UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2023.e3738
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Braz Dent Sci 2023 Jan/Mar;26 (1): e3738
UV-C light as an alternative for disinfecting orthodontic pliers
Luz UV-C como alternativa para desinfecção de alicates ortodônticos
Leidiani Rossi LUCAS
1
, Ricardo Scarparo NAVARRO
2
, Andreia de OLIVEIRA
2
, Selly Sayuri SUZUKI
1
,
Aguinaldo Silva GARCEZ
1
1 - Faculdade São Leopoldo Mandic, Post-Graduate Program Orthodontics. Campinas, SP, Brazil.
2 - Universidade Brasil, Post-Graduate Program Bioengineering. São Paulo, SP, Brazil.
How to cite: Lucas LR, Navarro RS, Oliveira A, Suzuki SS, Garcez AS. UV-C light as an alternative for disinfecting orthodontic pliers. Braz
Dent Sci. 2023;26(1):e3738. https://doi.org/10.4322/bds.2023.e3738
ABSTRACT
Objective: Orthodontists use orthodontic pliers continuously, and these tools have a strong potential for
nosocomial infections. This study aimed to compare the efciency of three methods for disinfecting orthodontic
pliers. Material and Methods: The active tips of 26 orthodontic pliers (distal end cutters and Weingart pliers)
were contaminated with
S. aureus, E. coli,
and
C. albicans
microorganisms, viruses, and spores. The microbial
control methods were 70% alcohol disinfection, glass bead sterilization (250 °C dry heat), and ultraviolet light
irradiation (250 nm UV-C) for 30 and 60 seconds. The number of colony-forming units (CFU) and plaque-forming
units (PFU) was quantied and compared for each microorganism after incubation in culture plates. Results: All
tips of the pliers in the groups that received ultraviolet light or were subjected to glass bead sterilization showed a
signicantly lower number of spores, bacteria, and fungi than their respective control samples (p<0.001). Physical
disinfection with UV-C light may represent a reliable alternative compared to other chemical and physical methods
due to the increase in microorganisms resistant to chemical products and the emission of harmful by-products
after chemical treatment. Conclusion: The tested microbial control methods were effective in the disinfection of
orthodontic pliers, making ultraviolet-C light a promising alternative to eliminate microorganisms from pliers.
KEYWORDS
Biosafety; Contamination; Disinfection; Microorganisms; Ultraviolet light.
RESUMO
Objetivo: Os ortodontistas usam alicates ortodônticos continuamente, e essas ferramentas têm um forte potencial
para infecções nosocomiais. Este estudo teve como objetivo comparar a eciência de três métodos de desinfecção
de alicates ortodônticos. Material e Métodos: As pontas ativas de 26 alicates ortodônticos (cortadores distais e
alicates Weingart) foram contaminadas com microrganismos, vírus e esporos
S. aureus, E. coli e C. albicans.
Os
métodos de controle microbiano foram desinfecção com álcool 70%, esterilização com esferas de vidro (250 °C
calor seco) e irradiação com luz ultravioleta (250 nm UV-C) por 30 e 60 segundos. O número de unidades
formadoras de colônias (UFC) e unidades formadoras de placas (UFP) foi quanticado e comparado para cada
microrganismo após incubação em placas de cultura. Resultados: Todas as pontas do alicate dos grupos que
receberam luz ultravioleta ou foram submetidos à esterilização com esferas de vidro apresentaram número
signicativamente menor de esporos, bactérias e fungos do que suas respectivas amostras controle (p<0,001).
A desinfecção física com luz UV-C pode representar uma alternativa conável em comparação com outros
métodos químicos e físicos devido ao aumento de microrganismos resistentes a produtos químicos e à emissão
de subprodutos nocivos após o tratamento químico. Conclusão: Os métodos de controle microbiano testados
foram ecazes na desinfecção de alicates ortodônticos, tornando a luz ultravioleta-C uma alternativa promissora
para eliminar os microrganismos dos alicates.
PALAVRAS-CHAVE
Biossegurança; Contaminação; Desinfecção; Microganismos; Luz ultravioleta.
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UV-C light as an alternative for disinfecting orthodontic pliers
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UV-C light as an alternative for disinfecting orthodontic pliers
INTRODUCTION
Healthcare-associated infections remain
a high public health concern. Also known as
“nosocomial” or “hospital” infections, they occur
in patients during assistance in a hospital or other
health units [1,2].
Microorganisms that cause healthcare-
associated infections belong to different groups,
such as Gram-negative bacteria (
Acinetobacter
baumannii, Pseudomonas aeruginosa,
and
Escherichia coli)
, Gram-positive bacteria
(
Staphylococcus aureus
), spore-producing
bacteria (
Bacillus spp
.), yeasts (
Candida albicans
),
and viruses (bacteriophage) [3].
Biosafety is highly significant for dental
practice [4] and needs to be more judicious,
especially at current times due to the wide SARS-
CoV-2 transmission [5,6].
Current orthodontic practice must extensively
reassess and restructure this infection control to
prevent cross-contamination [4,7], requiring
effective sterilization and disinfection methods.
Sterilization completely removes microorganisms,
including viruses, bacteria, fungi, and spores.
Disinfection is a short-term process that reduces
microbial contamination and does not remove
all vegetative spores. High-level disinfection
destroys all microorganisms except spores.
Intermediate-level disinfection extinguishes
most microorganisms, including the tuberculosis
bacillus, but not all viruses and spores. Finally,
low-level disinfection is when chemical agents
eliminate a few microorganisms [8-10].
However, diseases may be transmitted
in a dental environment from (1) patients
to dentists, (2) dentists to patients, (3) one
patient to another, and (4) the dental ofce to
the community. When communicable diseases
from saliva or blood contamination increase,
dentists are responsible for minimizing risks,
following strict aseptic principles in the dental
clinical environment, which includes the dental
chair, laboratory equipment, light cables, suction
tips, high- and low-rotation pens, curing units,
sinks, laptops, pens, loupes, and keys, among
others [11].
The infection control methods used in
dental ofces are steam autoclaving (121 °C -
20 minutes), dry-heat oven (180 °C - 60 minutes),
glass bead sterilization (218-240 °C - 10 to
60 seconds), exposure to gaseous agents (ethylene
oxide), and disinfection by chemical agent
immersion. The Brazilian Health Regulatory
Agency (ANVISA) recommends steam autoclaving
for sterilizing orthodontic pliers because it
completely removes microorganisms. However,
this method has some disadvantages, such as long
instrument exposure and cooling times, high cost,
and, given the metallic composition, large hinge
areas and sharp edges that must be cleaned and
dried before sterilization to minimize damage
and corrosion [9].
There are three categories of dental
instruments (critical, semi-critical, and non-
critical) according to the risk of infection, and
sterilization need is determined between use and
contamination levels [12]. Orthodontic pliers are
semi-critical instruments.
The most common disinfectants are
formaldehyde, glutaraldehyde, peracetic acid,
potassium peroxymonosulfate complexes,
phenols, alcohols, iodine compounds, chlorate
compounds, quaternary ammonium salts, and
chlorhexidine [4,13-18]. However, several
studies have shown that orthodontists still prefer
chemical disinfection, and only glutaraldehyde
can be considered a high-level disinfectant for
semi-critical materials, despite being a tissue
irritant and potentially causing allergic reactions
to handlers, which is a disadvantage for daily
use [19].
Isopropyl alcohol (70%) is an intermediate-
level disinfectant used for disinfecting surfaces
and instruments. Alcohol precipitates nucleic
acids, denatures proteins, and dissolves
fats, thus performing antimicrobial action.
It is a fast-acting bactericidal, slightly irritant,
inexpensive, non-toxic, and colorless, and does
not leave residues [13]. However, alcohol has
disadvantages, such as the absence of sporicidal
activity; decreased activity in the presence of
organic matter; fast volatilization with lower
antimicrobial activity in dry blood, saliva, and
other organic matter; non-acceptance by the
ADA (American Dental Association) as a xed
surface and instrument disinfectant, potentially
corroding metallic instruments; inactivity against
hydrophilic viruses; no residual action; and it
is an intermediate-level disinfectant [10,19].
Orthodontists use it extensively in clinical
practice to disinfect orthodontic pliers because
these instruments are expensive and unfeasible
to own several, especially because orthodontic
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care presents short appointments and simple,
relatively fast, and inexpensive procedures to
justify the process of microorganism elimination.
Glass bead sterilization can be used as a
fast and convenient method to sterilize directly
contaminated instruments. This method includes
a metal recipient and glass beads with a diameter
between 1.0 and 1.5 mm, at a temperature
of 218-240 °C, for three to five seconds.
Dutra et al. [16] showed disinfection potential
efcacy of this method with only 10 seconds of
exposure to pre-heated glass beads. Glass bead
sterilization has shown bactericidal and viricidal
effects, including the hepatitis B virus, when
used for ve seconds at 233 °C. Authors such as
Rane et al. [20] and Sinha [10] report that an
interval of three, seven, and 12 minutes is sufcient
for sterilization. Manufacturers recommend
using this method for 10 to 15 seconds but no
more than 60 seconds because the potential for
iatrogenic contact burns should be considered
during application. Therefore, a cooling time of
around two minutes should be allowed before
using the sterilized instruments. However, it is
a reliable method that can be used routinely in
clinical practice [10,16,20-23] but may present
a high corrosion index in metallic orthodontic
instruments, mainly damaging pliers by cutting.
Ultraviolet light has been used as a
disinfection method, showing a broad action
spectrum against several microorganisms, such as
bacteria, fungi, and viruses, destroying pathogens
with antimicrobial resistance [24]. The most
common ultraviolet bands are UV-C, UV-B,
and UV-A, with spectral bands of 200–280 nm,
280–315 nm, and 315–380 nm, respectively.
UV-C has the most potent antimicrobial/antiviral
properties because it inactivates microorganisms
by damaging DNA with photon absorption [25].
It can disinfect clinical environments, hospital
and radiology rooms, ICUs, electronic equipment,
hospital instruments, and PPEs [26-32]. The cycle
time required for disinfection is relatively short.
Authors report that 30 seconds are sufcient to
disinfect a 35-cm-high template, as long as the
UV-C source is close to the object to be disinfected.
However, UV-C efcacy remarkably decreases as
the distance from the lamps increases [33].
The present study aimed to compare the
efcacy of three disinfection methods (UV-C light,
glass bead sterilization, and 70% alcohol) in the
active tips of contaminated orthodontic pliers
using the microbiological method.
MATERIALS AND METHODS
This study was submitted to and approved by
the ethics committee of Faculdade São Leopoldo
Mandic, and it was exempt for not including
patients or animals (2021-0294).
Tested microbial species and materials
The microbiological study was performed
at the Microbiology Department of Faculdade
São Leopoldo Mandic to assess the efcacy of
three disinfection methods on the active tips of
orthodontic pliers. The microorganisms used in
the present study were
S. aureus
(ATCC 25923),
E coli
(ATCC 25922),
C. albicans
(ATCC 10231),
a non-enveloped virus (bacteriophage), and
Geobacillus stearothermophilus
spores (ATCC
7953).
Sample selection
The study sample included 26 pliers
(13 distal end cutters and 13 Weingart pliers).
These pliers were selected because their active
tips were different, and they were the most
used in orthodontic care. All pliers were from
the same brand; had the same characteristics
and metal constitution/alloy; did not present
grooves, wear, or fractures; were in excellent
condition; and were sterilized in an autoclave for
30 minutes at 121 °C before contamination with
microorganisms.
Preparation of the microbial inoculum and
contamination of pliers
The
S. aureus
and
E. coli
strains were sown in
BHI agar (Brain Heart Infusion KASVI, K25-1048,
Spain) at 37 °C for 24 hours. For achieving the
inoculum to contaminate the pliers, colonies were
collected from the plate with a platinum strap
and then homogenized in 5 ml of saline solution
until reaching standard 1 in the McFarland
scale, corresponding to a nal concentration of
3x10
8
CFU/ml.
C. albicans
was sown in Sabouraud agar at
37 °C for 24 hours. For achieving the inoculum
to contaminate the pliers, colonies were collected
from the plate with a platinum strap and then
homogenized in 5 ml of saline solution until
reaching standard 1 in the McFarland scale,
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corresponding to a final concentration of
3x10
8
CFU/ml.
As for spores, a biological indicator
disc (Attest, 3M, USA) for monitoring steam
sterilization cycles was homogenized in 30 ml
of sterile saline solution in a vortex tube agitator
for 30 seconds to obtain a concentration of
3x10
4
CFU/ml.
Bacteriophages were cultivated with
E.
coli
to prepare the viral inoculum, and after
replication, the puried bacteriophage solution
was subjected to plaque-forming unit counts
to determine the initial concentration of viral
particles. A 30-ml saline solution was prepared
with 3x10
8
PFU/ml.
When the suspensions were ready, the
activated tips of the pliers were immersed for
15 minutes in an inoculum solution. Then, they
were removed and left to dry for 20 minutes
under sterile gauze in a laminar ow chamber
for 10 minutes on each side of the pliers.
Analyzed disinfection methods
Immediately after drying, the pliers
underwent the following disinfection procedures:
ultraviolet-C light radiation for 30 and 60 seconds,
glass bead sterilization (STERI 350, Sweden) at a
temperature of 218-240 °C for 30 and 60 seconds,
and 70% isopropyl alcohol (Dell Cosméticos
Ltda., Ibaté, SP, Brazil) by the rubbing method
(gauze soaked in 1 ml of 70% alcohol) in three
interpolated phases with a natural drying period
of 10 minutes, as recommended by ANVISA RDC
#15, 1503/2012.
This study developed a device composed of a
stainless-steel box (for reecting light) of 14.5 cm
in width, 23.5 cm in height, and 25 cm in length
to use the UV-C light. Also, two 8-watt ultraviolet
lamps (200-240 nm) were placed at the bottom
of the box (base) and another on the top (lid)
(Figure 1). Stainless steel was the selected box
material because of its reection ability.
Microbiological analysis
The active surfaces of the pliers contaminated
with spores, bacteria, and fungi were collected
with a sterile swab soaked in sterile saline
solution and rubbed on the active surfaces of the
pliers. Next, this swab was sown in specic agar
with the scattering technique. After seeding, the
plates were incubated in a bacteriological oven
at 37 °C for 24 hours. The colony-forming units
(CFU) were counted with the help of a colony
counter.
For the virus, the swab tip was cut with
sterile scissors and placed in an Eppendorf
microtube with 1 ml of sterile saline solution.
The microtube was homogenized for 30 seconds,
and three aliquots of 10 µL were dripped on the
overlayer of Trypticase Soy Broth (TSB) 0.7%
agar-agar (previously contaminated with
E. coli
at the concentration of 1.5x10
8
CFU/ml) in a Petri
dish with Tryptic Soy Agar (TSA). The plates were
incubated at 37 °C for 24 hours for PFU counts.
Figure 1 - UV-C light box design.
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A single examiner performed the entire
procedure and a second examiner randomly
assessed the samples to prevent an outcome bias.
Statistical analysis
Considering the dichotomous nature
(presence and absence) in the groups subjected
to 70% alcohol, rst, the ultraviolet light and
glass bead values were also dichotomized into the
presence and absence of spores,
E. co
li + S. aure
us,
and
Candida
, and subjected to Fisher’s exact or
G test to allow their comparison with the other
groups presenting quantitative data. Next, t-tests
for one sample veried the potential difference
among the sterilization/disinfection method data
with ultraviolet light and glass beads compared
to their respective controls. Mann-Whitney tests
were applied because the quantitative data
(ultraviolet light and glass beads) did not adhere
to a normal distribution and homoscedasticity for
comparing pliers, methods, and times. In turn,
Kruskal-Wallis and Dunn tests jointly compared
the groups composed of the two pliers, two
disinfection methods, and two times. The SPSS
23 (SPSS INC., Chicago, IL, USA) and BioEstat
5.0 (Fundação Mamirauá, Belém, PA, Brazil)
performed the statistical calculations at a 5%
signicance level.
RESULTS
First, the mean values of the groups evaluated
in a bar diagram of the relative frequency (%)
of distal end cutters and Weingart pliers with
tips containing spores,
E. coli + S. aureus
and
Candida, according to the method and time of
sterilization/disinfection (Figure 2).
When converting the quantitative data of
ultraviolet light and glass beads into dichotomous
answers (present and absent) to compare them
with the similar data achieved for 70% alcohol,
the study did not nd a statistically signicant
difference between distal end cutters and
Weingart pliers for spores,
E. coli
+
S. aureus
and
Candida
.
This finding applies to the individual
comparison (p-values in each row in the last
column of Table I) of groups that received 70%
alcohol, ultraviolet light (30 and 60 seconds), or
glass bead sterilization (30 and 60 seconds) and
the joint contrast of all groups (p-values identied
as “global comparison between the two pliers”
in Table I).
The proportion of distal end cutters
presenting tips with spores was not signicantly
affected by the sterilization/disinfection method,
Figure 2 - Bar diagram of the relative frequency (%) in distal end cutters and Weingart pliers with tips containing with spores,
E. coli
+
S. aureus
and Candida, according to the method and time of sterilization/disinfection. Source: Produced by the authors.
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Table I - Absolute (n) and relative (%) frequencies of distal end cutters and Weingart pliers with tips containing spores,
E. coli + S. aureus,
and
Candida
, according to the sterilization/disinfection method and time (CFU/ml)
Method
Distal end cutter
Pliers p-value (comparison
between pliers for
each of the methods)
Weingart
Spores
Ultraviolet light - 30 seconds 3 (23.1%) 3 (23.1%) 1.000*
Ultraviolet light - 60 seconds 1 (7.7%) 0 (0.0%) 1.000*
70% alcohol 3 (23.1%) 5 (38.5%) 0.673*
Glass beads - 30 seconds 3 (23.1%) 0 (0.0%) 0.220*
Glass beads - 60 seconds 1 (7.7%) 0 (0.0%) 1.000*
p-value (global comparison between
methods for each of the pliers)
0.580** 0.002** —
p-value (global comparison between
the two pliers)
0.138** —
Method
Distal end cutter
Pliers p-value (comparison
between pliers for
each of the methods)
Weingart
E. coli
and
S.
aureus
Ultraviolet light - 30 seconds 5 (38.5%) 2 (15.4%) 0.378*
Ultraviolet light - 60 seconds 9 (69.2%) 9 (6.2%) 1.000*
70% alcohol 2 (15.4%) 2 (15.4%) 1.000*
Glass beads - 30 seconds 1 (7.7%) 0 (0.0%) 1.000*
Glass beads - 60 seconds 0 (0.0%) 0 (0.0%) 1.000*
p-value (global comparison between
methods for each of the pliers)
< 0.001** < 0.001** —
p-value (global comparison between
the two pliers)
0.703** —
Method
Distal end cutter
Pliers p-value (comparison
between pliers for
each of the methods)
Weingart
Candida
Ultraviolet light - 30 seconds 10 (76.9%) 7 (53.8%) 0.411*
Ultraviolet light - 60 seconds 4 (30.8%) 9 (69.2%) 0.115*
70% alcohol 1 (7.7%) 0 (0.0%) 1.000*
Glass beads - 30 seconds 0 (0.0%) 0 (0.0%) 1.000*
Glass beads - 60 seconds 0 (0.0%) 0 (0.0%) 1.000*
p-value (global comparison between
methods for each of the pliers)
< 0.001** < 0.001** —
p-value (global comparison between
the two pliers)
0.425** —
Legend: p-values ≤ 0.05 indicate a statistically significant difference by Fisher’s exact (*) or G (**) test.
Source: Produced by the authors.
as seen in the p-value in the penultimate row
of results for spores in Table I. However, the
tips of Weingart pliers showed significantly
more samples with spores using 70% alcohol
than ultraviolet light for 30 seconds. Glass bead
sterilization for 30 or 60 seconds and ultraviolet
light applied for longer (60 seconds) did not
show spores (penultimate column and row called
“global comparison between methods for each of
the pliers” in Table 1).
As for
E. coli
and
S. aureus
, the proportion
of samples with bacteria was signicantly higher
when applying ultraviolet light for 60 seconds
for both tested pliers. Using this same light
for 30 seconds caused a significantly higher
proportion of distal end cutter tip samples with
bacteria than those treated with 70% alcohol.
The
E. coli + S. aureus
proportion was equal
in the samples subjected to ultraviolet light
for 30 seconds and 70% alcohol. The tips of
Weingart pliers did not show bacteria in the
groups sterilized with glass beads for either 30 or
60 seconds, but distal end cutters did not show
spores when applying the beads for 60 seconds
(Figure 2 and Table I).
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Regarding the data of the presence/absence
of
C. albicans
, the proportion of tips of distal end
cutters with this fungus was signicantly higher
when using ultraviolet light as a sterilization/
disinfection method for 30 seconds than
60 seconds. In turn, the latter showed more
samples with
C. albicans
than the group treated
with 70% alcohol. Glass bead sterilization did not
show
Candida
in the tips of distal end cutters and
Weingart pliers. However, the tips of the latter
instruments sterilized with 70% alcohol also did
not show fungi, which appeared in 69.2% and
53.8% of samples subjected to ultraviolet light
for 60 and 30 seconds, respectively (Figure 2 and
Table I).
When focusing on groups with quantitative
original data of spores,
E. coli
,
S. aureus
, and
C. albicans
, meaning the groups that received
ultraviolet light or glass bead sterilization, the
analyses showed a signicantly lower number of
spores, bacteria, and fungi in the tips of all pliers
and all methods than their respective controls
(p < 0.001) (Table II).
Regarding the quantification data, the
application time of 30 or 60 seconds did not
Table II - Quantification (CFU/ml and PFU/ml) of spores,
E. coli + S. aureus, Candida
, and viruses in the tips of distal end cutters and Weingart
pliers, according to the sterilization/disinfection method and time
Method
Distal end cutters Weingart pliers
30 seconds 60 seconds p-value* 30 seconds 60 seconds p-value*
Spores
Ultraviolet light 0.23 (0.44) 0.00 0.08 (0.28) 0.00 0.505 0.38 (0.87) 0.00 0.00 (0.00) 0.00 0.317
Glass beads 0.23 (0.44) 0.00 0.08 (0.28) 0.00 0.505 0.00 (0.00) 0.00 0.00 (0.00) 0.00 1.000
p-value** 1.000 1.000 — 0.317 1.000 —
Control p-valueΨ p-valueΨ
Ultraviolet light 4 2 < 0.001 3 6 < 0.001
Glass beads 1 1 < 0.001 1 1 < 0.001
Method
Distal end cutters Weingart pliers
30 seconds 60 seconds p-value* 30 seconds 60 seconds p-value*
E. coli/S.
aureus
Ultraviolet light 2.85 (3.89) 0.00 6.31 (7.30) 5.00 0.191 0.69 (1.80) 0.00 6.46 (11.10) 2.00 0.021
Glass beads 0.08 (0.28) 0.00 0.00 (0.00) 0.00 0.739 0.00 (0.00) 0.00 0.00 (0.00) 0.00 1.000
p-value** 0.144 0.003 — 0.505 0.003 —
Control p-valueΨ p-valueΨ
Ultraviolet light 300 300 < 0.001 300 136 < 0.001
Glass beads 277 277 < 0.001 44 44 < 0.001
Method
Distal end cutters
Weingart pliers
30 seconds 60 seconds p-value* 30 seconds 60 seconds p-value*
Candida
Ultraviolet light 5.38 (7.61) 3.00 1.62 (3.43) 0.00 0.003 1.62 (2.06) 1.00 2.38 (3.59) 1.00 0.663
Glass beads 0.00 (0.00) 0.00 0.00 (0.00) 0.00 1.000 0.00 (0.00) 0.00 0.00 (0.00) 0.00 1.000
p-value** < 0.001 0.182 — 0.020 0.003 —
Control p-valueΨ p-valueΨ
Ultraviolet light 300 300 < 0.001 300 980 < 0.001
Glass beads 300 300 < 0.001 99 99 < 0.001
Method
Distal end cutters Weingart pliers
30 seconds 60 seconds p-value* 30 seconds 60 seconds p-value*
Viruses
Ultraviolet light 0.08 (0.15) 0.00 1.08 (1.38) 0.33 0.017 0.28 (0.47) 0.00 0.28 (0.36) 0.33 0.778
Glass beads — — — — — —
p-value** — — — — — —
Control p-valueΨ p-valueΨ
Ultraviolet light 16.8 (9.0) < 0.001 2.8 (1.6) < 0.001
Glass beads — — — — — —
*Comparisons between times for the same sterilization/disinfection method and pliers (comparisons within each row). **Comparisons
between sterilization/disinfection methods for the same time and pliers (comparisons within each column). Ψp-value for the comparison with
respective control groups.
Legend: Mean and standard deviation values (in parentheses) in the first row of each group and median under them. p-values ≤ 0.05 indicate
a statistically significant difference by Mann-Whitney tests.
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signicantly interfere with spore counts in the
tips of any of the two pliers and sterilization/
disinfection methods (ultraviolet light and glass
beads). This lack of difference between counts
from the application time (30 versus 60 seconds)
was repeated for
E. coli, S. aureus
, and
C. albicans
quantication, but with two exceptions. First, the
tips of Weingart pliers that received ultraviolet
light for 60 seconds showed a significantly
higher number of
E. coli
and
S. aureus
than the
30 second application time. Second, the tips of
distal end cutters that received ultraviolet light
for 30 seconds showed a significantly higher
number of
C. albicans
than the 60-second
application time (Figure 2). As for viruses in
which only ultraviolet light was investigated,
the time affected counting signicantly only for
the tips of distal end cutters, and application for
60 seconds produced a signicantly higher viral
load than 30 seconds how observed in Table II.
The comparison of ultraviolet light and
glass bead methods for spores did not show a
signicant difference, regardless of pliers and
time (30 or 60 seconds). However, bacteria
presented a significantly higher number of
E. coli
and
S. aureus
when using ultraviolet
light than glass beads in the tips of both pliers,
but only for the 60 second application time.
Moreover, the number of fungi in the tips of
pliers was signicantly higher for the ultraviolet
light application than for glass beads. There was
no signicant difference in
C. albicans
counts
between ultraviolet light and glass beads only
when subjecting distal end cutters to these
methods for 60 seconds.
DISCUSSION
This study addressed the need for a new
disinfection method, comparing it with the ones
most commonly used by orthodontists. UV-C light
was compared with 70% alcohol and glass bead
sterilization.
The oral cavity is a natural habitat for
numerous biological agents (microorganisms).
This ecological niche may represent a reservoir
of opportunistic and pathogenic microorganisms
and a risk of cross-contamination and infection,
potentially causing systemic infections [4,7].
The microorganisms tested in this study
are often used for controlling and monitoring
the action of disinfectants in specific culture
media [3]. During orthodontic care, pathogens
may be transposed through a direct interaction
of contaminated instruments or materials [5,6].
However, orthodontists often neglect the
sterilization method, treating it as something
that may reduce profitability and efficacy in
the dental ofce due to the need for investing
in several orthodontic pliers and the time
demand, respectively. This situation makes
orthodontists consider disinfection an alternative
to sterilization, which is a common mistake [19].
Orthodontic pliers present high contamination
rates, so microorganism dissemination through
these tools must not be neglected [12]. The present
study did not show statistically significant
differences in pliers contaminated with spores,
E. coli + S. aureus,
and
C. albicans
, but the CFU
percentage decreased for microorganisms, thus
promoting disinfection instead of sterilization.
The tests to verify the sufciency of 70%
alcohol rub, glass bead sterilization, and exposure
to UV-C light after the clinical use of these
pliers showed a decrease in microorganisms, as
expected. However, all pliers maintained some
degree of contamination, remaining potential
infectants from the biological standpoint.
The 70% alcohol is an intermediate-level
disinfectant efcient in disinfecting semi-critical
items, showing consistent disinfection in this
study. However, the ease of use, low cost, and
virtually non-existent toxicity associated with the
false impression of infection control make several
clinicians to use it in their instruments between
patient appointments [10,13,17,19].
The glass bead method applied for
30 and 60 seconds did not show microorganisms,
corroborating a previous study, which is similar
to the results of Kangane et al. [21], who found
that 30 seconds of exposure would be sufcient to
disinfect the tips of orthodontic pliers. Therefore,
it would take approximately 20 minutes to
warm the beads to 250 °C, increasing the
time for instrument use and representing a
fast and convenient method for high-level
disinfection. However, it presents a high potential
for iatrogenic contact burns and a high corrosion
index and requires a cooling time of two minutes
before using the sterilized instruments.
Although there was no statistically
signicant difference among the tested methods,
contamination with
S. aureus
and
E. coli
was
9
Braz Dent Sci 2023 Jan/Mar;26 (1): e3738
Lucas et al.
UV-C light as an alternative for disinfecting orthodontic pliers
Lucas et al.
UV-C light as an alternative for disinfecting orthodontic pliers
more frequent in the UV-C light method for
30 or 60 seconds, corroborating authors who
deemed the assessment of irradiation and time of
exposure to UV-C light essential for disinfection
with this method [24,25,30,33]. A study by El
Haddad et al. [27] found that two minutes of
exposure would be sufcient to reduce by 70%
the bacterial load of surfaces in hospital operating
rooms, showing that time and irradiation affect
disinfection efciency [28].
The comparison of light with other methods
and microorganism varieties involved in health-
related infections did not find an adequate
disinfection capacity for UV-C light even
after 60 seconds of exposure to irradiation.
The insufcient disinfection efcacy with this
method might be due to its low ability to reach
all sides of the active tips of pliers, suggesting
an alternative for further studies to develop a
movement in pliers for complete irradiation.
However, this study showed that UV-C light
disinfects the active tips of orthodontic pliers.
This method is not adequate for sterilization
but is often used for disinfection, indicating a
reliable alternative compared to other physical
and chemical methods. The present study shows
the antimicrobial effectiveness of UV-C light, but
future studies with new UV-C light equipment
with greater emission power can be tested in
order to reduce the application time.
The impact of glass bead sterilization on
viruses was not assessed for the active tips of
orthodontic pliers, so the results do not guarantee
complete instrument disinfection. It is worth
noting that the microbial load used for infecting
the instruments is perhaps much higher than that
applied in the clinical routine.
CONCLUSION
Glass bead sterilization was the most
effective of the three disinfection methods in
the active tips of orthodontic pliers when used
for microorganisms, compared to 70% alcohol
and UV-C light.
The 70% alcohol is easy to use, inexpensive,
and virtually non-toxic, but it is not an effective
method for semi-critical instruments.
UV-C light signicantly reduced contamina-
tion levels in orthodontic pliers but less than glass
bead sterilization. Nonetheless, it represented
an alternative method due to the increase in
microorganisms resistant to chemical products
and the emission of harmful by-products after
chemical treatment. Therefore, further studies are
required because the simplicity and low resource
demand may suggest promising dental clinical
applicability.
Author’s Contributions
LRL: Conceptualization, Investigation,
Resources, Data Curation, Writing – Original
Draft Preparation. RSN, AO: Writing – Original
Draft Preparation, Writing – Review & Editing.
SSS, ASG: Conceptualization, Methodology,
Supervision, Project Administration, Writing
Review & Editing.
Conict of Interest
The authors have no proprietary, nancial,
or other personal interest of any nature or kind
in any product, service, and/or company that is
presented in this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
This study was conducted in accordance with
national guidelines for the supervision of human
and animal research. The study was carried out
after approval by the Research Ethics Committee
of Faculdade São Leopoldo Mandic. The study
was waived because it did not include patients
or animals, standard microbiological samples
acquired for laboratory studies were used. The
approval code for this study is 2021-0294.
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Date submitted: 2022 Dec 13
Accept submission: 2023 Feb 01
Aguinaldo Silva Garcez
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