Effects of a Chlorhexidine Varnish on Shear Bond Strength in Indirect Bonding

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1 Originl Article Effects of Chlorhexidine Vrnish on Sher Bond Strength in Indirect Bonding Ömür Polt ; Tncn Uysl b ; Ali Ihy Krmn c Abstrct: The purpose of this study ws to evlute the effects of n ntimicrobil vrnish on the sher bond strength (SBS) of metllic orthodontic brckets bonded with n indirect bonding resin. For this purpose, 60 noncrious humn premolrs were divided into three equl groups. Group 1 ws n indirect bonding control group nd, fter cid etching of the enmel, the brckets were indirectly bonded to the teeth with n indirect bonding resin. In group 2, before bonding, n ntimicrobil vrnish ws pinted on the etched enmel nd indirect bonding ws crried out s in group 1. In group 3, Trnsbond MIP primer nd the ntimicrobil vrnish were thoroughly mixed in 1:2 proportion, pplied to the enmel surfce, light cured for 20 seconds, nd the brckets were direct bonded. A universl testing mchine ws used to determine the mximum lod necessry to debond the brckets, the SBS vlues recorded, nd the dhesive remnnt index scores determined. Dt were nlyzed using nlysis of vrince (ANOVA), Tukey HSD, nd chi-squre tests. Results of ANOVA reveled sttisticlly significnt differences in the SBS mong the vrious groups tested (P.05). Indirect bonding of brckets with Sondhi Rpid Set fter the ppliction of the ntimicrobil vrnish showed significntly lower SBS when compred with both the group 2, indirect bonding control group, nd the group 3, direct bonded-ntimicrobil vrnish group. (Angle Orthod 2005;75: ) Key Words: Cervitec; Indirect bonding; Sher bond strength INTRODUCTION Brckets cn be bonded on teeth by either direct or indirect methods. Silvermn nd Cohen 1 introduced the first indirect bonding method in They used methylmethcrylte dhesive to ttch plstic brckets to model csts in the lbortory. An unfilled bis- GMA resin ws used s n dhesive between the etched enmel nd previously plced dhesive. Most clinicins who bond brckets indirectly tody use the Thoms 2 method. In this technique, the lbortory procedure is done by plcing filled bisgma resin on the brcket bse. After hrdening of the filled Clinicl Instructor, Deprtment of Orthodontics, Fculty of Dentistry, Bskent University, Ankr, Turkey. b Assistnt Professor, Deprtment of Orthodontics, Fculty of Dentistry, Erciyes University, Kyseri, Turkey. c Professor, Deprtment of Orthodontics, Fculty of Dentistry, Selcuk University, Kony, Turkey. Corresponding uthor: Omur Polt, DDS, PhD, Bskent Universitesi Diş Hekimliği Fkültesi, Ortodonti A.D. 11. sk. No: 26 Bhçelievler, Ankr, Turkey (e-mil: omur@bskent.edu.tr) Accepted: September Submitted: July by The EH Angle Eduction nd Reserch Foundtion, Inc. resin, brckets re crried to the mouth using flexible trnsfer try. Brckets re bonded using liquid ctlyst resin pplied to the etched enmel surfce nd bse resin pplied to the brcket bse. The try is removed when polymeriztion is completed. Severl studies hve been mde to modify this technique 3 11 nd to compre the bond strengths of the direct nd indirect methods Although these studies conclude tht no differences exist between the two methods, most of them were mde with direct bonding dhesives even when indirect techniques were used. Currently, two dhesives tht were specificlly developed for indirect bonding re on the mrket. One of them is Custom IQ (Relince Orthodontics, Itsc, Ill) nd the other is Sondhi Rpid Set (3M Unitek, Monrovi, Clif). Recently, Klocke et l 16 investigted the bond strengths of these mterils nd found tht the indirect Sondhi Rpid Set method showed similr strength compred with the Trnsbond XT direct bonding control group nd tht Custom IQ showed lower vlues compred with the other groups. Polt et l 17 compred these systems both in vitro nd in vivo nd found tht, even though Sondhi Rpid Set showed significntly lower bond strength thn both Custom IQ nd direct bonding Trnsbond XT group, the in vivo 1036

2 CHLORHEXIDINE VARNISH IN INDIRECT BONDING results showed no differences in long-term filure rtes. Different mterils nd methods for bonding brckets either by indirect or direct methods re constntly being developed, but in certin cses, the problem of declcifiction fter orthodontic tretment still remins. Ptients undergoing orthodontic therpy hve chnges in orl ecology such s lower ph environment, incresed retentive sites for Streptococcus mutns, nd incresed retention of food prticles, which my led to incresed proportions nd bsolute numbers of slivry S. mutns These chnges my be responsible, in prt, for the observtions of postorthodontic tretment declcifiction. 24,25 Øgrd et l 26 indicted tht high prevlence of cries my be cused by the high criogenic chllenge previling in the plque round orthodontic pplinces. Proper orl hygiene is more difficult to mintin nd ph levels below 4.5 hve been mesured in the plque round the brckets nd bnds during orthodontic tretment. 26 At such low ph, the reminerliztion phse is hmpered nd more fluoride will not necessrily give better criosttic effect. 26 For tht reson, Øgrd nd Røll 27 suggested tht fluoride gents could be further improved by the ddition of ntibcteril gents. Bishr et l 28 nd Dmon et l 29 both studied the effects of chlorhexidine vrnish on the bond strength of orthodontic dhesives on etched enmel surfces. Bishr et l 30 lso published dt on the effects of vrious methods of chlorhexidine ppliction on sher bond strength (SBS). They indicted tht SBS is not significntly ffected when chlorhexidine is pplied, if the vrnish is premixed with the selnt nd pplied on the etched enmel surfces nd then light cured. Krmn nd Uysl 31 lso investigted the effects of n ntimicrobil vrnish on SBS nd the brcketdhesive filure modes of metllic orthodontic brckets. They found tht the bond strengths of the direct bonding Trnsbond XT with Trnsbond MIP (moisture insensitive primer) (3M Unitek, Monrovi, Clif) group nd Trnsbond XT with n ntimicrobil vrnish, Cervitec, mixed with Trnsbond MIP were cliniclly cceptble. They lso found tht, lthough the primer they used hd hydrophilic chrcter (Trnsbond MIP), the ntimicrobil gent in mouthwsh form premixed with primer ws cliniclly uncceptble. The purpose of this study is to evlute the effects of n ntimicrobil vrnish (Cervitec) on SBS of metllic orthodontic brckets bonded with n indirect bonding resin (Sondhi Rpid Set) nd compre it with n indirect bonding control group (Sondhi Rpid Set) nd direct bonded group prepred with hydrophilic primer-ntimicrobil vrnish mixture pinted on the previously etched enmel. TABLE 1. Chemicl Composition of Cervitec Vrnish Components % Ethyl cette 50% Ethnol 41% Thymol 1% Chlorhexidine 1% Polymer not given 1037 Dt derived from Mteril Sfe Dt Sheets of Ivoclr Vivdent. MATERIALS AND METHODS Sixty noncrious humn premolrs, extrcted for orthodontic indictions, were used in this study. After extrction, the teeth were stored in distilled wter continuously. The smple ws divided into three rndom groups of 20 ech. Ech tooth ws mounted verticlly in self-cure crylic so tht the crown ws exposed. Before the strting procedure, the surfce of ech tooth ws polished for one minute using the combintion of polishing gent nd brush t low speed (3000 rpm). A 37% phosphoric cid gel (3M Dentl Products, St Pul, Minn) ws used for cid etching for 30 seconds. The teeth were rinsed with wter for 30 seconds nd dried with n oil-free source for 20 seconds. In ll etched cses, the frosty white ppernce of etched enmel ws pprent. After cid etching, the brckets were bonded in the following mnner: Group 1 (indirect bonding control): the brckets were bonded to stone models using Trnsbond XT ccording to the recommendtions of Sondhi. 11 Resin A ws pplied to the etched enmel nd resin B ws pplied on the brcket bse. They were then trnsferred to etched teeth using Sondhi Rpid Set. Group 2 (indirect bonding with n ntimicrobil vrnish, Cervitec ): before the bonding procedure, Cervitec vrnish (Cervitec, Vivdent, Schn, Lichtenstein) ws pinted on the etched enmel nd left to dry. The indirect bonding procedure ws crried out s in group 1. Group 3 (direct bonding/ntimicrobil vrnish, Cervitec ): primer (Trnsbond MIP) nd Cervitec vrnish were thoroughly mixed in 1:2 proportion, pplied to the enmel surfce. The enmel surfce ws light cured for 20 seconds, nd the brckets were bonded. The Cervitec vrnish used in this study contins equl mounts of chlorhexidine nd thymol. The chemicl components re given in Tble 1. The embedded specimens were secured in jig ttched to the bse plte of universl testing mchine (Micro 500, Testometric, Mywood Instruments Limited, Bsingstoke, UK). A chisel-edge plunger ws mounted in the movble crosshed of the testing m-

3 1038 POLAT, UYSAL, KARAMAN TABLE 2. Descriptive Sttistics of the Three Groups Groups Tested N Men (MP) SD (MP) Rnge Tukey Test* Group 1 (direct bonding Cervitec) A Group 2 (indirect bonding) A Group 3 (indirect bonding Cervitec) B N indictes smple size; SD, stndrd devition. * Groups with different letters re significntly different from ech other. TABLE 3. Groups Tested Frequencies of the ARI Scores,b ARI Scores n Multiple Comprison A B C Group A NS ** Group B NS ** Group C ** ** ARI scores: 1 ll of composite, with impression of brcket bse, remined on tooth; 2 more thn 90% of composite remined; 3 more thn 10% but less thn 90% of composite remined on tooth; 4 less thn 10% of composite remined on tooth surfce; 5 no composite remined on enmel. Group A, Sondhi; group B, Sondhi Cervitec; group C, Trnsbond Cervitec. b ARI indictes dhesive remnnt index; NS, not significnt. ** P chine nd positioned so tht the leding edge ws imed t the enmel-dhesive interfce before the leding edge ws brought into contct t crosshed speed of 0.5 mm/min. The mximum lod necessry to debond the brcket ws recorded. The force required to tke off the brckets ws mesured in Newtons, nd the SBS (one MP one N/mm 2 ) ws clculted by dividing the force vlues by the brcket bse re (14 mm 2 ). After debonding, ll teeth nd brckets were exmined t 10 mgnifiction with light microscopy. Any dhesive remining fter brcket removl ws ssessed with the dhesive remnnt index (ARI) 32,33 nd scored with respect to the mount of resin mteril dhering to the enmel surfce. The ARI scores were used s more comprehensive mens of defining the sites of bond filure between the enmel, the dhesive, nd the brcket bse. Descriptive sttistics were clculted for ech of the three groups of teeth tested. Comprisons of mens were mde using nlysis of vrince (ANOVA) nd Tukey HSD tests. The chi-squre test ws used to determine significnt differences in the ARI scores mong the different groups. All sttisticl nlyses were performed using the SPSS softwre pckge (Sttisticl Pckge for Socil Sciences for Windows, version , SPSS Inc, Chicgo, Ill). RESULTS Sher bond strength The descriptive sttistics, including the men, stndrd devition, nd minimum nd mximum vlues, for ech of the three groups re presented in Tble 2. Dt were nlyzed using ANOVA nd Tukey HSD tests. Results of ANOVA reveled sttisticlly significnt differences in bond strengths mong the vrious groups tested (P.05). The Tukey multiple rnge nlysis indicted tht group 1 (indirect control) (men MP) nd group 3 (direct bonding/cervitec vrnish) (men MP) hd similr SBS vlues. However, group 2 (indirect bonding/cervitec) (men MP) hd significntly lower SBS vlues compred with the other two groups. Adhesive remnnt index The mounts of residul dhesive on the enmel surfces s evluted by the ARI scores re given in Tble 3. There were sttisticlly significnt differences present mong the vrious groups (P.0001). In groups 1 nd 2, there ws higher frequency of ARI scores of five, which indicted little or no dhesive remining on the tooth. These filures were mostly t the resin-enmel interfce. However, in group 3, some mount of dhesive ws found on the tooth surfce, which differed from groups 1 nd 2. DISCUSSION Despite ll the dvnces in orthodontic mteril nd tretment mechnics, deminerliztion round orthodontic brckets still remins mjor problem for the orthodontic ptient. Hhn et l 34 indicted tht microbes ccumulte on restortive mterils. Among these, S. mutns is known to cuse secondry cries t the mrgins of composite restortions s well s directly ttck the enmel. Chlorhexidine is n ntimicrobil gent with brod

4 CHLORHEXIDINE VARNISH IN INDIRECT BONDING spectrum tht hs proven to be very effective in the mintennce of plque control nd gingivitis in both short- 35 nd long-term 36 studies. Sndhm et l 37 hd found tht there ws reduction in slivry S. mutns levels with the use of chlorhexedine vrnish on the teeth in children undergoing orthodontic tretment. Even though brown stining of the teeth, incresed clculus deposition, nd n unplesnt tste re common side effects, these effects re minor when it is used s locl vrnish. Applying chlorhexidine vrnish to the enmel surfce could ct s protective lyer ginst microorgnisms round the brcket periphery, but in return could decrese the bond strength. Bishr et l 28 nd Dmon et l 29 reported tht bond strength ws not ffected fter the ppliction of hydrophilic primer (Trnsbond MIP) with chlorhexidine vrnish on etched enmel. Krmn nd Uysl 31 hd lso obtined the sme result with the ppliction of the sme hydrophilic primer premixed with Cervitec vrnish. However, they hd lso found decrese in bond strength with the ppliction of either nother ntimicrobil vrnish tht contined chlorhexidine nd ethnol or chlorhexidine mouthwsh. No informtion is vilble on the effects of Cervitec vrnish on SBS in indirect bonding procedures. Therefore, the purpose of this study ws to evlute the effects of ppliction of Cervitec vrnish on SBS nd the dhesive filure modes of metllic orthodontic brckets bonded with n indirect bonding resin. A direct bonding group with Cervitec vrnish Trnsbond MIP mixture ws used on the bsis of the results of previous studies. The results indicte tht, even though n indirect bonding control group nd the direct bonding group tht used hydrophilic primer premixed with Cervitec vrnish showed similr nd cliniclly cceptble bond strength vlues ( nd ), Cervitec vrnish used on etched enmel before indirect bonding with Sondhi Rpid Set showed significntly lower SBS vlues ( ) compred with the other two groups. Bishr et l 30 pplied Cervitec under different conditions. They found tht the SBS ws not significntly ffected when the vrnish ws pplied over the brcket nd tooth surfces fter the bonding procedure ws completed, s prophylctic pste over the unetched enmel before bonding, nd when the vrnish ws premixed with the selnt nd pplied on etched enmel. On the other hnd, in ll the experimentl groups in which the chlorhexidine vrnish ws pplied s lyer on the etched enmel surfce or over the selnt, SBS vlues nd brcket-filure rtes were too low to be cliniclly cceptble. In this study, the vrnish ws pplied on the etched enmel before the ppliction of resin A of Sondhi Rpid Set. Sondhi Rpid 1039 Set resin A is hydrophobic in nture. Therefore, it ws believed tht possible reson for the decresed levels of bond strength chieved in group 2 ws the incomplete mixing of resin A nd vrnish. Higher SBS vlues could be chieved if the vrnish ws premixed with different hydrophobic form of resin A of Sondhi Rpid Set. Reynolds 38 determined the rnge of cliniclly cceptble miniml bond strength vlues in orthodontics s 5.9 to 7.9 MP. The bond strength vlues of groups 1 nd 3 compre fvorbly with Reynolds vlues, but most of the specimens in group 3 were below this minimum limit. However, Polt et l 17 hd found previously tht n indirect bonding group tht showed n in vitro SBS vlue of MP hd similr clinicl filure rte with nother indirect bonding resin group tht indicted n in vitro SBS vlue of Mp. Becuse of the probble differences in in vitro nd in vivo test conditions, finl conclusion cnnot be mde without direct comprisons in the clinic. The results of ARI scores between the first two groups nd group 3 reflect the common filure mode differences between indirect bonding nd direct bonding systems. In indirect bonding, it seems resonble tht t debonding, the lower filled resin lyer would frcture nd most of the composite resin would be removed with the brcket. Different ntimicrobil gents such s chlorhexidine, benzydimine, or triclosn cn be pplied in the form of mouthrinses, vrnishes, or orl sprys. These gents hve been shown to be useful djuncts in plque nd inflmmtion control. Further investigtions of the effects of these gents on microbil ccumultion nd bond strength in both indirect nd direct bonding pplictions re needed. CONCLUSIONS The findings of this study re s follows: Indirect bonding of brckets with Sondhi Rpid set fter the ppliction of Cervitec ntimicrobil vrnish showed significnt decrese in SBS when compred with direct bonding/cervitec nd n indirect bonding group. The seprte use of the Cervitec vrnish nd Resin A of Sondhi Rpid Set seemed to hve incresed the in vitro filure rtes of the brckets. Appliction of n ntimicrobil gent before indirect bonding resin did not significntly lter the site of filure during debonding. The filure pttern ws similr to tht of the indirect bonding control group. REFERENCES 1. Silvermn E, Cohen M. Current dhesives for indirect bonding. Am J Orthod. 1974;65:76 84.

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