'Brien and Yee
[24]
, clinical wear mechanisms of composite resin are described as
follows: (1) organic matrix wear, (2) loss of filler bond to the matrix, (3) shear of filler, (4) matrix
cohesive failure, and (5) exposure of air blisters. Some of these phenomena still occur in nanofilled
composites and can be seen in
Figures 4.15-4.19
. Morphological aspects observed in SEM in differ-
ent simulated periods of three body wear show rounded fillers exposed by the organic phase removal,
small cracks, and loss of fillers due to debonding.
