الفهرس 
DENTURE BASE MATERIAL
Reinforcement of polymethylmethacrylateOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
Our study aimed to investigate the effect of adding a
different concentration of silver nanoparticles on impact strength,
transverse strength, fracture toughness, surface roughness,
hardness and water sorption of heat-cured acrylic resin.
According to literature, silver nanoparticles were used in
this study due to its ductility, electrical and thermal
conductivity, and antimicrobial activity. (174,175) silver
nanoparticles were reported to have antimicrobial effects on
many microorganisms. In addition to, silver nanoparticles have
the potential to impart ‘mechanical properties’ to some dental
materials, (179)
Silver nanoparticle was incorporated to heat cured
acrylic resin in four different concentrations of silver
nanoparticles 0.5wt%, 1wt%, 2wt%, 3wt%. Heat cured acrylic
resin/ silver nanoparticles complex was cured in boiling water
for 25 minutes.
The following properties were tested: impact strength,
transverse strength, fracture toughness, surface roughness,
Vicker’s microhardness as well as water sorption.
Impact strength was measured using Izod impact tester
model CS- 137. Each notched specimen was held as a vertical
cantilever beam. It was broken by a single swing of the pendulum
with impact line above the notch and on its same side.Transverse strength was tested by subjecting rectangular
specimens to 3-point loading test using the universal testing
machine. The load was applied at the centre of the specimen till
fracture.
Fracture toughness was tested by a single edge notch
specimen using the three-point loading using the universal
testing machine (Instron® Bluehill Lite Software). The notch
was directed downward and the load was applied in the middle
of the specimens up to fracture and fracture toughness was
calculated.
Surface roughness was tested by a circular discs
specimen. The surface roughness was tested using a
profilometer (TR100 surface roughness tester, time group Inc.
USA.). It is based on measuring the Ra value which is
Arithmetic mean of the movement of the profile above and
below the central line of the surface. The mean of five tracing
for every specimen was been calculated and taken as the
surface roughness value of the specimens.
Vicker’s microhardness was measured using a microindentation
tester (Model VHS-50, Laizhou Huayin Testing
Instrument Co., Ltd. China) with a Vicker’s diamond pyramidal
indenter having a square base and 136° pyramidal angle
attached to a universal research microscope. The specimens
were individually positioned in such a way that the test surface
was kept perpendicular to the indentator.Water sorption was measured by drying the circular
specimens at 37±2 °C for 24 hours in a desiccator containing
thoroughly dry anhydrous silica gel. The specimens were then
weighed with sensitive balance capable of measuring. The discs
were then immersed in distilled water at 37 °C for 7 days. After
a week the specimens were removed from the water and
weighed again. Water sorption was calculated in the unit of
mg/cm2.
By observing the data obtained from impact strength test
of the present study, our results showed a significant increase in
the impact strength of the 0.5wt% and the 1wt% silver
nanoparticle modified groups in comparison to the control
group. However, the 3wt% silver nanoparticle modified group
showed a significant decrease differences. While, the 2wt%
silver nanoparticle modified group showed no significant
differences in comparison to the control group.
By observing the data obtained from transverse strength
test of the present study, our results showed no significant in
the transverse strength of the 0.5wt% and the 1wt% silver
nanoparticle modified groups in comparison to the control
group. While, the 2wt% and the 3wt% silver nanoparticle
modified groups showed a significant decrease differences
compared to the control group.
By observing the data obtained from the fracture
toughness test of the present study, our results showed a significant increase in the fracture toughness strength of the
0.5wt% silver nanoparticle modified group in comparison to the
control group. However, the 1wt% and the 2wt% silver
nanoparticle modified groups showed no significant differences
in comparison to the control group. Furthermore, the 3wt%
silver nanoparticle modified group showed a significant decrease
differences in comparison to the control group.
By observing the data obtained from surface roughness test
of the present study, our results showed a significant decrease in
the surface roughness between all nanosilver modified groups in
comparison to the control group. 0.5wt% silver nanoparticles
modified showed the least significant difference, followed by the
1wt%, 2wt%, and then the 3wt% silver nanoparticles modified
groups in comparison to the control group.
Our results for vicker’s microhardness showed a
significant increase between all nanosilver groups in comparison
to the control group. The 0.5wt% silver nanoparticles modified
group showed the highest significant difference, followed by the
1wt%, 2wt%, and then the 3wt% silver nanoparticles modified
groups in comparison to the control group.
By observing the data obtained from water sorption test of
the present study, our results showed a significant increase in the
water sorption between all nanosilver modified groups in
comparison to the control group. The 0.5wt% silver
nanoparticles modified showed the least significant difference,followed by the 1wt%, 2wt%, and then the 3wt% silver
nanoparticles modified groups in comparison to the control
group.
Regarding the results of our study, the 2wt% and the
3wt% silver nanoparticles modified groups showed the lowest
significant mean values in comparison with the control group in
impact strength, transverse strength, fracture toughness as well
as microhardness.
Finally, within the limitations of the present study, we
can conclude that the incorporation of silver nanoparticles in
heat-cured acrylic resin had a great influence on the mechanical
as well as physical properties.