Evaluation of mechanical properties of five cements for orthodontic band cementation

Transcription

1 Orthodontics Evlution of mechnicl properties of five cements for orthodontic bnd cementtion Diego Andrei Aguir () Dltro Enés Ritter () Roberto Roch () Arno Locks () Adrino Ferreti Borgtto (b) () Progrm de Pós-Grdução em Odontologi, Univ Federl de Snt Ctrin - UFSC, Florinópolis, SC, Brzil. (b) Deprtmento de Informátic e Esttístic, Univ Federl de Snt Ctrin - UFSC, Florinópolis, SC, Brzil. Abstrct: The im of this in vitro study ws to compre the flexurl, compressive nd dimetrl tensile strengths of five cements used in orthodontics for bnd cementtion. Twelve specimens of ech cement were tested: 1 - GC Fuji Ortho Bnd (FJ), GC Americ Inc.; 2 - Meron (MR), Voco; 3 - Multi-Cure Glss Ionomer Bnd Cement (MC), 3M Unitek; 4 - Bnd-Lok (BL), Relince Orthodontic Products; nd 5 - Ketc Cem (KC), 3M ESPE. The results (men) for dimetrl tensile strength were: MP (FJ), 9.60 MP (MR), MP (MC), MP (BL), nd 4.08 MP (KC). The results for compressive strength were (in the sme order): MP, MP, MP, MP, nd MP. The results for flexurl strength were (in the sme order): MP, MP, MP, MP, nd MP. The sttisticl nlysis ws performed by two-wy ANOVA nd Tukey tests with p-vlue In terms of dimetrl tensile strength, BL showed the highest strength sttisticlly, nd MC, the second highest. In terms of compressive tensile strength, BL showed the highest strength sttisticlly, nd FJ did not ttin the minimum recommended strength. In terms of flexurl tensile strength, BL cement ws superior to MC, nd MR, FJ nd KC were equivlent nd inferior to BL nd MC. Descriptors: Bsic Reserch; Dentl Mterils; Dentl Cements. Declrtion of Interests: The uthors certify tht they hve no commercil or ssocitive interest tht represents conflict of interest in connection with the mnuscript. Corresponding Author: Dltro Enés Ritter E-mil: dltroritter@hotmil.com Submitted: Sep 04, 2012 Accepted for publiction: Dec 03, 2012 Lst revision: Dec 17, 2012 Introduction The use of direct bonded bnds decresed considerbly fter polymeric dhesives for orthodontic brcketing were developed. However, these bnds still represent vluble resource for some teeth, e.g., molrs, nd re frequently mde use of. Filure of molr tubes bonded with either chemiclly cured or light-cured dhesive is considerbly higher thn the filure of molr bnds cemented with glss ionomer cement. 1 Bnd retention is mechniclly influenced by the mnner in which bnds re dpted on teeth, nd by the properties of the cements used. 2 4 Tody, the cements most widely used to cement molr bnds re conventionl glss ionomers (CGI), which hve significnt dvntges, such s constnt fluoride relese nd uptke, microbil inhibition, chemicl dhesion to teeth nd to metl, 5 10 low therml coefficient of expnsion 6 nd low solubility. 11 The introduction of light polymerized systems enhnced initil CGI resistnce. 7 McCbe 12 seprtes these most widely used cements into the following ctegories: 136 Brz Orl Res., (São Pulo) 2013 Mr-Apr;27(2):136-41

2 Aguir DA, Ritter DE, Roch R, Locks A, Borgtto AF Modified Composites, Resin Modified Glss Ionomer Cements (RMGIC) nd Compomers. Modified Composites re cured by light polymeriztion; they contin glss prticles tht re chelted in n ttempt to relese fluoride (ex.: Bnd- Lok). RMGIC re cured by n cid-bse rection, nd my optionlly be light ctivted; they re composed of composite nd glss ionomer components (ex.: Fuji Ortho Bnd, 3M Multi-Cure Glss Ionomer Cement). Compomers re cured by light polymeriztion rection; lthough they relese less fluoride thn RMGICs, their criosttic properties re mintined (ex.: Ultr Bnd-Lok). Currently, RMGICs pper to offer the best blnce between fluoride relese, orl environment fluoride uptke nd gretest clinicl durbility for ptients with high cries risk. 13 They re lso light polymerized, chieve mximum resistnce in less time 14 nd pper to be more resistnt thn CGI. 7 However the literture shows tht there is insufficient high-qulity evidence to confirm the most effective dhesive for ttching orthodontic bnds to molr teeth. 2,3 Becuse of the gret vriety of different glss ionomers recently vilble on the mrket, more reserch is needed to compre their mechnicl behvior to support their clinicl use. The objective of this study ws to evlute the compressive, dimetrl tensile nd flexurl strengths of 5 mterils used to cement orthodontic bnds. Methodology The cements submitted to mechnicl tests re specified in Tble 1. Flexurl strength test Twelve specimens of ech cement were rndomly mde with two-prt metllic mtrix, mesuring 25 mm by 2 mm in length nd height, respectively, ccording to ISO 15 (Interntionl Orgniztion for Stndrdiztion) Stndrd The cement specimens were mixed ccording to the mnufcturer s recommendtions nd plced in the mtrix over Mylr strips. After insertion of the mteril, nother Mylr strip ws plced on the top surfce followed by nother glss slb pressed mnully to obtin regulr surfce. 16 After curing t the recommended time nd without dding pressure, the specimens nd the mtrix were immersed in distilled wter t 37 C for 15 minutes. The specimens were then ground nd polished with 600 grit snd pper, nd stored in wter t 37 C for 24 hours. The flexurl strength ws determined by three point test using n Instron Universl Test Mchine, model 4444 (Instron Corp., Cnton, USA). This device is in greement with ISO Stndrd The flexurl strength ws clculted in MP, using the following eqution: 15 Flexurl resistnce (MP) = 3Fd / 2wh 2 where F is the mximum lod exerted on the specimens (N), d is the distnce between supports (mm), w is the width of the smple (mm) nd h is the height of the smple (mm). Compressive nd dimetrl tensile strength tests Twelve cylindricl specimens of ech cement Tble 1 - Mterils used in this reserch. Mterils GC Fuji Ortho Bnd (FJ) Meron (MR) Multi-Cure Glss Ionomer Bnd Cement (MC) Bnd-Lok (BL) Ketc Cem (KC) Seril number Lot Lot Lot. 7EB/7FR Lot Lot Kind of mteril ARMGI CGI PRMGI PMC CGI Mnufcturer GC Americ Inc., Cost Mes, USA Voco, Cuxhven, Germny 3M Unitek, St Pul, USA Relince Orthodontic Products, Itsc, USA 3M Espe, St Pul, USA CGI: uto polymerized conventionl glss ionomer cement. ARMGI: uto polymerized resin modified glss ionomer cement. PRMGI: photo polymerized resin modified glss ionomer cement. PMC: photo polymerized polycid modified composite. Brz Orl Res., (São Pulo) 2013 Mr-Apr;27(2):

3 Evlution of mechnicl properties of five cements for orthodontic bnd cementtion were mde to test compressive strength, nd the sme number were mde to test dimetrl tensile strength, using two-prt metllic mtrix, mesuring 6 mm in height nd 4 mm in dimeter, ccording to ADA specifiction #66 dted The sme procedures of mixing nd finl preprtion of specimens used to perform the flexurl strength test were used to perform the compressive strength nd the dimetrl tensile strength tests. Furthermore, the specimens for these tests were tested in the sme Instron mchine. The specimens were positioned verticlly to their long xis for the compressive strength test, nd horizontlly to their long xis for the dimetrl tensile strength test. The compressive strength vlues were clculted in MP, ccording to the following formul: 17 Compressive strength (MP) = 4F/πd 2 where F is the frcture lod (N) nd d is the smple dimeter. The dimetrl tensile strength (MP) ws clculted using the following formul: 17 Dimetricl trction tension (MP) = 2F/πdL where F is the frcture lod (N), d is the smple dimeter (mm) nd L is the smple length (mm). Sttisticl nlysis One-wy ANOVA (nlysis of vrince) ws pplied for ech mechnicl test, using PASW 18.0 softwre (IBM Corportion, New York, USA), where the isolted fctor ws cement group. Becuse the F-test for ech one-wy ANOVA detected significnt sttisticl differences (p-vlue 0.05) mong the mens of ech cement group for ech mechnicl test, the Tukey test ws pplied to determine which cement groups were sttisticlly different. Results The dimetrl tensile strength results re pre- Tble 2 - Results for dimetrl tensile strength. Mens followed by the sme letter do not differ ccording to the Tukey test; significnce level of 5% (p-vlue > 0.05). Mechnicl test Dimetrl tensile strength Cement FJ MR MC BL KC b 9.60 b c d 4.08 Tble 3 - Results for compressive strength. Mens followed by the sme letter do not differ ccording to the Tukey test; significnce level of 5% (p-vlue > 0.05). Mechnicl test Compressive strength Cement FJ MR MC BL KC b c d bc Tble 4 - Results for flexurl strength. Mens followed by the sme letter do not differ ccording to the Tukey test; significnce level of 5% (p-vlue > 0.05). Mechnicl test Flexurl strength Cement FJ MR MC BL KC b c sented in Tble 2. The compressive strength results re described in Tble 3, nd the flexurl strength results re shown in Tble 4. Discussion Most mteril-relted clinicl filures occur becuse of the low tensile resistnce of the mteril. 18 The dimetrl tensile strength (DTS) test is n dpttion of the tensile strength test, since it is impossible to perform tensile strength tests on brittle mterils, like glss ionomer cements. 19 In the DTS test, compressive force is pplied to the cylinder over its dimeter. In this study, Bnd-Lok (BL) cement ws found to be sttisticlly superior over the other tested cements, showing n verge (v.) strength of MP (Tble 2). Multi-Cure Glss Ionomer Bnd Cement (MC) hd the second highest verge (20.04 MP) in this test. It ws sttisticlly different from Meron (MR) cement (v MP) nd Fuji Ortho (FJ) cement (v MP), which were similr. Ketc Cem (KC) cement (v MP) hd the 138 Brz Orl Res., (São Pulo) 2013 Mr-Apr;27(2):136-41

4 Aguir DA, Ritter DE, Roch R, Locks A, Borgtto AF lowest DTS verge sttisticlly. These results indicte tht BL cement hs the highest cohesive properties nd is the most resistnt to frcture lods, followed by Multi-Cure. Frret et l. 16 found no sttisticl difference in DTS tests for Ketc Cem (7.41 MP) nd Meron (6.05 MP) (both conventionl glss ionomers). In our study, Meron ws sttisticlly superior to Ketc Cem for DTS, compred to resin modified glss ionomer cement (FJ), but ws inferior to BL nd MC sttisticlly (Tble 2). Millett et l. 4 compred the men retentive strength of microetched orthodontic bnds cemented to extrcted humn third molrs with modified composite, resin-modified glss ionomer cement, nd conventionl glss ionomer cement. The men retentive strength of the modified composite (0.415 MP) ws significntly less thn tht of either the resin-modified (1.715 MP) or the conventionl glss ionomer cements (1.454 MP; p <.001). Although modified composites hd higher DTS levels in our study, Millett et l. 4 lbortory results shows tht their retentive strength ws lower thn tht of glss ionomer cements (conventionl nd resin modified glss ionomer). Becuse both our study nd tht of Millett et l. 4 used different methodologies, comprison of direct results should be voided nd interpreted with cution. The compressive strength (CS) test llows good representtion of the mechnicl integrity of different mterils, nd cn be used to test brittle mterils like glss ionomer cements. 20 CS is n extremely importnt fctor, prticulrly regrding mstiction. In determining CS, two xil forces re pplied to the mteril in opposite directions, thus bringing its moleculr components closer together. 21 In the present study BL cement (v MP) showed sttisticlly superior vlues, in comprison to other cements tested (Tble 3). MC (v MP) ws similr to KC (81.93 MP) nd superior to MR nd FJ. KC ws sttisticlly equl to MR (v MP) nd superior to FJ. MR ws similr to FJ (v MP) sttisticlly. FJ cement (v MP) showed the lowest CS verge, nd did not even ttin the ADA recommendtion for CS (minimum of 65 MP). 17 Frret et l. 16 found no difference in the CS tests for Ketc Cem (52.4 MP) nd Meron (38.09 MP). Our study ws in greement with tht of Frret et l., 16 insofr s it showed no sttisticl difference between MR (77.71 MP) nd KC (81.93 MP) in CS tests. The flexurl strength (FS) test mesures tensile, compressive nd sher strengths simultneously, thus reproducing orl environment conditions. 22 BL nd MC cements showed the highest vlues (v MP nd v MP, respectively) for FS, nd were sttisticlly different between ech other nd in comprison to the other cements studied (Tble 4). No sttisticl differences were observed mong cements FJ (v MP), MR (v MP) nd KC (v MP). The literture reltes tht the FS vlues for RMGIC re normlly twice s high s those for conventionl glss ionomers. 23,24 This ws confirmed in the present study for MC but not for FJ. The findings of Millett et l. 14 indicte tht lthough there ppers to be equivlence in the men sher-peel bond strength of the bnd cements ssessed, the ftigue properties of the conventionl GIC, when subjected to simulted mechnicl stress, seem inferior to those of the other cements (RMGIC nd modified composite) for bnd cementtion. 14 This mens tht CGI bnd cementtion is more relible thn the modified composite used in the Millet et l. 14 study. Becuse of the different testing methods employed in the Millet et l. 14 study versus those used in the present investigtion, it would not be vlid to drw ny comprisons between the results obtined for either investigtion. Komori nd Kojim 11 describe RMGIC s better lterntive thn polycid-modified resins nd CGIs, becuse of its excellent durbility, good enmel dhesion nd fluoride relese/uptke cpbility. RMGICs re usully mrketed in powderliquid form nd require mnul mixing procedure criticl to producing n dequte preprtion. The development of two-pste system such s FJ helps surmount this issue. 11 After the bnd is cemented, the glss ionomer cement dheres to enmel nd metl, cusing possible filures minly t the cement/bnd interfce, probbly due to its low cohesion force. 10 In order to over- Brz Orl Res., (São Pulo) 2013 Mr-Apr;27(2):

5 Evlution of mechnicl properties of five cements for orthodontic bnd cementtion come this issue, sndblsting the bnd with luminum oxide is recommended to increse the dhesion force. 25 Modified resins such s BL hve very little cidbse rection nd re less likely to ioniclly bond to enmel, compred to CGI. Gillgrss et l. 10 found no clinicl filure differences between BL nd KC; however, BL filed minly t enmel/cement interfces, nd KC filed minly t cement/bnd interfces. Gillgrss et l. 10 did not find ny differences in white spot lesions between BL nd KC. It seems prudent when choosing mteril for bnd cementtion not to consider mechnicl properties s isolted fctors. Comprisons of lbortory tests for the mterils used in this study my not reflect clinicl sitution ppropritely. For exmple, polycid-modified composites could fil without cement brekge, due to their low dhesion to enmel. 10 This kind of filure is uncommon with CGIs or RMGICs becuse of their high dhesion to metl nd enmel; however, filures my be observed upon cement cohesion brekge. The mechnicl dpttion of bnd to the tooth structure is s importnt s the selection of mterils, since the bnd will help support the occlusionl forces, nd will no longer hve to rely solely on the mechnicl properties of the cements used. Conclusions According to the lbortoril strength tests performed, it cn be concluded tht:. Dimetrl tensile test: BL presented the highest strength, nd MC hd the second highest verge. KC presented the lowest verge results. b. Compressive test: BL presented the highest strength. FJ hd the lowest results, nd did not ttin the ADA recommendtion. c. Flexurl test: BL presented the highest strength. MR, FJ nd KC were equivlent nd inferior to BL nd MC. References 1. Flores-Mir C. Bonded molr tubes ssocited with higher filure rte thn molr bnds. Evid Bsed Dent Sep;12(3): Millett D, Mndll N, Hickmn J, Mttick R, Glenny AM. Adhesives for fixed orthodontic bnds. A systemtic review. Angle Orthod Jn;79(1): Millett DT, Glenny AM, Mttick RCR, Hickmn J, Mndll NA. Adhesives for fixed orthodontic bnds. Cochrne Dtbse Syst Rev Apr 18;(2):CD Millett DT, Duff S, Morrison L, Cummings A, Gilmour WH. In vitro comprison of orthodontic bnd cements. Am J Orthod Dentofcil Orthop Jn;123(1): Wilson AD, Pddon JM, Crisp S. The hydrtion of dentl cements. J Dent Res Mr;58(3): Kerby RE, Knobloch L, Thkur A. Strength properties of visible-light-cured resin-modified glss-ionomer cements. Oper Dent Mr-Apr;22(2): Li J, Betzen M, Sundström F. Strength nd setting behvior of resin-modified glss ionomer cements. Act Odontol Scnd Jn;53(5): Plmer G, Jones FH, Billington RW, Person GJ. Chlorhexidine relese from n experimentl glss ionomer cement. Biomterils Oct;25(23): Youn Y, Lee Y, Lee D, Kim N, Lim Y. Effect of surfce tretment nd type of cement on the retentive strength of orthodontic bnds on gold lloy crowns. Am J Orthod Dentofcil Orthop Dec;132(6):728.e Gillgrss TJ, Benington PCM, Millett DT, Newell J, Gilmour WH. Modified composite or conventionl glss ionomer for bnd cementtion? A comprtive clinicl tril. Am J Orthod Dentofcil Orthop Jul;120(1): Komori A, Kojim L. Evlution of new 2-pste glss ionomer cement. Am J Orthod Dentofcil Orthop Jun;123(6): Mccbe JF. Resin modified glss ionomers. Biomterils Apr;19(6): Xu X, Burgess JO. Compressive strength, fluoride relese nd rechrge of fluoride relesing mterils. Biomterils Jun;24(14): Millett D T, Cummings A, Letters S, Roger E, Love J. Resinmodified glss ionomer, modified composite or conventionl glss ionomer for bnd cementtion- n in vitro evlution. Eur J Orthod Dec; 25(6): Interntionl Orgniztion for Stndrdiztion. ISO Stndrd Dentistry - Polymer-bsed filling, restortive nd luting mterils. Genebr: ISO; Frret MM, Lim EM, Mot EG, Oshim HMS, Brth V, Oliveir SD. Cn we dd chlorhexidine into glss ionomer cements for bnd cementtion? Angle Orthod My;81(3): Brz Orl Res., (São Pulo) 2013 Mr-Apr;27(2):136-41

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