Received: 10 th Mrch 2014 Accepted: 2 nd June 2014 Conflict of Interest: None Source of Support: Nil Originl Reserch Comprison of Impct Strength nd Frcture Morphology of Different Het Cure Denture Acrylic Resins: An In vitro Study B Prveen 1, Hrsh V Bji 2, B G Prsnn 3, Sntosh Kumr Rjlndi 4, T V Shreehrsh 3, G M Prshnt 5 Contriutors: 1 Assistnt Professor, Deprtment of Prosthodontics, College of Dentl Sciences, Dvngere, Krntk, Indi; 2 Assistnt Professor, Deprtment of Orl nd Mxillofcil Surgery, College of Dentl Sciences, Dvngere, Krntk, Indi; 3 Reder, Deprtment of Prosthodontics, College of Dentl Sciences, Dvngere, Krntk, Indi; 4 Reder, Deprtment of Prosthodontics, AME s Dentl College, Richur, Krntk, Indi; 5 Reder, Deprtment of Pulic Helth Dentistry, College of Dentl Sciences, Dvngere, Krntk, Indi. Correspondence: Dr. Rjlndi SK. Reder, Deprtment of Prosthodontics, AME s Dentl College, Richur - 584 103, Krntk, Indi. Emil: srjlndi@gmil.com How to cite the rticle: Prveen B, Bji HV, Prsnn BG, Rjlndi SK, Shreehrsh TV, Prshnt GM. Comprison of impct strength nd frcture morphology of different het cure denture crylic resins: An in vitro study. J Int Orl Helth 2014;6(5):12-6. Astrct: Bckground: The frcture of crylic resin denture is rther common occurrence nd cuses inconvenience to the ptients. This study ws crried out to evlute nd compre the impct strength nd frcture morphology of four different het cure crylic mterils. Mterils nd Methods: Acrylic resin specimens were prepred using preformed metl die of dimension 65 10 3 mm. The specimens were finished, polished nd sujected to impct strength evlution using impct testing mchine. The lods t which the specimens frcture re recorded nd sujected to sttisticl nlysis. Frcture surfce nlysis ws done. Mcroscopic nlysis ws performed y visul inspection of the frctured surfces using stereoscopic microscope. Aout 5 mm sections of ll the frgments were sujected to scnning electron microscopy for microscopic nlysis to verify frcture morphology. Results: Men vlues of the impct strength were compred y sttisticl methods. The impct strength dt were sujected to vrince homogeneity tests. Frcture surfce nlysis dt ws nlyzed y sttisticl methods. The men impct strength of Lucitone 199 ws higher thn Acrylyn-H, DPI Het cure & Trevlon. Conclusion: Within the limittions of this study, it ws concluded tht the impct strength of the crylic resins is ffected y the reinforcement of fiers. Incresed intermedite frctures incresed impct strength. Brittle frctures morphology showed fewer undercuts nd clerer surfce. Intermedite frctures morphology showed more undercuts thn cler surfces. Key Words: Denture se resin, frctogrphic nlysis, frcture morphology, impct strength, polymethyl methcrylte Introduction The mteril most commonly used for fricting removle prtil nd complete denture is polymethyl methcrylte. Despite its populrity, the mteril lthough dequte in stisfying esthetic demnds is not idel in fulfilling the mechnicl requirements of such pplince. This mteril presents limittions prticulrly in flexurl strength nd impct strength. 1 The frcture of crylic resin denture is rther common occurrence nd cuses inconvenience. In ddition to this, frcture hs een ttriuted to porosity, presence of residul monomer, crcks, nd poor dpttion of the removle prosthesis to the residul ridge. Removle prosthesis is susceptile to high impct extr orl forces, such s eing ccidentlly dropped. As result, stress concentrtion is generted, nd the denture se crylic resin cn initite or propgte the existent crcks, thus y influencing filure rte. 2 Therefore, studies on morphology nd micro structurl ehviour, surfce defects nd frcture initition sites my help to identify the cuse of the frcture. To simulte experimentlly, impct tests such s IZOD or CHARPY re used to study the energy sored y the crylic resin until it frctures. Although, impct testing is influenced y the loding configurtion, there is good correltion etween the CHARPY nd IZOD impct mesurements. This study is n effort to evlute nd compre the impct strength nd frcture morphology of four commercilly used het cure denture crylic resins. Mterils nd Methods Friction of smples Metl dies were prepred for mentioned dimension (65 mm 10 mm 3 mm) (Figure 1). The dies were coted with thin lyer of petroleum jelly nd were invested in the lower hlf of the denture flsk. While tking cre, the one-hlf of the thickness ws emedded in the dentl plster ut in the se of the flsk. This ws llowed to set for hlf n hour, nd single lyer of seprting medium ws pplied. Second pour ws mde in the dentl plster, nd the flsk ws held in compression till the finl set of dentl plster. The denture flsk ws then opened, nd the preformed dies were retrieved from the dentl plster (Figure 1). The steps tht followed were similr to one used for processing conventionl complete denture. Lucitone 199 (P:M) 21 g:8 ml nd DPI Het cure 21 g:10 ml; Trevlon (P:M) 21 g:9 ml nd Acrylyn-H 21 g:10 ml were 12
Figure 1: () Preformed metl dies. () Moulds fter retrievl of dies. mnipulted ccording to mnufcturer s instructions nd mteril ws pcked into the mould in the dough stge. Cre ws tken to void porosities due to entrpment of ir ules. Tril closure ws performed. Bench curing ws done for 3 h nd short curing cycle ws followed for cryliztion i.e. 74 C for 2 h nd 100 C for 1 h. Finishing nd polishing Totlly 120 test smples were trimmed y using crylic trimmer. Finishing ws done y snd pper (Emery 120 grit). Polishing ws done using pumice nd polishing cke (Figure 2). Grouping of smples One hundred nd twenty test smples were lelled on ech end efore testing s follows: Totl numer of specimen: 120 specimens Totl numer of group: 4 groups Totl numer of specimens in ech group: specimens Group D (DPI) ws lelled s D 1, D 2, D 3. D Group A (Acrylyn-H) ws lelled s A 1, A 2, A 3 A Group L (Lucitone 199) ws lelled s L 1, L 2, L 3 L Group T (Trevlon) ws lelled s T 1, T 2, T 3. T Evlution of impct strength For impct strength, the smples were tested with Pendulum impct tester (S.C. Dey & Co., Clcutt, Indi) (Figure 3) using IZOD method. The specimens were clmped t one end verticlly, nd the swinging pendulum ws used to rek the unnotched specimens (Figure 3). The lod t which the specimen frctures were noted nd vlues otined were tulted for sttisticl nlysis. The frcture surfce of the specimen ws evluted y stereoscopic microscope (Lwrence nd Myo [London] LM-52-1802 Trinoculr Reserch Microscope [N-400M]) to determine the type of frcture. The smples were exmined with scnning electron microscope (SEM) (Leo, Jpn) (Figure 4) nd photo microgrphs of respective res were otined to verify frcture morphology. Sttisticl methods used were onewy ANOVA, Scheffe s Post hoc test, t-test, Contingency co-efficient test. Figure 2: Specimens of four crylic resins used. Figure 3: () Pendulum impct tester. () Position of smple in impct tester. Figure 4: Scnning electron microscope. Results The 120 specimens of het cure denture se resins were tested for impct strength y using impct testing mchine nd frcture morphology ws oserved y using SEM. The SEM microscopy showed tht rittle frctures exhiited welldefined, flt, compct nd orgnized surfce frctures wheres intermedite frctures presented disorgnized nd jgged surfces (Figures 5 nd, 6 nd ). The vlues of impct strength were sttisticlly nlyzed. 13
Tle 1: Results of Scheffe s Post hoc tests for men vlues on impct scores of different mterils. Mteril N Suset for lph=0.05 1 2 DPI 0.1447 Acrylyn H 0.1463 Trevlon 0.1727 Lucitone 0.1973 Figure 5: () Photomicrogrph of Acrylyn-H rittle nd intermedite frctures. () Photomicrogrph of DPI rittle nd intermedite frctures. Figure 6: () Photomicrogrph of Lucitone 199 rittle nd intermedite frctures. () Photomicrogrph of Trevlon rittle nd intermedite frctures. Impct strength of DPI is 0.1447 nd stndrd devition (SD) of 2.623 nd men impct strength of Acrylyn-H is 0.1463 nd SD of 3.429 nd men impct strength of Lucitone 199 is 0.1973 nd SD of 4.638 nd men impct strength of Trevlon is 0.1727 nd SD of 4.510.When the F vlues (12.339) using one-wy ANOVA re significnt then individul men is different from other so we must nlyze using Scheffe s post hoc tests, which showed significnce (Tle 1). Vlues etween the DPI Het cure nd Acrylyn-H were not sttisticlly significnt. The men impct scores of DPI Het cure nd Acrylyn-H mterils nd results of independent smples y t-test were otined. The SD for DPI ws 0.026 nd Acrylyn ws 0.034, the t vlue ws 0.211. The vlues were not sttisticlly significnt ecuse P = 0.833 (Tle 2). Tle 2: Men impct scores of DPI nd Acrylyn H mterils nd results of independent smples t test. Mteril Men Stndrd devition t vlue P vlue DPI 0.1447 0.026 0.211 0.833 (NS) Acrylyn H 0.1463 0.034 NS: Non significnt The men impct scores of Trevlon nd Lucitone 199 mterils nd results of independent smples were nlyzed y t-test. The SD of Lucitone 199 ws 0.046 nd for Trevlon ws 0.045; the t vlue otined ws 2.088. The vlues were significnt (Tle 3). The occurrence of the type of frcture in ech mteril used ws s follows (21-rittle nd 9-intermedite in DPI, 20-rittle, nd 10-intermedite in Acrylyn-H, 10-rittle nd 20-intermedite in Trevlon, 9-rittle nd 21-intermedite in Lucitone 199) percentge of occurrence ws clculted in ech mteril nd cross tultion of ll mterils nd type of frctures ws done using contingency coefficient test (CC). The vlue y CC test ws 0.346 nd ws sttisticlly significnt (Tle 4). Discussion The frcture of crylic resins is n unresolved prolem in removle prosthodontics despite numerous ttempts to determine the cuses. Modifiction of crylic resins designed to improve the specific properties include plsticiztion copolymeriztion cross-linking nd reinforcement. An ttempt hs een done to study the influence of the cross linking gent on the mechnicl properties of crylic resin, nd it hs een found tht n improvement in impct strength with the use of 10% cross-linking gent dded to the monomer is possile, ut the impct strength decreses progressively with higher concentrtions. One such ttempt led to the production of high impct resins tht contin low moleculr weight utdiene- styrene- co-polymer the exct nture of this inclusion is regrded s mnufcturers trde secret nd requires extensive reserch in chemicl engineering. 2-5 This study investigted the impct strength properties nd frctogrphic nlysis of 4 het-cure crylic resins. To compre the performnce of different products, vrious mechnicl tests were crried out for the study; impct strength is tken into considertion ecuse of their influence on the selection of denture se resin mterils. The smple preprtion followed here ws similr to the one dopted y John et l. 6 14
Tle 3: Men impct scores of Lucitone 199 nd Trevlon (Fier reinforced) mterils nd results of independent smples t test. Mteril Men Stndrd devition t vlue P vlue Lucitone 199 0.1973 0.046 2.088 0.041 (S) Trevlon 0.1727 0.045 S: Significnt Tle 4: Cross tultion of mterils nd type of frctures nd results of contingency coefficient test. Groups Frcture Totl Brittle Intermedite DPI Acrylyn H Trevlon Lucitone Totl CC=0.346; P=0.001 (S) 21 35.0 20 33.3 10 16.7 9 15.0 60 9 15.0 10 16.7 20 33.3 21 35.0 60 120 In this study, metl strips were preferred over wx ptterns to void distortion in mould spce nd for ese of preprtion nd finishing. The preformed metl strips were directly invested in the dentl plster to form plster moulds for friction of test smples. 6 It ws oserved tht the men impct strength showed higher vlues when tested under dry conditions, nd long curing cycle when compred to wet conditions nd short curing cycle. 7,8 The smple dimension of 65 10 3 mm ws prepred s per the ADA specifictions no. 12 to test the impct strength. 6 Impct strength ws tested y impct pendulum tester. There re siclly two types of test, CHARPY nd IZOD for evlution of impct strength. 9-13 Depending upon the loding configurtion, specimen dimensions nd presence of notches nd their geometry, these tests cn result in different vlues. 10 The IZOD impct test ws used in this study. Although there is good co-reltion etween the two tests, the solute vlues differ from ech other. Unnotched smples were cntilevered, nd swinging pendulum ws used to rek the specimens. The reduction in the swing of the pendulum or the energy sored y the mteril ws mesured. Comprison of impct strength vlues mong four crylic resins showed DPI Het cure nd Acrylyn-H presented the lower vlues which re not re-in forced. Lucitone 199 nd Trevlon presented higher vlues tht re re-in forced; this my e ttriuted to reinforcement of fiers in the resin. The men impct strength vlues etween DPI het cure nd Acrylyn-H ws not sttisticlly significnt nd the vlues etween Lucitone 199 nd Trevlon were sttisticlly significnt. The vlues etween DPI het cure, Lucitone 199 nd Trevlon were sttisticlly significnt. The vlues etween Acrylyn-H, Lucitone 199 nd Trevlon were sttisticlly significnt. By the help of stereoscopic microscope, the frctures were clssified into rittle frctures nd intermedite frctures. Lucitone 199 nd Trevlon exhiited more intermedite frctures thn rittle frctures. Acrylyn-H nd DPI Het cure lso exhiited more rittle frctures thn intermedite frctures. Anlysis of frctured surfces y SEM reveled the micro structurl ehviour of rittle nd intermedite frctures. Acrylyn-H nd DPI het cure showed well-defined crystllogrphic surfce compred to Lucitone 199 nd Trevlon. Although irregulrities could e seen in ech crylic resins frcture, common finding ws tht grnulr micro structure ws clerly distinguishle demonstrting tht crylic resin fils y trnsgrnulr or trnscrystlline frcture. 14 The results from impct strength indicte tht differences oserved cn e ttriuted to the composition of the crylic resins. Conclusion In this study, impct strength nd frcture morphology ws compred etween four het cure denture se resins. The mechnicl ehvior of denture in services depends not only on the strength ut lso on the design nd construction, ut lso on the effect of residul stresses nd the conditions of loding. Within the limittions of this study, it ws concluded tht, 1. The impct strength of the crylic resins is ffected y the reinforcement of fiers. 2. Incresed intermedite frctures incresed impct strength. 3. Brittle frctures morphology showed fewer undercuts nd clerer surfce. 4. Intermedite frctures morphology showed more undercuts thn cler surfces. References 1. Fot F, Cost MA, Del Bel Cury AA, Rodrigues Grci RC. Impct strength nd frcture morphology of denture crylic resins. J Prosthet Dent 2006;96(5):367-73. 2. Arundthi R, Ptil NP. An investigtion into the trnsverse nd impct strength of new indigenous high-impct denture se resin, DPI-TUFF nd its comprison with most commonly used two denture se resins. J Indin Prosthodont Soc 2006;6(3):133-8. 3. Cycik S, Jgger RG. The effect of cross-linking chin length on mechnicl properties of dough-molded poly (methylmethcrylte) resin. Dent Mter 1992;8(3):153-7. 4. Jgger D, Hrrison A, Vowles R, Jgger R. The effect of the ddition of surfce treted chopped nd continuous poly 15
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