Biodegradation of nickel

BIODEGRADATION OF NICKEL
FROM ORTHODONTIC
APPLIANCES
www.indiandentalacademy.com

Introduction
• Orthodontic bands, brackets & wires are
universally made of austenitic stainless steel.
• Nickel titanium alloys were introduced into
Orthodontics in the 1970’s.
• Biodegradation of metals is seen quite
frequently in the Oral environment due to its
ionic, thermal, microbiological & enzymatic
properties.
• Park & Shearer in 1983, reported that Nickel is
the most common cause of allergic reactions
than all other metals put together.www.indiandentalacademy.com

• The average dietary intake for nickel is around
200-300 mic.gm/day(Schroeder 1962 ).
• The hypersensitivity reaction to nickel may be
caused by ingestion or direct contact with the
skin & / mucosa.
• Nickel release from dental alloys has been
reported to be 4.2 mic.gm/sq.cm /day(Moffa
1982).
• In-vitro nickel release rate for orthodontic
appliances has been reported as
40mic.gm/day(Park & Shearer 1983 ).
• Nickel release rate for orthodontic archwires
was found to be 0.26 mic.gm /day (Gjerdet
1987).

• The age range affected by the
hypersensitivity reaction is between 10 &
20 yrs, which corresponds to the period in
which orthodontic treatment is usually
undertaken(Guilherme & Janson 1998 ).
• Recent Ion implanted NiTi wires were
originally introduced to reduce friction, but
they were also reported to have reduced the
nickel release from the archwires( Burstone
& Farzin-nia 1995 ).

Aim Of The Study
• To estimate in-vitro nickel release from
orthodontic appliance set-up, consisting of
brackets-bands at three different time
intervals viz 7,14 & 21 days.
• To compare the nickel release between four
different archwires-untreated NiTi,Stainless
steel, Ion implanted NiTi & Cu NiTi wires.
• To estimate the maximum nickel release of
each archwire at three different time
intervals. www.indiandentalacademy.com

Review Of Literature
• Park & Shearer (1983), measured the
release of nickel & chromium from
simulated orthodontic appliances by atomic
absorption spectrophotometry in-vitro, and
reported that the average release for nickel
was 40 mic.gm /day & that for chromium
was 36 mic.gm /day.
• Blanco-Dalmau et al. (1984), according to
their study reported that 31.9% of women
& 20.7% of men tested were hypersensitive
to nickel. www.indiandentalacademy.com

• Dunlap & coworkers(1989), reported a
case of allergic reaction to orthodontic wire.
• Barrett and Co- workers (1993),compared
invitro the corrosion rate of Nickel and
Chromium from a standard orthodontic
appliance consisting of bands, brackets and
either stainless steel or Nickel Titanium
arch wires.samples were taken on days 1, 7,
14, 21& 28 and was analyzed by using
atomic absorption spectrophotometry.Their
result indicated that the Nickel release
reaches a maximum after 1 week, then the

-rate of release diminishes with time .On the
other hand, chromium release increases
during the first two weeks & levels off
during the subsequent two weeks
• Barrett and co - workers(1993) collected
blood samples from Orthodontic patients
and analysed Nickel by AAS. They reported
that patients did not show any significant
increase in Nickel blood levels during the
first 4-5 months of Orthodontic therapy

• Bass and co-workers(1993), in their study
reported that the prevalence of Nickel
allergy was higher in females than males &
that Orthodontic treatment may induce
Nickel sensitivity.
• Kerosuo (1995),analysed in-vitro release of
Nickel & Chromium from fixed appliance
in both static and dynamic conditions.They
concluded that the fixed appliance with
simulated function showed a significantly
higher cumulative release of Nickel than in
static conditions.www.indiandentalacademy.com

• Hamula &co-workers (1996),suggested
the use of pure Titanium brackets
(Rematitan)for nickel hypersensitivity
patients. Its one-piece construction requires
no brazing layer and thus it is solder and
nickel free.
• Baswa (1998), determined the amount
Nickel & Chromium released in artificial
saliva at varying values of pH 5,6,7&8
using atomic absorption
spectrophotometer.Results showed that
decrease in pH caused an increase in
nickel&chromium release levels.www.indiandentalacademy.com

• Kim & Johnson (1999),suggested that
titanium wires & epoxy coated Nickel
titanium wires exhibited the least corrosive
potential & hence recommended for
patients allergic to nickel.

Materials and Methods
• Twelve identical sets of pre-adjusted
appliance were used. Each appliance was
bonded & cemented to a maxillary denture
made from a standard edentulous mould.
This was done to eliminate the possibility of
corrosion from the inner aspect of bands &
brackets, thereby simulating the intra-oral
conditions more closely.

• The complete full arch set up consisted of
two first molar preformed bands with
double tubes, two- second premolar, first
premolar, canine, lateral, and central incisor
brackets. (Roth prescription)
The archwires compared were:
Untreated Nickel Titanium
Stainless steel wire
Copper Niti wire &
Ion implanted Niti wire

MATERIALS TESTED

• The archwire length was measured from the
distal point of first maxillary right molar to
that of left molar on the denture in this
experiment. For comparative purpose, the
archwires were not fixed to the brackets
instead they were tested separately. All the
archwires, brackets and bands were used in
the “as received” condition from the
dealers.

Experimental Conditions
• Nickel release was tested by placing each of
the 60 samples in separate polyethylene
screw top bottles containing 100ml of
artificial saliva.The pH of artificial saliva
was adjusted to 6.75 +0.15 with 10 N
sodium hydroxide. The pH value coincided
with that reported for human saliva.
(Afonsky 1984)

• The simulated saliva medium (Barrett et al
1993) consisted of:
Sodium chloride - 0.4 gm
Potassium chloride - 1.21 gm
Sodium hypophosphate - 0.78 gm
Sodium sulphide - 0.005 gm
Urea - 1 gm
Distilled & Deionised water - 1000 ml

• The sample bottles were placed in an
incubator (Adair Dutt Company-Calcutta)
and maintained at 37deg C for 3 weeks.On
days 7&14 the entire 100 ml of the artificial
saliva solution was removed for evaluation
from each bottle and replaced with fresh
solution.On day 21 the 100 ml solution was
taken for evaluation of Nickel release. The
replacement of the solution was performed
to avoid saturating the artificial saliva
medium with corrosion products.
• Nickel analysis was performed on the
solutions removed from 60 samples atwww.indiandentalacademy.com

7,14&21 experimental periods. This resulted
in a total of 180 solution samples available
for analysis.
• For control, five similar polyethylene
screw top bottles with 100 ml artificial
saliva and plain acrylic dentures were used.
These solutions were also maintained at 37
degC in the incubator. All the 5 control
samples were tested at the 3 experimental
periods(7,14&21 days) which resulted in a
total of 15 control sample solutions.

• Measurement technique: AAS
The analyses were performed with a flame
atomic absorption spectrophotometer(GBC
Avanta, Australia).AA is a technique based
on the unique spectrum of each element.
For every element analysed, characteristic
wavelengths are generated in a discharge
lamp and in turn are absorbed by a vapour
of that element. The amount of absorption is
proportional to the concentration of the
element that is vaporized into the light
beams. Commercially available Nickel
standard stock solutions were used towww.indiandentalacademy.com

1,2,4&6 mic gm/ml with distilled and
deionized water. Calibration plots were
generated at the start of every run using
freshly prepared working standards. All
glassware were first cleaned with a 1:1:1
solution of sulfuric acid, nitric acid and
water and then stored in a solution
containing 0.6 nitric acid. Before use, all
glassware were rinsed at least three times
with deionized water, inverted and allowed
to dry.

Results

Results
• Statistical Analysis:
Mean and Standard deviation(S.D) were
estimated from the sample for each group at
different time points viz.7th,14th,&21st
day.Significance of change in mean values
at two time points were tested by students
paired t-test.
One-way analysis of variance was employed
to compare the mean “Average/day”nickel
contents between different study groups.www.indiandentalacademy.com

• Multiple comparison test by Tukeys
Honestly significant difference procedure
was employed to identify the significant
groups.
• The statistical package SPSS PC+ was used
for data processing and statistical analysis.

Discussion
• Nickel, which is one of the corrosive
products leached out from stainless steel
and nickel titanium orthodontic alloys is
recognized as a potent sensitizing agent.
(Ralph W.Phillips,1982)
• Characteristic lesions of contact stomatitis
vary from barely visible mild erythema to a
fiery red colour with or without edema.
Symptoms may include loss of
taste,numbness, burning sensation andwww.indiandentalacademy.com

Soreness of the involved area, often
accompanied by angular cheilitis.
• The present study was aimed at measuring
the release rate of nickel from brackets-
bands and between 4 groups of archwires.
All the orthodontic appliances used in this
study contained, nickel as one of their
components. The nickel release was
measured at 3 different time intervals to
find out whether the nickel release increases
constantly or it decreases after an initial
increase. www.indiandentalacademy.com

Ion implantation
• Ion implantation is a process by which
various elements or compounds are ionized
and then accelerated towards a target
(archwire).Ion implantation takes place in a
vacuum chamber, where a vapour flux of
ions is generated with an electron beam
evaporator and deposited on the substrate.
Nitrogen ions are extracted from plasma
and accelerated in the growing physical
vapour deposition film at energies ofwww.indiandentalacademy.com

hundred to several thousand volts. The ions
penetrate the surface of the wire on impact,
building up a structure that consists of both
the original wire and a thin layer on the
surface and immediate subsurface. The
depth, distribution and concentration can be
controlled by varying the ion dosage and
energy.This allows improvement of surface
characteristics without degradation of other
mechanical properties. This process reduces
friction;breakage and more over reduces the
release of nickel in the mouth. (Rose Mary
Ryan - 1997)

The present results indicate a detectable
release of nickel from (a)brackets-bands
(b)various archwires
• The amount of nickel released from
brackets-bands was in the range of 16.51
mic gm/day.
• The maximum amount of nickel released
per day from the archwires tested after 21
days was from Group 1(NiTi wire) 0.93mic
gm followed by Group 4(Cu NiTi wire)
0.77 mic gm, Group 3(Ion Implanted NiTi
wire) 0.67 mic gm and Group 2 (Stainless
steel wire) 0.66 mic gm.www.indiandentalacademy.com

• The release rates of nickel at various time
intervals were found to be common in
brackets-bands and in all the archwires.
When the concentrations of nickel were
measured at various time intervals, a
maximum level was found on day 7, which
steadily decreased during the subsequent
two weeks.This coincided with Park and
Shearer 1983 and Barrett et al 1993
• The total nickel release of nickel from
brackets-bands and archwires during the 3
week period averaged approximately 17.44
mic gm/day.If this value is doubled to

Simulate the equivalent release from
mandibular arch the release would be 34.8
mic gm/day.(Park and Shearer 40 mic gm;
Barrett et al 26 mic gm) These values are
thus well below the normal daily intake of
nickel . However, the amounts are not
directly comparable because the nickel ions
released from the orthodontic appliances
have higher local concentrations and may
thus play a more active role in local nickel
hypersensitivity reactions.

• Hence, Orthodontic treatment for nickel
sensitive patients may prove challenging.
Further studies are required to examine the
cytotoxic effects of released nickel in in-
vitro cell cultures and how much of the
corrosive products are actually absorbed by
the patients. Platt and Co-workers
suggested to use 2205 duplex stainless steel
brackets which has got a low nickel
content(4-6%) in conjunction with various
archwires.

• Recently nickel free brackets like Titanium
brackets and Ceramic brackets can be used
effectively for nickel sensitive patients.
Among the archwires Ion Implanted NiTi
can be used instead of untreated NiTi wires

Summary & Conclusion
The results indicate that:
• Orthodontic appliances release measurable
amounts of nickel when placed in an
artificial saliva medium.
• The nickel release from all the appliances
reaches a maximum after 7 days,then the
rate of release diminishes with time.
• Maximum nickel release was from brackets
and bands combined.www.indiandentalacademy.com

• Among the archwires tested NiTi wire
leaches more of nickel followed by Copper
NiTi wire, Ion implanted NiTi and Stainless
steel wires.
• Ion implanted NiTi wire releases less nickel
when compared to untreated NiTi wire.
• How much of these corrosive products are
actually absorbed by the patients
undergoing orthodontic treatment needs
further research.
• For nickel sensitive patients, it is suggested
to use nickel free brackets with Ion
implanted (NiTi) & SS archwireswww.indiandentalacademy.com

GRAPH 1
0
20
40
60
80
100
120
140
160
180
200
0 7 14 21
Days
Concentrationinmicgms
B&B

GRAPH 7
0.93
0.66
0.67
0.77
NITI
SS
ION NITI
CU NITI

GRAPH 6
0
1
2
3
4
5
6
7
8
0 7 14 21
DAYS
CONCENTRATIONINmicgms
NITI
SS
ION NITI
CU NITI

GRAPH 5
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
samples
concentrationinmicgms
7
14
21

GRAPH 4
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Samples
7
14
21

GRAPH 2
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
Samples
7
14
21

GRAPH 3
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Samples
7
14
21

Biodegradation of nickel

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