thesis

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EFFECT ON BOND STRENGTH OFEFFECT ON BOND STRENGTH OF
PRE-ADJUSTED EDGEWISEPRE-ADJUSTED EDGEWISE
METALLIC BRACKETS RECYCLEDMETALLIC BRACKETS RECYCLED
BY ACID BATH, SAND BLASTING &BY ACID BATH, SAND BLASTING &
ELECTROLYTIC METHODSELECTROLYTIC METHODS
- A comparative In-Vitro Study- A comparative In-Vitro Study

IntroductionIntroduction
The birth place of ideas, where just asThe birth place of ideas, where just as
day follows night, the new replacesday follows night, the new replaces
old and innovation wipes away theold and innovation wipes away the
common place. Where every problem iscommon place. Where every problem is
but a creative opportunity.but a creative opportunity.

INTRODUCTIONINTRODUCTION
One of the most commonly faced problems duringOne of the most commonly faced problems during
the treatment in orthodontics is of bracket failure .the treatment in orthodontics is of bracket failure .
A significant number of teeth must be re-bonded inA significant number of teeth must be re-bonded in
a busy orthodontic practice.a busy orthodontic practice.
Typically clinicians would discard a dislodgedTypically clinicians would discard a dislodged
bracket and replace it with a new bracket inbracket and replace it with a new bracket in
subsequent visits.subsequent visits.
Hence increasing the cost of treatment andHence increasing the cost of treatment and
prolonging the treatment duration.prolonging the treatment duration.

AIMS AND OBJECTIVESAIMS AND OBJECTIVES
The objectives of the present study were:The objectives of the present study were:
– To evaluate and compare the effect on bond strength ofTo evaluate and compare the effect on bond strength of
new and recycled pre-adjusted edgewise stainless steelnew and recycled pre-adjusted edgewise stainless steel
brackets using various methods for recycling.brackets using various methods for recycling.
– To determine the most efficient in-house method ofTo determine the most efficient in-house method of
recycling stainless steel brackets.recycling stainless steel brackets.
– To compare the integrity of new bracket bases withTo compare the integrity of new bracket bases with
recycled bracket bases under a scanning electronrecycled bracket bases under a scanning electron
microscope.microscope.

MATERIALS AND METHODSMATERIALS AND METHODS
This study was carried out on one hundred andThis study was carried out on one hundred and
fifty extracted upper premolar teeth forfifty extracted upper premolar teeth for
orthodontic treatment.orthodontic treatment.
After extraction, the teeth were cleansed of softAfter extraction, the teeth were cleansed of soft
tissue and after careful debridement ,the teethtissue and after careful debridement ,the teeth
were stored in normal saline at room temperature.were stored in normal saline at room temperature.
The teeth used were between one month and sixThe teeth used were between one month and six
months after extractionmonths after extraction

Criteria For Teeth SelectionCriteria For Teeth Selection
Inclusion criteriaInclusion criteria ::
The teeth included for the study were premolarsThe teeth included for the study were premolars
which were extracted from healthy patients forwhich were extracted from healthy patients for
orthodontic purpose and of normal morphology.orthodontic purpose and of normal morphology.
Exclusion criteriaExclusion criteria ::
Teeth which have an abnormal morphology, carious,Teeth which have an abnormal morphology, carious,
hypoplastic and damaged teeth were not included inhypoplastic and damaged teeth were not included in
the studythe study ..

MATERIALS AND METHODSMATERIALS AND METHODS
These one hundred and fifty teeth were mountedThese one hundred and fifty teeth were mounted
on specially fabricated cylindrical metal jigs usingon specially fabricated cylindrical metal jigs using
pink acrylic with only its buccal surface exposed.pink acrylic with only its buccal surface exposed.
The jigs were colour coded inThe jigs were colour coded in REDRED,, GREENGREEN andand
BLUEBLUE colours for proper identification of samplescolours for proper identification of samples
for various recycling techniques.for various recycling techniques.
The buccal surfaces of the teeth were polishedThe buccal surfaces of the teeth were polished
using non-fluoridated oil free pumice slurry and ausing non-fluoridated oil free pumice slurry and a
rubber cup mounted on a slow handpiece.rubber cup mounted on a slow handpiece.

Group A
33.33%
Group B
33.33%
Group C
33.33%

SAMPLE SPECIMENSSAMPLE SPECIMENS

They were then washed with distilled water and driedThey were then washed with distilled water and dried
using compressed oil free air.using compressed oil free air.
The teeth were then etched with Transbond etchant , 35%The teeth were then etched with Transbond etchant , 35%
phosphoric acid (3M Unitek) for fifteen seconds and thenphosphoric acid (3M Unitek) for fifteen seconds and then
rinsed with water and dried with compressed oil free air.rinsed with water and dried with compressed oil free air.
This was followed by applying the Transbond X T (3MThis was followed by applying the Transbond X T (3M
Unitek) primer using an applicator brush.Unitek) primer using an applicator brush.
They were then bonded with upper premolar metalThey were then bonded with upper premolar metal
brackets (Gemini series, 3M Unitek) using Transbond XTbrackets (Gemini series, 3M Unitek) using Transbond XT
light cure composite (3MUnitek).light cure composite (3MUnitek).
The bracket was then light cured (3M ESPE Elipar 2500The bracket was then light cured (3M ESPE Elipar 2500
Halogen curing light) for twenty seconds.Halogen curing light) for twenty seconds.

The same procedure was followed for theThe same procedure was followed for the
one hundred and fifty brackets.one hundred and fifty brackets.
All brackets were bonded at 4mm from theAll brackets were bonded at 4mm from the
buccal cuspal tips.buccal cuspal tips.
The teeth were then stored in normalThe teeth were then stored in normal
saline at room temperature for 24 hourssaline at room temperature for 24 hours
prior to testingprior to testing ..

TEST PROCEDURETEST PROCEDURE
All the samples wereAll the samples were
then tested for theirthen tested for their
shear bond strengthshear bond strength
using an Instronusing an Instron
universal testinguniversal testing
machine (Modelmachine (Model
no.4467).no.4467).
The cross headThe cross head
speed was set atspeed was set at
0.5mm per minute0.5mm per minute
and having a load celland having a load cell
of 30KN.of 30KN. www.indiandentalacademy.comwww.indiandentalacademy.com

A gingivo-occlusal load wasA gingivo-occlusal load was
applied to the bracketapplied to the bracket
producing a shearing force atproducing a shearing force at
bracket tooth interface.bracket tooth interface.
The stainless steel braidedThe stainless steel braided
wire loop used to apply thewire loop used to apply the
debonding force to the bracketdebonding force to the bracket
occupied the entire bracketoccupied the entire bracket
wings, so that the point ofwings, so that the point of
application is at the sameapplication is at the same
distance from the bracket/resindistance from the bracket/resin
interface in all samples.interface in all samples.

These groups were designated as.These groups were designated as.
GROUP A :GROUP A : codedcoded redred comprising of fiftycomprising of fifty
teeth which were subjected to recycling byteeth which were subjected to recycling by
Acidbath MethodAcidbath Method..
GROUP BGROUP B: coded: coded greengreen comprising of fiftycomprising of fifty
teeth which were recycled byteeth which were recycled by SandblastingSandblasting
method.method.
GROUP CGROUP C: coded: coded blueblue comprising of fiftycomprising of fifty
teeth which were recycled byteeth which were recycled by Electrolytic /Electrolytic /
Thermal Method.Thermal Method.

ACID BATH TECHNIQUEACID BATH TECHNIQUE
Group A were recycled by this method.Group A were recycled by this method.
The acid solution consisted ofThe acid solution consisted of
32% hydrochloric acid and32% hydrochloric acid and
55% nitric acid55% nitric acid
mixed in a 1: 4 ratiomixed in a 1: 4 ratio
The acid bath method consisted of subjecting the brackets to flame.The acid bath method consisted of subjecting the brackets to flame.
These discoloured brackets were then submerged for 5-15 secondsThese discoloured brackets were then submerged for 5-15 seconds
in the acidbath. This process removed any tarnish, dissolved anyin the acidbath. This process removed any tarnish, dissolved any
adhesive residue and had a disinfectant effect.adhesive residue and had a disinfectant effect.
The bracket is then essentially rinsed under running water for 30-60The bracket is then essentially rinsed under running water for 30-60
sec after removing from the acid bath.sec after removing from the acid bath.
After this a sodium bicarbonate solution was used to neutralizeAfter this a sodium bicarbonate solution was used to neutralize
residual acid if any present. The bracket was then air dried usingresidual acid if any present. The bracket was then air dried using
compressed oil free air.compressed oil free air. www.indiandentalacademy.comwww.indiandentalacademy.com

ACID BATH TECHNIQUEACID BATH TECHNIQUE

SANDBLASTING METHODSANDBLASTING METHOD
Group B were recycled by this method.Group B were recycled by this method.
This method consisted of subjecting the bracket bases toThis method consisted of subjecting the bracket bases to
sandblastingsandblasting
Aluminum oxide particles of size 50 μm were used for recyclingAluminum oxide particles of size 50 μm were used for recycling
stainless steel brackets.stainless steel brackets.
The distance between the sandblasting handpiece and the bracketThe distance between the sandblasting handpiece and the bracket
base was fixed at 10mm. To ensure the distance is 10 mm onebase was fixed at 10mm. To ensure the distance is 10 mm one
piece of stainless steel wire was measured and taped to thepiece of stainless steel wire was measured and taped to the
sandblasting device.sandblasting device.
Each bracket was sandblasted within the range of 20-40secondsEach bracket was sandblasted within the range of 20-40seconds
under a pressure of 80psi, until bonding resin was no longer visibleunder a pressure of 80psi, until bonding resin was no longer visible
to the naked eye and the bracket base appeared frosted.to the naked eye and the bracket base appeared frosted.

SANDBLASTINGSANDBLASTING
METHODMETHOD

Electrolytic / Thermal methodElectrolytic / Thermal method
Group C were selected for this methodGroup C were selected for this method
The electrolytic / thermal method of recycling theThe electrolytic / thermal method of recycling the
brackets incorporated the following process.brackets incorporated the following process.
The process consisted of three steps:The process consisted of three steps:
– Burning off the old bonding material.Burning off the old bonding material.
– Removing the remaining inorganic filler- PreliminaryRemoving the remaining inorganic filler- Preliminary
Polishing.Polishing.
– Electropolishing the attachment – Final Polishing.Electropolishing the attachment – Final Polishing.

Burning off the old BondingBurning off the old Bonding
MaterialMaterial

Removal of Remaining Inorganic Filler —Removal of Remaining Inorganic Filler —
Preliminary PolishingPreliminary Polishing

Final Treatment —ElectropolishingFinal Treatment —Electropolishing
The final polishing was carried out individually.The final polishing was carried out individually.
A high density current supply is developed, which speedsA high density current supply is developed, which speeds
up the polishing considerably.up the polishing considerably.
Each bracket was clipped using a steel alligator clip usingEach bracket was clipped using a steel alligator clip using
ligature wire and dipped into the polishing tank.ligature wire and dipped into the polishing tank.
Usually, five seconds were needed to produce a brilliantUsually, five seconds were needed to produce a brilliant
finish.finish.
They were then washed in distilled water and placed backThey were then washed in distilled water and placed back
in the pouch to which it belonged.in the pouch to which it belonged.

Final Treatment —ElectropolishingFinal Treatment —Electropolishing
The electrolyte used for this process was made up of 37 volumes of technicaThe electrolyte used for this process was made up of 37 volumes of technica
phosphoric acid (85%), 56 volumes of glycerol, 7 volumes of water.phosphoric acid (85%), 56 volumes of glycerol, 7 volumes of water.

REBONDING OF TEETHREBONDING OF TEETH
The one hundred and fifty recycled bracketsThe one hundred and fifty recycled brackets
belonging to Group A, B and C respectivelybelonging to Group A, B and C respectively
were then rebonded on to the same re-were then rebonded on to the same re-
prepared tooth to which they were bondedprepared tooth to which they were bonded
earlier in the similar fashion.earlier in the similar fashion.
The teeth were prepared by removing theThe teeth were prepared by removing the
residual composite resin using a tungstenresidual composite resin using a tungsten
carbide bur.carbide bur.
They were then washed with distilled water andThey were then washed with distilled water and
dried using compressed oil free air.dried using compressed oil free air.

Bond strength was calculated usingBond strength was calculated using
the formula :the formula :
Bond strength (in Mpa) = Debonding Force (in Newton’s) x 9.81Bond strength (in Mpa) = Debonding Force (in Newton’s) x 9.81
Surface area of brackets (sq. mm)Surface area of brackets (sq. mm)
The surface area of the GeminiThe surface area of the Gemini
series, 3 M Unitek bracket was 10.61series, 3 M Unitek bracket was 10.61
square mm as given by thesquare mm as given by the
manufacturermanufacturer ..

Scanning Electron MicroscopicScanning Electron Microscopic
REPORTREPORT
Group – N1, New brackets (control group) at x30Group – N1, New brackets (control group) at x30
magnificationmagnification
Group – N2, New brackets (control group) at x150Group – N2, New brackets (control group) at x150

Group –A1, Brackets recycled with acidbath technique at x30 magnificationGroup –A1, Brackets recycled with acidbath technique at x30 magnification
Group –A2, Brackets recycled with acidbath technique at x150 magnificationGroup –A2, Brackets recycled with acidbath technique at x150 magnification
REPORTREPORT

Group – B1, Brackets recycled with sandblasting technique at x30Group – B1, Brackets recycled with sandblasting technique at x30
Group – B2, Brackets recycled with sandblasting technique at x150Group – B2, Brackets recycled with sandblasting technique at x150
REPORTREPORT

Group C1,Brackets recycled with electrolytic technique. at x30 magnificationGroup C1,Brackets recycled with electrolytic technique. at x30 magnification
Group C2,Brackets recycled with electrolytic technique at x150Group C2,Brackets recycled with electrolytic technique at x150
magnification respectively.magnification respectively.
REPORTREPORT

It was concluded that the amount of adhesiveIt was concluded that the amount of adhesive
remnants wereremnants were
Maximum in sample GroupA,Maximum in sample GroupA,
Significantly minimal in sample GroupC andSignificantly minimal in sample GroupC and
Not clearly evident in sample GroupBNot clearly evident in sample GroupB
As sandblasting had roughened the remainingAs sandblasting had roughened the remaining
adhesive resin surface and damaged the integrity ofadhesive resin surface and damaged the integrity of
the mesh.the mesh.
REPORTREPORT

COMPARISON OF BONDCOMPARISON OF BOND
STRENGTHSTRENGTH

Mean Pattern of Bond StrengthMean Pattern of Bond Strength
(Mpa)(Mpa)

Percentage Change of ShearPercentage Change of Shear
Bond Strength after RecyclingBond Strength after Recycling

DISCUSSIONDISCUSSION
The retentive strength of these brackets on the toothThe retentive strength of these brackets on the tooth
surfaces has increased considerably with time, but bracketsurfaces has increased considerably with time, but bracket
dislodgement still continues to haunt orthodontists.dislodgement still continues to haunt orthodontists.
Efforts are on to curtail this inevitable problem with researchEfforts are on to curtail this inevitable problem with research
being aimed at improving the retentive strength of thesebeing aimed at improving the retentive strength of these
orthodontic brackets, by the advent of newer and betterorthodontic brackets, by the advent of newer and better
bonding materials and also better bracket base designs.bonding materials and also better bracket base designs.
Recycling the orthodontic brackets has a major advantageRecycling the orthodontic brackets has a major advantage
in ecological conservation and reduction in cost apart fromin ecological conservation and reduction in cost apart from
the other advantages. The question of cross contaminationthe other advantages. The question of cross contamination
does not arise in this case as it was carried out on andoes not arise in this case as it was carried out on an
individual basisindividual basis

Some of the disadvantages of recyclingSome of the disadvantages of recycling
the brackets include:the brackets include:
Reduction in bracket qualityReduction in bracket quality
Loss of identification marksLoss of identification marks
Reduction in its bond strength whichReduction in its bond strength which
may vary between 6% - 20%.may vary between 6% - 20%.

SUMMARY & CONCLUSIONSUMMARY & CONCLUSION
Using of new brackets may prove to make the inventory expensive and atUsing of new brackets may prove to make the inventory expensive and at
the same time reattaching the debonded brackets may pose a problem ofthe same time reattaching the debonded brackets may pose a problem of
decreased bond strength.decreased bond strength.
There are many techniques to recycle the debonded brackets, but toThere are many techniques to recycle the debonded brackets, but to
determine which one of the recycling procedure proves to be moredetermine which one of the recycling procedure proves to be more
clinically efficient, cost effective and has a superior bond strength was theclinically efficient, cost effective and has a superior bond strength was the
aim of this studyaim of this study
The electrolytic/thermal method has given out better results over the otherThe electrolytic/thermal method has given out better results over the other
two techniques. The brackets recycled by this technique had a better bondtwo techniques. The brackets recycled by this technique had a better bond
strength and the end product was more lustrous with the integrity of thestrength and the end product was more lustrous with the integrity of the
mesh maintained, almost resembling a new bracket. Hence from this studymesh maintained, almost resembling a new bracket. Hence from this study
electrolytic technique proved to be more efficient and satisfactory to theelectrolytic technique proved to be more efficient and satisfactory to the
clinician with respect to bond strength and appearance of the bracket.clinician with respect to bond strength and appearance of the bracket.
Electrolytic / thermal technique was the most superior method forElectrolytic / thermal technique was the most superior method for
recycling followed by the sand blasting method and lastly the acid bathrecycling followed by the sand blasting method and lastly the acid bath
method.method.

According to REYNOLDS the clinical bondAccording to REYNOLDS the clinical bond
strength sufficient for bonding is 6-8mpa.strength sufficient for bonding is 6-8mpa.
Hence all these methods may be used forHence all these methods may be used for
recycling as they have clinically acceptedrecycling as they have clinically accepted
bond strength.bond strength.
The ease of recycling, clinical feasibility ,The ease of recycling, clinical feasibility ,
material inventory and shelf life , avaliabilitymaterial inventory and shelf life , avaliability
and cost play an important role whileand cost play an important role while
selecting the best method for recycling.selecting the best method for recycling.

THANK YOU…
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