nanoparticles effect on silicone elastomers on properties

1. JOURNAL CLUB PRESENTATION
Effect of adding silver nanoparticle on physical and
mechanical properties of maxillofacial silicone
elastomer material-an in-vitro study
Chowdhary R. J Prosthodont Res. 2020:64(4):431-5.
DELLA S INDRAN
I MDS

2. Introduction
Aim
Materials and Methods
Results
Conclusion
Related articles
Reference
CONTENTS

3. INTRODUCTION
Maxillofacial prosthesis has revolutionized in the field of prosthodontics rendering
solutions to restore facial mutilations associated with congenital malformations,
acquired surgical defects and trauma.
There are 2 types :-
• Room Temperature Vulcanizing (RTV) Silicone
• Heat Temperature Vulcanizing (HTV) Silicone

4. IDEAL PHYSICAL AND MECHANICAL PROPERTIES
High resistance to abrasion
High tear strength
High tensile strength
Low coefficient of friction
Low surface tension
Low thermal conductivity
No water sorption
Ease of processing
Ease of repair or re-fabrication if needed

5. The main challenge encountered in the performance of an better facial
prosthesis is the degradation in appearance, either due to changes in
colour or deterioration of Physical properties.

6. NANOPARTICLES AND PROPERTIES
Nanoparticles are synthetic or natural macromolecules of size 10 to 100 nm.
Enhanced electrical and heat conductivity.
Increased tensile properties and strength.
Magnetic properties.
Optical properties.

7. EFFECT OF ADDING SILVER NANOPARTICLES ON
PHYSICAL AND MECHANICAL PROPERTIES OF
MAXILLOFACIAL SILICONE ELASTOMER:AN
INVITRO STUDY
PURPOSE:
The purpose of the study was to evaluate the impact of silver nanoparticle
incorporation into maxillofacial silicone material (Teksil 25) on its tear strength,
hardness and colour stability.
MATERIALS AND METHODS
Total of 180 specimens were fabricated, 90 dumbbell and 90 trouser shaped
specimens prepared according to American Society of Testing and Materials( ASTM
) No: D412, No: D624.

9. GROUP I( 60 )specimens GROUP II( 60 )specimens GROUP III(60 ) specimens
For hardness test Tear strength Colour stability
Gp I a Gp I b Gp 2a Gp 2b Gp 3a Gp 3b
(Without AgNps) (with AgNps) ( without AgNps ) ( with AgNps ) ( without AgNps) (with AgNps)
30 specimens 30 specimens 30 specimens 30 specimens 30 specimens 30 specimens

10. MAKING OF SPECIMENS
 By weighing in an electronic weighing machine, base and catalyst
parts are mixed together in ratio 9:1.
 For half of the part, silver nanoparticles added in a concentration
of 20 ppm and the rest without addition of silver nanoparticles, used as
control groups.
 The mixed silicone material then poured in dumbbell and trouser shaped
mould specimens.

11. PROPERTIES CHECKING
HARDNESS
 Durometer is used for checking.
 Digital shore A hardness test is used.
 Two dumbbell specimens of 3mm were stacked together to obtain a
minimum thickness of 6 mm at a time.
 Five sites were measured for each specimen, with 12 mm distance
between each sites and a 6 mm distance from the edge of the specimen.
 The measured specimens removed and new specimens placed,
the procedure repeated.

12. TEAR STRENGTH
Tear strength defined as maximum force required to break the specimen
divided by the thickness of the specimens.
The thickness of the specimen measured at the intersection of the trouser
leg with Vernier calliper.
To measure force required for breaking specimen, specimen placed in the
jaws of the universal testing machine and stretched at a rate of 500 ram / rain.

13. COLOUR STABILITY
Spectrophometer used to measure colour stability.
Data measured in CIE L*a*b* system. CIE Lab colour scale
used to measure the colour.

14. RESULTS
Tear strength, hardness, colour stability measured.
The mean difference and standard deviation of silicones
without nanoparticles in comparison to silicones with
nanoparticles were calculated.
The independent sample’s “t” test used to test significance
differences in the properties.

16. CONCLUSION
Silver nanoparticles at 20 ppm concentration, decreased hardness and
there is no much significant change for tear strength and colour stability
of silicone elastomer.

17. RELATED ARTICLES

18. EFFECT OF NANO-OXIDE CONCENTRATION
ON THE MECHANICAL PROPERTIES OF A
MAXILLOFACIAL SILICONE ELASTOMER
Han Y, Kiat-amnuay S, Powers JM, Zhao Y. The Journal of Prosthetic Dentistry. 2008 Dec 1;100(6):
465-73.
AIM
 The aim of this study was to evaluate the effect of different concentrations of
nano sized oxides of various composition on the mechanical properties of
a commercially available silicone elastomer.
MATERIALS AND METHODS
 Silicone A-2186 maxillofacial elastomer used.

19.  Nano sized oxides (Ti, Zn, or Ce) were added in various concentrations
(0.5%, 1.0%, 1.5%, 2.0%, 2.5%,or 3.0% by weight) to a commercial
silicone elastomer (A-2186). Silicone elastomer A-2186 without
nano sized oxides taken as a control group.

20. Dumbbell shaped mould (ASTM D 421) used for making specimens for
checking tensile and percentage elongation.
Trouser shaped mould (ASTM D 624 )used for making specimens for
checking tear strength.

21. GROUPS
 Total of 180 specimens prepared.
 Eighteen experimental groups of elastomers were made by combining
the silicone elastomer A-2186 with various amounts of 3 nano-oxides:
0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%.
 Silicone elastomer A-2186, without added nanosized oxides, served as
the control group.
 Five dumbbell shaped specimens of each combination were made for
testing ultimate strength and elongation according to ASTM D412.
 Five trouser-shaped specimens were made for testing tear strength
according to ASTM D624.
 To prepare specimens for the 18 experimental groups, nano oxides were
mixed with the silicone base by hand for 20 minutes using wooden
tongue depressors on a glass plate

22. TENSILE STRENGTH ( TS ) AND PERCENTAGE ELONGATION ( PE )
TS = peak force
width x thickness
Thickness and width calculated using Vernier calliper.
To check force, dumbbell shaped specimen was placed in the grips of the universal
testing machine, the specimen was symmetrically adjusted so as to distribute tension
uniformly over the cross section.
The rate of grip separation was 8.5 mm/ min, the maximum load immediately prior
to breaking (N) was obtained, and the tensile strength was calculated.

23.  The length of specimen after break is calculated using Vernier calliper.
 PE = Lb – Lo x 100
Lo
where Lb = length of specimen at break
Lo = original length.

24. TEAR STRENGTH
 Tear strength is the max force required to break the specimen divided by
thickness of the specimen.
 Thickness measured by using Vernier calliper.
 To check force required to break specimen, specimen placed in the jaws of
the universal testing machine and stretched at a rate of 500 ram / rain.

25. RESULT
 Mean values of tear strength, tensile strength, percentage elongation was measured.
 2 - Way ANOVA test used to measure difference in significance.
TEAR STRENGTH( mean )

26. • TENSILE STRENGTH (mean )

27. • PERCENTAGE ELOGATION (mean )

28. CONCLUSION
 It was concluded that the addition of Nano-oxide particles of Ti, Zn, or Ce to silicone
elastomer improved mechanical properties when the concentrations ranged between
2.0% and 2.5% by weight

29. BIOMECHANICAL PROPERTIES OF NANO TIO2
ADDITION TO A MEDICAL SILICONE
ELASTOMER:THE EFFECT OF ARTIFICIAL
AGING.
Wang L, Liu Q, Jing D, Zhou S, Shao L. Journal of dentistry. 2014 Apr 1;42(4):475-83.
AIM:
 The aim of the study was to evaluate the effect of titanium dioxide
nanoparticles on mechanical and anti-aging properties of a silicone elastomer.
MATERIALS AND METHODS
 Medical elastomer MDX4-4210 used.
 Titanium dioxide of concentration of 2%, 4%, 6% (w/w) used.

30.  Thirty six dumbbell shaped specimens made for checking tensile strength,
elongation at break.
 Twenty four crescent shaped specimens prepared to measure tear strength.
 Twelve bar shaped specimens prepared to check shore A hardness.

31. TENSILE STRENGTH AND PERCENTAGE ELONGATION
 Thirty six dumbbell shaped specimens prepared, force measured
with tensile strength testing machine.
 Thickness measured with Vernier calliper.
 TS = FORCE
THICKNESS
 Elongation = Lb – Lo x100
Lo

32. • TEAR STRENGTH
 Twenty four cresent shaped specimens prepared, strength at tearing
measured using tensile testing machine.
 Thickness of specimen measured by Vernier calliper.
 Tear strength = Force at tear
Thickness

33. SHORE A HARDNESS
Twelve bar shaped specimens prepared, each specimens read at 5 points.
Shore A hardness measured using durometer.

34. • ANTI AGEING TEST
• THERMAL AGING
The 6 % (w/w ) composites and the blank silicone elastomer were subjected to thermal
aging procedures in a high temperature chamber.
Aging procedures were conducted at high temperaturesof 50, 100, 150, 200 degree
celcius for 72 hrs.
The tensile strength before and after aging was calculated.

35. • UV AGEING
• The ageing test performed in the QUV Weathering Tester.
• The 6% composites were exposed to UV irradiation by applying a lamp type
• UVA-340 for 24, 48, 72 hrs.
• The values of tensile strength before and after ageing were recorded.

36. STRESS FATIGUE
The specimens were subjected to stress fatigue for 66 700, 133 300, 200 000,266 700
cycles at room temperature.
The load was applied through a stainless steel plate at force of 75 N at a speed of 72
times / min.
The tensile strength before and after ageing were tested

37. RESULT
Data collected was analysed by one – way ANOVA test.
Tensile strength insignificant increase, at 2 and 4 % , while at 6 % tensile strength
increased.
There is an increase in elongation at break at 2 %, and has a significant decrease
at 6 %.
At 2 % there is an increase in tear strength, at 6 and 4% there is an decreased
trend.
Shore A hardness increased at 2,4,6 %, with significant increase at 6 %.

39. • AGEING
THERMAL AGEING
The effect of aging at 6% was not statistically significant, however at 0 % ,there is
significant decrease in reduction of tensile strength.

40. • UV AGING
At 6 % w / w, there is an increase in tensile strength irrespective of ageing interval
compared to 0 % w/w.

41. • STRESS FATIGUE
The effect of accelerated stress cycling on the tensile strength was not statistically
significant in 6 % group, slight decrease was there with 0 % group.

42. CONCLUSION
Silicone elastomer with 2 % nanoparticles increased physical properties, however
elongation at break and tear strength at 6 % w/w was significantly compromised.
Titanium dioxide nanoparticles improved anti thermal ageing properties of silicone
elastomer.

43. IN VITRO COMPARISON OF COMPRESSIVE AND
TENSILE STRENGTHS OF ACRYLIC RESINS
REINFORCED BY SILVER NANOPARTICLES AT 2%
AND 0.2% CONCENTRATIONS
• Ghaffari T, Hamedi-Rad F. . J Dent Res Dent Clin Dent Prospects. 2015;9(1):40-43.
AIM
This study was undertaken to investigate the effect of adding silver nanoparticles
(AgNPs) to PMMA at 2% and 0.2% concentrations on compressive and tensile
strengths of PMMA.
MATERIALS AND METHODS
 Polymethyl methacrylate (PMMA; SR Triplex Hot) heat curing acrylic was used.

44.  silver nanoparticles (AgNPs) with a diameter of <35 nm were used.
AgNPs in two concentration groups at 0.2 and 2 wt% were mixed with
heat-curing acrylic resin.
 A total of 36 specimens were prepared,
 18 specimens of each test were divided into 3 groups as follows:
• Group A: 6 specimens of pure acrylic resin were used as the control group.
• Group B: 6 specimens of PMMA were mixed with 0.2 wt% of AgNPs.
• Group C: 6 specimens of PMMA were mixed with 2 wt% of AgNPs

45. GROUPS
• TOTAL= 36 SPECIMENS
• 18 SPECIMENS FOR 18 SPECIMENS FOR
COMPRESSIVE STRENGTH TENSILE STRENGTH
•
• GROUP A GROUP A
• GROUP B GROUP B
• GROUP C GROUP C

46. Compressive strength measurement apparatus and universal tensile
strength measurement apparatus were used to determine compressive
and tensile strengths of the samples.
 Based on ASTM D 695-02a (ISO 604) standard recommended by the
measurement device manufacturer, eighteen compressive strength test
samples were prepared.
The specimens were formed in cylinders with dimensions of 25×38 mm
with a metal mould.
 Another eighteen specimens were prepared for tensile test with
rectangular cubic shape, measuring 2×20×200 mm in size according
ASTM D638-10 (ISO 527).
The specimens recovered were checked for tear and compressive strength.

47. RESULT
Mean of values calculated.
One way ANOVA test used to check difference in significance.
The compressive strengths in various groups showed that acrylic resin at 0.2% and
2% AgNPs concentrations had a significantly higher compressive strength compared
with the control group.
 The strength difference between the groups containing 0.2% and 2% AgNPs was not
of much significance.

48. • TENSILE STRENGTH
Tensile strength has significantly decreased in case for 2 % as compared
with control groups.

49. CONCLUSION
The results showed that the effect of AgNPs significantly depends on its
concentration.
 Based on the results adding AgNPs with proper concentrations to PMMA
can improve its mechanical characteristics without any adverse effects.

50. EFFECT OF INCORPORATION OF SILVER
NANOPARTICLES ON THE TENSILE BOND
STRENGTH OF A LONG TERM SOFT DENTURE
LINER
• Habibzadeh S, Omidvaran A, Eskandarion S, Shamshiri AR. European Journel of Dentistry. 2020 Mar,
14(2),268.
• AIM
This study aimed at assessing the effect of the addition of silver nanoparticles (SNPs)
to a silicone soft liner on its tensile bond strength to denture base resin.
• MATERIALS AND METHODS
A two-compartment mould stainless steel (length: 65 mm, width: 22 mm, height: 15
mm) was prepared by laser cutting and used to fabricate 120 acrylic blocks
(Acropars) by the lost wax technique.

51.  The mould was lubricated with petroleum jelly. Cereswax
was melted in a heater and poured into the mould. After about
15 minutes, the two compartments of the mould were
separated and the wax pattern was removed and placed in
20°C water to prevent the dimensional changes.
 Each wax pattern was divided into two equal halves measuring
8 × 8 × 20 mm to create a 4 mm thickness of liner between
the two acrylic blocks.

52. Heat-cured acrylic resin (Acropars) with a powder liquid ratio of 3:1 was prepared
according to the manufacturer’s instructions and after trial packing (under 3000 Psi
hydraulic press) baked at 70°C in water for 9 hours.
The soft liner selected in this study was Mucopren autocure silicone long-term liner
supplied as two pastes .

53.  The base and the catalyst were injected equally by an injection gun on two separate
pads. The base, catalyst, and pad were separately weighed by a digital scale. SNPs (
80–100 nm in size) in 0.5, 1, 2, and 3 wt% were weighted and mixed first with the
base of the soft liner for 100 seconds and then the mixture was added to the catalyst
and mixed for another 60 seconds.

54. Stainless steel moulds were lubricated with petroleum jelly, and acrylic
blocks were placed in them. Mucopren bonding agent was applied on
the acrylic surface, according to the manufacturer’s instructions. One
layer was applied first and the second layer after one minute and allowed
to dry for 30 seconds. Using a 3 mL volume syringe the soft liner was
injected into the space between the acrylic blocks. To create a smooth
surface, a thin glass slide measuring 22 × 22 × 13 mm was placed over
the blocks, allowing 10 minutes for the complete set. The acrylic blocks/
soft liner combination was removed from the mould and incubated at 37°C
for 2 days.

55. TENSILE STRENGTH AND AGEING PROCEDURE
 After two days, 60 samples were subjected to the tensile bond strength test at a crosshead
speed of 5 mm/minute using a universal testing machine.
The remaining 60 samples were subjected to 3000 thermal cycles in 5 and 55°C
temperatures with a dwell time of 30 seconds before the tensile bond strength test. For
each specimen, the maximum tensile strength before failure was recorded.
Data were summarized as mean and standard deviation. As the interaction effect of NPs
concentrations and thermocycling on tensile bound strength became significant, data was
analyzed by one-way analysis of variance (ANOVA) and independent t-test using SPSS
version.

56. One-way ANOVA was carried out to assess the effect of the addition of
different concentrations of NPs on tensile bond strength in thermocycled
and nonthermocycled groups.
 Independent t-test was performed to compare the effect of thermocycling
in each NP concentration.

58. RESULTS
 In nonthermocycled group, the addition of SNPs in all concentrations decreased the
tensile bond strength.
 However, in the thermocycled group, the addition of SNPs had an inverse effect on the
tensile bond strength and by an increase in the concentration of SNPs, the tensile bond
strength increased.
Thermocycling in 0 (control) and 1wt% SNP groups caused a significant reduction in the
bond strength compared with the nonthermocycled group.
The same results were obtained in 2 wt% and 3 wt% SNP groups. Therefore, the effect of
thermocycling on the tensile bond strength was also significant in all concentrations and
the tensile bond strength of the nonthermocycled group was significantly higher than
that of the thermocycled group.

60. CONCLUSION
 The results showed that the addition of 0.5, 1, 2, and 3 wt% SNPs to mucopren
soft liner reduced its tensile bond strength to denture acrylic resin.
Thermocycling decreased the tensile bond strength of soft liner to denture acrylic
resin. Therefore, SNP addition to mucopren soft silicone liner to improve its
antifungal properties may adversely affect its tensile bond strength to denture
acrylic resin.

61. IN VITRO ANTIMICROBIAL EFFECT OF THE TISSUE
CONDITIONER CONTAINING SILVER NANOPARTICLES
• Nam KY. The journal of advanced prosthodontics. 2011;3(1):20.
PURPOSE. The aim of this study was to identify in vitro antimicrobial activity of the tissue
conditioner containing silver nanoparticles on microbial strains, Staphylococcus aureus,
Streptococcus mutans and Candida albicans.
• MATERIALS AND METHODS
• 1. Preparation of silver nanoparticles
• Aqueous silver sol was prepared with 10.0 mm of analytical grade AgNO3 in distilled
water and 2.0% PVP (Polyvinyl Pyrrolidon) used as stabilizer. All solutions were
deaerated by bubbling with argon gas for 1 hour and then they were irradiated in the
field of 20 KGy Co Gamma-ray sources.

63. • 2. Sample fabrication (Ag - tissue conditioner)
• The tissue conditioner selected in this study was GC Soft-Liner (GC cooperation,
Tokyo, Japan) supplied as powder and liquid. Colloidal Ag was combined and
homogenized with the conditioner liquid in a sterile glass beaker at the concentration
ranging from 0 (control), 0.1, 0.5, 1.0, 2.0 to 3.0% (vol/vol %: Colloidal Ag
/conditioner liquid) respectively. Immediately afterwards, the conditioner powder was
added and mixed for 30 seconds at designated powder/liquid ratio as manufacturer's
instruction. In order to fabricate samples into uniform shape with regular surface, the
mixed paste of conditioner was poured onto a custom-made brass mould with the
hole (20 mm diameter × 3.0 mm depth). The mixed paste was sandwiched between
glass-slides until it was solidified under humid condition. The total 162 samples were
prepared and they were divided into six groups (n = 27) according to the
concentration of Ag incorporated.

64. • 3. Microorganisms
• Three standard strain organisms were used: S. aureus (ATCC 6538), S. mutans
(ATCC 10449) and C. albicans (ATCC 14053). Microbial suspensions were
obtained from single colony isolated on agar plates, inoculated in appropriate
broth for overnight cultures. Bacterial strains were grown in brainheart infusion
(BHI) broth and Mueller Hinton agar plates at 37℃ and C. albicans strain was
grown in Schaedler broth and Sabouraud agar plates at 30℃. After incubating
microbial cells at 37℃ overnight, optical density (OD) of the suspension at 600 nm
was adjusted to 1.0 using a spectrophotometer (Milton Roy spectrophotometer ).
The suspension was diluted with phosphate-buffered saline (pH 7.4) to 1:100 and
suspended to final concentration of 1.0 × 107 cells/mL.

65. • 4. Antimicrobial assay
• Each disc sample of Ag -tissue conditioner and control were placed on the flat
bottom of the separate 12-well cell culture plate of 22.1 mm well diameter and
100 μL of initial microbial suspensions in 1.0 ml of Sabouraud broth were
inoculated to each well and incubated at 37℃. After incubation for 24 hrs and
72 hrs for extended contact period, suspension (100 μL) was withdrawn, viable
cells (CFU: Colony Forming Unit) in the suspension were determined by using the
spread plate method at a level of detection with in 500 CFU per plate through the
serial dilution. Assays were independently performed with three repetitive tests
and data were recorded as means and standard deviations. According to
conventional standards, the borderline of antimicrobial effect was determined at
0.1% viable cells. Data were analyzed by oneway ANOVA and Student t-test at a
0.05 probability level.

66. • RESULTS
• When compared to CFU at 0 hour, Control group (0% Ag) did not showed any
microbial inhibitory effect against all tested strains. For two bacterial strains, S.
aureus and S. mutans, Ag-tissue conditioner samples showed the minimal
bactericidal effects (MBC) at the dose of above 0.1% and no viable cells were detected
(no CFU) from the conditions of 1.0% above. And for fungal strain of C. albicans, Ag-
tissue conditioner samples showed the minimal fungicidal concentration at the dose
of above 0.5% and no CFU was detected in 2.0% above. There was no statistical
difference between 24 hrs and extended 72 hrs incubation time (P > .05) for the
antimicrobial effect.

68. • CONCLUSION
• Within the limitations of present in vitro study, the modified tissue conditioner
combined with silver nanoparticles displayed antimicrobial properties against
S. aureus, S. mutans at 0.1% Ag incorporated and C. albicans at 0.5% Ag
incorporated after a 24 hrs and 72 hrs incubation period.

69. REFERENCES

70. Chowdhary R. Effect of adding silver nanoparticle on physical and mechanical
properties of maxillofacial silicone elastomer material-an in-vitro study. J Prosthodont
Res. 2020:64(4):431-5.
Ghaffari T, Hamedi-Rad F. Effect of silver nano-particles on tensile strength of acrylic
resins. J Dent Res Dent Clin Dent Prospects. 2015;9(1):40-43.
Han Y, Kiat-amnuay S, Powers JM, Zhao Y. Effect of nano-oxide concentration on the
mechanical properties of a maxillofacial silicone elastomer. The Journal of Prosthetic
Dentistry. 2008 Dec 1;100(6):465-73.
Habibzadeh S, Omidvaran A, Eskandarion S, Shamshiri AR. Effect of Incorporation of
Silver Nanoparticles on the Tensile Bond Strength of a Long term Soft Denture Liner.
European Journel of Dentistry. 2020 Mar, 14(2),268.
Wang L, Liu Q, Jing D, Zhou S, Shao L.Biomechanical properties of nano-TiO2 addition
to a medical silicone elastomer: The effect of artificial ageing. Journal of dentistry. 2014
Apr 1;42(4):475-83.