ISSN eissn Original Article Influence of water absorption on flexural strength and ela

https://doi.org/10.14368/jdras.2018.34.2.72 ISSN 2384-4353 eissn 2384-4272 Original Article Influence of water absorption on flexural strength and elastic modulus in several resinous teeth splinting materials Bae-Young Park, Soo-Yeon Kim, Jin-Woo Kim, Se-Hee Park, Kyung-Mo Cho* Department of Conservative Dentistry, College of Dentistry, Gangneung-Wonju National University School of Dentistry, Gangneung, Republic of Korea Purpose: The purpose of this study was to compare flexural strength and elastic modulus of several splinting materials dependent on water absorption. Materials and Methods: Three different materials; LightFix, G-FIX, G-aenial Universal Flo; were used in this study. Thirty rectangular bar specimens (25 2 2 mm) of each materials were prepared. Fifteen specimens of each materials were stored in 100% relative humidity atmosphere, 37 C for 24 hours. The other specimens were stored in distilled water, 37 C for 30 days. Flexural strength and elastic modulus were calculated using Universal testing machine. One-way ANOVA and Scheffe s post hoc test at 95% level of significance were used on all test results. Results: In LightFix, flexural strength and elastic modulus were significantly decreased after aging. In G-FIX, there was no significant change in flexural strength and elastic modulus after aging. In G- aenial Universal Flo, flexural strength was significantly decreased, but elastic modulus did not change significantly. Statistical analysis reveals that flexural strength and elastic modulus increased in the order of LightFix, G-FIX, G-aenial Flo in both 24 hours and 30 days. Conclusion: It could be deduced from this study that flexural strength and elastic modulus of some resins could be changed when it aged in oral environment. Thus this should be considered when choosing a resin to perform a resin-bonded splint. (J Dent Rehabil Appl Sci 2018;34(2):72-9) Key words: aging; elastic modulus; flexural strength; splint; tooth mobility 서론 일반적으로레진기질과무기질필러, 커플링제로구성되는치과용복합레진은좋은기계적성질, 심미성, 빠른중합, 용이한조작성, 법랑질에의접착능력을지녀치면열구전색, 접착제, 레진시멘트, 충전재등치과에서다양한용도로사용되고있다. 1,2 복합레진은동요치고정에도사용할수있으며최근에는치아고정을위한전용제품도개발되고있다. 이는짧은술식시간, 간편한임상적적용, 우수한심미성을지니고구강위생에유리하며치아삭제가거의필요하지 않아보존적이라는면에서장점을지닌다. 3 동요치고정에사용되는레진은치아의생리적인움직임을허용하는낮은탄성계수가요구된다. 그이유는치아고정재료가유연하면어느정도의변형에도파절이되지않지만과도하게단단하면응력내구성이적어약화가점진적으로진행되기쉽기때문이다. 4 또한레진계치아고정재료를이용하여동요치를고정할때인접치의법랑질에직접재료를접착시켜사용하기때문에법랑질에의믿을만한접착강도를지녀야한다. 그리고구강내의수복물은저작압에노출되고온습한환경을견뎌야하기때문에높은강도가요구된다. 3 *Correspondence to: Kyung-Mo Cho Professor, Department of Conservative Dentistry, College of Dentistry, Gangneung-Wonju National University, 7, Jukheon-gil, Gangneung, 25457, Republic of Korea Tel: +82-33-640-3155, Fax: +82-33-640-3103, E-mail: drbozon@gwnu.ac.kr Received: January 16, 2018/Last Revision: March 27, 2018/Accepted: April 22, 2018 Copyright 2018 The Korean Academy of Stomatognathic Function and Occlusion. cc It is identical to Creative Commons Non-Commercial License. 72

Influence of water absorption on flexural strength and elastic modulus in several resinous teeth splinting materials 이러한요구를충족하더라도복합레진이구강환경에노출되면시간이지날수록분해와부식에의해변화를겪는다는점을고려해야한다. 5 이는연하와저작과연관된스트레스에의한화학적파괴, 수용성구성요소의침출에의한화학적조성변화, 크랙을야기하는침전과팽창현상, 계면에서의누출, 부식에의한강도소실, 가수분해등을포함한다. 5-9 특히레진의수분흡수는미반응모노머, 모노머의불순물, 부가재, 분해산물의방출과필러이온의침출과같은부정적인영향을야기하고인장강도, 굴곡강도, 탄성계수, 마모저항성과같은물리적, 기계적성질에부정적인영향을미친다. 10-12 수분흡수가레진에영향을미치는이유는두가지가있는데이는가수분해와가소화작용이다. 13 가수분해는수분흡수시실란과필러입자사이의접착이분해돼궁극적으로필러-레진기질의탈착을야기한다는것인데 1,13 이는확산속도의존적과정으로중합종류, 필러종류, 필러입자의표면처리에의해영향을받는다. 14 가소화작용은수분이중합체의네트워크를팽창시키고체인사이의마찰력을감소시키는작용을통해중합체구성요소의연화가된다는것이다. 13,14 따라서동요치고정에사용되는여러레진재료들이에이징을겪은후어떤물리적성질의변화를보이는지가임상적으로중요하나이에대한연구는부족하며특히최근에시판됐거나시판준비중인제품에관한연구는거의없다. 이에본연구에서는동요치고정에사용되는여러광중합형레진계치아고정재료의에이징에따른굴곡강도와탄성계수를비교해물리적성질에대한정보를제공, 임상가들이재료를선택하는데에도움이되고자했다. 연구재료및방법 1. 실험재료 실험군으로 3종의레진을사용했다. 광중합동요치고정재료인 LightFix (Sun Medical Co., Shiga, Japan), G- FIX (GC Co., Tokyo, Japan), 치아고정재료로사용가능한흐름성복합레진인 G-aenial Universal Flo shade A2 (GC Co.) 를사용했다. 각재료의구성성분은 Table 1 에나타냈다. 1) 시편제작가로 25 mm, 세로 2 mm, 높이 2 mm의홈을파놓은스테인리스강재질의주형 (Fig. 1) 을이용해각실험군당 30개씩총 90개의시편을제작했다. 주형을조립한상태에서홈에각재료를유입시키고 celluloid matrix를압접하고슬라이드글라스로압력을주어균일한두께가되도록한후중합했다. LED를이용한광중합기인 G-Light (GC Co.) 를이용해다른위치에서 3회중첩되게 20초씩중합을완료한후주형을분리해시편을주형에서제거했다. 상대습도 100%, 37ºC 항온기 (SIB-1, Seo- 25 mm 2 mm 2 mm Fig. 1. Schematic drawing of specimen. Table 1. Composition and shade of materials used in this study Material Manufactures Shade Composition LightFix Sun Medical Clear G-FIX GC Clear G-aenial Universal Flo GC A2 Methacrylic acid ester (UDMA, 4-META, etc), acylic acid ester, photo initiator Glass filler, methacrylic acid ester, phosphoric acid ester monomer, photo initiator Matrix (31%wt.): TEGDMA, UDMA, Bis-MEPP Filler (69%wt., 50%vol.): Strontium glass (200 nm) silicon dioxide (16 nm) pigment Initiator: Photo initiator Data from manufacturers websites and/or product catalogs. UDMA: Urethane dimethacrylate; TEGDMA: Triethyleneglycoldimethacrylate; Bis-MEPP: 2,2-Bis(4-methacryloxypolyethoxyphenyl)propane; 4-META: 4-methacryloyloxyethy trimellitate anhydride. J Dent Rehabil Appl Sci 2018;34(2):72-9 73

Park BY, Kim SY, Kim JW, Park SH, Cho KM kwang Science Co., Seoul, Korea) 에서각실험군당시편 15개씩은 24시간동안보관했고나머지시편은 37ºC, 증류수에 30일간보관했다. 0.01 mm 단위까지측정가능한디지털캘리퍼 (Mitutoyo CD-15CP, Kawasaki, Japan) 를이용해각각의시편의높이와두께를측정한후 3점굽힘시험을시행했다. 3) 통계분석각실험재료의 24시간군과 30일군간비교를위해 Independant T-test를이용했다. 측정된각실험재료의굴곡강도와탄성계수는 One-way ANOVA test로분석했고사후검정으로 95% 유의수준에서 Scheffe s test를이용했다. 2) 굴곡강도및탄성계수측정 만능시험기 (RB-306, R&B Inc., Daejeon, Korea) 를이 용해분당 1.0 mm 의 cross-head 속도, 최대하중 800 kg 의조건에서시편이파절되는시점까지하중을줬다. 시 편에가해진최대힘 (N) 을측정하고기록했으며굴곡강 도와탄성계수는다음공식에따라계산했다. 굴곡강도 F = 3P f L / 2BH 2 (MPa) B 와 H 는각각시편의폭과두께 (mm), P f 는시편파괴 시점의최대힘 (N), L 은지지대사이의간격 (10 mm) 이다. 탄성계수 E= δ f / δ y L 3 / 4BH 3 (GPa) B 와 H 는각각시편의폭과두께 (mm 단위 ), L 은지지 대사이의간격 (10 mm), δ f / δ y 는단위변형률 (δ y ) 에대한 응력의변화율 (δ f ) 이다. 결과 굴곡강도와탄성계수의평균과표준편차, Independent T-test를이용하여알아본각실험재료의 24시간군과 30일군사이의유의성을 Table 2, 3에나타냈다. Oneway ANOVA test 및 Scheffe s test를시행해통계적유의성을알아본결과를 Fig. 2, 3에나타냈다. 본연구의결과 LighFix군에서는에이징후에굴곡강도와탄성계수가유의하게감소했다. 반면 G-FIX군에서는에이징후에굴곡강도와탄성계수에유의한차이가없었다. G-aenial Universal Flo군에서는굴곡강도는유의하게감소했으나탄성계수는유의한변화가없었다. 한편굴곡강도와탄성계수는 24시간군, 30일군모두 G-aenial Universal Flo가유의하게가장컸고 LightFix 가유의하게가장작았다. Table 2. Flexural strength of tested materials [Mean (MPa) and Standard deviation] Group Mean (MPa) ± Standard deviation 24 hours 30 days Significance LightFix 66.9 ± 3.4 38.3 ± 4.3 * G-FIX 72.4 ± 3.9 72.3 ± 9.7 G-aenial Universal Flo 112.3 ± 6.7 89.0 ± 16.1 * *: Significant differences were detected in each materials (Independent T-test, P < 0.05). Table 3. Elastic modulus of tested materials [Mean (GPa) and Standard deviation] Group Mean (GPa) ± Standard deviation 24 hours 30 days Significance LightFix 28.5 ± 5.5 8.3 ± 6.0 * G-FIX 40.7 ± 8.2 38.0 ± 5.6 G-aenial Universal Flo 101.7 ± 9.5 98.0 ± 10.6 *: Significant differences were detected in each materials (Independent T-test, P < 0.05). 74 J Dent Rehabil Appl Sci 2018;34(2):72-9

Influence of water absorption on flexural strength and elastic modulus in several resinous teeth splinting materials MPa 120 100 80 60 40 20 0 24 hours 30 days 120 100 80 60 40 20 0 24 hours 30 days LightFix G-FIX G-aenial Universal Flo LightFix G-FIX G-aenial Universal Flo GPa Fig. 2. Result of flexural strength (Scheffe s test). *: Significant differences were detected (P < 0.05) in each materials. Fig. 3. Result of elastic modulus (Scheffe s test). *: Significant differences were detected (P < 0.05) in each materials. 고찰 ISO-4049 기준에따르면, 15 3점굽힘시험시지지대사이의간격을 20 mm로설정해야하지만이번실험에서는지지대사이의간격을 10 mm로설정했다. 그이유는예비실험시지지대사이의간격을 20 mm로설정했을때 LightFix의파절이일어나지않아측정이불가했기때문이다. LightFix는 UDMA, 4-META를포함하는광중합형레진계치아고정재료로다른실험재료들에비해굴곡강도와탄성계수가유의하게낮았다. 복합레진의기계적성질은모노머의종류와양, 변환의정도, 무기질필러의종류와크기, 커플링제의종류, 개시제의양등레진의조성과연관된많은요소와관련이있다. 16 무기질필러입자들은기질보다강한기계적성질을나타내므로무기질필러의함량이높으면레진은높은굴곡강도와탄성계수를가진다. 16,17 이를통해 LightFix가다른복합레진들에비해낮은기계적성질을보이는이유중하나는무기질필러를포함하지않기때문이라고볼수있다. 이에반해 G-aenial Universal Flo는이산화규소, 스트론튬글라스등의무기질필러를 69% 중량비로함유하는데이것은비교적높은기계적성질을나타내는이유중하나가될수있다. 어떤연구에서건조한환경에서보다습한환경에서레진의굴곡강도와탄성계수가감소했는데, 18 이는이번연구에서 LightFix가에이징시굴곡강도와탄성계수가감소한것과일치한다. 이를통해 LightFix가상대적으로더많은수분흡수를했거나수분저항성면에서불리하다고볼수있다. 치과용레진의대다수는무기질필러의첨가를위해희 석용모노머가필요하고, 19,20 일반적으로 Triethyleneglycoldimethacrylate (TEGDMA) 가사용되는데이는분자량과점도가낮아중합률을높이지만중합수축이크다. 21-23 따라서 Ethoxylated bisphenol-a dimethacrylate (Bis-EMA) 와같은점도는낮고분자량은큰모노머가최근 TEGDMA을일부또는전부대체하고있다. 24 하지만 Bis-EMA가포함된레진은 TEGDMA가포함돼있는레진보다더낮은굴곡강도를보인다는연구가있다. 24 그이유는 TEGDMA가더효과적인수소결합수용기를가지고 Bis-EMA가높은분자량으로인해중합체의가교결합밀도를감소시키며이는가소화작용에영향을주기때문이라고했다. 11,24,25 어떤논문에따르면 G-FIX 는 Bis-EMA를포함하는데, 26 이는 Bis-EMA를포함하는 G-FIX가 TEGDMA를포함하는 G-aenial Universal Flo보다굴곡강도가낮은이유를일부설명할수있다. 어떤연구에따르면멸균증류수는레진의압축강도에장기간의영향이없었는데저자는그이유를수분으로인한복합레진의가수분해가표본의표층부에만영향을주기때문이라고분석했다. 14 이를통해본연구에서에이징후에도 G-FIX의굴곡강도와탄성계수가유의한변화를보이지않은이유를일부설명가능할수도있다. 하지만 G-FIX는제조사에서구성성분과함량에대한자세한정보를제공하지않기때문에실험결과를설명하기에어려움이있다. G-FIX 제조사에서제공하는설명에따르면새롭게개발한고인성모노머를사용해동요치고정에적합한유연성과점인성을부여했다고하며이를설명하기위해서는추가적인연구와정보가필요하다. 3 어떤연구에서여러복합레진을인공타액, 멸균증류수, 에탄올을이용하여에이징했을때바륨과스트론튬의침출이관찰됐다고했고이는용액이레진의이온소 J Dent Rehabil Appl Sci 2018;34(2):72-9 75

Park BY, Kim SY, Kim JW, Park SH, Cho KM 실을가속화시키는이온교환제로작용하고용액침투가레진기질의용해와입자소실을야기하며기질의이온을운반하기때문이라고설명했다. 5 이를통해수분이 G-aenial Universal Flo의레진기질의용해와스트론튬의소실을야기하여굴곡강도감소에일부영향을줬을수있다고추측할수있다. 하지만스트론튬이온이바륨이온보다직경이더작기때문에더잘확산되고실리콘이온도방출이잘된다고한어떤연구에서는이온방출과굴곡강도, 탄성계수와의관계는적다고했다. 27 그이유는레진의분해는글라스필러보다약한연결을하는레진기질과더연관성이있기때문이라고했다. 27 따라서이온방출이본실험의연구결과에영향을줬는지는알수없다. 마찬가지로 TEGDMA는분자가작아수분흡수시더많은용출을할수있다는연구가있지만, 28,29 G-aenial Universal Flo에포함돼있는 TEGDMA의용출이에이징시굴곡강도감소에영향을줬는지는알수없다. G-aenial Universal Flo의탄성계수는변하지않았지만굴곡강도는유의하게감소한점을동시에명확하게설명하기힘들다. 이는모노머의종류가반응성, 점도, 중합수축, 기계적성질, 수분흡수, 수분에의한팽창과강한연관이있고, 30 필러, 모노머그리고커플링제의종류, 함량등에의한영향이복합적으로작용해실험결과에나타나기때문으로생각된다. 이번연구에서에이징시굴곡강도와탄성계수의유의한감소를나타낸 LightFix는장기간의동요치고정에사용하기에는적절하지않다는점이임상적으로의미가있다. 하지만낮은탄성계수를보인다는점에서외상으로인해생긴동요치의고정이단기간으로필요한경우또는치주질환으로인해비생리적인동요가생겼지만치주치료후에안정이되기까지단기간으로고정시킬목적이라면임상적으로유용하게사용할수있을것으로사료되나다양한고정기간에따른추가적인연구가더필요하다. G-FIX의경우 24시간군, 30일군모두 LightFix보다높은굴곡강도, G-aenial Universal Flo보다낮은탄성계수를보이고에이징후에도굴곡강도와탄성계수의유의한차이가나타나지않아단기간, 장기간의동요치고정에적절할것으로생각된다. 에이징시굴곡강도의유의한감소를나타낸 G-aenial Universal Flo는에이징후에도높은굴곡강도를보이지만, 24시간군, 30일군모두탄성계수가유의하게높기 때문에다른재료에비해치아의생리적인동요를허용하지않을것으로사료된다. 치아고정재료의선택시고려되는성질은이번연구에서조사한굴곡강도와탄성계수뿐아니라심미성, 용해도, 조작성, 생체적합성, 중합수축, 법랑질과의접착강도, 인장강도, 마모저항성등다양한물리적, 기계적성질및다양한요소가복합적으로고려돼야한다. 또한레진의구강내의분해과정에연관된메커니즘은수분흡수와관련된가수분해, 가소화작용만관여하는것이아니라교합과정, 온도, 화학적분해, 효소, 단백질, 세균, 다양한화학물질, 생물학적요소등이연관되어상당히더복잡하다. 14 그러므로이러한새로운재료들의성능에대한 in vitro 연구가더필요하다. 결론 3점굽힘시험을통해치아고정에사용할수있는여러레진의굴곡강도와탄성계수를알아봤고이에대한결과는다음과같다. 1. LightFix는에이징후에굴곡강도와탄성계수가유의하게감소했으나 G-FIX는유의한차이가없었고 G-aenial Universal Flo는굴곡강도는유의하게감소했으나탄성계수는유의한차이가없었다. 2. 굴곡강도와탄성계수는 24시간군, 30일군모두 G-aenial Universal Flo, G-FIX, LightFix 순으로유의하게컸다. 이상의결과를바탕으로 G-FIX는굴곡강도와탄성계수에있어에이징의영향을덜받는다고간주할수있으며비교적높은굴곡강도와낮은탄성계수를가져동요치고정에유리할것으로생각된다. LightFix는다른재료에비해탄성계수가낮아유연하고에이징후에더탄성계수가낮아진다는장점이있다. 하지만에이징후에굴곡강도또한낮아지고에이징의영향을상대적으로많이받으므로단기간의동요치고정에적절할것으로생각된다. G-aenial Universal Flo는탄성계수가비교적높아치아의생리적인동요를허용하지않을것으로사료된다. Acknowledgements 이논문은 2017년도강릉원주대학교학술연구조성비지원에의하여수행되었다. 76 J Dent Rehabil Appl Sci 2018;34(2):72-9

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Original Article 수분흡수가여러레진계치아고정재료의굴곡강도와탄성계수에미치는영향 박배영, 김수연, 김진우, 박세희, 조경모 * 강릉원주대학교치과대학치과보존학교실 목적 : 본연구의목적은수분흡수가여러레진계치아고정재료의굴곡강도와탄성계수를미치는영향을비교함으로써물리적성질에대한정보를제공하는것이다. 연구재료및방법 : 치아고정에사용하는레진으로 LightFix, G-FIX, G-aenial Universal Flo를이용했다. 가로 25 mm, 세로 2 mm, 높이 2 mm의시편을각재료당즉시용 15개과에이징용 15개를제작했다. 즉시용은 37ºC, 100% 상대습도에 24시간동안보관됐고에이징용은 30일동안 37ºC, 증류수에보관했다. 만능시험기를이용해굴곡강도와탄성계수를측정했고 independent t-test를이용해각실험재료의 24시간군과 30일군간비교를했다. 실험재료간의비교는 oneway ANOVA test로분석했고 95% 유의수준으로 Scheffe s test를이용해사후검정했다. 결과 : 본연구의결과 LighFix군에서는에이징후에굴곡강도와탄성계수가유의하게감소했고 G-FIX군에서는에이징후에굴곡강도와탄성계수에유의한차이가없었다. G-aenial Universal Flo군에서는굴곡강도는유의하게감소했으나탄성계수는유의한변화가없었다. 한편굴곡강도와탄성계수는 24시간군, 30일군모두 LightFix가가장낮은수치, G- aenial Universal Flo가가장높은수치를보였다. 결론 : 어떤레진의굴곡강도와탄성계수는구강환경에서에이징시변화할수있으므로동요치고정을목적으로레진을선택할때이를고려해야한다. ( 구강회복응용과학지 2018;34(2):72-9) 주요어 : 에이징 ; 탄성계수 ; 굴곡강도 ; 고정 ; 치아동요 * 교신저자 : 조경모 (25457) 강원도강릉시죽헌길 7 강릉원주대학교치과대학치과보존학교실 Tel: 033-640-3155 Fax: 033-640-3103 E-mail: drbozon@gwnu.ac.kr 접수일 : 2018 년 1 월 16 일 수정일 : 2018 년 3 월 27 일 채택일 : 2018 년 4 월 22 일 79