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4 감사의글 본논문이완성되기까지사랑과배려로지도해주신정문규교수님께진심으로감사드리며, 논문의진행과정동안관심을가지고조언을아끼지않으신이근우교수님께깊은감사를표합니다. 또한본논문에많은가르침을주시고격려해주신심준성교수님께도감사를드립니다. 본연구에도움을주신유지성선생님과치과재료학교실의박혜옥선생님께도감사를드리며, 끝으로늘변함없는사랑으로기도해주시고걱정해주시는사랑하는부모님께이논문을바칩니다 년 12 월 정유경드림

5 목 차 도표목차 ⅲ 국문요약 ⅳ Ⅰ. 서론 1 Ⅱ. 연구재료및방법 4 1. 연구재료 4 2. 연구방법 4 가. 시편의제작 4 나. 누프경도 (Knoop hardness) 측정 6 3. 통계분석 7 Ⅲ. 연구성적 8 1. 누프경도 (Knoop hardness) 8 Ⅳ. 총괄과고찰 12 Ⅴ. 결론 16 참고문헌 17 영문요약 21 i

6 도표목차 Fig. 1. Result of Knoop hardness 10 Fig. 2. Degree of conversion 10 Table 1. Materials used in this study 6 Table 2. Mean and standard deviation(s.d.) of Knoop hardness 9 Table 3. Result of ANOVA 11 ii

7 국문요약 자가접착레진시멘트 (Self-adhesive resin cement) c 의초기중합후표면경도측정에의한중합율의변화 최근상실된치아구조의간접적수복을위한재료의범주가금속의지지를받지않는세라믹에까지확장되었고, 이는우수한심미성때문이라하겠다. 이에따라치아구조에결합하여접착을이루는레진시멘트의필요성이증가하고있다. 레진시멘트는접착술식에서전단계표면처리와결합제처리등술식에민감하여사용하기에쉽지않았으나, 부가적인접착단계를줄인자가접착레진시멘트가최근에개발되어적용되고있다. 자가접착레진시멘트에서문제점으로예상되는것은경화후의초기산도가높아가수분해의우려가있고그로인해중합초기에중합속도를지연시킬수있다는사실이다. 본연구의목적은자가접착레진시멘트중이원중합방식인 RelyX TM Unicem과자가중합방식인 Multilink, 기존의레진시멘트중이원중합방식인 Panavia F(Kuraray, Okayama, Japan) 의초기중합후시간경과에따른표면경도측정을통한중합율의변화를알아보아레진시멘트의물성의차이를비교하여임상적용시응용해보고자하는것이며다음과같은결과를얻었다. 누프경도값에있어서 Multilink 로시편을제작한군이가장낮은경도값을보였고 Panavia F로제작한군, RelyX TM Unicem으로제작한군순으로큰경도값을보였다. 초기중합후경과시간대별로중합율을구한결과, 5분에는 RelyX TM Unicem이세군중가장높은값을보였고, Multilink, Panavia F 순으로낮아지는결과를보였다. 시간경과후에도중합율은위와동일한순서로낮아지는값을보였다. 누프경도의중합시간대별결과사이의유의차를보면, Multilink 에서 30분과 1시간사이, 1시간과 2시간사이를제외하고는모두유의차가있는것으로나타났다 (α=0.05). iii

8 자가접착레진시멘트의초기중합후시간경과에따른표면경도측정을통한중합율의변화를비교한결과, 자가접착레진시멘트는기존의레진시멘트보다높은중합율을보였고, 시간이진행됨에따라중합율이증가하는것을알수있었으나, 본연구에서보다더장기간의연구를시행하여중합율의증가추이를관찰해볼필요가있으며, 구강내의조건에서도추가적인연구가필요하리라생각된다. 핵심되는말 : 자가접착레진시멘트, 표면경도, 중합율 iv

9 자가접착레진시멘트 (Self-adhesive resin cement) 의초기중합후표면경도측정에의한중합율의변화 ( 지도정문규교수 ) 연세대학교대학원치의학과 정유경 Ⅰ. 서론 고정성수복물을위한치과용시멘트는수복물의유지력을증진시키고변연부누출을예방해야한다. 치과용시멘트는 20세기초부터개발되어사용되어왔고최근에는다양한레진시멘트들의이용이늘어나고있다 (Trevor FJ, 2005). 최근상실된치아구조의간접적수복을위한재료의범주가금속의지지를받지않는세라믹에까지확장되었고, 이는우수한심미성때문이라하겠다 (Sahar E, 2005). 이에따라치아구조에결합하여접착을이루는레진시멘트의필요성이증가하고있다. 레진시멘트는공간충전재, 변연부봉인뿐아니라접착재로서, 수복물과치아양면에결합하여수복물의유지력증진을돕는다 (Trevor FJ, 2005). 레진시멘트는뛰어난물리적성질에도불구하고접착술식에서전단계표면처리와결합제처리등술식이민감 (technique sensitive) 하여사용하기에쉽지않았으나 (Brunton PA, 2005, Bouillaguet S, 2002), 부가적인접착단계를줄인자가접착레진시멘트 (Self-adhesive resin cement) 가최근에개발되어적용되고있다 (Trevor FJ, 2005). 자가접착레진시멘트는법랑질과상아질의전처리과정이필요없어접착과정을단순화시켰다. 최근개발되어사용되는 - 1 -

10 자가접착레진시멘트에는 Multilink (Ivoclar Vivadent AG, Liechtenstein), Maxcem TM (Kerr, Orange, CA, USA), RelyX TM Unicem(3M ESPE, Seefeld, Germany) 등이있다. RelyX TM Unicem은이원중합방식, Multilink 는자가중합방식의레진시멘트이며, Maxcem TM 은자가부식 (self-etching) 및자가접착할수있는페이스트타입의이원중합방식의레진시멘트이다. 자가접착레진시멘트에대한연구가이루어져왔다. RelyX TM Unicem과기존의이중중합레진시멘트를이용하여접착후결합강도에대해연구되었고 (Piwowarczyk A, 2007), 자가접착레진시멘트를적용하여상아질에서세라믹베니어 (veneers) 의변연상태 (marginal integrity) 가뛰어남을보고한연구도있다 (Ibarra G, 2007). 자가접착레진시멘트와기존의시멘트들의보철물에대한전단결합강도 (shear bond strength) 를비교연구한결과, 레진시멘트와자가접착레진시멘트가기존의시멘트들보다유의차있게높은전단결합강도를보였고, 자가접착레진시멘트가가장높은전단결합강도값을보였다고보고되었다 (Piwowarczyk A, 2004). 자가접착레진시멘트는자가접착을위해 acidity가필요하나, 초기에산성인재료의장기적인체적안정성을보장하려면경화되는과정에서중성화될때까지 ph 값을상승시켜야하며그렇지않으면글래스아이오노머에서유사하게볼수있는가수분해가일어나게된다. 따라서그로인한문제점으로예상되는것은경화후의초기산도가높아가수분해의우려가있고그로인해중합초기에중합속도를지연시킬수있다는사실이다 (Technical data sheet: Espertise RelyX Unicem, 2002). 비교적최근에개발된재료라서장기적인결과와관련된연구도찾아보기힘들다. 중합의정도는물리적성질, 용해도, 체적안정성, 색상변화, 생체적합성등에영향을주기때문에, 수복물의성공에중요한역할을한다 (Ferracane JL, 1985). 레진시멘트의임상적적용시중합방식에따른차이점이있다면자가중합방식은균일하게경화되고작업시간이길어조작이용이하나보철물의 - 2 -

11 변연부에서결과가좋지않을수있으며, 광중합방식은도재베니어등의접착에유용하게사용되지만레진의빛에대한반투과성때문에완전한중합이어렵다. 이원중합방식은자가중합과광중합의장점을동시에가지고, 물리적강도가높고심미성이뛰어나며 (Li ZC, 1999), 깊은부위에서중합이용이하고경화시간이단축된다 (Peutzfield A, 1995, Caughman WF, 2002, El-Mowafy OM, 2000). 본연구의목적은현재임상적으로사용되고있는자가접착레진시멘트중이원중합방식인 RelyX TM Unicem과자가중합방식인 Multilink 를실험군으로, 기존의레진시멘트중장기간임상에서널리사용하고있는이원중합방식인 Panavia F(Kuraray, Okayama, Japan) 를대조군으로하여, 초기중합후시간경과에따른표면경도측정을통한중합율의변화를알아보아임상에서사용되는레진시멘트의물성의차이를비교하여레진시멘트의임상적용시응용해보고자하였다

12 Ⅱ. 연구재료및방법 1. 연구재료 본연구에서사용된자가접착레진시멘트중이원중합형인 RelyX TM Unicem과자가중합형인 Multilink 를실험군으로, 기존의레진시멘트중이원중합형인 Panavia F를대조군으로하였다 (Table 1). RelyX TM Unicem은혼합시 ph가 1이되는 phosphoric acid modified (meth)acrylate resin으로이루어진이원중합방식의레진시멘트이다. Multilink 는자가중합방식의자가부식레진시멘트로제품구성중프라이머 B는 HEMA, phosphonic acid와아크릴산단량체 (acrylic acid monomer) 를포함한다. Panavia F는불소방출형의진보된이중중합형접착레진시멘트이며, 기계적속성및마모강도를갖게해주는무기필러를함유하고있다고제조사에서는밝히고있다. 2. 연구방법 가. 시편의제작 직경 10mm, 두께 2mm의원형구멍이있는테플론몰드를이용하여군당 15개씩 45개의디스크형태의시편을만들었다. 유리판위에몰드를위치시키고레진시멘트를혼합하여몰드에주입한후, 그위에다시유리판을얹고아래와같이중합시키고유리판과몰드로부터시편을분리해냈다. 대조군인 Panavia F는치아색조의 paste A와 B 동량을연화지상에서 20초간스파츌러를이용하여손으로균일하게혼합하여몰드에주입한후, 광중합기 (Bisco VIP, Shaumburg IL, U.S.A.) 로 300mW로 20초간상부 - 4 -

13 유리판에밀착시켜광조사하였다. 그후상온에서실내조명에노출된상태로자가중합시켰다. Multilink 는 double-push 시린지에서투명한색조의두 paste를동량짜내어연화지상에서 20초간혼합한후몰드에주입하고 8분동안상온에서방치후시편을분리하였다. RelyX TM Unicem은투명한색조의캡슐을 activator에넣고 lever를 2초동안손으로눌러서캡슐이터지도록한후 Rotomix(3M ESPE, St. Paul, Minnesota, USA) 에넣고 12초간혼합하여 Applier에장착하고몰드에주입한후대조군처럼 20초간광중합시킨후 5분동안상온에서방치후시편을분리하였다

14 Table 1. Materials used in this study Cements Manufactures Primary composition LOT Number RelyX TM Unicem 3M ESPE, Seefeld, Germany Paste A: Bis-GMA, TEGDMA, zirconia/silica filler, dimethacrylate polymer, amine, photoinitiator, pigments Paste B: Bis-GMA, TEGDMA, zirconia/silica filler, dimethacrylate polymer, peroxide, inhibitor Multilink Ivoclar Dimethacrylate, HEMA, Barium K06826 Vivadent AG, glass filler, silicon dioxide filler, Liechtenstein ytterbium trifluoride, catalysts, stabilizers, pigments Panavia F Kuraray, Paste A: 10-methacryloxydecyl Paste A Okayama, dihydrogen phosphate, 00277A, Japan dimethacrylate, silica filler, Paste B initiator 00042A Paste B: dimethacrylate, barium glass filler, sodium fluoride, initiator, accelerators, pigments 나. 누프경도 (Knoop hardness) 측정 누프경도측정을위하여미세경도시험기 (Micro hardness tester, DMH-2, Matsuzawa Seiki, Japan) 를이용하여시행하였다. 혼합후몰드에위치시킨 - 6 -

15 때부터 5분 (Multilink 는 8분 ), 30분, 1시간, 2시간, 1주일에각각의경도를같은시편에서위치를달리하여연속적으로측정하였다. 다이아몬드압자로 300g의하중을 10초간가하여재료의표면에압흔을형성하고형성된마름모꼴압흔의장축대각선의길이를장착된현미경을통해측정하였고계산된누프경도를기록하였다. 레진시멘트가빛에대해반투과성을보이므로압흔이잘보이도록시편에유성펜으로색을칠한후측정하였다. 3. 통계분석 각군의누프경도를측정한후측정시간대별평균값을구하였고각시간대별평균값들이유의성이있는지를확인하기위하여일원배치분산분석법 (one-way ANOVA) 을이용하여유의수준 5% 에서분석하였으며다중비교검정 (multiple comparison test) 인 LSD 방법으로유의수준 5% 에서시행하였다

16 Ⅲ. 연구성적 1. 누프경도 (Knoop hardness) 이원중합형, 자가중합형자가접착레진시멘트에서세군의누프경도의 평균값을비교한결과 RelyX TM Unicem 으로시편을제작한군이가장큰 경도값을보였다. 그다음으로는 Panavia F로시편을제작한군이, Multilink 로시편을제작한군은가장작은경도값을보였다. 중합후 1주일경과시 100% 중합된것으로보고초기중합후경과시간대별로중합율을구하였다. (Table 2, Fig. 1,2) 5분후는 RelyX TM Unicem이 51.44% 로세군중가장높은중합율을나타내었고, Multilink, Panavia F 순으로낮아지는결과를보였다. 시간경과후에도중합율의크기는위와동일한순서로낮아지는결과를보였다. 실험군간의결과가통계학적으로유의성이있는차이를보이는지를검정하기위하여분산분석 (ANOVA) 을시행하였다. 분산분석결과실험군간의평균값들이통계학적으로유의한차이를보인다고나타났다.(P<0.05)(Table 3) 위의결과를놓고다중비교검정 (multiple comparison test) 인 LSD 방법을시행하였다. 검정결과, Panavia F, RelyX TM Unicem에서시간대별로모두유의한차이를보였다 (α=0.05). Multilink 에서 30분과 1시간, 1시간과 2시간사이에서만유의차가없었다

17 Table 2. Mean and standard deviation(s.d.) of Knoop hardness according to classes of resin cements and time progress after initial curing. Degree of conversion(dc) was calculated regarding DC of 1 week as 100% Cements N Time Mean(Mpa) s.d.(mpa) DC(%) Panavia F 15 5 min min hr hrs wk Multilink 15 8 min RelyX TM Unicem min hr hrs wk min min hr hr wk

18 Knoop hardness(mpa) min 30 min 1 hr 2 hrs 1 wk Panavia F Multilink TM RelyXTM Unicem Time Fig. 1. Result of Knoop hardness. Knoop hardness according to time progress after initial curing DC(%) Panavia F Multilink min 30 min 1 hr 2 hrs 1 wk TM RelyXTM Unicem Time Fig. 2. Degree of conversion. DC according to time progress after initial curing

19 Table 3. Result of ANOVA Cements Panavia F Source of Variation Between groups Within groups Sum of squares d.f. Mean squares F-value Sig Total Multilink Between groups Within groups Total RelyX TM Unicem Between groups Within groups Total

20 Ⅳ. 총괄과고찰 레진시멘트는전부도재관, 도재베니어등의금속이없는수복물에서심미적인이유로광범위하게이용되고있다 ( 치과재료학제 3판군자출판사 ). 비교적최근에개발된자가접착레진시멘트는결합면의전처리필요성을없앴으며 (Pisani-Proenca J, 2006), 글래스아이오노머시멘트에서의조작의간편성과레진시멘트에서의물리적특성 (Piwowarczyk A, 2003), 심미성 (Li ZC, 1999), 증가된접착력을결합하여개발되었다 (Nakabayashi N, 1982). 자가접착레진시멘트의유기기질 (organic matrix) 은치아표면을처리하여접착을가능하게하는 multifunctional phosphoric-acid methacrylates로구성된다 (Pisani-Proenca J, 2006). 자가부식접착시스템 (Self-etching adhesive system) 은 water-hema 혼합물에서산성단량체 (acidic monomers) 의함량을증가시켜만들어졌다 (Salz U, 2005). 자가부식접착제는 30-40% 의수분을함유한다. 물과산성단량체가혼합되면, 물은산성화되고대부분의치과용접착제에서발견되는 HEMA, TEGDMA 또는 GDMA와같은 (meth)acrylic acid 유도체의에스테르결합을천천히가수분해할수있다. 자가부식법랑질-상아질프라이머에의해경조직표면이변화되고, cross-linking dimethacrylates를함유하는더소수성인결합제 (bonding agents) 로봉인된다. HEMA와같은친수성단량체는프라이머가잘섞이게하고, 젖음성을좋게하며, 부식된법랑질과상아질로단량체가잘확산되게한다 (Pashley DH, 2002). 본연구에서는현재임상에서사용되고있는자가접착레진시멘트중 RelyX TM Unicem과 Multilink, 기존의레진시멘트인 Panavia F를이용하였다. 레진시멘트를중합시켜디스크형태의시편을제작하고중합시간을달리하여누프경도를측정하였다. 전술하였듯이 Multilink 로시편을제작한군이가장

21 작은경도값을보였고 Panavia F, RelyX TM Unicem으로제작한군의순서로큰경도값을보였다. 중합후 1주일경과시 100% 중합된것으로보고초기중합후경과시간대별로중합율을구한결과, 5분에는 RelyX TM Unicem이 51.44% 로가장높은중합율을나타내었고, Multilink, Panavia F 순으로낮아지는결과를보였다. 시간이경과해도중합율의크기는위와동일한순서로낮아지는결과를보였다. 50% 정도의중합에도달하는데 RelyX TM Unicem은 5분, Multilink 는 30분, Panavia F는 1시간소요됨으로써재료사이에차이가나타났다. 대조군인 Panavia F는 5분에서의중합율이 28.23% 로가장낮은값을보였다. 다중비교검정인 LSD 방법을시행한결과, Panavia F와 RelyX TM Unicem에서는모든시간대에서유의한차이를보였고, Multilink 에서만 30분과 1시간사이, 1시간과 2시간사이에서만유의차가없었다. 그러나 30분과 2시간사이에는유의성있는차이가있었다. RelyX TM Unicem, Multilink 는대조군인 Panavia F보다높은중합율을보였고, 이원중합형인 RelyX TM Unicem은자가중합형인 Multilink 보다높은중합율을보였다. 본연구에사용된재료중여타재료들의초기중합시간이 5분인것과달리 Multilink 가 8분인이유는중합시작으로부터 5분경과하였을때시편으로완성될정도로경화되지못하고부스러져시편제작이불가능했기때문이다. 그러나이후의측정시간은 30분, 1시간, 2시간, 1주일로여타재료들과동일하게하였다. 기존연구에서열순환 (thermocycling) 후지르코니아 (zirconia) 에접착된레진시멘트의결합강도를측정한결과 Multilink 는 RelyX TM Unicem보다낮은강도를보였다 (Irie M, 2007). 전부도재관을레진시멘트로접착하여 1년간수중보관후유지력을측정한결과 Multilink 가 Panavia F보다더큰유지력을보인연구결과도있다 (Ernst CP, 2007). 레진시멘트는단량체와개시제의조성을통해충분한중합율을만족시켜야한다. 레진시멘트의불완전한중합은술후민감성의가능한원인이된다고하였다 (Caughman WF, 1990; Kasten FH, 1989; Darr AH, 1995)

22 중합율은치과용레진의경도, 마모저항성, 수분흡수, 잔존단량체등을결정한다 (Ferracane JL, 1985, Rueggeberg FA, 1988). 높은중합율은재료에표면경도와강도를갖게한다 (Ozturk N, 2005). 3개의다른광중합기로중합된세라믹수복물하방의레진시멘트의중합율과표면경도값에관한연구에서, 중합율과표면경도사이에상관관계가있다는결과를얻었다 (Ozturk N, 2005). 경도의측정은레진시멘트에서중합율을측정하는데사용되는가장일반적인방법이다. 레진시멘트의경도는일반적으로비커스 (Vickers) 또는누프 (Knoop) 경도를측정하여결정되며 (Jung H, 2001; Usumez S, 2003), 본연구에서는누프경도를이용하였다. 문헌에따르면, 비커스와누프경도모두레진시멘트의경도를평가하는데사용되어왔다 (Ozturk N, 2005). 비커스에서형성되는압흔 (indentation) 은재료가이완되면서변형된다고하여 ( 누프에서형성되는압흔의장축대각선은영향받지않는다 ), 누프경도가중합체에더적합하다고주장되고있다. 그러나이러한관점을지지하는과학적자료나두가지방법중어느하나를지지하는국제적인기준은없다. 연구에의하면, 비커스와누프경도둘다레진시멘트를연구하기에적합하므로둘사이에유의한선상의상관관계가있다고하였다 (Hofmann N, 2000). 레진시멘트에서, 물리적성질은중합율과밀접한관련이있으며, 경도의측정은중합의깊이를평가하는데에도효과적인방법이다 (Haitz RH, 1995). 중합의깊이는직접또는간접적으로평가될수있는데, 직접적인방법으로는적외선분광기의사용 (infrared spectroscopy) 이있으며가장민감하나시간과비용이많이들며 (Asmussen E, 1982a,b; Eliades GC, 1987; Ferracane JL, 1984; Ruyter IE, 1978), 간접적으로경도나굴곡강도와같은물리적성질을이용하여중합의깊이를평가할수있다 (Ozturk N, 2005). 이중중합형과자가중합형레진시멘트의중합율을비교하기위해여러레진시멘트의표면경도와굴곡강도, 압축강도를평가한연구도있다 (Kumbuloglu O, 2004)

23 레진의중합율이반드시물리적성질과명백한상관관계가있는것은아니라고주장한연구도있으며 (Asmussen E, 1998), 레진필러의형태와함량또한물성에영향을미칠수있다고하였다 (Kumbuloglu O, 2004). 다른연구에서는레진기질과필러의특성이중합후의중합율과경도에도영향을미친다고하였으며 (Asmussen E, 1982; Chung KH, 1990), 레진의경도와무기필러의함유량사이에도명백한상관관계가확립되어왔다고하였다 (Chung KH, 1990; Raptis CN, 1979). 본연구는중합시간을 1주일까지로하여실험하였는데, 누프경도값과중합율은시간이지남에따라계속증가하는경향을보였다. 그러나중합율이시간이경과함에따라상승하다가어느특정한시점에서부터정체하는고원 (plateau) 을형성한다면, 그특정한시점이언제인지알기위해서는 1주일이상의장기적인연구가요구될것이며, 연구결과에따라중합율의결과도달라질것이다. 본연구에서부족했던점은구강외에서시편을제작하였으므로구강내에서재료를치아에적용하는것과는차이가있으며, 구강내와의온도, 습도의차이, 구강내에서작용하는저작압의영향등차이점이존재하므로결과가달라질수있다고생각된다

24 Ⅴ. 결론 본연구에서는자가접착레진시멘트인 RelyX TM Unicem과 Multilink, 기존의레진시멘트인 Panavia F를이용하여초기중합후시간경과에따른중합율의변화를표면누프경도를측정하여비교하였고다음과같은결과를얻었다. 1. 누프경도값에있어서 Multilink 로시편을제작한군이가장낮은경도값을보였고 Panavia F로제작한군, RelyX TM Unicem으로제작한군순으로큰경도값을보였고, 군간평균값이통계적으로유의한차이를보였다 (P<0.05). 2. 초기중합후경과시간대별로중합율을구한결과, 5분에는 RelyX TM Unicem이 51.44% 로세군중가장높은값을보였고, Multilink, Panavia F 순으로낮아지는결과를보였다. 시간경과후에도중합율은위와동일한순서로낮아지는값을보였다. 3. 누프경도의중합시간대별결과사이의유의차를보면, Multilink 에서 30분과 1시간사이, 1시간과 2시간사이를제외하고는모두유의차가있는것으로나타났다 (α=0.05). 자가접착레진시멘트의초기중합후시간경과에따른표면경도측정을통한중합율의변화를비교한결과, 자가접착레진시멘트는기존의레진시멘트보다높은중합율을보였고, 시간이진행됨에따라중합율이증가하는것을알수있었으나, 본연구에서보다더장기간의연구를시행하여중합율의증가추이를관찰해볼필요가있으며, 구강내의조건에서도추가적인연구가필요하리라생각된다

25 참고문헌 1. Trevor FJ. Trends in Indirect Dentistry: 3. Luting Materials. Dental Update 2005;32: Sahar E. Bond strength of a new universal self-adhesive resin luting cement to dentin and enamel. Clin Oral Invest 2005;9: 치과재료학제 3판군자출판사 p.249, p Brunton PA, Christensen GJ. Contemporary dental practice in the UK: indirect restorations and fixed prosthodontics. British Dental Journal 2005;198: Bouillaguet S. Bonding to dentin achieved by general practitioners. Schweiz Monatsschr Zahnmed 2002;112: Technical data sheet: Espertise RelyX Unicem(2002) 3M ESPE, Seefeld Germany 7. Piwowarczyk A, Bender R, Ottl P, Lauer H. Long-term bond between dual-polymerizing cementing agents and human hard dental tissue. Dent Mater 2007;23: Ibarra G, Johnson GH, Geurtsen W, Vargas MA. Microleakage of porcelain veneer restorations bonded to enamel and dentin with a new self-adhesive resin-based dental cement. Dent Mater 2007;23: Piwowarczyk A, Lauer HC, Sorensen JA. In vitro shear bond strength of cementing agents to fixed prosthodontic restorative materials. J Prosthet Dent 2004;92:

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29 Abstract Alteration of the degree of conversion in self-adhesive resin cement by measuring the surface hardness after initial curing You-Kyung ung Jung ung,, D.D.S. Department of Prosthodontics, Graduate School, Yonsei University (Directed by Professor Moon oon-kyu Chung hung,, D.D.S., M.S.D., Ph.D.) Currently, the materials for indirect restoration of lost tooth structures have incorporated ceramics without the support of metals; this has provided excellent esthetics. Accordingly, the need for resin cements that facilitate adhesion by bonding to the tooth structure and provide esthetics has increased. Resin cements have been difficult to use because of their technicsensitivity to etching and bonding. However, the self-adhesive resin cements that decrease additional adhesion procedures have been developed and are currently in use. The problem with the self-adhesive resin cements is potential hydrolysis due to their low initial ph after the initial curing. Thus, the rate of curing can be delayed at the time of initial curing. The purpose of this study was to study alteration of the degree of conversion in selfadhesive resin cement and whether or not the DC declines by delaying in the rate of curing at the time of initial curing comparing with the conventional

30 resin cement, and the products studied were dual-cured RelyX TM Unicem, self-cured Multilink and the conventional resin cement, dual-cured Panavia F. Test specimens were made with these products and they were evaluated by measuring their surface hardness at 5 minutes, 30 minutes, 1 hour, 2 hours, and 1 week after initial curing. They were tested in the clinical setting and the differences compared. The Multilink group had the lowest Knoop hardness; a strong Knoop hardness was observed in the Panavia F group and RelyX TM Unicem group respectively. For the degree of conversion(dc) according to time after the initial curing, the RelyX TM Unicem group had the highest DC at 5 minutes and the lowest DC was noted in the Multilink group and the Panavia F group respectively. The DC was also low respectively over time. Significant differences in the results according to the curing time, of Knoop hardness, were observed at all curing times except in the Multilink group. They were between 30 minutes and 1 hour and 1 hour and 2 hours (α=0.05). The degree of conversion in self-adhesive resin cements was higher than in the conventional resin cement and increased with time. Further study is needed to confirm our findings in intraoral condition. Key words : self-adhesive resin cement, surface hardness, degree of conversion