Metallic Brackets Bonded with Resin-reinforced Glass Ionomer Cements under Different Enamel Conditions

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1 Originl Article Metllic Brckets Bonded with Resin-reinforced Glss Ionomer Cements under Different Enmel Conditions Mtheus Melo Pithon ; Rogério Lcerd dos Sntos ;Márlio Vinícius de Oliveir ; Antônio Crlos Oliveir Ruells b,c,d ;Fábio Lourenço Romno d,e ABSTRACT Objective: To ssess the sher bond strength of metllic orthodontic brckets bonded with either Fuji Ortho or Ortho Glss LC resin-reinforced glss ionomer cements to enmel surfces under different conditions, nmely, enmel without etching, enmel conditioned with 37% phosphoric cid nd enmel conditioned with Trnsbond Plus Self Etching Primer (TPSEP). Mterils nd Methods: One hundred nd five bovine inferior incisors were divided into seven groups (n 15). In group 1 (control) Trnsbond XT ws used ccording to the mnufcturer s recommendtions. In groups 2, 3, nd 4 ll using Fuji Ortho LC, the brckets were bonded, respectively, to enmel nonetched, enmel etched with 37% phosphoric cid, nd enmel etched with TPSEP. In groups 5, 6, nd 7, the bonding ws performed using Ortho Glss LC under the sme enmel conditions observed in the other experimentl groups. After 24 hours, sher bond strength tests were performed for ll smples t crosshed speed of 0.5 mm/min. Results: The results (MP) showed no sttisticlly significnt difference between groups 1, 3, nd4(p.05). However, such groups were sttisticlly superior to the others (P.05). No sttisticlly significnt difference ws observed between groups 2, 6, nd 7 (P.05). Group 5 showed the lowest sher strength vlue, which ws lso sttisticlly inferior to the other groups (P.05). Conclusions: Regrdless of the enmel tretment, Fuji Ortho LC yielded sher strength vlues superior to those from Ortho Glss LC. (Angle Orthod 2006;76: ) KEY WORDS: Glss ionomer cement; Sher strength; Dentl bonding; Orthodontic brckets INTRODUCTION In orthodontics, the white spot lesions nd mrginl gingivitis worry most prctitioners; s result, they re well wre of the new mterils for minimizing nd Specilist of Orthodontics, Alfens Phrmcy nd Dentl School Efo/Ceufe, Alfens, Mins Geris, Brzil. b Doctor of Orthodontics, Dentl School of Federl University of Rio de Jneiro FOUFRJ, Rio de Jneiro, Brzil. c Professor Assistnt of Orthodontics, Dentl School of Federl University of Rio de Jneiro FOUFRJ, Rio de Jneiro, Brzil. d Professor of Orthodontics, Alfens Phrmcy nd Dentl School Efo/Ceufe, Alfens, Mins Geris, Brzil. e Mster of Orthodontics, Pircicb Dentl School UNI- CAMP, São Pulo, Brzil. Corresponding uthor: Dr. Mtheus Melo Pithon, EFOA, Prosthestic, Ru Mexico 78 Recreio, Vitóri d Conquist, Bhi , Brzil (e-mil: mtheuspithon@bol.com.br) Accepted: August Submitted: Jnury by The EH Angle Eduction nd Reserch Foundtion, Inc. preventing such lesions. Among these mterils, the glss ionomer cement stnds out from ll the others. Developed by Wilson nd Kent, 1 the glss ionomer cement llows chemicl dhesion to enmel, dentin, nd other surfces nd releses fluoride. 2 4 The evolution in glss ionomer cements hs contributed to the reduction in dentl cries in orthodontic ptients becuse of the biologicl nd chemicl chrcteristics of this mteril. 5 However, despite the fvorble chrcteristics of such mterils, the brckets do not provide dequte retention to the enmel, sometimes resulting in insufficient bond strength In recent yers, the mnufcturers of such mterils hve developed new glss ionomer cements incorporting resin mtrix to minimize this problem. As result, both the resin s retentive cpcity nd other ionomer properties could be llied. Such mterils re commonly clled resin-reinforced glss ionomer cements. Some uthors 14,15 hve demonstrted the efficcy of these glss ionomer cements for bonding brckets to 700

2 SHEAR BOND STRENGTH OF GLASS IONOMER CEMENTS dried nonconditioned enmel. Other tests hve demonstrted sufficient bond strength when these mterils re pplied onto contminted nd moistened surfces. Indeed, the dhesion, in some cses, hs been found to be superior to other mterils. 14,16 21 Enmel conditioning using phosphoric cid or cid primer before bonding the brckets with resin-reinforced glss ionomer cement hs demonstrted dequte dhesive results. In fct, some studies hve found vlues close to or higher thn those from nonconditioned surfces. 17,22 24 The im of this study ws to ssess the sher bond strength of metllic brckets bonded with either Fuji Ortho LC (GC Americ Corp, Tokyo, Jpn) or Ortho Glss LC resin-reinforced glss ionomer cements (DFL, Rio de Jneiro, Brzil) to nonconditioned enmel, enmel conditioned with 37% phosphoric cid, nd enmel conditioned with Trnsbond Plus Self Etching Primer (TPSEP) (3M Unitek, Monrovi, Clif). MATERIALS AND METHODS A totl of 105 bovine mndibulr incisors were used in this in vitro study. They were clensed, stored in 10% formldehyde solution, nd kept refrigerted t pproximtely 6 C. A specil gypsum stone (Durone, Dentsply, Petrópolis, Brzil) ws used for embedding the teeth in polyvinyl chloride rigid rings (Tigre, Joinville, Brzil) so tht only their crowns were exposed. The buccl surfces of these crowns were perpendiculrly positioned in reltion to the shering die s bse by using glss squre plced t n ngle of 90 to enble the mechnicl test. After the gypsum crystlliztion, ll the smple sets were stored in distilled wter nd plced gin in the refrigertor. Before bonding the brckets, the buccl surfces of ll the teeth were clened with rubber cups (Viking KG Sorensen, Brueri, Brzil), using nonfluoridted pumice (SS White, Juiz de For, Brzil) nd wter for 15 seconds. Next, the smples were wshed with ir-wter spry for 15 seconds nd ir-dried for the sme period of time using n ir-syringe free of oil nd humidity. The rubber cup ws replced fter every five prophylxis tretments. The smples were rndomly divided into seven groups (n 15), nmely, group 1 (Control), brckets bonded with Trnsbond XT composite (3M Unitek); groups 2, 3, nd 4, brckets bonded with Fuji Ortho LC resin-reinforced glss ionomer cement (GC Americ Corp); nd groups 5, 6, nd 7, brckets bonded with Ortho Glss LC resin-reinforced glss ionomer cement (DFL), s follows. Group 1: enmel conditioned with 37% phosphoric cid (3M Dentl Products, Monrovi, Clif) for seconds, clensed, dried for the sme period of time, XT primer pplied, nd brckets bonded with Trnsbond XT. Group 2: enmel not conditioned nd brckets bonded with Fuji Ortho LC cement. Group 3: enmel conditioned with 37% phosphoric cid (3M Dentl Products) for 15 seconds, wshed, nd dried for the sme period of time. Brckets were bonded with Fuji Ortho LC cement. Group 4: enmel conditioned with TPSEP (3M Unitek) by rubbing the mteril on the surfce for three seconds. An ir-dried jet ws slightly pplied to the enmel, nd the brckets were bonded with Fuji Ortho LC cement. Group 5: enmel not conditioned nd brckets were bonded with Ortho Glss LC cement. Group 6: enmel conditioned with 37% phosphoric cid for 15 seconds (3M Dentl Products) nd wshed nd dried for the sme period of time. Brckets were bonded with Ortho Glss LC cement. Group 7: enmel conditioned with TPSEP by rubbing the mteril on the surfce for three seconds. An ir-dried jet ws slightly pplied to the enmel nd brckets were bonded with Ortho Glss LC cement. Orthodontic centrl incisor brckets with bse surfce re of 13.8 mm 2 were used for ll teeth (Abzil Lncer, São José do Rio Preto, Brzil). The sme opertor performed ll the bonding procedures. All the smples were light cured for 40 seconds (10 seconds for ech fce mesil, distl, incisive border, nd gingivl) t one mm distnce from the brcket using Light Curing 2500 (3M Dentl Products) with light intensity of 550 mw/cm 2. The intensity light ws clibrted for ech polymeriztion using rdiometer (Demetron, Dnburry, Conn). After the bonding procedure, the smples were stored in distilled wter for 24 hours t constnt temperture of 37 C. The sher strength test ws performed by using chisel-edge mounted in the crosshed of the universl testing mchine (Instron Corportion, Cnton) operting t crosshed speed of 0.5 mm/min. A stereoscopic mgnifying glss (Crl Zeiss, Goettingen, Germny) with mgnifiction of 8 ws used for evluting the buccl surfce of ech smple. According to the criteri determined by Årtun nd Berglnd, 25 the dhesive remnnt index (ARI) is quntified s follows: 0 no dhesive remining, 1 less thn hlf of dhesive remining; 2 more thn hlf of dhesive remining; 3 ll dhesive remining. The results of the sher bond strength tests were submitted to nlysis of vrince in 2 3 fctoril

3 702 PITHON, DOS SANTOS, DE OLIVEIRA, RUELLAS, ROMANO Tble 1. Men Sher Bond Strength Vlues nd Sttisticl Anlysis Groups Men (MP) Sttisticl Anlysis (2.53) A (1.18) B (2.00) A (2.00) A (0.77) C (1.34) B (1.18) B Equl letters bsence of sttisticlly significnt difference (P.05). Tble 2. Groups ARI Scores nd Men Vlues Presented by Group,b ARI Scores , no dhesive remining; 1, less thn hlf of dhesive remining; 2, more thn hlf of dhesive remining; 3, ll dhesive remining. b ARI indictes dhesive remnnt index. schem (mteril condition) with control tretment. The Tukey s test ws used for compring the fctors, wheres the Dunnett s test ws used for verifying the control involving other tretments (5% significnce). The ARI scores were ssessed by using the Kruskll-Wllis test. RESULTS There ws no sttisticlly significnt difference in the sher bond strength vlues (P.05) between group 1 (Trnsbond XT), group 3 (Fuji Ortho LC cement on enmel etched with 37% phosphoric cid), nd group 4 (Fuji Ortho LC cement on enmel etched with TPSEP) (Tble 1). These groups, however, were sttisticlly superior to the other groups (P.05). No sttisticlly significnt difference ws observed between group 2 (Fuji Ortho LC cement on enmel nonconditioned), group 6 (Ortho Glss LC cement on enmel etched with 37% phosphoric cid), nd group 7 (Ortho Glss LC cement on enmel etched with TPSEP) (P.05). Group 5 (Ortho Glss LC cement on enmel nonconditioned) showed the smllest sher bond strength vlue, thus being considered sttisticlly inferior to the other groups (P.05). In the evlution of the ARI, the scores within ech group re shown in Tble 2. There ws no sttisticlly significnt difference between groups 1 nd 3 (P.0635), groups 1 nd 4 (P.1764), groups 1 nd 6 (P.4812), groups 2 nd 5 (P.6595), groups 3 nd4(p.6146), groups 3 nd 7 (P.4943), groups 4 nd 7 (P.8573), nd groups 6 nd 7 (P.0606). However, sttisticlly significnt difference ws present between groups 1 nd 2 (P.0006), groups 1 nd 5 (P.0026), groups 2 nd 3 (P.0000), groups 2 nd 4 (P.0000), groups 2 nd 6 (P.0060), groups 2 nd 7 (P.0000), groups 3 nd 5 (P.0000), groups 3 nd 6 (P.0015), groups 4 nd5(p.0000), groups 4 nd 6 (P.0398), groups 5 nd 6 (P.0210), nd groups 5 nd 7 (P.0000). DISCUSSION The composite is one of the most used bonding mterils in orthodontics over the yers. 2 The glss ionomer cements were developed in n effort to ggregte the dhesive chrcteristics s well s the biologicl nd chemicl properties into one mteril. Such cements not only provide enmel bonding but lso hve mechnism for relesing nd reloding fluoride so tht the white spot lesions round the orthodontic brckets nd bnds cn be reduced. In ddition, this mteril fcilittes the debonding procedures without injuring the enmel surfce. 1 5 In this study, there ws no sttisticl significnce in the sher bond strength vlues between group 1 (Trnsbond XT, control), group 3 (Fuji Ortho LC cement on enmel conditioned with 37% phosphoric cid), nd group 4 (Fuji Ortho LC cement on enmel conditioned with TPSEP). Although some studies do not gree with these findings, 7,8,11 13 this study suggests tht Fuji Ortho LC cn be cliniclly pplied to conditioned enmel, thus corroborting findings by others uthors. 7,23,24 Group 2 (Fuji Ortho LC cement on enmel nonconditioned) nd group 5 (Ortho Glss LC cement on enmel nonconditioned) hd the lowest sher bond strength vlues, the ltter being sttisticlly inferior to the other groups. The low dhesive vlues of these groups, whose enmel hd not been conditioned, cn be explined by the lck of mechnicl retention between mteril nd tooth nd bond tht likely occurred by chemicl dhesion only. 6 8,11 13 The results presented by groups 2 nd 5 were not similr to the results presented by the other groups. 14,15 To decrese the number of conventionl bonding procedures nd to mke this technique fster, new system combining primer nd cid into one solution ws developed, the Self Etching Primer. Although this study ws not imed t evluting the bonding time spent in ech type of system, such procedures were simplified when TPSEP ws used. Group 4 (Fuji Ortho LC cement on enmel condi-

4 SHEAR BOND STRENGTH OF GLASS IONOMER CEMENTS tioned with TPSEP) nd group 7 (Ortho Glss LC cement on enmel conditioned with TPSEP) hd sttisticlly significnt differences when compred with ech other. The use of Fuji Ortho LC cement showed higher sher bond strength thn Ortho Glss LC cement, probbly becuse of the improved chemicl chrcteristics presented by the former, which llowed better dhesion to the enmel. Cccifest et l 24 evluted the bonding procedure of Fuji Ortho LC cement under the sme conditions used for group 4 in this study. They lso found the sher bond strength of this mteril suitble, thus mking fesible the use of this glss ionomer mteril in conjunction with TPSEP. In groups 3 nd 6, the enmel smples were conditioned with 37% phosphoric cid nd the brckets were bonded with Fuji Ortho LC nd Ortho Glss LC cements, respectively. Group 3 presented higher vlues for the sher bond strength in comprison with group 6. Considering tht both groups used the sme type of enmel conditioning, this suggests tht such chemicl differences between these mterils reflected the incresed dhesiveness with Fuji Ortho LC. The ARI nlysis reveled sttisticl superiority for groups 1, 3, 4, nd 7 becuse there ws no sttisticlly significnt difference between them. Such superiority is due to the fct tht these groups hd their enmel smples conditioned with 37% phosphoric cid or TPSEP, thus resulting in both chemicl nd mechnicl ssocition between mteril nd tooth. Although group 6 presented inferior ARI vlues even using phosphoric cid conditioning, Fuji Ortho LC nd Ortho Glss LC cements showed differences using this sme type of surfce tretment. Such sttisticl superiority, which is similr to the results for sher bond strength, shows tht the groups presenting greter ARI vlues, on verge, lso hve greter dhesiveness vlues. Groups 1, 3, 4, 6, nd 7 presented the mjority of frctures t the brcket-composite interfce, lthough some dhesive mteril could be observed following the debonding. On the other hnd, groups 2 nd 5 presented the mjority of frctures in the enmel-composite interfce, which ws predominntly expressed by ARI scores of zero (no dhesive remining). The vlues presented by both groups corroborte the mjority of studies existing in the literture. 12,23,24 CONCLUSIONS 703 Both conventionl Trnsbond XT nd Fuji Ortho LC cements presented stisfctory sher bond strength results for brckets bonded to enmel surfce conditioned with 37% phosphoric cid or TPSEP. Both glss ionomer cements, Fuji Ortho LC nd Ortho Glss LC, presented low dhesiveness vlues for nonconditioned enmel. Regrdless of the type of enmel surfce, the men sher bond strength vlues obtined by Fuji Ortho LC cement were superior to those obtined by Ortho Glss LC cement. 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