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" 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 . RE FERENCES: 1. Ma!asa CG. Pros and cons of the reuse of direct bonded appliances. promoters, their effect on the bond strength of metal brackets . Am J OrthodDentofacial Orthop 1995; 108:237-241 Am J Orthod Denrofacial Orthop 1989; 96; 72-76. 21. Quick AN, Harris AM£: Joseph VP. 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The e((ects of in o(fice reconditioning on the morphology of slolS and bases of stainless steel brackets and on the shear/peel bond srrength.Journa/ofOrthodonlics 2001; 28:231-236. 10. Zachrisson BU. Bonding in orthodontics. C raber T.M, 5wain B.F. Orthodontics: Current principles and techniques. 5t Louis: C V Mosby; 19B5: 511 11 . Gorelick L, Geiger AM, GwinneU Aj. Implications of the failure rates of bonded brackets and eyelets: a clinical study. Am J Orthod 1984; 86:403-6. 12. Kinch A£: Taylor H, War/tier R. Oliver RG, Newcombe RG. A clinical trial compa ring the failure rates of directly bonded brackets using etch times of 15 or 60 seconds. Am J Orthod Dentofacial Orthop 198B; 94: 476-83. 13 . Wertz RA. Beginning bonding-state of the art W. Angle Orfhod 1980; 50:245-7. 14. Evans LB, Powers JM. Factors affecting in vitro bond strength of nomixorthodonticcemenU. AmJ Orthod 1985; 87:508-12. 15. Knoll M, Gwinnett Aj, Wolff MS. Shear strength of brackets bonded to anterior and posterior teeth. Am J Orthod 1986; 89:4 76-9. 16. Calil KA, Wright CZ. Acid etching pauerns on buccal surfaces of permanent teeth. PediatrDent 1979; 1 :230-4. 17. Wang WN, Sheen DI-f. The e((ecr of pretreatment with fluoride on the tensile strength of orthodontic bonding. Angle Orthod 1991; 61 :31-4. 18. Reynolds fR. A review of direct orthodontic bonding. Br J Orthod.1975; 2: 171 -8. 19. Siomka LV. Powers JM.ln viera bond strength of treated direct bonding metal bases. Am J Orthod 1985; 88; 133- 136. 20. Newman G\I, Newman RA.. Sun BI, Ha JlJ, Ozsoylu SA. Adhesion 96 22. Millett D, McCabe JF,Gordon PH The role of sandblasting on the retention of metallic brackel$ applied with glass ionomer cement. Br J O rthod 1993; 20:117-122. 23. Sonis At. Air abrasion of failed bonded metal brackets: A study of shear bond strength and surface cha racteristics as determined by scan ning electron microscopy. Am J Orthod Dentofac Orthop 1996; 110:96-8. 24 . Grabouski JK, Staley RN, Jakobsen JR. The effect of microelching on (he bond strength of metal brackets when bonded to previously bonded (eeth : An in virrostudy.AmJOrthodDentofacOrthop 1998; 11 3:45260. 25. Ma cColI GA.. Rossouw PE, Ti!ley KC, Yamin C. The relationship between bond strength and orthodontic bracket base surface area with conventional and microetched foil-mesh bases. Am J Orthod Dentofac Orthop 1998; 11 3:276-81 . 26. Buchman DJl, EffeclS of recycling on metallic direct -bond orthodontic brackets. Am J Orthod 1980; 77:654-668. 27. Regan D, LeMasney. Van Noort R. The tensile bond strength of new and rebounded stainless steel orthodontic brackets. Eur J Orthod 1993; 15:125- 135. 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.