http://dx.doi.org/10.5933/jkapd.2015.42.4.281 ISSN (print) 1226-8496 ISSN (online) 2288-3819 Evaluation of Shear Bond Strength and Microleakage of Bulk-fill Resin Composites Hanbyeol Lee, Hyunwoo Seo, Juhyun Lee, Howon Park Department of Pediatric Dentistry, Oral Science Research Center, College of Dentistry, Gangneung-Wonju National University Abstract The aim of this study was to evaluate shear bond strength (SBS) of bulk-fill resin composites (RCs) to dentin and their micro-leakage. One high-viscosity bulk-fill RC and 2 low-viscosity bulk-fill RCs were compared with 1 conventional RC. 7thgenerationbondingagentswereused. In order to evaluate SBS values, 40 permanent molars were selected and divided into 4 groups. The bulk-fill RCs were applied in 4 mm thickness, whereas the conventional RC was applied in 2 mm thickness. In order to evaluate micro-leakage, class I cavities (5 2 4 mm) were prepared in 32 permanent molars. The teeth were divided into 4 groups and restored with resin composites in an increment of 4 mm for the bulkfill RC and in 2 horizontal increments of 2 mm for the conventional RC. The mean SBS value of conventional RC showed no statistically significant difference when compared with those of low-viscosity bulk-fill RCs. However, the mean SBS value of high-viscosity bulk-fill RC was significantly lower than that of conventional RC (p < 0.05). There were no statistically significant differences in micro-leakage between the 4 groups. For SBS and micro-leakage, the use of low-viscosity bulk-fill RCs might help clinicians simplify the procedure. Key words : Bulk-fill resin composites, Shear bond strength, Micro-leakage, 7thgenerationbondingagent Ⅰ. 서론심미수복에대한요구가전치부뿐만아니라구치부로확대되면서수복재료로써복합레진의사용이증가해왔으며, 이와관련한물리적, 기계적성질개선및수복술식의발전이이루어져왔다. 현재사용되는대부분의복합레진은 methacrylate 계열로, 제한된중합깊이및중합수축과관련하여깊은와동에서는한번에중합하는복합레진의깊이가 2 mm를초과하지않도록수회에걸쳐적층충전하는방식이추천되어왔다 1,2). C-factor (cavity-configuration factor) 는접착면과비접착면의비율로, 적층충전을시행할경우 C-factor가감소됨에따라 2.9-7.1vol% 의체적중합수축및 7 MPa에달하는복합레진내의중합수축응력을감소시킬수있다고알려져왔다 2). 그러나적층충전의경우긴술식시간및수복물내의기포함입등의단점과적층충전이항상수축응력을완화시키는것은아니며, 오히려 bulk충전에비해더큰중합수축을발생시킨다는주장이제기되면서술식시간을단축하고, 술식과정을단순화할수있는복합레진에대한연구가진행되었다 3,4). 이러한노력으로한번에 4 mm 깊이또는그이상까지한번에충전가능한 bulk-fill 복합레진이개발되었다 5,6). Bulk-fill 복합레진의증가된중합깊이는반투명성 (tranlucency) 의증가및광에대한높은반응성과관련이있으며, 중합수축응력을감소시키는기전으로는중합수축응력이완제와중합조절제 Corresponding author : Juhyun Lee Department of Pediatric Dentistry, College of Dentistry, Gangneung-Wonju National University, 7 Jukheon-gil, Gangneung, 25457, Korea Tel: +82-33-640-2452 / Fax: +82-33-640-3113 / E-mail: ljh55@gwnu.ac.kr Received April 6, 2015 / Revised June 24, 2015 / Accepted June 24, 2015 281
등을이용함이보고되고있다 7-9). Bulk-fill 복합레진은저점도 (low-viscosity) bulk-fill 복합레진과고점도 (high-viscosity) bulk-fill 복합레진으로분류할수있는데, 전자의경우 4 mm 깊이에서의충분한중합률 (degree of conversion) 이보고되고있으며, 기계적강도가낮아깊은와동에서이장재또는기저재로사용되어진다 6,7,10). 후자의경우제조사의설명에따르면상부의기존복합레진수복없이 4 mm 깊이로단일층수복이가능하고, 치아구조를재현할수있는특징을가지고있다. 현재 bulk-fill 복합레진을대상으로기계적성질, 투광성, 중합률및중합깊이, 중합수축및중합수축응력, 교두굴곡, 미세누출, 변연적합도, 전단결합강도와 creep변형등에관한연구결과가보고되고있다 6-19). 그러나이전연구의대다수는저점도 bulk-fill 복합레진에국한되어진행되었으며, 특히저점도및고점도 bulk-fill 복합레진에관한전단결합강도평가와 bulkfill 복합레진을 4 mm 깊이로충전했을때의미세누출에관한연구는부족하다. 따라서본연구에서는각제조사에서추천하는 7세대상아질접착제를사용하여 1종의고점도 bulk-fill 복합레진과 2종의저점도 bulk-fill 복합레진의상아질전단결합강도및미세누출을 conventional 복합레진과비교평가하고자한다. Ⅱ. 연구재료및방법본연구는강릉원주대학교치과병원임상심사위원회 (IRB) 의승인을받아시행되었다 (IRB File NO.: IRB 2015-01). 1. 연구재료이번연구에서는 1종의고점도 bulk-fill 복합레진 (Tetric N- Ceram Bulk Fill; TBF), 2종의저점도 bulk-fill 복합레진 (Venus bulk fill; VB, surefil SDR flow; SDR) 그리고대조군으로 1종의 conventional 복합레진 (Filtek Z350; FZ) 을사용하였다 (Table 1). 동일제조사의복합레진-상아질접착제의조합으로군을분류하였으며 (Table 2), 사용한 7세대상아질접착제 4종은 Table 3과같다. 2. 전단결합강도측정 1) 시편제작발거된제3대구치및치주질환으로발거된제1, 2대구치중우식이나파절또는수복물이존재하지않는 40개를선택하여실험전까지생리식염수에보관하였다. 치아를자가중합아크릴릭레진 (Jet Tooth Shade TM Powder, Lang Dental Mfg Inc, Wheeling, U.S.A.) 에임상치관을노출시켜매몰한후주수하에 low-speed diamond saw (Accutom-50, Struers, Copenhagen, Denmark) 를이용하여교합면에평행하게치관중앙부을절단하였다. 치아의상아질면은동일한도말층형성을위해주수하에 600-grit sand paper로표면을 30초간연마하였고, sand paper는 10개시편마다새것으로교체하였다. 제작된시편은무작위로 4개의군 (n = 10) 으로분류하였으며, 시편제작후 1시간이내에치수와 DEJ 간거리 1/2 지점 Table 1. Resin composites used in this study Resin type Product Composition Shade High-viscositybulk-fill resin composites Tetric N-Ceram Bulk Fill Matrix: UDMA, Bis-GMA, Bis-EMA Filer load: 60-61vol%, 79-81wt% IVA Low-viscositybulk-fill resin composites Venus bulk fill Matrix: UDMA, EBADMA Filer load: 38vol%, 65wt% Universal SureFil SDR flow Matrix: UDMA, EBPADMA, TEGDMA Filler load: 44vol%, 68wt% Universal Conventionalresin composites Filtek Z350 Matrix: UDMA, BIS-GMA, BIS-EMA, TEGDMA, PEGDMA Filer load: 63.3vol%, 78.5wt% A2 Bis-GMA = Bisphenol A glycidyl dimethacrylate, Bis-EMA = Bisphenol A polyethylene glycol diether -dimethacrylate, UDMA = urethane dimethacrylate, EBPADMA = epoxylated Bisphenol A dimethacrylate, TEGDMA = triethyleneglycol dimethacrylate, PEGDMA = poly ethylene glycol dimethacrylate Table 2. Coupling of resin composites and dentin adhesive system Group Materials Resin composites Dentin adhesive Manufacture TBF Tetric N-Ceram Bulk Fill Tetric N bond self etch Ivoclar Vivadent,Schaan, Liechtenstein VBVenus bulk fill ibond Self Etch Heraeus-Kulzer, Hanau, Germany SDR SureFil SDR flow Xeno V+ Dentsply-Caulk, Molford, DE, USA FZ Filtek Z350 Singlebond universal 3M ESPE, St. Paul, MN, USA TBF = Tetric N-Ceram Bulk Fill, VB = Venus bulk fill, SDR = SureFil SDR flow, FZ = Filtek Z350 282
에상아질접착제와복합레진을제조사의지시에따라적용하였다 (Fig. 1, Table 3). Bulk-fill 복합레진은내경 2 mm, 높이 4 mm의 teflon mold를이용하여레진블록을축조하였고, conventional 복합레진은내경 2 mm, 높이 2 mm의 teflon mold를이용하여레진블록을축조하였다. LED 광중합기 (Bluephase, Ivoclar Vivadent, Schaan, Liechtenstein) 를 이용하여복합레진직상방에서 20초간광조사를시행하였으며, 실험전과각군에대한실험후 Power intensity meter (Dentamerica, California, U.S.A.) 를이용하여광중합기의광도가약 800 mw/cm 2 임을확인하였다. 제작된시편을 24시간동안상온의증류수에보관하였다 20). A B Fig. 1. Schematic diagram of the specimen (A) and the shear bond strength test set-up (B). Table 3. 7th generation bonding agents used in this study Product Composition General procedures (according to manufacturer) Tetric N bond self etch Bis-acrylamide derivative 1. Adhesive application (1 coat, 30s) Bismethacrylamide 2. Air dry (5s) dihydrogenphosphate 3. Light polymerization (10s) amino acid acrylamide hydroxyalkyl methacrylamide nano-fillers (SiO 2) initiators stabilizers water ibond Self Etch 4-META 1. Adhesive application (1 coat, 20s) glutaraldehyde 2. Air dry (5s) UDMA 3. Light polymerization (20s) TEGDMA Photoinitiator stabilizers acetone water Xeno V+ bifunctional acrylic amides acrylamido alkylsulfonic acid 1. Adhesive application (1 coat, 20s) functionalized phosphoric acid ester 2. Air dry (5s) acrylic acid 3. Light polymerization (10s) camphoroquinone photoinitiator stabilizers butylated benzenediol tertiary butanol water Singlebond universal Bis-GMA 2-hydroxyethyl methacrylate decamethylene dimethacrylate 1. Adhesive application (1 coat, 20s) silane treated silica 2. Air dry (5s) 2-Propenoic Acis, 2-Methyl-, 3. Light polymerization 10s) reactionproducts with 1, 10-Decanediol phosphorous oxide copolymer o f acrylic and itaconic acid camphorquinone dimethylaminobenzoat (-4) tolueneethanol water 283
2) 전단결합강도측정 24시간동안증류수에보관한시편을건조시킨후 Universal Testing Machine (R&B Inc., Daejeon, Korea) 을이용하여 cross head speed 1 mm/min의속도로전단력을가했다. 치아표면에서복합레진이탈락될때의최대힘을컴퓨터에연결된 Helio X 프로그램을이용하여 kgf 단위로측정하였으며, 치아-복합레진간접촉면적으로나누어 MPa단위로환산하였다. 가. Bulk-fill 복합레진 : 4 mm 단일층을교합면으로부터 40 초간광중합하였다. 나. Conventional 복합레진 : 2 mm씩 2회수평적층충전하였고, 각층마다교합면으로부터 40초간광중합하였다. 중합된복합레진표면을주수하에 extra-fine diamond finishing bur를이용하여각시편당 15초씩마무리와연마를시행하였으며, 모든과정은동일한술자가진행하였다. 3) 파절양상의판별전단결합강도측정후시편의각접착계면에서의파절부위를 10 nm 백금입자코팅후전계방사형주사전자현미경 (Inspect TM F50, Oregon, U.S.A.) 을이용하여 100배의비율로관찰하였다. 파절양상은다음과같은기준으로판별하였다. (1) 부착성파절 (adhesive failure): 상아질과접착제사이의계면에서파절이발생한경우 (2) 응집성파절 (cohesive failure): 치아또는복합레진내에서파절선이존재하는경우 (3) 혼합성파절 (mixed failure): 접착계면에서파절선이시작하여한기질 ( 치아또는복합레진 ) 로진행되는경우 3. 미세누출측정 1) 치아준비및와동형성, 복합레진충전발거된제3대구치및치주질환으로발거된제1, 2대구치중우식이나파절또는수복물이존재하지않는 32개를선택하여실험전까지생리식염수에보관하였다. 고속엔진용 #330 carbide bur, #556 carbide bur를이용하여주수하에치아의교합면에근원심길이 5 mm, 협설길이 2 mm, 깊이 4 mm의 I 급와동을형성하였으며, 5개의와동을형성할때마다새로운 bur를사용하였다. 형성된와동을무작위로 8개씩 4개의군으로분류하였고, 제조사의지시대로상아질접착제를도포한후 (Table 3) 해당복합레진을다음과같은방법으로충전하였다. 2) 시편처리수복물의완전한경화를위해시편을 24시간동안상온의증류수에보관한한후한군당제작된 8개의시편을무작위로 4 개씩두소집단 (subgroup) 으로나누었다. 소집단 A에서는열순환을시행하지않았으며, 소집단 B에서는 5 와 55 에서각각 30초씩침적시키는방법으로총 500회의열순환을시행하였다 21). 치근단공을통해염색액이침투하는것을막기위해치근단공부위를복합레진으로봉쇄한후수복물주위 1 mm를제외한전치면에 nail varnish를 2회도포하였다. 시편을건조시킨후 2% methylene blue 용액에넣어 24시간동안침적시킨후흐르는물에세척하였다. 시편을저속 diamond disk를이용하여주수하에각수복물의중앙부가통과되도록치아의장축에평행하게협설방향으로이등분하였다. 각시편의절단면을주수하에 600-grit sand paper로최종연마하여한개의와동에대해 diamond disk의두께및연마된두께만큼떨어져위치한서로다른부위의 2개의시편을제작하였다 (n = 16). 3) 미세누출의판별광학현미경 (Global dental microscope, St. Louis, MO, U.S.A) 를이용하여 19.2배율로염색용액의침투정도를협측, 설측의치아-복합레진간계면을관찰하고이를기록하였다. 염색용액의침투도판정기준은다음과같다 (Fig. 2). 0: 색소침투가없는경우 0 1 2 3 4 Fig. 2. Pictures of sectioned specimens for the rating of the methylene blue penetration ( 19.2). 284
1: 색소가와동축벽길이의 1/3이하로침투한경우 2: 색소가와동축벽길이합의 1/3을초과하였으나 2/3이하인경우 3: 색소가와동의축벽길이합의 2/3를초과하였으나치수벽에도달하지않은경우 4: 색소가치수벽까지침투한경우 4. 통계처리연구에사용된자료의분석및통계처리는 SPSS 21.0 (SPSS Inc., Chicago, IL, U.S.A.) 을사용하였고유의수준은 0.05로하였다. 각군간의전단결합강도를비교하기위해 One-way ANOVA를이용하였으며, Tukey's honest significant difference test로사후검정하였다. 각군간의미세누출에대한유의성검증은 Kruskal-Wallis test와 Mann- Whitney test (p < 0.0083, Bonferroni correction) 를이용하여시행하였으며, 소집단간의차이는 Wilcoxon signed rank test를이용하여분석하였다. Ⅲ. 연구성적 1. 전단결합강도측정각군의평균전단결합강도는 Table 4와같다. 평균전단결합강도는 SDR군에서 21.91 MPa로가장높게나타났고, TBF군에서 11.11 MPa로가장낮게나타났다. SDR군과 FZ 군사이에는통계적으로유의한차이가존재하지않았으며, 두 군모두 TBF군보다유의하게높은값을나타내었다 (p < 0.05). VB군은다른군과는유의한차이가없었으나, SDR군에비해유의하게낮은전단결합강도값을보였다 (p < 0.05). 2. 파절양상본실험에서평균전단결합강도값이가장높게나타난 SDR 군에서는혼합성파절양상 (60%) 과응집성파절양상 (40%) 이관찰되었다. FZ군과 TBF군에서는세가지파절양상이모두관찰되었으나평균전단결합강도가비교적높은 FZ군에서는주로응집성파절양상 (50%) 과혼합성파절양상 (30%) 이관찰되었고, 평균전단결합강도가비교적낮은 TBF군에서는주로부착성파절양상 (70%) 이관찰되었다. VB군의경우부착성파절양상 (80%) 과혼합성파절양상 (20%) 이관찰되었다 (Table 5, Fig. 3-6). 3. 미세누출측정각군의미세누출점수는 Table 6와같다. 열순환처리를하지않은소집단 A에서 FZ군이가장높은미세누출을보였고, SDR군에서가장낮은미세누출을보였으나각군간의통계적으로유의한차이는존재하지않았다. 열순환처리한소집단 B 에서는 VB군에서가장높은미세누출을, SDR군에서가장낮은미세누출을보였으나각군간의통계적으로유의한차이는존재하지않았다. 모든군에서열순환처리한소집단 B에서열순환처리를하지않은소집단 A보다유의하게높은미세누출이관찰되었다 (p < 0.05). Table 4. Descriptive statistics of the shear bond strength values, results of the multiple comparison test (N = 10) Group Mean ± SD (MPa) Minimal (MPa) Maximal (MPa) TBF 11.11 ± 6.19 a 5.07 22.08 VB15.80 ± 4.73 ac 8.65 24.03 SDR 21.91 ± 2.43 b 18.02 24.95 FZ 21.16 ± 5.52 bc 11.77 28.11 TBF = Tetric N-Ceram Bulk Fill, VB = Venus bulk fill, SDR = SureFil SDR flow, FZ = Filtek Z350 SD = standard deviation Within the same column, different superscript letters denote significant differences between groups at the p = 0.05 level according to the Tukey's honest significant difference test. Table 5. Distribution of the mode of fracture according to the scanning electron photomicrographs (N = 10) Group Mode of fracture adhesive mixed cohesive TBF 7 (70%) 1 (10%) 2 (20%) VB8 (80%) 2 (20%) 0 (0%) SDR 0 (0%) 6 (60%) 4 (40%) FZ 2 (20%) 3 (30%) 5 (50%) TBF = Tetric N-Ceram Bulk Fill, VB = Venus bulk fill, SDR = SureFil SDR flow, FZ = Filtek Z350 285
Table 6. Microleakage score (mean ± SD) of the groups tested (N = 16) Microleakage score Mean ± SD Group Subgroup A (without aging) Subgroup B (with aging) 0 1 2 3 4 0 1 2 3 4 Subgroup A Subgroup B TBF 4 8 2 0 2 2 3 3 2 6 1.25 ± 1.23 a 2.44 ± 1.50 b VB6 5 2 1 2 1 4 3 1 7 1.25 ± 1.39 a 2.56 ± 1.45 b SDR 4 6 6 0 0 1 3 7 2 3 1.13 ± 0.80 a 2.19 ± 1.16 b FZ 6 4 3 0 3 3 4 0 0 9 1.38 ± 1.50 a 2.50 ± 1.78 b TBF = Tetric N-Ceram Bulk Fill, VB = Venus bulk fill, SDR = SureFil SDR flow, FZ = Filtek Z350 SD = standard deviation Within the same row, different superscript letters denote significant differences between groups at the p = 0.05 level according to the Wilcoxon signed rank test. Fig. 3. Scanning electron photomicrographs of representative failure mode in TBF (Tetric N-Ceram Bulk Fill) group (Left: adhesive failure, Right: cohesive failure). Fig. 4. Scanning electron photomicrographs of representative failure mode in VB (Venus bulk fill) group (Left: adhesive failure, Right: mixed failure). Fig. 5. Scanning electron photomicrographs of representative failure mode in SDR (surefil SDR flow) group (Left: mixed failure, Right: cohesive failure). 286
Fig. 6. Scanning electron photomicrographs of representative failure mode in FZ (Filtek Z350) group (Left: mixed failure, Right: cohesive failure). Ⅳ. 총괄및고찰복합레진의중합수축은중합이일어날때생성되는짧은공유결합에기인한단량체분자간의거리감소로인해발생한다. 중합과정중겔지점에도달하면중합사슬이얽히게되어공유-교차결합네트워크가형성되는데, 이때수축응력이복합레진내부에발생하게된다 22). 중합수축응력은접착치질의변위를초래하며, 결과적으로변연부소실, 미세누출, 이차우식, 법랑질의미세파절, 치아교두굴곡및술후과민증이야기될수있다. 또한중합수축응력의크기가복합레진-상아질간결합력보다클경우에는결합실패가발생한다 23-25). 저점도 bulk-fill 복합레진인 surefil SDR flow와 Venus bulk fill의경우큰크기의필러를사용하여필러-매트릭스접촉면적을감소시킴으로써광투과성이개선되어중합깊이가증가하였다고생각되며, 최대수축응력도달시간의연장및낮은탄성계수가중합수축응력을감소시키는기전으로보고되고있다 11,14,26,27). 고점도 bulk-fill 복합레진인 Tetric N-Ceram bulk fill의경우기존개시제와더불어새로운광개시제인 Ivocerin 을사용하여중합효율과중합깊이가증가되었고, 중합수축응력이완제및미리중합된필러의사용이탄성계수를낮추어중합수축응력을감소시켰다고알려져있다 28). Bulk-fill 복합레진의전단결합강도에대한이전의연구에서는 Tetric EvoCeram Bulk Fill (TECBF) 보다 SDR에서높은전단결합강도를보고하고있다 17,18). TECBF는이번연구에서사용한 TBF와성분은동일하나 matrix함량을약 1.5% 줄이고, 필러함량을약 1.5% 증가시킨북미지역에서출시된동일제조사의제품이다. 이번실험결과 TBF군 (11.11 MPa) 과비교하였을때 SDR군 (21.91 MPa) 에서유의하게높은평균전단결합강도값을보여이전의연구결과와일치함을확인하였다. 대조군인 FZ군과비교하였을때, 저점도 bulk-fill 복합레진인 SDR군과 VB군에서는유의한차이가존재하지않았으나, 고점도 bulk-fill 복합레진인 TBF군에서는유의하게낮은전단결합강도값이관찰되었다. 이러한결과의요인으로복합레진 의흐름성과중합깊이를생각해볼수있다 10,14,17,29). 이번연구에서는복합레진을축조하기위하여 2 mm 직경의 teflon mold를사용하였는데상아질-복합레진접촉면적이좁아복합레진의흐름성이부족한경우제대로치면과접촉되지않아전단결합강도에영향을미쳤을것으로판단되며, 특히표준편차값이가장컸던 TBF군에서그영향이컸으리라생각한다. 중합깊이와관련하여저점도 bulk-fill 복합레진에서는 4 mm 깊이에서충분한중합률이보고되는반면, 고점도 bulk-fill 복합레진에서는논란이있다 10,14,29). 복합레진전체깊이에충분한광이도달하지못한다면중합률감소와더불어복합레진-상아질결합강도가약화되므로이에대한후속연구를통해상관성확인이필요하다 30). 이번연구결과저점도 bulk-fill 복합레진인 SDR군과 VB군사이에유의한전단결합강도의차이가존재하였다. 이는 SDR 군에비해 VB군의높은중합수축응력을보고한이전연구를근거해서 VB군에서낮은전단결합강도값이나타났다고생각할수있다 14,31). Leloup 등 32) 은결합강도가클수록응집성파절양상의비율이높다고보고하였으며, Ilie 등 17) 은혼합성또는응집성파절양상이높은전단결합강도와연관있음을보고하였다. 이번연구에서도평균전단결합강도가높은 SDR군과 FZ군에서는혼합성또는응집성파절양상이주로관찰된반면, 평균전단결합강도가낮은 VB군, TBF군에서는주로부착성파절양상이관찰되어기존의연구와일치함을확인하였다. 이번연구에서는 bulk-fill 복합레진의미세누출을확인하기위하여교합면에 4 mm깊이의 box형태의와동을형성하였다. 이와동처럼높은 C-factor를가지는경우에는중합수축으로인해접착면이파괴되어미세누출이발생하기쉬워진다 16). 수복물의미세누출을평가하는방법으로는색소침투법, 주사전자현미경을이용한변연적합도분석법, 공기압력이용법, 방사선동위원소이용법, 중성자활성분석법등을이용할수있으며, 최근에는 3차원재구성법, 미세단층촬영법등이이용되고있다. 이중 2차원적정성평가로색소침투법과주사전자현미경을이용한변연적합도분석법이널리사용되고있는데, 이두방법을이용 287
한외부변연적합도와내부변연적합도사이에유의한상관관계가있다는연구결과에따라이번연구에서는미세누출을확인하기위하여색소침투법을사용하였다 33). 이번연구결과열순환처리유무에상관없이 SDR군에서가장낮은미세누출값을보였으나 FZ군과통계적으로유의한차이가존재하지않아 SDR이기존복합레진과비슷한수준의변연적합도를보인다는이전의연구결과와일치하였다 8,13,15,16). 또한 VB군과 TBF군에서도 FZ군과통계적으로유의한차이가존재하지않아저점도뿐만아니라고점도 bulk-fill 복합레진의사용역시미세누출정도에영향을미치지않았음을확인하였다. 이번연구에서사용한 7세대상아질접착제들은표층의도말층을녹이거나변형시켜집적접착시키는방식으로, 높은미세누출, 낮은결합강도그리고수분흡수증가로인한장기간의제한적인내구성등이문제점으로대두되어왔다 34). 그러나 Margvelashvili 등 35) 은유기용매를포함한 7세대상아질접착제가 4세대상아질접착제와통계적인관점에서비견될만한결합강도를보임을보고하였으며, 적용과정의단순성과편리성으로인해최근 7세대상아질접착제의사용이증가하고있다. Roggendorf 등 15) 은 SDR을기저재로사용하였을때시효처리전에는 4세대및 7세대상아질접착제모두에서높은변연적합성을보였으나, 시효처리를가하고난후에는 4세대상아질접착제를사용했을때변연적합성이유의성있게높았음을보고하였다. 7세대상아질접착제를사용한이번연구에서열순환처리를했을때모든군에서미세누출이유의하게증가함을확인하였다. 이러한경향에는상아질접착제가주요요인으로작용할수있으며, 상아질접착제자체가전단결합강도에도영향을미칠수있으므로다양한세대의접착시스템을사용한후속연구가필요하다. 저점도 bulk-fill 복합레진은강도보강을위해상부피복층이필요하므로단일층충전이가능한고점도 bulk-fill 복합레진과비교시시술시간이늘어나게되나기존의적층술식에비해서는시간을단축할수있다. 고점도 bulk-fill 복합레진의경우흐름성이낮아좁고접근이어려운와동에충전하는데제한이있으며, 본실험결과미세누출에서는유의한차이가없었으나, 4 mm 깊이에서유의하게낮은전단결합강도를보였다. 따라서전단결합강도와미세누출측면에서생각했을때저점도 bulk-fill 복합레진의사용이술식간소화와관련하여임상에서의활용도가높을것으로생각되며, 고점도 bulk-fill 복합레진에관해서는후속연구를통해임상적효용성에대한논의가필요하다. Ⅴ. 결론본연구는 1종의고점도 bulk-fill 복합레진 (Tetric N- Ceram Bulk Fill; TBF) 과 2종의저점도 bulk-fill 복합레진 (Venus bulk fill; VB, SureFil SDR flow; SDR) 의상아질전단결합강도및미세누출을 conventional 복합레진 (Filtek Z350; FZ) 과비교평가하여다음과같은결과를얻었다. 평균전단결합강도값은 SDR (21.91 MPa), FZ (21.16 MPa), VB (15.80 MPa), TBF (11.11 MPa) 순으로관찰되었고, 대조군인 FZ군과비교하였을때저점도 bulk-fill 복합레진 (SDR, VB) 에서는통계적으로유의한차이가존재하지않았으며, 고점도 bulk-fill 복합레진 (TBF) 에서는유의하게낮은전단결합강도값을보였다 (p < 0.05). 미세누출과관련하여각군간의통계적으로유의한차이는존재하지않았으며, 모든군에서열순환처리를했을때열순환처리를하지않았을때보다유의하게높은미세누출이관찰되었다 (p < 0.05). References 1. Kubo S, Yokota H, Yokota H, Hayashi Y : The effect of light-curing modes on the microleakage of cervical resin composite restorations. J Dent, 32:247-254, 2004. 2. Karthick K, Sivakumar K, Geetha P, Shankar S : Polymerization Shrinkage of Composites - A Review. J Ind Acad Dent Spec, 2:32-36, 2011. 3. Winkler MM, Katona TR, Paydar NH : Finite element stress analysis of three filling techniques for class V light-cured composite restorations. J Dent Res, 75:1477-1483, 1996. 4. Versluis A, Douglas WH, Cross M, Sakaguchi RL : Does an incremental filling technique reduce polymerization shrinkage stresses? J Dent Res, 75:871-878, 1996. 5. Manhart J, Hickel R : Bulk-fill-composites. Modern application technique of direct composites for posterior teeth. Swiss Dent J, 124:19-37, 2014. 6. Czasch P, Ilie N : In vitro comparison of mechanical properties and degree of cure of bulk fill composites. Clin Oral Investig, 17:227-235, 2013. 7. Bucuta S, Ilie N : Light transmittance and micromechanical properties of bulk fill vs. conventional resin based composites. Clin Oral Investig, 18:1991-2000, 2014. 8. Moorthy A, Hogg CH, Fleming GJ, et al. : Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials. J Dent, 40:500-505, 2012. 9. Campos EA, Ardu S, Krejci I, et al. : Marginal adaptation of class II cavities restored with bulk-fill composites. J Dent, 42:575-581, 2014. 10. Alrahlah A, Silikas N, Watts DC : Post-cure depth of bulk fill dental resin-composites. Dent Mater, 30: 149-154, 2014. 288
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국문초록 Bulk-fill 복합레진의상아질전단결합강도및미세누출 이한별 서현우 이주현 박호원 강릉원주대학교치과대학소아치과학교실및구강과학연구소 본연구의목적은 bulk-fill 복합레진의상아질전단결합강도및미세누출을평가함에있다. 실험군으로 1종의고점도 bulk-fill 복합레진과 2종의저점도 bulk-fill 복합레진을사용하였고대조군으로 1종의 conventional 복합레진을사용하였다. 상아질접착제는 7세대를사용하였다. 영구치를 4군으로나눈후전단결합강도측정을위해레진블록을실험군은 4 mm, 대조군은 2 mm 두께로축조하였고, 미세누출을평가를위해실험군은 4 mm 단일층충전, 대조군은 2 mm씩 2회적층충전을시행하였다. 전단결합강도와관련하여대조군과비교하였을때저점도 bulk-fill 복합레진에서는통계적으로유의한차이가존재하지않았으나, 고점도 bulk-fill 복합레진에서는유의하게낮은값이관찰되었다 (p < 0.05). 미세누출과관련하여 4군사이에통계적으로유의한차이가존재하지않았다. 주요어 : Bulk-fill 복합레진, 전단결합강도, 미세누출, 7 세대상아질접착제 290