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치의학석사학위논문
상온 상압 플라즈마가 세라믹/ 시멘트 중층 시편의
굴곡 강도에 미치는 영향
2 0 1 5 년 2 월
서울대학교 치의학대학원
치의학과
노 성 은
상온 상압 플라즈마가 세라믹/ 시멘트 중층 시편의
굴곡 강도에 미치는 영향
Ef f e c tofnon- t he r ma la t mos phe r i cpr es s ur e pl a s maon t hef l e x ur a ls t r e ngt h of
c e r a mi c / c e mentbi l a ye rs pec i mens
지도교수 조 병 훈
이 논문을 치의학석사학위논문으로 제출함
2 0 1 4 년 1 1 월
서울대학교 대학원
치의학과
노 성 은
노성은의 석사학위논문을 인준함 2 0 1 4 년 1 2 월
위 원 장 ( 인 )
부 위 원 장 ( 인 )
위 원 ( 인 )
국문초록
상온 상압 플라즈마가 세라믹/시멘트 중층 시편의
굴곡 강도에 미치는 영향
노 성 은 서울대학교 치의학대학원
치의학과
목 적 :본 연구는 저전압 상온 상압 플라즈마(Non-Thermal AtmosphericPressure Plasma,이하 NT-APP)처리가 세라믹 수복 물의 굴곡 강도에 미치는 영향을 알아보기 위한 것이다.
방 법 :레진 시멘트 유무와 세라믹 표면 처리 방법(무처리,불산 처 리,플라즈마 처리),두 가지 요인의 조합에 따라 세라믹 시편군 6종 을 설정하였다.IvoclarVivadent사의 루사이트 강화형 유리도재인 IPSEmpressCAD ceramic을 4mm x2mm x16mm 블록 형태 로 절삭하여 시편을 제작하였고,시멘트는 같은 제조사의 복합레진 시멘트인 Variolink N을 사용하였다.만능 시험기(LF Plus,Lloyd Instruments,Fareham,UK)를 이용한 3점 굴곡 실험을 통하여 굴곡 강도를 측정하였고,이 때 시편에서 시멘트가 아래로 향하게 하였 다.이원분산분석을 통하여 시멘트의 유무와 표면 처리 방법이 굴곡
강도에 미치는 영향을 관찰하였다.
결 과 :이원분산분석 결과 시멘트 유무와 표면 처리 방법 사이에 통계적으로 유의한 교호작용이 존재하였다(p < 0.05).일원분산분석 결과 6개의 군 사이에 통계적으로 유의한 차이가 존재하였다(p <
0.05).Tukey사후검정 결과 불산 처리 후 시멘트를 적용하였을 때 다른 어떤 군보다 굴곡 강도가 통계적으로 유의하게 상승하였다 (262.51±32.08MPa,p < 0.05).플라즈마 처리 후 시멘트를 적용하 였을 때는 굴곡 강도에 있어서 대조군과 통계적으로 유의한 차이가 없었다(p = 0.237).본 연구에 한하여,저전압 상온 상압 플라즈마는 세라믹 시편 그 자체 또는 레진 시멘트가 접착된 세라믹 시편의 굴 곡 강도를 개선하지 못하였다.
주요어 :상온 상압 플라즈마,루사이트 강화형 유리도재,복합레 진 시멘트,3점 굴곡 실험,굴곡 강도
학 번 :2011-22435
Ta bl eofCont e nt s
I .I nt r oduc t i on 1
I I .Ma t e r i a l sa ndMe t hods 5
I I I .Re s ul t s 9
I V.Di s c us s i on 1 0
V.Conc l us i on 1 2
Re f e r e nc e s 1 3
Abs t r a c t 2 2
Li s tOfTa bl e s
[Table.1]Two factorialstudy design according to cementand surfacetreatmentmethods
18
[Table.2]Flexuralstrengths (in MPa)ofceramic plates treated withcombinationsofHF,plasmaandcement
18
[Table.3]Summary oftwo-way ANOVA for flexuralstrengths
19
[Table.4]Summary ofone-way ANOVA for flexuralstrengths
19
[Table.5]TukeyHSD testforflexuralstrengths
20
Li s tofFi gur e s
[Figure.1]Plotofthe flexuralstrengths(in MPa)and standard deviations of ceramic plates treated with combinations of HF, plasmaand cement
21
I .I nt r oduc t i on
The recent rapid developments of dental ceramics such as alumina-reinforced ceramic, porcelain veneers, ceramic glass casting,zirconia,and CAD/CAM system improve the strength, esthetics and fit.1-3 With developments in adhesive dentistry, various types of composite resin cement are introduced and indirectestheticdentalrestorationsareveryfrequentlyperformed.
The dental ceramic material has superior esthetics, high compressivestrength,high modulusofelasticity,low thermaland electrical conductivity,good biocompatibility and translucency.4 Theyarechemicallystableand similartonaturalteeth.However, thebrittlenatureofceramicsisaprimarydisadvantage.Ceramics arethoughtto havelow tensilestrength becauseofthepresence offlaws thatinitiate and propagate fractures.For this reason, improvements and new methods to strengthen ceramics are continuallyresearched.
Clinicalsuccessofceramicrestorationsalso influenced by the adhesion between theceramicand hard tissuesoftooth.Various cements are used for such adhesion and each ofthe physical propertiesofthesecementsaredifferent.Glassionomercements in generalaresusceptibletoelasticdeformationwith low rigidity.
Because of such problems, they are undesirable than zinc phosphate cementwhen itisapplied to allceramiccrown and greatertensilestresscan begenerated when biteforceisapplied.
Also, fracture toughness which means the energy for crack propagation is lower than composite resin. Composite resin
cement is insoluble in saliva of the oral cavity and exhibits higherfracturestrength than othercements.5Theycan bebonded to dentin using adhesivesand formsahigh durableadhesion to enamel.They can be applied to cementation of any type of prostheses,especiallyallceramiccrownsofpoorretentionorwith high estheticneeds.Foraceramicwith astructureoftwolayers, ithasbeen reported thatfracture resistance can be differed by the strength of the core layer.The fracture resistance of the ceramic is known to be influenced by physicalproperties and distribution ofcracks.Flexuralstrengthisoneoftheindicesused toevaluatethephysicalpropertiesoftheceramic.
Recently in thebiomedicaldomain,plasmahasdrawn copious interest.6,7Theterm ‘plasma’referstoapartially ionized gasand is the fourth fundamental states of matter.8 Plasma can be generated by heating a gas or subjecting it to a strong electromagneticfield applied withalaserormicrowavegenerator. Therearediverseutilization ofplasma such assurfacecleaning, surfaceactivation,and depositionofthinfilms.9Therearevarious typesofplasmas,and non-thermalatmospheric pressure plasma (NT-APP)is particularly usefulin biomedicaldomain.NT-ATT hasa relatively low temperature compared with othertypes of plasmasand doesnotrequire a onerousvacuum system.There have been various attempts to utilize plasma in the clinical dentistry.7First,plasma hasbeen applied on surface ofvarious materialsto enhancetheadhesion.Acrylicresin used fordenture base,10,11 glass fibers treated with EDA monomers,12 fiber- reinforced composite posts (methacrylate-based and epoxy-resin
based),13,14feldspathicporcelain,15,16alumina and zirconia17-19were chosen as substrates for resin-based adhesives or cements.In addition,low-temperatureplasmahasbeen used fornaturaltooth in clinicalapplication such as rootcanaldisinfection process20,21 andtoothbleachingtreatment.22
Ritts et al.23 showed that NT-APP treatment had significant effectin enhancing the bonding strength ofresin composite to dentin.They reported the 64 % increase ofmicrotensile dentin bond strengthafter30secondsofplasmatreatmenttoanincrease in carbonyl groups. Nishigawa et al.11 reported that during repairing ofa fractured denture base,the plasma treatmenton the heat-cured acrylic resin surface showed significantly higher shearbond strength than thatofthecontrolgroup.Theplasma equipment was operated under atmospheric pressure and no special gas was used. They also reported on the long-term reliability of the adhesion.10 Using plasma polymerization and surfacedeposition ofspecificmonomers,adhesion promotion was alsosuggested tobemediated bytheplasmapolymerscontaining functional groups.15-19 Cho et al. and Han et al. applied low-power,non-thermalatmospheric pressure helium plasmasto dentalceramicadhesion with orwithoutmonomersand observed increased bond strengths through increases in the number of hydrophilicgroupsand inthechemicalinteractionofC=C double bonds.15,16Previously,Derand etal.and Piascik etal.improved the bond strengths ofresin composite cements to alumina and zirconia ceramics with plasma spray coating of hexamethyl disiloxane using radiofrequency plasma devices in vacuum
reactors.17-19 The plasma polymers deposited on a substrate surface are known to be densely cross-linked and water resistant,24and asaresult,maycontributetothedurabilityofthe plasmaadhesion.
The purpose of this study is to explore the effect of low-power,non-thermalatmospheric pressure plasma treatments on the flexural strength of ceramic restorations using a three-pointbend test.
I I .Ma t e r i a l sa nd Me t hods
As materials for specimen, leucite-reinforced feldspathic porcelain IPS Empress CAD (Ivoclar Vivadent AG, Schaan, Liechtenstein) and resin cement Variolink N (Ivoclar Vivadent AG) were used. Meeting the requirements of ISO recommendation,ceramicplatesof2.0mm x4.0mm x16.0mm were fabricated by sectioning ceramic blocks using a low-speed diamond saw (Isomet,BuehlerLtd.,Lake Bluff,IL,USA).Their surfaces were polished with 600-grit silicon carbide abrasive papersunderwater-cooling.
Six groupsofceramic specimenswere made by two factorial studydesign accordingtoresincement(absenceorpresence)and surface treatmentmethods (no treatment,HF orplasma)before cementation.As in Table 1,Specimens in group A are simple ceramic plates itself.So group A is no treatmentgroup as a control. Specimens in group B were applied HF etchant. Specimensin group C wereplasma treated.Specimensin group D were not etched and applied silane and resin cement. Specimensingroup E wereetched byHFand applied silaneand resin cement according to conventional method.Specimens in group F were plasma treated and applied silane and resin cement.
Forgroup C and F,a pencil-typetorch plasma with a4 mm innerdiameter25,26wasused and itwascomposed with afloating electrodedielectricbarrierdischarge(FE-DBD)jet.Two L/min of helium was supplied into the tube as a process gas. A
conventional plasma plume was generated by continuous sinusoidal power source of 2.4 kV, 2.5 mA, 8.0 kHz, and 21.6kWh which wasrelatively low energy.Gaseous1,3-butadiene (BD)was supplied into the torch and simultaneously deposited with He gas by the connected tube.The amount of BD as precursormonomerswas3standard cubiccentimeters(sccm).The distance between the torch tip and the ceramic surface was settledat0.5cm.Thetreatmenttimewas30seconds.
For group E,the ceramic plates were etched and silanized, strictly following the manufacturer’s instructions. The ceramic surface was etched with 4.9% hydrofluoric acid (HF,Ceramic etchant,BISCO Inc.,Schaumburg,IL,USA)for60 seconds and thereafterrinsed with water.Allsurfaceswere completely dried with compressed air.Afteretching,a primeragent(Monobond S, IvoclarVivadentAG)was applied with a brush to the etched surface for 60 seconds and once again completely dried with compressed air.Variolink N base and catalystwere mixed in a 1:1 ratio on a mixing pad for10 seconds.Afterapplying resin cementon theceramicsurface,a cover-glasswasplaced on the cemented ceramic block.Due to the high viscosity ofthe resin cement,pressure for30 secondsby 200 gram cylindricalweight was used to assure a appropriate thickness and distribution of the cement avoiding voids. Then, resin cement was light-polymerized for 60 seconds using an LED curing unit (EliparFreeLight2,3M ESPE).
Forothergroups,selective stepsofsurface treatmentsamong the above-mentioned process were done according to study
designscheme.
Allspecimenswerestored in awaterbath attemperatureof3 7℃ for24 hoursbeforemeasuring the flexuralstrength using a three-pointbending test.Exactdimensionsofallspecimenswere measuredusingadigitalcaliper.Thespecimenswereplaced ona steelsupportwith the span of12.0 mm.An axialcompressive load was applied to the middle partofceramic plates with a crosshead speed of0.5 mm/min in a universaltesting machine (LFPlus,Lloyd Instruments,Fareham,UK)untilfractureoccurs.
Flexuralstrength ofeach specimen wascalculated by following equationaccordingtoISO standard :
where
istheflexuralstrengthinmegapascals;
isthemaximum load,innewtons,exerted onthespecimen;
isthedistance,inmillimeters,betweenthesupports;
is the width,in millimeters,of the specimen measured immediatelypriortotesting;
is the height,in millimeters,of the specimen measured immediatelypriortotesting.
The flexural strength data were analyzed using statistical software (SPSS Statistics 21, IBM Corp., Armonk, NY, USA). Two-way analysis of variance (ANOVA) was conducted to examine the effectofcementand surface treatmenton flexural strength.Then one-way ANOVA and Post-hocTukey testwere conducted for pairwise comparisons of the flexural strength within the each conditions respectively. The analyses were
performed atasignificancelevelofα = 0.05.
I I I .Re s ul t s
Table2and Figure1 showsthemean and standard deviation offlexuralstrength foralltestgroups.Two-way ANOVA (Table 3) reveals that there was statistically significant difference in mean flexuralstrength between absence and presence ofcement (p < 0.05), and there were statistically significant differences between surface treatments(p < 0.05).In addition,there wasa statistically significant interaction effect between cement and surface treatment (p < 0.05). Then one-way ANOVA was conducted (Table 4) and there was a statistically significant differencebetween 6groups(p < 0.05).Post-hocTukeytest(Table 5) revealed that flexural strength was statistically significantly higherwhen HF and cementwere both applied (262.51±32.08 MPa,p < 0.05) compared to any other groups.In multiple comparison,therewerestatistically significantdifferencesbetween the cementgroup and plasma-and-cementgroup (p < 0.05)and no statistically significantdifferences between the controlgroup and plasma-and-cement group (p = 0.237). Likewise, in homogeneous subsets analysis, the cement group, the plasma-and-cement group,and the HF-and-cement group were significantlydifferentfrom eachother.
Meansforgroupsin homogeneoussubsetsare displayed.The group sizesareunequal.Theharmonicmean ofthegroup sizes (12.15)isused.
I V.Di s c us s i on
There have been a number of studies previously aboutthe effects of plasma coating on bond strength of ceramic and composite resin.Cho etal.15 investigated the effectofplasma polymercoatingontheadhesionofcompositeresintofeldspathic porcelain using shearbond strength test.They reported thatthe shearbond strength valuesofplasma-coated groupswerebelow those ofroutine porcelain bonding processwith HF and silane. Butin subsequentstudy,16atmosphericpressureplasmaimproved adhesion by producing carboxylgroups on the ceramic surface. The resultwasinterpreted thathydrophiliccarboxylgroupshad enhanced surface wettability.In addition,the ratio ofcarboxyl group contentson the ceramic surface increased asthe applied powerofplasmaincreased.Lateron,variousdeposition materials wereresearched.25,26When1,3-butadienewasdeposited byfloating electrodedielectricbarrierdischargejet,adhesionbetween ceramic and composite resin was improved. The adhesion effect was interpreted to be originated from chemical reactions between carbon doublebondsremaining in theplasmadeposited polymer and thosein theadhesivemonomers.Also,hydrophilicesterand ethergroupsin deposited materialenhanced surface wettability.
When benzene and HMDSO/benzene were used, plasma polymerization ofthem increased thebond strength ofcomposite resin to dentalceramic by notonly hydrophilic ether,carbonyl and estergroupsbutalso chemicalbonding with active species such as carbon double bonds and silanolgroups.Furthermore,
bond strength between composite resin and enamel was investigated.27 The plasma polymer deposition of benzene and 1,3-butadiene using a low-power, non-thermal atmospheric pressure plasma enhanced the adhesion of resin composite to enamel.
In thisstudy,theeffectofplasmacoating on flexuralstrength of ceramic and composite resin was investigated.Typical HF etching method was used in controlgroups.HF application in dental porcelain and glass ceramics generates minute surface irregularities. Before application of resin cement, those irregularities facilitate crack propagation as initiation point at compressed area.However,aftertheapplication ofresin cement, they are infiltrated to empty space and be cured.As a result, resin cementgeneratesmicromechanicalbond effectand enhance flexuralstrength.On theotherhand,plasmacoating method has advantage of not exhibiting the weakening effect of flexural strength at the first place.But after the application of resin cement,improvementofflexuralstrength wasnotsignificantas HFetchingmethod.Itseemsthatchemicaladhesiongenerated by deposited plasmamonomerwasnotpowerfulasmicromechanical bond by traditionalacid etchingprocess.Although theeffectwas notsufficientto replacethecontemporary protocolinvolving HF etching and silane coupling agent coating, further study is required to improve the flexural strength incorporating other materials and conditions such as applied energy and pulse frequency.
V.Conc l us i on
Within the limitation of this study, there was a slight improvementin flexuralstrength ofceramicspecimen supported with resin cement when applied non-thermal atmospheric pressureplasma.Butcompared to routineprotocolinvolving HF etching and silane coupling agentcoating,the resultwas not sufficientto replace the protocol.Further study is required to improve the flexuralstrength incorporating other materials and conditionssuchasapplied energyand pulsefrequency.
Re f e r e nc e s
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2.Blatz MB.Long-term clinicalsuccess ofall-ceramic posterior restorations.QuintessenceInt2002;33:415-26.
3.MalamentKA,Socransky SS.SurvivalofDicorglass-ceramic dentalrestorations over16 years.Part3:effectofluting agent and tooth or tooth-substitute core structure. J Prosthet Dent 2001;86:511-9.
4.Kelly JR.Dentalceramics:Currentthinking and trends.Dent ClinNorthAm 2004;48:513-530.
5.KramerN,LohbauerU,FrankenbergerR.Adhesive luting of indirectrestorations.Am JDent2000;13:60D-76D.
6.Fridman G,Friedman G,GutsolA,ShekhterAB,VasiletsVN, Fridman A. Applied plasma medicine. Plasma Process Polym 2008;5:503-533.
7.Kim JH,Lee MA,HAN GJ,Cho BH.Plasma in dentistry:A review of basic concepts and applications in dentistry. Acta OdontolScand2014;72:1-12.
8.Chen FF,Lieberman MA.Introduction to plasma physicsand controlledfusion.New York:Plenum Press,1984.
9.LiebermanMA,LichtenbergAJ.Principlesofplasmadischarges and materials processing.2nd ed.Hoboken,New Jersey:John Wiley& Sons,Inc.,2005.
10.Nishigawa G,Maruo Y,Oka M,Okamoto M,MinagiS,Irie M, Suzuki K. Effect of plasma treatment on adhesion of self-curing repair resin to acrylic denture base.Dent Mater J 2004;23:545-549.
11.Nishigawa G,Maruo Y,Oka M,OkiK,MinagiS,Okamoto M.Plasmatreatmentincreased shearbond strength between heat cured acrylic resin and self-curing acrylic resin.JOralRehabil 2003;30:1081-1084.
12.Çökeliler D,Erkut S,Zemek J,Biederman H,Mutlu M.
Modification ofglassfibersto improve reinforcement:A plasma polymerizationtechnique.DentMater2007;23:335-342.
13.Costa Dantas MC,Do Prado M,Costa VA,Gaiotte MG, Simao RA,Bastian FL.Comparison between theeffectofplasma and chemical treatments on fiber post surface. J Endod 2012;38:215-218.
14.Yavirach P,ChaijareenontP,Boonyawan D,Pattamapun K, Tunma S, Takahashi H, Arksornnukit M. Effects of plasma treatment on the shear bond strength between fiber-reinforced composite posts and resin composite for core build-up.Dent MaterJ2009;28:686-692.
15.ChoBH,HanGJ,OhKH,ChungSN,ChunBH.Theeffectof plasma polymer coating using atmospheric-pressure glow discharge on the shear bond strength of composite resin to ceramic.JMaterSci2011;46:2755-2763.
16.Han GJ,Chung SN,Chun BH,Kim CK,Oh KH,Cho BH.
Effectofthe applied powerofatmospheric pressure plasma on theadhesion ofcompositeresin to dentalceramic.JAdhesDent 2012;14:461-469.
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Pulsed atmospheric pressure cold plasma for endodontic disinfection.IEEE TransPlasmaSci2009;37:1190-1195.
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Surface Treatment Cement
NoTreatment HF Plasma
NoCement A B C
ResinCement D E F
N Mean Standard Deviation NoTreatment 9 138.16 33.59
HF 9 136.88 26.64 Plasma 15 150.25 24.07 Cement 15 128.72 21.90 HFand Cement 14 262.51 32.08
Plasmaand
Cement 15 162.90 21.14 [Table.1]Two factorialstudy design according to cementand surfacetreatmentmethods
[Table.2]Flexuralstrengths (in MPa)ofceramic plates treated withcombinationsofHF,plasmaandcement
Sum of
squares df Mean
Square F Sig.
Between
groups 169721.00 5 33944.20 49.02 .000 Within
groups 49160.16 71 692.40 Total 218881.16 76
Source Sum of
Squares df Mean
Square F Sig.
Cement 33628.67 1 33628.67 48.57 .000 Surface
Treatment 50362.29 2 25181.14 36.37 .000 Cement*
Surface Treatment
59522.23 2 29761.11 42.98 .000 [Table.3]Summaryoftwo-wayANOVA forflexuralstrengths
[Table.4]Summaryofone-wayANOVA forflexuralstrengths
[Table.5]TukeyHSD testforflexuralstrengths
N Subsetforalpha=0.05
1 2 3
Cement 15 128.72
HF 9 136.88 136.88 NoTreatment 9 138.16 138.16 Plasma 15 150.25 150.25 Plasmaand Cement 15 162.90
HFandCement 14 262.51 Sig. .343 .157 1.000
[Figure.1]Plotofthe flexuralstrengths(in MPa)and standard deviations of ceramic plates treated with combinations of HF, plasmaand cement
Abs t r a c t
Ef f ec t sofnon- t her mal
at mos pher i cpr e s s ur epl as maon t hef l exur als t r engt h of
c e r ami c - c eme ntbi l aye r s pe c i mens
Se ong- e unRoh Sc hoolofde nt i s t r y TheGr a dua t eSc hool Se oulNa t i ona lUni ve r s i t y
Objectives:Thepurposeofthisstudywastoexploretheeffectof low-power, non-thermal atmospheric pressure plasma(NT-APP) treatmentsontheflexuralstrength(FS)ofceramicrestorations.
Materials and Methods:Six groups of ceramic specimens were made by two factorialstudy design according to resin cement (absence or presence) and surface treatment methods (no
treatment,HForplasma)beforecementation.VariolinkN (Ivoclar Vivadent)and IPSEmpressCAD ceramic(IvoclarVivadent)were used.FS was measured by a three-pointbending testwith the resin cement facing downward.Two-way analysis of variance (ANOVA)was conducted to examine the effectofcementand surfacetreatmentonFS.
Results:There was a statistically significant interaction effect between cementand surfacetreatment(p < 0.05).Then one-way ANOVA wasconducted and there wasa statistically significant differencebetween 6groups.Post-hocTukey testrevealed thatFS was statistically significantly higherwhen HF and cementwere applied (262.51±32.08 MPa,p < 0.05)compared to any other groups.Therewereno statistically significantdifferencesbetween thecontrolgroupand plasma-and-cementgroup(p =0.237).
Conclusions:Within the limitation of this study, low-power NT-APP failed to improve the FS ofceramicspecimen itselfor ceramicspecimensupported withresincement.
Keywords : non-thermal atmospheric pressure plasma, leucite-reinforced glass ceramic, composite resin cement, three-pointbendingtest,flexuralstrength
Studentnumber:2011-22435
