evaluation of leaching from orthodontic

 INTRODUCTION
 AIMS AND OBJECTIVES
 REVIEW OF LITERATURE
 MATERIALS AND METHODS
 PHOTOGRAPHS
 RESULTS
 DISCUSSION
 SUMMARY AND CONCLUSION
 BIBLIOGRAPHY
www.indiandentalacademy.com

 Polymers are the base or matrix substance for
many plastics and devices (like adhesives,
retainers, elastomeric chemicals, elastic ligation
rings) used in orthodontics, many of which are
placed in direct contact with human soft tissues,
often for years.
 Many manufacturers do not disclose the
ingredients or the procedures used in the
manufacturing of their products.
 Hence there is a need to devise a simple yet
effective test to detect and measure the amount
of hazardous by-products released from
routinely used orthodontic materials

 Bisphenol- A (BPA) is an industrial chemical,
used to manufacture polycarbonate and
numerous plastic articles.
 Recent studies have shown that it can leach out
from certain products
 Low levels of BPA have also been found to cause
biological effects
 Mode of action appears to mimic that of the
female hormone, oestrogen
 BPA therefore belongs to a group of chemicals
termed “hormone disruptors” or “endocrine
disruptors”

 There is growing international concern about
man- made endocrine disrupting chemicals,
causing
1. Disruption of the development of offspring in
the womb.
2. Decline in sperm counts
3. Increased rates of hormone related cancers,
such as cancers of the breast, testes and
prostate.
4. Birth defects and other hormone related effects
such as early puberty in girls.

 Generally, manufacturers promote their materials, by giving
more importance to their physical properties of handling and
bond strength with little emphasis on biological
compatibility.
 Manufacturers do not disclose the ingredients or the
procedures used in the manufacturing of their products.
 In the past tests have been conducted to detect the
presence of amount of harmful by-products released from
certain orthodontic materials.
 The major drawback of these studies is that they are
expensive, highly sophisticated and requires specific
equipment.
 Hence there is a need to devise a simple yet effective test
to detect and measure the amount of hazardous by-products
released from routinely used orthodontic materials

1. To evaluate the release of potentially
harmful monomer from routinely used
Orthodontic materials.
 Group I (Adhesives)- Transbond -XT and
Rely-a-bond
 Group II (Retainers)- Self cure acrylic and
Bioplast sheets
 Group III –Elastomeric chains and rings

Photograph1: Group I Samples (adhesives) :
Rely-a-bond (no-mix), Transbond-XT (light cure)

Photograph 2 : Group II Samples (Retainers):
Self cure acrylic Retainers and Bioplast sheets

Photograph 3: Group III Samples: Elastomeric chains (Ortho-
organizers and Ormco) and Elastomeric ligating rings (3M and Ormco)

2. To compare the amount of potentially harmful
monomer leached from various Orthodontic
products using simple chemical tests by
studying color changes at different time
intervals, keeping in mind that faster the
discoloration time, the greater the amount of
leached products present.
 Different time intervels are:
After 5 minutes
After 30 minutes
After 8 hours
After 24 hours

 A test was performed by Matasa1
, where in polymer samples were
immersed in a solution of Potassium Permanganate and the color
changes were observed and compared with controls.
 It was concluded that this test could be used to quantify the
amount of monomer leached depending upon the color change in
the polymer samples immersed in a solution of potassium
permanganate from purple to brown and ultimately to clear.
Purple Brown Clear
Red Yellow

MnO2; Mn2O3
KMnO4 Mn2+
Organic material Leached
No YES

 Eight commercially available orthodontic bonding
materials were tested by Fredericks3
for
mutagenecity as judged by the Ames test.
 The materials all tested negative for mutagenecity
except System I activator and Lee Unique Primer.
 The widespread introductionof materials for direct
bonding into Orthodontic practices and numerous
reports of a variety of toxic reactions to similar
materials had prompted a study of the toxicity of six
adhesives in an animal model which was performed
by Davidson et al4
.
 The monomer component of one adhesive
consistently caused gross irritation and histologic
inflammation in twelve animals in which it was used.
Other adhesives and components did not have this
effect.

 Examination of the potential toxic effects of several
Orthodontic adhesives immediately after
polymerization and at various time intervals up to two
years post polymerization by means of an in-vitro
Overlay Assay performed by Tell et al7
showed
cytotoxic effects immediately after polymerization
and the toxic effect decreased with time, post
-polymerization.

 The present study was done on the commonly used
Orthodontic materials which have been listed bellow.
 THE MATERIALS ARE AS FOLLOWS:
GROUP I
(Adhesives)
GROUP II
(Retainers)
GROUP III
(Elastomeric chains and
Elastic ligating rings)
Transbond – XT
(3M UNITEK, Monrovia
light cure)
(Sample-1)
Rely-.a. bond
( No mix,
Reliance Orthodontic
Products, illinois, USA)
(Sample-2)
Self cure acrylic
(Sample-3)
Bio-Plast sheets
(Sample-4)
Elastomeric chains:
Ortho-Organizers (sample-5)
Ormco (sample-6)
Elastic ligating rings:
Ormco (sample-7)
3M (sample-8)

 Preparation of disclosing solution:
 The disclosing solution was prepared using 1.6mg potassium
permanganate ACS reagent grade, (99%) which was added to 1
liter of distilled water. The solution was stored in a closed
container for at least an hour before use.
 The solution was then placed in 10ml capped test tubes with
the various polymeric products to be tested such as adhesives,
retainers, Elastomeric chains and elastic ligating rings.
 The reaction proceeded in two ways depending on the pH of the
solution.
 In neutral environment, the permanganate (KMnO4) which was
purple in color, reduced to MnO2 and Mn2O3 that gave the
solution a brownish- yellow tint.
 further adding a few drops of an acid such as phosphoric or
hydrochloric acid ,to lower the pH to about 1-2, the color
further changed to clear as the manganese was reduced to
colorless salts.

METHOD
The study was divided into 3 different experiments.
Experiment I
 After the preparation of the disclosing solution, in parallel Group
I materials were prepared for testing, i.e., transbond -XT light
cure was spread on a Teflon surface and cured. Simultaneously
Rely- a bond was cured chemically. After curing, the foils were
cooled and reduced to small particles by using a coffee grinder.
 Group II samples i.e., self cure acrylic retainers and Bio-Plast
sheets were also grounded to fine particles using the same
method.
 As group III samples i.e., elastomeric chains and elastic ligating
rings are rubber-like, grinding will not result in fine-enough
particles.
 The samples were first cooled by immersion in stainless steel tea-
baskets into liquid nitrogen and then immediately crushed with a
hammer that yielded fine enough particles.

Photograph 4: Mincing of Liquid Nitrogen-cooled
Elastomeric chains and Elastomeric ligating rings

 All the samples of group I, group II and group III of 1gm
each was weighed and immersed in 5ml of potassium
permanganate disclosing solution taken in 10cc capped
test tube and they are numbered from zero to eight which
contain different testing samples.
0 - Control
1 - Transbond -XT (light cure)
2 - Rely-a-bond (no mix)
3 - Self cure acrylic
4 - Bio-plast sheets
5 - Elastomeric-chain (Ortho- organizers)
6 - Elastomeric-chain (Ormco)
7 - Elastic ligating rings – (Ormco)
8 - Elastic ligating rings – (3M)

 Using Sony digital (5.1 mega pixels, cyber-shot)
camera, the samples were photographed for
color changes during different time intervals.
a) After 5min
b) After 30min
c) After 8hrs
d) After 24hrs

Photograph 5: Test tubes with Group I, II and III Samples
(After 5 minutes in neutral potassium permanganate)
Photograph 6: Test tubes with Group I, II and III samples
(After 30 minutes in neutral potassium permanganate)
(After 8 hours in neutral potassium permanganate)
(After 24 hours in neutral potassium permanganate)

Experiment II
The potassium permanganate disclosing solution
was diluted with distilled water to a ratio of 1:3
and the test samples were immersed in the
resulting solution and photographed for color
changes as in experiment I.

(After 5 min in diluted potassium permanganate)
Photograph 10: Test tubes with Group I, II, and III samples
(After 30 min in diluted potassium permanganate)
(After 8 hrs in diluted potassium permanganate)
(After 24 hrs in diluted potassium permanganate)

Experiment III
• To the potassium permanganate disclosing
solution, an acid is added to lower the pH to 1
and the same samples will be immersed in the
resulting solution and photographs are taken for
color changes as in experiment I.
• Each fresh test material will be subjected to test
on ten different days, the results tabulated and
statistically evaluated keeping in mind that the
faster the discoloration time, the greater the
amount of leached product present.

(After 5 min in acidified potassium permanganate)
(After 30 min in acidified potassium permanganate)
(After 8 hrs in acidified potassium permanganate)
(After 24 hrs in acidified potassium permanganate)

 Each fresh sample was subjected to test on
ten different days, the results tabulated
and statistically evaluated keeping in mind
that faster the discoloration time, the
greater the amount of leached product
present.
 Results between different orthodontic
materials were compared utilizing the
computer software SPSS version 11 and Chi-
square test. P value less than 0.05 indicates
statistically significant.

Comparison analysis of polymer
leaChing from two adhesives
 After 5 minutes, 30 minutes and 8 hours (In neutral
Potassium permanganate)
 Results indicates that Rely-a-bond adhesive had leached
more amount of polymer than Transbond –XT adhesive,
but when statistically analyzed there is no difference in
polymer leaching between the two adhesives.

 After 24 hours (Neutral Potassium
permanganate)
 Results indicates clearly that Rely-a-bond
adhesive had leached more amount of polymer
than Transbond-XT adhesive.When statistically
compared it was found that there is high
significant amount of difference in polymer
leaching between the two adhesive.

 After 8 hours and 24 hours (In diluted
 Results indicates Rely-a-bond adhesive has leached
significantly more amount of polymer than
Transbond- XT adhesive in diluted solution. When
both are compared statistically there is significant
amount of difference observed in polymer leaching
between the two adhesives.

 After 8 hours and 24 hours (In acidified
 Results indicates that Rely-a-bond adhesive had
leached out more amount of polymer. Since
potassium permanganate was acidified, the reaction
was faster. It indicates statistically high significant
difference between the two adhesives.

leaChing from two retainers
 After 5minutes , 30 minutes, 8 hours and 24 hours
(Neutral Potassium permanganate)
 Results indicates that Self cure acrylic had leached
more amount of polymer than Bioplast sheets.
However when statistically compared there is no
significant difference between the two retainers.

leaChing from two elastomeriC
Chains
 After 5minutes (Neutral potassium
permanganate)
 Results indicates that there is no polymer leached from
both elastomeric chain samples after 5 minutes .
 After 30 minutes ,8 hours and 24 hours
(Neutral potassium permanganate)
 Results indicates that Ortho-organizer Elastomeric chains
had leached more polymer than Ormco Elastomeric chain.
But when statistically compared, there is no significant
difference between the two elastomeric chains.

 After 24 hours (In diluted as well as acidified
potassium permanganate)
 Results indicates that Ortho-organizer
Elastomeric chain had leached more amount of
polymer than Ormco Elastomeric chains. But
when compared statistically there is no
significant difference.

leaChing from two elastiC modules
 After 5minutes and 30 minutes (Neutral potassium
permanganate)
 Result indicates that both elastic modules not leached
polymer.
 After 8 hours and 24 hours(Neutral potassium
permanganate)
 Results clearly indicates that Ormco elastic modules had
leached more amount of polymer than 3M elastic modules.
 When analyzed there is statistically significant difference in
the polymer leaching observed between the Ormco and 3M
elastic modules.

 After 24 hours (Diluted as well as acidified
potassium permanganate)
 Results indicates that there is high statistically
significant difference of polymer leaching between
the two elastic modules.

 BPA has recently also been shown to exhibit antiandrogenic
activities, which may prove to be detrimental in organ
development.
 Studies have shown that estrogenicity of resin compounds is
mainly associated with BPA and BPA dimethacrylate (BPA-DM),
which are monomers found in the base paste of dental
composites.
 In vitro reports have confirmed that BPA and BPA-DM applied to
cancer cells significantly increase cell proliferation and DNA
synthesis, similar to the effect of estrogen.
 In vivo studies with mammals have revealed numerous effects
such as delayed and sustained hyperprolactaemia changes in
estrogen receptors in the hypothalamus and pituitary glands.
 Controversy surrounds this issue because it is unclear how much
BPA or BPA-DM is released to the oral cavity and what dosage is
enough to affect human health.
 BPA also showed mutagenic reactions.

 In Group I, the reaction occurs some what differently in neutral,
diluted and acidic environment.
 In neutral environment, after 5 minutes, after 30minutes, after
8hours and after 24hours, it was found that Transbond- XT light
cure adhesive had leached significantly less amount than Rely-
a-bond no mix adhesive.
 This is because Rely-a-Bond adhesive has all the inherent
disadvantages of the chemical curing mechanism. Mixing of the
paste and liquid components of the chemically cured adhesive
forms voids and induces air entrapment in the bulk material
increasing the porosity and polymerization inhibition, this
increases the amount of unreacted polymer in the adhesive
which in turn increases the chance of polymer leaching.

 In Group II samples, Retainers Self cured acrylic had
leached more polymer than Bio-plast sheets.
 This is because Self cured acrylic is chemically cured;
degree of polymerization is not complete.
 This indicates that there is a greater amount of unreacted
polymer. After 24 hours, when observed for discoloration
Bio-plast sheets also leached to a certain extent as
evidenced by discoloration.
 Bio-plast also leached to a certain extent as evidenced by
discoloration. When both retainers are compared for
leaching statistically there is no significant difference
between the two.

 In Group III two brands of elastomeric chains and two brands of
elastomeric ligating rings were tested.
 In elastomeric chains, Ortho-organizers elastomeric chains had
leached more amount of polymer than Ormco elastomeric
chains.
 In case of Elastomeric ligating rings, Ormco Elastomeric ligating
rings had leached more amount of polymer than 3M Elastomeric
ligating rings.
 The elastomeric chains have the additional disadvantage of not
being inert in the oral environment.

 It is not clear why some elastomeric products leach more
than the other. One reason may be method of
manufacturing.
 There are two methods of manufacturing elastomeric
products: Injection molding and Die stamping. In the past,
studies have showed that die stamped polymers have been
found to be more consistent in physical properties, hence
they may leach less but further studies are required to
confirm this.
 In this study, Elastic ligating rings(Ormco) had leached
significantly more amount of polymer than Elastic ligating
rings (3M). The reason may be that Elastic ligating
rings(Ormco) is manufactured by Injection molding
technique and Elastic ligating rings(3M) by die stamping
method.

Under the conditions of this study, the following
conclusions can be drawn:
a) There is statistically significant amount of polymer leached
from Rely-a-bond no mix adhesive than Transbond- XT light
cure adhesive.
b) No statistically significant difference in the amount of
leached polymer was found among Retainers Self cured
acrylic and Bio-plast sheets.
c) No statistically significant difference in the amount of
leached polymer was found among Ortho-organizers
elastomeric chains and Ormco elastomeric chains.
d) In case of Elastomeric ligating rings, Ormco Elastomeric
ligating rings had leached statistically more amount of
polymer than 3M Elastomeric ligating rings.

 This ex-vivo study evaluated and compared the amount of
potentially harmful monomer leached from various orthodontic
polymer products using a simple and inexpensive “do-it-
yourself” (DIY) test.
 The decision to use materials in the mouth is one that is based
on balance between risks and benefits. Ultimately, the
practioners must determine whether the benefits to the
patient outweigh the risks in his or her own mind.
 By indicating the degree of leaching, the method allows the
manufacturers to optimize their polymer containing products
and the clinician to select the least harmful ones.
 Current findings suggest that the short term risk of estrogenic
effects from dental treatments using Bisphenol-A (BPA) based
resins is insignificant, research should be directed at evaluating
the pharmacokinetics and pharmaco-dynamics of the long term
release of contaminants from BPA based polymer used in the
mouth.

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