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Evaluation of Antibacterial Effect of Silver Nanoparticle Coated Stainless Steel Band Material – A in Vitro Study

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Introduction: Decalcification, caries, inflammatory periodontal disease are the most common iatrogenic effects of orthodontic treatment because of failure to maintain proper oral hygiene. Although various methods have been tried to minimize the incidence of white spot lesions, none of them proved to be effective. The purpose of this study was to develop a hard coating of silver nanoparticles on stainless steel band material and to evaluate the antibacterial efficacy against most common cariogenic pathogens. Materials & Method: Stainless steel band material was cut into 45 pieces of about 0.5 x 1 cm in dimension, of these 25 band material strips were coated with silver nanoparticles using thermal evaporation technology in a Vacuum coating unit (Indovision, India) at a vacuum of 4.5 ×10−5 millibar at 961°C for 5 minutes and remaining strips served as control. Scanning electron microscopy (SEM) study of coated band material showed a uniform deposition of silver nanoparticles of about 18.63 percent by weight. Five coated and five uncoated band material strips were utilized for each test to evaluate the antibacterial effect of the coated band material against Streptococcus mutans, Lactobacillus acidophilus using zone of inhibition and direct contact test. In zone of inhibition test, the bacterial growth inhibition zone was measured after a period of 24-48 hours, where as in direct contact test, the number of bacterial colonies were counted after 24 hours, 48 hours and 1 week. Five coated band materials were immersed separately in a container having 5 ml of artificial saliva and the amount of silver nanoparticles released from coated samples was evaluated after 24 hrs, 48 hrs, and 1 week using atomic absorption spectrophotometer. Result: A stable uniform coating of silver nanoparticles on the band material was obtained by physical vapor deposition. The coated band material showed a potent antibacterial activity against L.acidophilus and S.mutans. The maximum amount of silver nanoparticles released from the silver nanoparticle coated band material was 0.0236 ± 0.0067 ppm, which is below the maximum permissible level set by WHO [0.1 mg /l], proving it as biocompatible. Conclusion: Silver nanoparticle coating on orthodontic band surfaces can provide suitable antimicrobial activity during active orthodontic treatment.
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Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
INTRODUCTION
Fixed orthodontic treatment involves placement of
bands and brackets on the teeth, and orthodontic
bands are often seated in supra and subgingival
areas. Banding of molar teeth has more tendencies for
retention of plaque due to the greater area of band
material compared to bonded attachments and also
due to the obstruction caused by band material to
oral prophylactic measures. Accumulation of plaque
around bands results in decalcication, white spot
lesions and gingival inammation which may progress
Dr S Hima Bindu,1 Dr S V Kala Vani,2 Dr G Nirisha,3 Dr N Madhuri,4
Dr B Sai Deepa,5 Dr S Hemadri6
1Clinical Practitioner, Smile Care Multispeciality Dental Clinic, 2Professor and HOD,
3,6Post Graduate Student, Department of Orthodontics and Dentofacial Orthopaedics,
C.K.S. Theja Institute of Dental Sciences & Research, 4Clinical Practitioner, 5Clinical Practitioner, India
Correspondence: Dr. S.V. Kala Vani; Email: drsvkvaniortho@gmail.com
Evaluation of Antibacterial Effect of Silver Nanoparticle Coated
Stainless Steel Band Material – A in Vitro Study
Research Article
ABSTRACT
Introduction: Decalcication, caries, inammatory periodontal disease are the most common iatrogenic effects of orthodontic
treatment because of failure to maintain proper oral hygiene. Although various methods have been tried to minimize the
incidence of white spot lesions, none of them proved to be effective. The purpose of this study was to develop a hard coating of
silver nanoparticles on stainless steel band material and to evaluate the antibacterial efcacy against most common cariogenic
pathogens.
Materials & Method: Stainless steel band material was cut into 45 pieces of about 0.5 x 1 cm in dimension, of these 25 band
material strips were coated with silver nanoparticles using thermal evaporation technology in a Vacuum coating unit (Indovision,
India) at a vacuum of 4.5 ×10−5 millibar at 961°C for 5 minutes and remaining strips served as control. Scanning electron
microscopy (SEM) study of coated band material showed a uniform deposition of silver nanoparticles of about 18.63 percent
by weight. Five coated and ve uncoated band material strips were utilized for each test to evaluate the antibacterial effect of
the coated band material against Streptococcus mutans, Lactobacillus acidophilus using zone of inhibition and direct contact
test. In zone of inhibition test, the bacterial growth inhibition zone was measured after a period of 24-48 hours, where as in direct
contact test, the number of bacterial colonies were counted after 24 hours, 48 hours and1 week. Five coated band materials
were immersed separately in a container having 5 ml of articial saliva and the amount of silver nanoparticles released from
coated samples was evaluated after 24 hrs, 48 hrs, and 1 week using atomic absorption spectrophotometer.
Result: A stable uniform coating of silver nanoparticles on the band material was obtained by physical vapor deposition. The
coated band material showed a potent antibacterial activity against L.acidophilus and S.mutans. The maximum amount of
silver nanoparticles released from the silver nanoparticle coated band material was 0.0236 ± 0.0067 ppm, which is below the
maximum permissible level set by WHO [0.1 mg /l], proving it as biocompatible.
Conclusion: Silver nanoparticle coating on orthodontic band surfaces can provide suitable antimicrobial activity during active
orthodontic treatment.
Keywords: Antibacterial effect, Band material, Decalcication, Silver nanoparticles
to periodontal disease. Poor oral hygiene is also shown
to increase the orthodontic treatment time, as the cells
involved in the tooth movement such as osteoclasts, do
not efciently perform in an inammatory environment.1
Routine oral hygiene measures depend on
patient compliance. Even higher concentration
of chlorhexidine was not effective in reducing the
Streptococcus mutans count.2 The issue of bacterial
infection can be solved by adjusting the antimicrobial
properties of a metal surface prior to appliance
placement. Various techniques described in the
Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
14
literature include direct impregnation with antibiotics
and the use of antibiotics or silver doped polymer
coatings.3 Among various metals, silver, zinc, copper
exhibits high antibacterial property.4 Nanoparticles (NP)
have a greater surface-to-volume ratio (per unit mass)
compared to non-nanoscale particles, interacting
more closely with microbial membranes and provide
considerably larger surface area for antimicrobial
activity.5 The growing numbers of bacterial strains are
becoming antibiotic-resistant and bacteria are less
likely to develop resistance against metal NPs than
conventional antibiotics.6-9
As silver nanoparticles (SNP) were known to have
good antibacterial activity and biocompatibility,10
stainless steel band material was coated with silver
nanoparticles. Various methods of coating were
described in the literature, which includes thermal
vacuum evaporation1,3,8 spray pyrolysis,13 high vacuum
magnetron sputtering equipment14-16 silanization,9
electroplating,11 dip coating method.17 In the present
study, stainless steel bands are coated with silver
nanoparticles using thermal vacuum evaporation
technology because this method is capable of
producing very high purity thin lm with high deposition
rate and damage to the substrate can be minimized.
Antibacterial efcacy of silver nanoparticle coated
band material against most common cariogenic
pathogens was evaluated.
MATERIALS AND METHOD
Stainless steel band material (0.005’’ x 0.018’’) was
cut into 45 pieces of about 0.5 x1 cm in dimension.
Twenty ve stainless steel strips were coated with silver
nanoparticles and included in the test group; the
remaining strips served as controls. [Table1]
The coating was done by thermal evaporation
technique using - Vacuum coating unit (Indovision,
India) at a vacuum of 4.5 ×10−5 millibar at 961°C for
5 minutes. The substrate (band material) temperature
was maintained at 100° C. The silver wire was kept over
tungsten lament at a distance of 15 cm from the band
material and vaporized to form a uniform coating of
silver nanoparticles on the band material.
Characterization of the coated surface
The surface morphology of the coated and uncoated
samples was examined by scanning electron
microscopy (SEM) and the atomic composition was
determined by energy-dispersive x-ray spectroscopy
(EDS).
Antimicrobial activity test
The antibacterial properties of the samples were
evaluated against Gram-positive S.mutans and
L.acidophilus using zone of inhibition test and direct
contact test.
Zone of inhibition test
The medium (brain heart infusion agar for Lactobacillus
and mutans sanguis agar for S.mutans) (HiMedia,
Mumbai) was prepared from dehydrated media as
per manufacturer’s instructions. Medium at pH 7.2
to 7.4 was transferred to 9 cm diameter Petri dishes
and stored at 2-8° C. Lactobacillus and S.mutans
suspensions were prepared in 0.5 McFarland standard
concentration (108 bacteria per mL) and transferred
to culture medium. Each coated (test sample) and
uncoated (control sample) band were placed in
the culture using sterile forceps at specic millimeter
distance, and all ve plates were incubated for 24-
48 hours at 37° C. Then the bacterial growth inhibition
zone was measured in millimeters.
Direct contact test
Five coated and ve uncoated band materials were
placed in separate micro-tubes containing 1mL of
brain heart infusion broth for Lactobacillus and mutans
sanguis broth for S.mutans. When the strains reached
Bindu SH, Vani SVK, Nirisha G, Madhuri N, Deepa BS, Hemadri S : Evaluation of antibacterial effect of silver nanoparticle coated stainless steel band material – an in vitro
study
Table 1.Distribution of samples
Total number of sample ( n ) – 45
Control sample (nc) – 20 Test sample ( nt) – 25
Lactobacillus Disk diffusion test 5 5
Direct contact test 5 5
Streptococcus Disk diffusion test 5 5
Direct contact test 5 5
Amount of silver ion released - 5
15
Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
Bindu SH, Vani SVK, Nirisha G, Madhuri N, Deepa BS, Hemadri S : Evaluation of antibacterial effect of silver nanoparticle coated stainless steel band material – an in vitro
study
the standard 0.5 McFarland concentration, they were
diluted in 1:10 ratio and 5 μL of this suspension were
then poured into each tube containing 1 mL of the
culture medium. The microtubes were incubated at
37° C and after a period of 24 hours, 48 hours and 1
week, ten μL of the suspension were taken from each
microtube (ve coated, and ve uncoated) using
a micropipette and cultured on a separate culture
medium. These cultures were incubated at 37°C for 24-
48 hours and the colonies, each composed of a single
set of cultures, were counted.
Amount of silver ion released
Five coated band materials were immersed separately
in a container having 5 ml of articial saliva with gentle
shaking. The saliva was replaced and analyzed after
24 hours, 48 hours, and 1 week. The amount of silver
ions leached from the coated samples were measured
using atomic absorption spectrophotometer.
Data obtained from the results were analyzed
statistically using the paired t-test for intragroup
comparison of test and control and independent t-test
for intergroup comparison.
RESULT
Surface morphology and atomic composition
SEM images showed a uniform deposition of silver
nanoparticleson coated band material, whereas
uncoated sample showed only generic metal striations
(Fig.1a,1b). The EDS spectra of the uncoated sample
showed elemental ion content of typical bands such as
Cr, Fe, and Ni. However, no silver ions were detected.
EDS spectra of the coated stainless steel band material
showed the presence of silver ions in addition to the
typical composition of the steel. The amount of Ag
nanoparticles deposited on the coated band material
was about 18.63 percent by weight. (Fig. 2a, 2b)
Antibacterial effect
Zone of inhibition test
A clear zone of inhibition of about 4 mm was observed
around the coated samples against both L.acidophilus
and S. mutans. Whereas, inhibition zone was not
observed around the uncoated SS strips. (Fig. 3a,3b)
[Table 2]
Table 2: Comparison of the zone of inhibition values between
control and test groups against Lactobacillus and Streptococ-
cus using disk diffusion assay.
Group N Lactobacillus Streptococcus
Mean SD Mean SD
Control 5 0.00 mm 0.000 0.00mm 0.000
Test 5 4.300 mm .2739 4.000 mm .3536
Mean Difference -4.3 -4
p value <0.001** <0.001**
Figure 2a: Image showing elemental composition of coated
band material
Figure 2b: Image showing elemental composition of
uncoated band material
Figure 1: SEM images coated
(a) and uncoated (b) band material
Figure 3: Petridishes showing zone of inhibition against
(a) Lactobacillus (b) Streptoccous
Fig. 1a Fig. 3a
Fig. 1b Fig. 3b
Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
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Bindu SH, Vani SVK, Nirisha G, Madhuri N, Deepa BS, Hemadri S : Evaluation of antibacterial effect of silver nanoparticle coated stainless steel band material – an in vitro
study
Direct contact test
The mean number of Lactobacillus colonies grown after
24 and 48 hours and 1 week continued to increase in
the control group but has decreased in the test group
which was statistically signicant. (Fig. 4, 5) [Table 4]
The mean number of Streptococcus colonies also
showed a similar pattern and the difference between
control and test groups after 24 hours, 48 hours and 1
week was statistically signicant. (Fig. 6, 7) [Table 5]
Table 3: Intergroup comparison of the zone of inhibition against Lactobacillus and Streptococcus in test and
control groups using disk diffusion assay.
Parameter N Lactobacillus Streptococcus Mean
Difference P value
Mean SD Mean SD
Control 5 0.00 mm 0.000 0.00mm 0.000 - 0.172 NS
Test 5 4.300 mm 0.2739 4.000mm 0.3536 0.3
Table 4: Comparison of the number of Lactobacillus coloniesin test and control groups
at different time intervals using a direct contact test
Duration N Control Test Mean difference P value
Mean SD Mean SD
24 hours 5 220.80 4.147 44.60 3.209 176.2 <0.001**
48 hours 5323.60 12.033 24.40 2.966 299.2 <0.001**
1 week 5 451.00 5.657 19.00 2.646 432.2 <0.001**
Table 5: Comparison of the number of Streptococcus colonies in test and control groups at various duration using a direct contact test
Duration N Control Test Mean difference P value
Mean SD Mean SD
24 hours 5 254.40 6.542 44.80 2.775 209.6 <0.001**
48 hours 5 333.60 9.711 32.20 3.033 301.4 <0.001**
1 week 5 522.80 14.755 18.60 3.050 504.2 <0.001**
Table 6: Comparison of silver nanoparticles release in the test group at different time intervals.
Duration N Mean SD P value
at 24 hours 5 .0236800 ppm .0067937
<0.001**at 48 hours 5 .0221720 ppm .0056420
at 1 week 5 .0160060 ppm .0032339
Figure 4: Petridishes showing Lactobacillus colonies of control
samples at (a) 24 hours, (b) 48 hours and (c) 1 week
Figure 4: Petridishes showing Lactobacillus colonies of control
samples at (a) 24 hours, (b) 48 hours and (c) 1 week
Figure 5: Petridishes showing Lactobacillus colonies of test
samples at (a) 24 hours, (b) 48 hours and (c) 1 week
Figure 5: Petridishes showing Lactobacillus colonies of test
samples at (a) 24 hours, (b) 48 hours and (c) 1 week
Fig. 4a
Fig. 6a
Fig. 5a
Fig. 7a
Fig. 4b
Fig. 6b
Fig. 5b
Fig. 7b
Fig. 4c
Fig. 6c
Fig. 5c
Fig. 7c
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Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
Bindu SH, Vani SVK, Nirisha G, Madhuri N, Deepa BS, Hemadri S : Evaluation of antibacterial effect of silver nanoparticle coated stainless steel band material – an in vitro
study
Measurement of silver ion released
There was a signicant decrease in the concentration
of silver ions released from coated samples at 24 hours,
48 hours and 1 week with maximum release of 0.0236
± 0.0067 ppm at 24 hours, which is less than maximum
permissible levels set by WHO (0.1mg/L). The mean
concentration of silver ions released at 24 hours, 48
hours, and 1 week were 0.0236 ± 0.0067 ppm, 0.0221 ±
0.0056 ppm, 0.016 ± 0.0032 ppm respectively. [Table 6]
The maximum silver ion release of about 0.0236 ± 0.0067
ppm was noted at 24 hrs which is less than maximum
permissible level set by WHO (0.1 ppm ).19
DISCUSSION
White spot formation or demineralization is a prevalent
unwanted side-effect of orthodontic therapy.
Orthodontic appliances can affect the self-cleaning
ability of teeth, alter the oral microora and increase
the levels of acidogenic plaque bacteria, i.e. mutans
streptococci and lactobacilli in saliva and dental
biolm during active wear of the appliance.
In the oral cavity, the antibacterial properties of NPs
have been used through two broad mechanisms
of combining dental materials with NPs or coating
surfaces with NPs to prevent microbial adhesion, with
the overall aim of reducing the biolm formation.6
An antibacterial coating on orthodontic appliances
offers a possible strategy for reducing such bacterial
damage.
The present study was designed with reference to the
unique antimicrobial properties of silver nanoparticles.
In this study, stainless steel band material used to band
molar teeth were coated with silver nanoparticles to
produce a potentially antimicrobial band material
effective against Gram-positive bacteria.
The coating technique used in this study was vacuum
evaporation technology. Vacuum evaporation is a
physical deposition method that uses resistive heating
to produce a metallic thin lm of solid on a suitable
substrate. The SEM images of coated and uncoated
band materials were compared to assess the presence
of surface SNPs. SEM images of coated band material
showed uniform deposition of SNPs, whereas uncoated
band material showed only generic metal striations.
EDS for coated surface showed the presence of silver
nanoparticles.
The amount of silver nanoparticles deposited as
reported in various studies ranged from 4.26 % 100
% by weight. Juan et al9 deposited 4.26 % of silver on
the titanium surface using silanization method, they
found negligible zones of inhibition against E.coli and
S.aureus, whereas study by Prabha et al deposited
28.22 % of silver on the band material surface using
thermal vacuum evaporation technology and
evaluated cytotoxicity with 3-(4, 5-dimethyl thiazol-2-
yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay which
shows that more than 80 percent viability in all coated
samples.1 In our present study, approximately 18.63 %
of silver nanoparticles by weight was deposited on the
stainless steel band material, which is thought to have
better antibacterial effect and biocompatibility.
The results of our study showed a clear zone of inhibition
of 4.3 mm and 4.0 mm diameter around coated
band material against L.acidophilus and S.mutans
respectively, whereas there is no growth inhibition
zone around uncoated band material. In contrast,
Prabha et al1 noted no growth inhibition around the
silver coated band material against S.mutans. Arash
et al11 evaluated the antibacterial effect of silver (8
10 μm) coated bracket against S.mutans using disk
diffusion assay. They showed that the inhibition halo
was absent around the silver coated bracket, which
was attributed to smaller physical contact between
the silver particles in the bracket and the surrounding
culture medium. Morita et al10 noted a clear zone of
inhibition of more than 4.2 mm diameter around Ag
ion-coated retainer against S.mutans indicating that
Ag ions on the coated wires diffused into the culture
medium and inhibited bacterial growth. No studies in
the literature reported the antibacterial effect of silver
nanoparticles against Lactobacillus using disk diffusion
assay. There was no difference in the antibacterial
effect of silver nanoparticles against L.acidophilus and
S.mutans using disk diffusion assay. [Table.3]
In the direct contact test, the number of bacterial
colonies continued to decrease in the test group,which
was attributed to the potent antibacterial effect
of silver nanoparticles against both S.mutans and
L.acidophilus. The results were similar to the study by
Arash et al11 in which S.mutans colonies increased
slightly after six hours and subsequently decreased
against silver (8 – 10 μm) coated SS brackets when
evaluated for a period of 30 days. A study by Mhaske
et al18 showed a signicant decrease in the total
Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
18
number of lactobacillus colonies around silver coated
SS wire (10 nm thick) compared with the control group
after 24 hours when evaluated using direct contact
test. The results of our study showed that there is no
signicant difference in the number of L.acidophilus
and S.mutans colonies in the test group at 24 hours and
1 week. This implies that silver nanoparticles exhibited
similar antibacterial effect against both L.acidophilus
and S.mutans.
In this study, the amount of silver ions released from
coated band material continued to decrease over a
period of 1 week, with a maximum release of 0.023 ±
0.0067ppm at 24 hours. This was less than the maximum
permissible levels set by the WHO (0.1 mg/L).19 No
studies in the literature evaluated the concentration
of silver ions released from the coated band material
over a period of 1 week. However, there are other
studies in literature, in which the silver ions release were
evaluated from silver nanoparticles coated retainers
and stainless steel sheets.
Rahmani et al8 noted that the amount of silver ions
released from silver coated (200μm) retainers using PVD
after 24 hours of immersion in articial saliva as 0.029 ±
0.005 ppm. Morita et al10 reported the amount of silver
ions released from silver coated (14.817±2.163μm)
titanium retainer after 24 hours as 0.043±0.005 ppm.
Chen et al12 developed a silver coated (2.68 μg/
cm2) stainless steel strip using a chemical method
and evaluated the amount silver ion released after
6,12,24,36 and 48 hours. They observed that the amount
of silver ion released at 24 hours was 0.07 ppm and
silver ion release rate during the rst 24 hours is lower
than in the next 24 hours. SogRyuet al3) measured
the amount of silver ion released from silver coated
(100% by weight) stainless steel strip after 1st, 2nd, and
8th day. The concentration of Ag ions released after
2nd and 8th day was 1.2ppm, 1.95ppm respectively.
They reported that the silver ion concentration on the
8thday was more than the 2nd day, as the solution was
not replaced after the 2nd day.
Although nanoparticle coating was done on different
materials for different purposes, in studies reported so
far, only one study reported silver nanoparticle coating
on stainless steel band material. Our data cannot be
compared with other studies because of difference
in the amount of silver nanoparticle deposited on the
surface, the method of coating used, size and surface
characteristics of a sample on which coating was
done.
As the orthodontic treatment lasts for about 12-24
months, it is pertinent to carry out long term studies
to establish standard protocols which would facilitate
continuous release of nanoparticles from coated band
material in order to maintain prolonged antibacterial
activity.
Since the in vitro studies can never simulate oral
conditions precisely. Further clinical trials are required
to study the antibacterial effect, biocompatibility.
CONCLUSION
In this short term study, band material coated with
silver nanoparticles showed a good antibacterial
effect against L.acidophilus and S.mutans for a period
of one week. This silver nanoparticle coated band
material is especially useful in cases where orthodontic
treatment lasts for longer duration such as cleft cases
and orthognathic surgery and in individuals who lacks
manual dexterity.
Financial support and sponsorship: Nil.
Conicts of interest: There are no conicts of interest.
OJN
Bindu SH, Vani SVK, Nirisha G, Madhuri N, Deepa BS, Hemadri S : Evaluation of antibacterial effect of silver nanoparticle coated stainless steel band material – an in vitro
study
19
Orthodontic Journal of Nepal, Vol. 9 No. 2, July-December 2019
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study
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Article
Full-text available
Objectives: White spots and enamel demineralization around orthodontic brackets are among the most important complications resulting from orthodontic treatments. Since the antibacterial properties of metals and metallic particles have been well documented, the aim of this study was to assess the antibacterial effect of stainless steel orthodontic brackets coated with silver (Ag) particles. Materials and methods: In this study, 40 standard metal brackets were divided into two groups of 20 cases and 20 controls. The brackets in the case group were coated with Ag particles using an electroplating method. Atomic force microscopy and scanning electron microscopy were used to assess the adequacy of the coating process. In addition, antibacterial tests, i.e., disk diffusion and direct contact tests were performed at three, six, 24, and 48 hours, and 15 and 30 days using a Streptococcus mutans strain. The results were analyzed using Student's t-test and repeated measures ANOVA. Results: Analyses via SEM and AFM confirmed that excellent coatings were obtained by using an electroplating method. The groups exhibited similar behavior when subjected to the disk diffusion test in the agar medium. However, the bacterial counts of the Ag-coated brackets were, in general, significantly lower (P<0.001) than those of their non-coated counterparts. Conclusions: Brackets coated with Ag, via an electroplating method, exhibited antibacterial properties when placed in direct contact with Streptococcus mutans. This antibacterial effect persisted for 30 days after contact with the bacteria.
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During the orthodontic treatment, microbial plaques may accumulate around the brackets and cause caries, especially in high-risk patients. Finding ways to eliminate this microbial plaque seems to be essential. The aim of this study was to compare the antibacterial effects of nano copper oxide (CuO) and nano zinc oxide (ZnO) coated brackets against Streptococcus mutans (S.mutans) in order to decrease the risk of caries around the orthodontic brackets during the treatment. Sixty brackets were coated with nanoparticles of ZnO (n=20), CuO (n=20) and CuO-ZnO (n=20). Twelve uncoated brackets constituted the control group. The brackets were bonded to the crowns of extracted premolars, sterilized and prepared for antimicrobial tests (S.mutans ATCC35668). The samples taken after 0, 2, 4, 6 and 24 hours were cultured on agar plates. Colonies were counted 24 hours after incubation. One-way ANOVA and Tukey tests were used for statistical analysis. In CuO and CuO-ZnO coated brackets, no colony growth was seen after two hours. Between 0-6 hours, the mean colony counts were not significantly different between the ZnO and the control group (p>0.05). During 6-24 hours, the growth of S.mutans was significantly reduced by ZnO nanoparticles in comparison with the control group (p< 0.001). However, these bacteria were not totally eliminated. CuO and ZnO-CuO nanoparticles coated brackets have better antimicrobial effect on S.mutans than ZnO coated brackets.
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The major hazard to the orthodontic tooth movement is the friction developing at the bracket wire interface. In the past, there have been various attempts to reduce this friction. We believe that coating the commercially available orthodontic wires with nanoparticles can result in a successful reduction of this friction. The objective of this study is to develop a novel method of coating orthodontic archwires with nanoparticles. Stainless steel (Ormco, CA, USA), titanium molybdenum alloy (Ormco, CA, USA) and nickel-titanium (G and H Wire Company, USA) orthodontic wires with a rectangular cross-section dimension of 0.019"× 0.025", were selected. The wires were later coated with a uniform and smooth nanoparticle film using 100 ml nanocremics. The coating procedure described in this article is a sol-gel thin film dip coating method. The coating procedure was verified by comparing the surface topography of nanocoated archwires with the commercially available archwires in an environmental scanning electron microscope (ESEM). The ESEM images prove that the surface topography of the coated wires was found to be smoother with less surface deteriorations as compared to the commercially available wires. Commercially available orthodontic wires can be successfully coated using a novel method of sol-gel thin film dip coating method.
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Silver has been used in medicine for centuries because of its antimicrobial properties. More recently, silver nanoparticles have been synthesized and incorporated into several biomaterials, since their small size provides great antimicrobial effect, at low filler level. Hence, these nanoparticles have been applied in dentistry, in order to prevent or reduce biofilm formation over dental materials surfaces. This review aims to discuss the current progress in this field, highlighting aspects regarding silver nanoparticles incorporation, such as antimicrobial potential, mechanical properties, cytotoxicity, and long-term effectiveness. We also emphasize the need for more studies to determine the optimal concentration of silver nanoparticle and its release over time.
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Abstract Nanoparticles (NPs) are insoluble particles smaller than 100 nm in size. In order to prevent microbial adhesion or enamel demineralization in orthodontic therapy, two broad strategies have been used. These are incorporating certain NPs into orthodontic adhesives/cements or acrylic resins (nanofillers, silver, TiO2, SiO2, hydroxyapatite, fluorapatite, fluorohydroxyapatite) and coating surfaces of orthodontic appliances with NPs (i.e. coating bracket surfaces with a thin film of nitrogen-doped TiO2). Although the use of NPs in orthodontics can offer new possibilities, previous studies investigated the antimicrobial or physical characteristic over a short time span, i.e. 24 hours to a few weeks, and the limitations of in vitro studies should be recognized. Information on the long-term performance of orthodontic material using nanotechnology is lacking and necessitates further investigation and so do possible safety issues (toxicity), which can be related to the NP sizes.
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