The effect of nanosilver particles on the physicomechanical properties of dental amalgam free of unbound mercury / Chanthiriga Ramasindarum
Dental amalgam has been widely used over the past 190 years in dentistry due to its low cost and durability. SilverfilTM was introduced into the Malaysian market in early 2000 as an amalgam free of unbound mercury (Hg). However, a large particle size variation of SilverfilTM alloy is the critical...
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| Format: | Thesis |
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2018
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| Online Access: | http://studentsrepo.um.edu.my/10337/ http://studentsrepo.um.edu.my/10337/4/chantiriga.pdf |
| Summary: | Dental amalgam has been widely used over the past 190 years in dentistry due to its
low cost and durability. SilverfilTM was introduced into the Malaysian market in early
2000 as an amalgam free of unbound mercury (Hg). However, a large particle size
variation of SilverfilTM alloy is the critical concern raised by its manufacturer. Therefore,
the present study focuses on introducing nano-sized silver particles (AgNPs) into the
manufacturing process of SilverfilTM in order to enhance its physical and mechanical
properties. The aims of this research were first to characterise the SilverfilTM starting
materials, followed by synthesis and characterisation of AgNPs, formulation of an
experimental nanosilver amalgam based on the conceptual SilverfilTM model, and to
finally compare the physical and mechanical characteristics of the optimised experimental
nanosilver amalgam with those of SilverfilTM as well as GS80 and Dispersalloy as two
other commercially available amalgams. The results obtained via the field emission
electron microscopy indicated a particle size distribution in the range of 146-786 nm for
the SilverfilTM alloy. Moreover, the X-Ray photoelectron spectroscopy analyses
confirmed the absence of unbound Hg in the triturated SilverfilTM, while elements such
as copper and tin were present as impurities in the composition of its starting materials.
AgNPs were synthesised by reaction of an aqueous silver nitrate (AgNO3) solution with
hydrazine hydrate as a reducing agent. The high resolution transmission electron
microscopy investigations indicated the formation of AgNPs with polygonal morphology
and mean particle size of 34.27±7.38 nm. The crystalline structure and size of AgNPs,
investigated respectively by X-ray diffraction and small angle X-Ray scattering, were
face centred cubic (FCC) and 54.20 nm. Among varied types of AgNPs synthesised with
different AgNO3 concentrations, those produced by a 2 M AgNO3 solution were chosen
for formulation of the optimised experimental nanosilver amalgam with the AgNPs:Hg
ratio of 1:2.9. The manipulation and handling of the optimised experimental nanosilver
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amalgam were evaluated by two dentists. The optimised experimental nanosilver
amalgam was consisted of polygonal-shaped particles with mean particle size of
approximately 141.55±52.12 nm and without the presence of unbound Hg in the triturated
formulation. According to the XRD analyses, both SilverfilTM and the optimised
experimental nanosilver amalgam showed a crystalline structure resembling
“moschellandsbergite”, a naturally occurring mineral (Ag2Hg3). The compressive
strength, diametral tensile strength, and Vickers microhardness values of the optimised
experimental nanosilver amalgam were quantified as after 24 hours and 7 days of
incubation in distilled water at 37°C. The compressive strength values measured after 24
hours for the optimised experimental nanosilver amalgam, SilverfilTM, GS80, and
Dispersalloy were 380.62±37.10 MPa, 449.66±173.98 MPa, 447.12±18.60 MPa, and
190.68±44.18 MPa, respectively. The diametral tensile strength measured at 24 hours for
the optimised experimental nanosilver amalgam was 128.77±63.59 MPa, which was
significantly higher than those of SilverfilTM (72.71±10.23 MPa), GS80 (39.32±7.79
MPa), and Dispersalloy (41.66±7.79MPa). On the other hand, GS80 exhibited the highest
Vickers microhardness value (233.82±15.68), followed by Dispersalloy (175.38±8.02),
and SilverfilTM (103.16±4.39) whereas Vickers microhardness for the optimised
experimental nanosilver amalgam was the lowest (89.77±5.55) after 24 hours.
Subsequent Bonferroni post hoc tests showed significant differences (P<0.005) between
the mean Vickers microhardness values of the tested amalgams after storage for 24 hours
and 7 days. In conclusion, although no detectable unbound Hg was present in SilverfilT M,
the impurities existing in the starting materials might contribute to its relatively high
mechanical strength. The large particle size variation of the SilverfilTM alloy was
addressed by utilisation of AgNPs synthesised with a particle size of 18.81±46.12 nm.
The optimised experimental nanosilver amalgam showed improved homogeneity and a
significantly higher diametral strength compared to SilverfilTM. The AgNPs:Hg ratio of
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1:2.9 was determined as the minimum applicable ratio for producing a well-triturated
dental amalgam |
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