Download " EVALUATING THE BRACKET BASES FOR THEIR EFFICIENCY IN

" EVALUATING THE BRAC KET BASES FOR THEIR EFFICIENCY IN BONDING,
AFTE R SUBJECTING STAINLESS STEEL P.E.A. BRACKETS TO DIFFERENT
M ETHODS OF CLINICAL RECONDITIONING ."
Dr. R.M . Sh ivalinga, M .D.S. (Co rrespo nding au tho rl
Professo r, De pt. of Orthodonti cs a nd De nto facia l Ortho p ae d ics,
J.5.5. Dental College and hospital,
M YSORE . (Karnataka) - 5 70 01 5 .
Pho ne: 098868448 40.
Dr. Ravi S., M. D.S.
Read e r, Dept. of Orthodo nti cs a nd De ntofa cia l O rtho paed ics
J.S.5. Denta l Co ll ege and hosp ital,
MYSORE (Ka rn ata ka) - 570 0 15.
Dr. Pa nchali Ba tra, B.D.S.
Post Graduate Stud e nt,
Dept. o f Orthodon tics a nd De ntofac ia l Orthopaed ics,
J.s.5. D ental Coll ege and hosp ital,
M YSORE . (Karnataka ) - 570 0 1 5.
The present study was cond ucted to determine a simple and effective in- office method o f reconditioning
stainless steel o rthodo ntic brackets, Ninety new stainless steel 0 .0 22"slo t PEA (Roth) pre mo lar brackets (American
Orthodontics, U.S.A.) we re bonded to pre mo lar teeth, the n de bonded a nd the bond stre ngth recorded as a
co ntro l (o r the reconditio ning process. The debonded brackets we re divided into six groups a nd eac h group
reconditio ned using diffe re nt techniques as fo llows: attach ments in four gro ups we re Aamed and then
e ithe r:(l )sandblasted a nd e lectro polishe d ,(2)ultrasonically cleaned and e lectropolished,(3)ulu asonicalty
clea ned, e lectro polished followed by sila ne tre atme nt(4 )re bonded witho ut fu rthe r treatme nt. Of the two
re maining groups, o ne was sandblasted , wh ile the brackets in the re mai n ing we re rough ned with a green sto ne .
The brackets were re bonded to the pre mo la r teeth afte r the e na me l surface had bee n re p re pared , and the ir bond
stre ngths measu red .The results indicated that fla ming, ultrasonic cleaning, fo llowed by e lectropolishing and
silane application, had the highest shear bond stre ngth,even greate r than the contro l gro up.No statistically
significant d iffe re nce was fo und between the means of gro up recycled by sandblasti ng alo ne a nd the control
gro up. Next lowest bond stre ngth was recorded fo r the gro up e mploying sandblasting in combinatio n of flaming
a nd electropolishing fo llowed by brackets that were recycled by grinding the composite with greensto ne . Flaming
a lo ne sho wed the least a nd cl inically unacceptable shear peel bond stre ngth .
lCe)wordl
Bracket recycling, in-office reconditio ning, 5tainlesssteel brackets, sheer peel bond stre ngth
In trod uction
Orthodontists are co m m o nly faced w it h t he d eci sio n o f
w hat to d o w ith aCcide ntall y dislo d ged b rackets and l o r
with in acc urate ly lo cated brac k e ts t h at n eed
rep ositio n ing d u ring treatment. A lt ho ugh recycl ing o f
stai nl ess stee l o rth od o ntic brackets re du ces t he in itial
co st o f providin g fi xed appliances, t h is ad va n tage is lost if
the bo nd s are m o re liable to failure d u ri ng t reatm ent. In
add it io n, the efficie n cy of treatm en t w ill be affected by
any d istortio n of brac ket base, or change in the slot size
p ro duced du ri ng the p revi o us removal o f the ap p liance
90
from the teeth , o r by t he subseque nt recycl ing p ro cess.
T he maj o r ad vantage of recycl ing is t he econo m ic
saving , w h ich cou ld be as h igh as 9 0 %, d ue to the fact
t hat a sin gle b rac ket c an be reused upto five ti m es.'
Othe r ad vantages incl ud e a smoother, m o re c o rrosio n
res ista nt brac ket after e lectro p o li Sh in g, and sterili ty as a
resu lt of t he te mperatures em pl oyed i n t he rec ycl ing
p rocess. The d isad va ntages of recycl ing m ay incl ud e a
reductio n in bracket q uali ty, lo ss of id e ntificati o n marks,
lac k o f ste ri lity and increased risk of cross infe ction .l
Comme rci al recycl ing , w heth er b y heat or chemica l
means, leads to a d egree of m etal loss in certai n areas o f
th e bracket and a red uctio n in the diam eter of the m esh
slrands ..J.5 Most investigators have reported a reduc tion
in b o nd strength after co mmercial recycli ng, varying
between 6 an d 20%··6 altho ugh this may be as high as
35 % for fin er m eshed bases.3 Furth er critic ism of
com m ercial recycl ing is the lo n g turnaround time of th e
proc ess and the inability to recognize brackets that have
been recycled m o re than o n ce. In ad diti o n
commercia lly recycled brac kets are more prone to
corrosio n, particularly brac kets m ad e from type 304
(A ISI) stainl ess steel. 7
G RO UP
NO.OF
COLOUR
METIIOD OF
RECYC I~I NG
TEETH
I
15
MAJENTA FLAMING+ ULTRASONI C
II
15
G K • •N
GROUND WIT lt G RE ENSTONl:
III
15
PINK
FLAMING+ULTRASONI C
CLEANING+ELl:CTROPOI.IS IIING
C Lt: AN ING+ ELECTROPOI.ISItING
+S ILANE COU PLING AGt: NT
To ove rco m e the delays associated w ith commercial
recycling, va rio us c hai rside tec hniqu es have been
d evelo ped . Purpose o f this study w as to d etermine a
simple a nd effec t ive method f o r c h a ir sid e
reconditi o ning of stainl ess steel o rthodon ti c brackets
and to d etermine a m ethod of reco nditi o ning whic h
ex hibits best shea r bond strength.
. ' L.AM ING+SANDBL.ASTI NG+
IV
15
PURPLE
V
15
YELLOW
FL.AM.ING+ ELECTROPOLISIIING
VI
15
WHITE
SANDBLASTING
E I. ECTROPOLlSIIING
Th ey were then bonded w ith uppe r pre m o lar m eta l
brackets (Fig.1 )using Tran sb o nd XT light c ure co mposite
(3 M Unitek) .Bondab le stainl ess steel 0.022"slot PEA
(Roth ) pre mol ar bra c kets w e re u sed (America n
AIMS AND OBJECTIVES OFTHE STUDY:
,.
To determine a simpl e and effective m ethod fo r
reco nditioning stainless steel PEA bracket base.
Orthodontics, U.s.A. )
2.
To compare t he shea r pee l bo nd strength of
reco nditioned stainl ess steel P.E.A. bracket bases (using
different m ethods) to t hatof a new o ne.
3.
To d etermine a m ethod of reco nditi o ning whic h
ex hibits best shea r bond stre ngth .
The surface area of brac ket base was 8 .686mm J
The bond ing procedure was pe rformed as pe r the
m anufacturer's instructio ns. The specime ns were then
stored in di stilled water at 37° C for more than 24 hrs.
MATERIALS AND METHODS:
Ninety human prem o lar teeth of young patie nts that had
bee n extracted as part o f orthodo nti c treatment were
used in th e stud y. The teeth used were betwee n o ne
month and three months afte r extraction. Carious,
h ypoplasti c and damaged teeth or teeth havi ng an
abnormal m o rpho logy were not included i n the study.
A her extraction the teeth were cleansed of soft tissue
and after ca reful d e bridement the teeth were sto red in
distill ed wa te r at room te mperature. The teeth were
the n embedd ed in specia lly fabricated cylindri ca l acrylic
b loc k w ith its lab ial and lingual surface ex posed above
th e cem entoenam el junction and tooth positioned
pa rallel to the face of the bl ock. For easy identifi cation of
different groups, acryli cs of six different colours were
u sed . These ninety teeth were rando mly divided into six
groups. There we re fiftee n teeth in each group.
91
FIC.l: Samples after Bonding
In this study in o rd er to e nsure standa rdiza tio n, fifteen
sa mpl es were random ly se lected to serve as contro l and
w ere d e bonded in an Uni versa l Testing Machine at a
cross head speed of O.5mm pe r minute. Th e load
required for d ebonding each brac ket was recorded.
Th ese readings beca m e th e contro l gro up. T he rest of
the sam ples were debonded with a bracket d ebo nding
plie r.Th e brackets in differe nt groups were recycled by
the following procedure:
GROU PI :
The brac ke ts are h e ld with a brac ke t h o lding tweezer
and the base of th e bracket is hea te d using the non
lu minous zo ne of the flame until th e d ebonded bracke t
beco mes cherry red in o rder to burn o ff the residu a l
composite resin from the base. S (Fig.2)Afte r this stage, a
pro perly hea ted brac ket is di sco lo red with a res idue o n
its mesh.
Fig.3.Grinding of adhesive by greenstone
FIG.2: Flaming the Bracket Case
They were then qu e nched in water. Th e brackets we re
plac ed in an ultrasonic b ath for twenty o r thirty minutes
until the fille r is gon e from the m esh a nd o the r areas o f
the attachment. The final e lectrop o li shing was d o ne
individually. A high density current suppl y is developed,
which speeds up th e po lishing considerably. The bracket
is tied o n to the stee l forceps using li gature wi re and
dipped into the po li shing tank.The cathode used was
copper and the bracket was m ad e as the anod e.
Ele ctrolyte used was Wi rolyt which con sists o f sulphuric
acid and glycol. Th e tem pe rature o f the bath was kept
arou nd 1 20°C . A current d e nSity of 100-400 am ps/fe
was used . Usually five seconds are need ed to produc e a
brilliant fini sh . Th ey are the n washed in distilled water
and pl aced bac k in the pou ch to whic h it b elo ngs.
After thi s a layer of m eta l adhes ive prime r, which consists
of ace tone, 10-Methacryloyloxydecyl dihydrogen
phosphate and 6-(4-Vinylbenzyl- n-propyl) amino-1, 3,
5-triazine-2 , 4-dithione, was app li ed with a cotto n swab
o n the bra cket base befo re app ly ing th e si lane co upling
age nt. The metal prime r was allowed to dry and then a
coating of silan e coupling agent (Si lan e coupling agent>
was applied with an appl icator sponge.(Fig.4 a,b) It was
then gently blown with an air syringe fo r 2-3 seconds to
evaporate thea lcoh o l in the mi x.
This is done since silan e c oupling agent is b aSically used
for increasing the bo nd strength o f ce ram ic brackets, and
for it to be effective in co njunc tio n with m etal brackets a
m etal prime r has to be app li ed first for the si lane
coupling agent to be effective wi th th e m etal brackets.
These bra ckets were the n air dri ed with a n air syringe
before bo nding. The brackets were then re placed back
in the ir res pec tive pouc hes.
GROU P II :
Teeth be lo ngin g to G ro up II were refurbi shed b y
using a green sto ne o n a straight slow speed hand pi ece
(KaVo Elektrotechnisches W erk GmbH. Type 4953 ) at a
sp e ed o f 25,000 revolution s per minute for
approx imate ly 25 seconds until the composite was
removed .'j (Fig.3) Ca re was taken during grinding not to
expose and damage the m etal mesh .' o
GROUP ilL
The sa me proced ure o f flaming, ultrasonic cleaning and
elec tropolishing as i n gro up I was re peated .
92
Fig.4a. Metal ad hes ive primer
(ku raray Medical inc., Okayama, Japan)
the residual composite resin using a tungsten carbide
bur. They were incubated again for twenty four hours in
distill ed water prior to test ing.
DETERMINATION OF SHEAR BOND STRENGTH :
Shearing tests were again performed with the universal
testing mac hine at the same cross head speed of 0 .5mm
per minute. Th e load required for debonding eac h
refurbished bracket was record ed.(Fig.5)
Fig.4b. C learfi l porcela in bo nd activator
(Ku raray Medica l inc., O kaya m a, Japa n )
GROUP IV:
The same procedure of flaming as in group I was
repeated. Thiswas followed by sa ndblasting .
The sandblasting method co nsisted of subjecting the
bracket bases to sandblasting after they are debonded
Alumin um oxide particles of size 50 pm were used for
refurbishing stain less steel brackets. The distance
between the sa ndblasting handpi ece and the bracket
ba se was fi xed at 10mm. To ensure the dista nce is 10
mm one piece of stai nless stee l wire was m easured and
taped to the sandblasti ng device. Each bracket was
sa ndblasted within the range of 20- 40 seconds· under a
pressure of five bars until bonding resin was no lo nger
v isible to the naked eye and the bracket base appeared
frosted. After sandblasting they were agitated in acetone
and dried in compressed air. After this the brackets were
e lectropolished
GROU PV:
Th e brackets in this group were subjected to on ly
flaming followed by electropolishing.
G ROUPVI:
The fifteen brackets in this group were on ly sa ndblasted
as described above and were then pl aced back in the
same pouch to which they be long.
REBONDINGOFTEETH
Ninety refurbished brackets belo nging to Croup I to VI
respectively are then re-bonded o n to the sa m e reprepa red tooth to whi ch they were bonded ea rli er in the
similar fashion . The teeth were pre pared by removing
93
Fig.5.Sam ples m o unted for testing
s hea r bond strength o n
Universa l Testing Machine.
METHOD AND D IRECTION OF DEBOND,
RESU LTS
After 24 hrs of storage in dist ill ed water a t a te mperature
STATISTI CAL METHODS A PPLI ED
of 3r C, the speci m en s we re dried and kept on the
uni versa l test ing m achine individu all y for testing th e
sh ea r peel bo nd strength .Th e wi re loop was introduced
under the gingival tie wings of th e brac ket w itho ut any
pres5ure.( Fig.6) The upper crosshead of th e testing
machine moved at a speed 0( 0 .5 mm/ minute t ill brac k et
got d ebond ed from the tooth surface. As the uppe r
c rosshead moved , the jo int was o rie nte d in such a way
that the debonding forces we re app lie d in a shea ring
mode.
FDirection of debondlng
force
Composite
Foll owing statistica l m e th ods were emp loyed in the
present study:
.:.
Descriptive statistics
.:.
Independ ent sa mples 't' test
.:.
ANOVA- One Way
.:.
Posthoc Sc h e ffe's test.
Table I . Comparison of shear bond strength values of
different groups
Groups
N
Mean(Mpa) Std. Deviation
Control group
15
11.06
2 .29
Group I
15
6 .5 7
1.24
Group II
15
6 .45
0 .93
G roup III
15
15.26
1.96
Group IV
15
8 .41
0.74
Group V
15
5 .36
0.8 7
Group VI
15
11.62
1. 72
Tota l
105
9.25
3.56
Cross section
of wire· loop
Graph 1 .Mean shear bond strength values of differe nt
groups
Fig.6. Direction of d ebonding force
Th e force va lue at whi ch t he bond failure occurred was
th en recorded from the display p an e l of th e m achin e in
n ewton s and sh ear bond stre ngth was subseque ntly
calculated in M ega Pasca ls using the fo rmul a:
Bond strength (in Mpa)
=
Oebonding Force (in Newton's)
Surface area of brackets (sq . mm)
The surface area of brac ket base was 8.686mml as given
b y the m anufa cture r.
94
The results indicated that the m ea n shear peel bond
strength decreased in the fo ll owing o rder for va rio us
groups:
Group III > Conto l group=group VI >gro up IV >group
I> groupll > groupv.
DISCUSSION
Bond failure can occur cl inicall y for m any reasons and,
occasiona lly, it may be desirable to intentionally d ebond
a brac ket and replace it in a more favorable
po sition .Many factors predisposing to bond failure have
been described. 1I • ' 7 The o ptimum bo nd strength value
for cli nical usage is yet a d ebata bl e question.Studies
have suggested shea r bond stre ngth values ranging from
a lowof 5.9 Mpa toa high of7.8 Mpa for clinical usage. 111
It is evident from the resu lts that Croup III, w hic h
consisted of flaming, ultrasonic cleaning , followed by
e lectropolishing and si lane appli catio n , had the hi ghest
shear bond strength The shea r bond strength was even
h ighe r than the contro l group which stood at 11 .06
MPa.This result of the m ea ns is statistically Significant. It
has been reported that appli cation of si lane may
increase bond stre ngth by as much as 21%.,,·20 though
some studies have shown no cl inically significa nt
increase in bond strength aftersiianation.21The result of
having no clini ca ll y significant difference after
appli cation of sil ane coupling agent can be attribu ted to
th e fact that a laye r of m eta l ad hesive primer, which
c on si sts o f ac eto n e , 10-Methacryloyloxydecyl
dihydroge n phosphate a nd 6-(4-Vinylbe nzyl-n-propyl)
amino- 1, 3, 5-tri az ine-2, 4-dithione, sho uld be appli ed
with a cotton swab o n t he bracket base before appl ying
th e silane coupling agent. This is done since sil ane
coupling agent is basically used for increasing the bond
strength of cerami c brackets, and for it to be effective in
conjunction with metal brackets a m etal primer has to
be applied first for th e si lane coup ling agent to be
effective with the metal brackets.
There is no statisti ca ll y signifi ca nt difference betwee n
th e means of group recycled by sandblasting alo ne and
th e co ntrol group as evident from th e independe nt
sa mple test. This is in agreement with the study
conducted to compa re the bond strength of previously
fai led bonded brackets subjected to ai r abrasion and
that of new brackets. luHu Though som e studies have
re ported th at sandblasti ng alone, without fl am ing is of
conce rn in that the period of time needed to remove all
the resid ual composite was relatively lo ng which might
effect the va luable undercut area that might get too
abraded and adversely affect the bond strength .1 l
The next highest bond stre ngth was recorded of group IV
wt'- :ch had a m ea n of 8.41MPa.This is the Buchman
m ethod which involves m echani ca l and thermal
methods. l f' The result is simil ar to the o ne found in a
study done to find the effects of in office reconditioning
o n the m o rpho logy of slots and bases of stain less stee l
brackets and o n the shea r/ peel bond strength.' Though it
contrad icts the study done in w hic h there was no
difference in the bond strengths of brackets recycled
e ithe r by greenstone o r by Buchman's m ethod .27 In this
study there is a statistica lly significant difference
between the group recycled by greenstone(C roup II)
and th e one recycled by Buchman's m ethod.There is no
stati stica ll y significa nt difference between group I which
consisted of flaming, ultrasonically cleaning followed by
electrpolishing and group II in w hich greenstone was
used which is in agreement with another study to
eval u ate the different m eth ods of in - offi ce
21
reco nditi o ning.
The lowest bond stre ngth was reported by group 5
which consisted of flaming o nly, which in agreement
with ano the r study to eva lu ate the different methods of
I I
in-office reconditio ning. Thi s result contradicts the
result found in a study done to find the effects of in-office
reconditioning o n the m o rph o logy of slots and bases o f
stainl ess steel brackets and o n the shear/ peel bond
stre ngth in which the method of recycling using
greenstone showed the least bond stre ngth followed by
fl aming.'
The resu lts indi cated that the mean shea r peel bond
stre ngth decreased in th e following order for various
groups:
Croup 3> Contol group=group 6>group 4 > gro up
1 >group 2>group 5.
CONCLUSION :
The fo ll owi ng conclusio n ca n be drawn from this study :
1.
Croup III, which consisted of flaming, ultrasoni c
cleaning, foll owed by electropolishing and si lan e
applicatio n, had th e hi ghest shear bond strength, even
greater than the co ntrol group.
2.
A layer of m eta l ad hesive primer, shou ld be applied
o n th e bracket base before app ly ing the si lane coupling
agent Thi s should be d o ne since silane coup ling agent is
bas ica lly used for increasing the bond strength of
ceramic brackets, and for it to be effective in
co njun ction with m eta l brackets a m eta l primer has to
be ap plied first for the si lane coupl ing agent to be
effective with the m eta l brackets.
3.
95
There
is no
statistically signifi ca nt diffe rence
betwee n the m ea n s of group recycled by sa ndblasting
alo ne and the control group. T herefore sa ndblasting
alone is also a v iable option for in ~office reco ndi t io ning
o f brackets.
4.
Sandblasti n g fl amed (Bu c hman'S m eth od) o r
unflamed metal brackets produced clinically acceptab le
results sandblasting for a period of 15 second s using 50
mi cron meter aluminium oxide granules at a pressure of
5 bars was adeq uate to re m ove the residual compos ite
witho ut compromising the bond strength .
5.
Flaming alone led to significantly lower sheer peel
bond stre n gth, that we re even lower than those
o btaine d w he n grinding the base with greensto ne o nl y,
th o ugh flaming combin ed with ultrasoni c clean ing an d
electro p o li shing produ ced cl inically acceptable b o nd
strength .
6.
On ly flaming the bracket appears to provid e no real
advantage to the cli nicia n .
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Correspondence
D r. B.M. Shivalinga, M.O.5. ICorresponding author]
Professor, De pt. of Orthodontics a ndDe ntofacial Orthopaedics,
J.5.5. Dental Co llege and h ospital,
MYSORE. (Karnata ka) - 570 0 1 5.
Phone: 09886844840.