대한치과보철학회지 :Vol. 45, No. 2, 2007 타이타늄의표면개질에따른도재결합특성 전남대학교치의학전문대학원보철학교실 * 전남대학교신소재공학부및기능성표면공학연구소, ** 타이타늄 특수합금부품개발지원센터 최택휴 박상원 방몽숙 양홍서 박하옥 임현필오계정 김현승 이광

대한치과보철학회지 :Vol. 45, No. 2, 2007 타이타늄의표면개질에따른도재결합특성 전남대학교치의학전문대학원보철학교실 * 전남대학교신소재공학부및기능성표면공학연구소, ** 타이타늄 특수합금부품개발지원센터 최택휴 박상원 방몽숙 양홍서 박하옥 임현필오계정 김현승 이광민 * 이경구** Ⅰ. 서론타이타늄은우수한내식성과생체적합성 (Biocompatibility), 높은강도와귀금속합금에비해경제적이라는장점때문에임플랜트뿐만아니라, 최근에는단일관이나계속가공의치, 금속알러지가있는가철성국소의치환자에서도사용범위가확대되어귀금속의대체금속으로주목받고있다. 1-6) 현재사용되고있는대표적인타이타늄계합금은 CP Ti, Ti-6Al-4V 합금등을들수있다. 순수타이타늄은두개의동소체로구성되어있는데, 조밀육방정 (HCP : Hexagonal Close-Packed) 의 α상과체심입방정 (BCC : Body Centered Cubic) 의 β상으로상온에서 883 까지는 α상이안정하고, 883 이상의온도에서는 β상이안정하다. Ti-6Al-4V 합금은순수타이타늄에 α상안정화원소로써합금의강도는향상시키고무게를감소시키는알루미늄을약 6% 첨가하고, β상안정화원소로써부식저항능력을향상시키는바나듐을약 4% 첨가한 α+β상합금으로순수타이타늄에비해높은인장강도와파절강도를나타내는것으로알려져있다. 7) 그러나타이타늄은용융점이높고고온에서산소와의화학적반응성이크고, 883 이상의온도에서는두꺼운산화층의형성으로도재와의결합력을약 화시킨다. 1,8-10) 이는도재소성온도에서타이타늄의산화와타이타늄주조시표면에형성되는 α-case 층이주요요인이다. α-case 층은타이타늄주조시고온에서매몰재내의산소가타이타늄격자사이로확산되어타이타늄표면에형성되는산화층으로연성과피로저항성을감소시켜결국타이타늄-도재결합력을저하시킨다. 1-6,11-13) 이러한문제점을해결하기위해타이타늄전용주조기가개발되고, 아르곤이나헬름등불활성가스분위기하에서주조하거나, 저온소성이가능하고타이타늄의열팽창계수와비슷하거나약간낮은열팽창계수를갖는타이타늄전용도재가개발되었다. 14) 또한타이타늄주조시형성되는산화층에대한문제점을해결하기위한대안으로순수타이타늄괴 (Ingot) 를직접가공하는방법이 Andersson 15) 등에의해고안되었는데 Copy milling spark erosion technique 또는 Procera technique이라고불리고있다. 이방법은타이타늄주조시생성되는 α-case 층이없어타이타늄-도재결합이유리하다는장점이있으나, 4,16-18) 특수한장비와숙련된기술을필요로할뿐아니라단일관제작에한정되기때문에고정성국소의치나복잡한보철물제작에는어려움이있다. 10,19-20) 도재-금속보철물의내구성과안정성을위해서도재와금속의강한결합력이중요한변수로작용함에 This study was supported by second stage Brain Korea 21 project for school of dentistry. 169

따라, 타이타늄과전용도재의결합강도에대한많은관심이모아지고있다. 이와관련하여도재소성동안과다한타이타늄산화를억제하고, 타이타늄-도재의결합력을개선시키기위한방법으로타이타늄표면에다양한금속이나세라믹을코팅하는연구가진행되어왔다. Wang과 Weltch 21) 는타이타늄표면에 Si3N4 코팅을시행하였으며, Wang과 Fung 등 22) 은타이타늄표면에 Cr 코팅을실시하여타이타늄의낮은산화율을보고하였고, 또다른연구에서는 silver 코팅을시행하여타이타늄-도재결합이개선되었음을보여주었다. 23-24) Oshida 등 25) 은타이타늄위에 TiN 코팅을시행함으로써타이타늄표면의질화 (Nitridation) 가고온에서타이타늄산화를제한하여도재와의결합에효과적이었다고보고하였다. 최근에는 Y2O3- ZrO2을코팅한타이타늄도도재와의결합을향상시켰다고보고되었다. 26) 타이타늄위에 Au 코팅을시행한연구들도시행되었다. 3-6,27) De rand와 Herψ 는주조와가공타이타늄에대한도재와의결합에관한연구에서 Au 결합제가타이타늄-도재의결합에비효과적이었다고보고하였다. 4) 그러나 Lee 등 3) 의연구에서는 Au sputter 코팅을시행한경우타이타늄표면에가장많은도재가부착되었음을보고하였는데, 이결과에서 Au 코팅이타이타늄표면과화학적결합을하여타이타늄-도재와의결합에효과적임을밝혔다. 이에본연구는주조타이타늄과가공타이타늄을각각 Au, TiN 코팅과 Al2O3 sandblasting으로표면처리후도재를축성소성하여도재와타이타늄의결합형태를관찰하고, 2축굴곡실험후 SEM/EDS, XRD 방법으로코팅층에따른타이타늄-도재와의계면반응및결합양상을알아보고자한다. Ⅱ. 연구재료및방법 2.1 연구재료 2.1.1 금속시편제작 (1) 주조타이타늄주조타이타늄은 CP-Ti(Grade 2) (Kobe still Co., Japan) 를사용하여, 13 13 1mm의아크릴 판을가공후, MgO계매몰재 (Selevest CB, Selec) 로매몰하였다. 850 에서소환하고주조전 350 를유지한후원심타이타늄주조기 (Ticast Super R, Selec, Osaka, Japan) 로주조하였다. 시편은 bench cooling시키고 250μm Al2O3 particle (Korox, Bego, Bremen, Germany) 로 sandblasting하여매몰재를제거한후 deionized water와 acetone에서각각 5분간초음파세척후건조되었다 (N=8). (2) 가공타이타늄가공타이타늄은 CP-Ti(Grade 2)(Kobe still Co., Japan) 판를 13 13 1mm크기로초정밀와이어가공기 (AP450L, Sodick, Japan) 로가공하였다 (N=8). (3) Au-Pd-In Alloy Au-Pd-In alloy는비교군으로 13 13 1 mm의납형을제작한뒤인산염계매몰재 (Powercast ; Whipmix, Louisville, Ky) 로매몰하고 Au-Pd-In 합금 (Alphadent, Korea) 를 gas-oxygen torch로용융시킨후원심주조기로주조하였다. 시편은 bench cooling시키고 250μm Al2O3 입자 (Korox, Bego, Bremen, Germany) 로 sandblasting하여매몰재를제거한후 deionized water와 acetone에서각각 5분간초음파세척후건조하였다 (N=8). 2.1.2 표면처리금속시편의종류와표면처리방법에따라군을분류하였다 (Table I). Au 코팅군은 sputter coater (ParaOne, Gold Ion Sputter, Model PS-1200) 로 40mA, 1000s로코팅하였다 (Fig. 1). TiN 코팅군은 Table I. Experimental groups of specimens used in study Groups Descriptions 1 Cast-Titanium, Gold Coating 2 Cast-Titanium, TiN Coating 3 Cast-Titanium, Al2O3 Blasted 4 Wrought Titanium, Gold Coating 5 Wrought Titanium, TiN Coating 6 Wrought Titanium, Al2O3 Blasted 7 Au-Pd-In Alloy 170

13mm Ti Plate 13mm t = 1.0mm 6mm 1.0mm Porcelain Ti 1.1mm Fig. 1. Dimensions of metal-ceramic specimen. Fig. 2. Specimens after porcelain firing. Table II. Settings of the porcelain furnace used for fusing of the Ultra-Low-Fusing dental porcelain in the present study Porcelain Layer Porcelain Furnace Setting Paste bonder Heat from 400 to 800 at 60 /min in vacuum, hold at 800 in vaccum for 1 min Opaque porcelain Heat from 400 to 790 at 110 /min in vacuum, hold at 790 in vaccum for 1 min First-layer dentin porcelain Heat from 400 to 770 at 50 /min in vacuum, hold at 770 in vaccum for 1 min Second-layer dentin porcelain Heat from 400 to 770 at 50 /min in vacuum, hold at 770 in vaccum for 1 min Glaze Heat from 400 to 790 at 60 /min in vacuum, hold at 790 in vaccum for 1 min AIP(Arc Ion Plating, 아텍시스템, Korea) 방법으로 300 에서 N2 유량 300sccm를유입하고, 공정압력 7.5mtorr에서바이어스 -30V, 아크전류 65A 로약 2 시간동안증착하였다. 2.1.3 도재소성각시편에서도재가소성될표면은 dental air abrasion unit (Blastmate II, Ney, Bloomfield, CT) 에서 110μm Al2O3 particle(korox, Bego) 로 air abrasion되었다. Air abrasion을위한기압은 0.55 MPa (80psi) 에서유지되었고, 표면과 nozzle 사이의거리는약 1mm를유지한채 20초동안 sandblasting하였다. 타이타늄시편의경우초저용융도재 (Vita Titankeramik, Vident, Brea, CA) 를시편의중심에 6 mm직경의원형이되게 porcelain bonder를바르고한층의 opaue porcealin과두층의 dentin porcelain을타이타늄전용도재로 (TiKROM, OROTIG) 에서제조회사의추천사이클로소성하였다 (Table II). 두번째 dentin porcelain 소성후도재의높이를 1.1mm가되게 SiC abrasive paper로연마하였다. 초음파세척기로 5분간세척후건조시키고최종 glaze firing을시행하였다 (Fig. 1). Au-Pd-In 합금시편에서는일반도재 (Creation, KLEMA) 를이용하여타이타늄시편에서와동일하게표본의중심에 6mm직경의원형으로 1.1mm높이가 171

되게통상적인도재로 (HIGH BAKE II, JAE MYONG) 에서제작하였다 (Fig. 2). 2.2 연구방법 2.2.1 2축굴곡실험 (Biaxial Flexure Test) 2축굴곡실험을위해만능시험기 (UH-100A 자, Shimazu, Japan) 에자체제작한 die와 plunger(fig. 3) 을사용하여모재에서도재가탈락될때까지 0.25 mm /min의 cross head speed로하중을가하였다. Plunger Specimen 2.2.2 SEM/EDS 분석도재소성후시편의단면과 2축굴곡시험후탈락한도재표면형상은주사전자현미경 (SEM, Scanning Electron Microscope, JSM 5400, JEOL, JAPAN) 으로관찰하였고, EDS(Energy Dispersive X-ray Spectroscopy, Noran, USA) 로시편표면에존재하는 Si 함량을도재부착의지표로이용하였고, Si 성분의분포를관찰하였다. SEM operating 조건은 20kV accelerating voltage, 38mm working distance, 64μA beam current, 41.3 take-off angle, 100s live time으로, Si 성분의원자량은시편의중심원내의 3.7 mm 2.7 mm사각형내에서시행되었다 ( 50). 시편표면에존재하는각성분원소의분포를관찰하기위한 EDS Mapping은시편의중앙부를분석하였다 ( 300). Ⅲ. 연구성적 Die 3.1 SEM photomicrographs Fig. 3. Schematic diagram of a special die and plunger. Fig. 4는타이타늄의코팅전과후그리고 Au- Pd-In 합금의 SEM사진으로타이타늄시편에서각코팅은주조타이타늄과가공타이타늄에서유사한코팅양상을보였다. (a) (b) (c) (d) (e) (f) (g) Fig. 4. SEM photomicrographs of surface treated specimens( 500). (a) cast titanium, (b) gold coated cast titanium, (c) TiN coated cast titanium, (d) wrought titanium, (e) gold coated wrought titanium, (f) TiN coated wrought titanium, (g) Au-Pd-In alloy. 172

(a) (b) (c) (d) (e) (f) (g) Fig. 5. The cross sectional SEM photomicrographs of titanium specimens after porcelain firing( 5000). (a) cast titanium, (b) gold coated cast titanium, (c) TiN coated cast titanium, (d) wrought titanium, (e) gold coated wrought titanium, (f) TiN coated wrought titanium, (g) Au-Pd-In alloy. (a) (b) (c) (d) (e) (f) (g) Fig. 6. SEM photomicrographs specimens after porcelain debonding( 30). (a) cast titanium, (b) gold coated cast titanium, (c) TiN coated cast titanium, (d) wrought titanium, (e) gold coated wrought titanium, (f) TiN coated wrought titanium, (g) Au-Pd-In alloy. Fig. 5는표면처리후주조타이타늄, 가공타이타늄및 Au-Pd-In alloy에저온도재소성후각층의단면을관찰한사진이다. 코팅에따른주조타이타늄과가공타이타늄의차이는나타나지않고유사한양상을보이고있다. Fig. 6은 2축굴곡실험후시편의표면양상을관찰한사진이다 ( 30). 시료의표면에도재축성시사용되는 dentin porcelain, bonding porcelain 및 opaque porcelain으로보이는물질이존재하는것을알수있다. 173

Table III. EDS Analyses results (at.%) on titanium surfaces before & after the porcelain debonding Surface Treatment Ti Au Al K Si Gold Coated 15.47 2.27 4.10 3.07 30.39(2.71) Debonded 32.90 3.22 4.58 3.36 19.98(3.50) Casting TiN Coated 21.85 0 3.30 2.52 27.42(1.60) Ti Debonded 37.68 0 2.63 2.77 18.43(1.30) Al2O3 Blasted 19.12 0 4.83 2.60 28.56(2.37) Debonded 69.17 0 3.60 1.15 8.33(1.31) Gold Coated 11.98 1.83 4.15 3.30 32.30(1.95) Debonded 31.74 3.94 4.64 3.19 20.59(3.12) Wrought TiN Coated 19.43 0 3.51 2.72 29.34(2.34) Ti Debonded 37.28 0 2.90 2.82 18.82(1.36) Al2O3 Coated 18.89 0 4.92 2.66 28.89(2.39) Debonded 45.65 0 4.56 2.26 16.62(2.15) Au-Pd-In Alloy 2.04 4.08 7.53 9.85 24.54(0.35) Debonded 2.02 33.81 6.96 10.05 19.14(1.54) Entries are mean values. Standard deviations are in parentheses. Data were based on analysis of eight specimens. (a) (b) (c) (d) (e) (f) (g) Fig. 7. EDS mapping photomicrographs specimens after porcelain debonding ( 300). (a) cast titanium, (b) gold coated cast titanium, (c) TiN coated cast titanium, (d) wrought titanium, (e) gold coated wrought titanium, (f) TiN coated wrought titanium, (g) Au-Pd-In alloy. 3.2 EDS 분석 Table III은 2축굴곡시험후도재가탈락된시편을 50배확대하여중심원내 (3.7mm 2.7mm ) 에존재하 는 Si 성분의원자량을비교한표이다. Au와 TiN 코팅한실험군과 Au-Pd-In alloy 비교군에서는 Si 원자량이비슷한값을보이고있으나, 주조타이타늄에 Al2O3 sandblasting만을시행한실험군에서가장 174

Intensity 낮은수치를보여주고있다. Fig. 7은도재탈락후시편표면에존재하는 Si 성분은 EDS mapping한사진으로주조타이타늄과가공타이타늄에 Au와 TiN 표면처리한실험군에서많은양의 Si 성분이다소균일한분포를나타내고있었으며, Al2O3 sandblasting한실험군에서는적은양의 Si 성분이불규칙한분포를나타내고있다. 3.3 XRD 분석 2theta C-Ti-Au ; Cast-Titanium, Gold Coating C-Ti-TiN ; Cast-Titanium, TiN Coating C-Ti ; Cast-Titanium, Al2O3 Blasted W-Ti-Au ; Wrought Titanium, Gold Coating W-Ti-TiN ; Wrought Titanium, TiN Coating W-Ti ; Wrought Titanium, Al2O3 Blasted Fig. 8. Fig. 8은 2축굴곡시험후도재가탈락된주조타이타늄과가공타이타늄의표면을 X-ray 회절분석한결과이다. Au와 TiN 코팅된실험군에서각각 Au2Ti 화합물과 TiN 코팅층이존재하였으며, 모든실험군에서타이타늄의대표적인산화물인 TiO2가형성되었음을알수있다. Ⅳ. 고찰 도재가갖는낮은전단및인장강도와충격에대한취약성을보완하기위해도재전장금속관이사용되고있다. 도재와금속과의결합증진을위한노력으로화학적결합방법이나기계적결합방법등을이용한여러가지연구들이시행되어왔다. 28-30) 기계적결합이효과적이긴하지만범위가제한되며, 대부분의문헌들은화학적결합을금속-도재간의결합 에서가장주요한요소로보고하였으며, 25) 화학적결합은금속표면에형성된산화물이도재내로확산되어도재내산화물과공유결합이나이온결합을함으로써이루어진다하였다. 10,31) 또한도재와금속간의결합에있어 Lautenschlager 등 30) 은다양한도재전장금관의계면연구에서전자현미경을통해철, 주석, 인듐등의미량원소를발견하였는데, 이들미량원소들이산소와결합하거나상호반응하여도재와금속사이에결합을형성한다고보고하였다. 도재용금속계면의산화막이너무두꺼울경우얇은산화막에비해접착실패의가능성이더클것으로알려져있으며, 32) 비귀금속은주성분들이쉽게산화되어과도한산화막이형성될수있으므로산화막두께조절은결합강도를확보하는데중요한요인이라할수있다. 33) 타이타늄은 883 이상의온도에서산소, 질소등과반응하여비교적두껍고쉽게분리되는타이타늄산화막을형성하기때문에 Kimura 등 34) 은도재용합금에서일반적으로시행하는 degassing 처리가타이타늄-도재수복물에는적합하지않을뿐아니라, 타이타늄표면의산화막형성을최소로하기위하여 800 이하에서도재소성을시행해야한다고보고하였다. 타이타늄과도재의결합은일반적인니켈-크롬합금과도재와의결합강도보다낮다고알려져있다. Adachi 등 35) 은타이타늄과도재간의낮은결합강도는타이타늄에대한산화막의부착이불안정하기때문이며, 이러한불안정한산화막은도재소성중에생성되고결합강도를저하시킨다고하였으며, 온도에따른순수타이타늄의부착성산화막형성능력을분석해본결과 1,000 에서는약 1 μm의두꺼운산화막을형성하여부착성산화막이전체표면의 1% 미만에서형성되었고, 750 에서는약 32nm의얇은산화층으로가장많은부착성산화막이형성되었다고하였다. Hautaniemi 등 36) 은소성주기와온도, 진공등의상태로생성된산화층의두께와결합강도에있어진공소성을시행하여 0.1 0.2μm의산화층을얻은실험군이가장강한결합강도를얻었다고하였으며, 진공상태가아니거나소성시간이길어질수록더낮은결합강도를나타내었다고하였다. 따라서도재와타이타늄의보철물의내구성과안정성을위해서타이타늄표면의산화막형성을조절하는것이결합강도를증가시킬수있는 175

중요한요인으로간주된다. 이와관련해 Atsü 등 37) 은타이타늄-도재간의결합을증진시키기위해서는주조타이타늄에서도재소성시환원성 Ar 대기 (Reduced Argon Atmosphere) 하에서소성해야한다고주장하였고, Abdulaziz 등 2) 도 Au 스퍼터코팅을시행한타이타늄이환원성 Ar 대기하에서도재가소성되었을때가장높은타이타늄-도재결합강도를보였다고보고하였다. Wang 등 21) 은타이타늄표면에실리콘질화코팅시도재와의결합력이증진되었다는연구결과에서, 타이타늄표면에 Si3N4 coating을하여파절실험후양상은 Si3N4 코팅층과도재사이보다는도재내의파절이발생한것으로도재와 Si3N4 코팅사이의결합력이향상되었음을보여주었는데, 이는 Si3N4 층이타이타늄과의계면에서 titanium silicide를형성하기때문이라고보고하였다. 도재소성동안타이타늄산화를조절하기위해타이타늄표면에질화코팅을하였을경우, 질화하지않은타이타늄보다약 5배더낮은산화속도를보여, 동일한산화정도에서비질화된타이타늄보다약 2.24배더긴산화시간을필요로했다고보고하였다. 25) Cai 등 26) 은 TiN 코팅층이금속표면의산화를억제함으로써마모저항이강한표면과낮은마찰계수와화학적안정성을제공해준다고보고하였다. 타이타늄표면의산화층은산소가고온에서타이타늄용매에쉽게용해되는일종의용질원소로작용한다고알려져왔으며, 아주소량의산소가용해되었다할지라도타이타늄의성질을급격히변화시켜파절을일으킬수있다. 열역학적으로 Ellin-Ghams/ Richardson Diagram에기초한 Ti/Oxygen의평형은 400 800 사이에서 10-110 10-90 atmospheres의산소분압을요한다. 따라서기존의치과도재로를사용하여그러한낮은압력에서과다한산화를막는것은거의불가능하므로타이타늄전용도재와도재로를사용해야한다. 3,38) 본연구에서도주조타이타늄에서 Au 코팅한실험군, TiN 코팅한실험군과가공타이타늄에서 Au 코팅한실험군, TiN 코팅한실험군이 Al2O3 sandblasting한주조타이타늄보다 Si 함량 (at.%) 이높게나타났으며, 표면에존재하는 Si 분포에서차이를나타내었다. 이는타이타늄표면의코팅처리가타 이타늄의산화를제한하여도재와의결합력을증진시킬수있다는가능성을보여주었다. 또한타이타늄표면코팅처리가기계적처리보다도재와결합력을증진시킴을보여준다. Al2O3 sandblasting한주조타이타늄에서의낮은 Si 함량과다소불규칙한분포는표면에형성된산화층이도재와의결합을방해하는것으로보인다. Al2O3 sandblasting 처리방법과기술에따라금속과도재의결합력이코팅군과동일할수있다는보고도있으나 39), 이에대한연구가더필요하리라생각된다. 치과용도재는용융온도에따라고용융도재 (1,201 1,450 ), 중용융도재 (1,051 1,200 ), 저용융도재 (870 1,050 ), 초저용융도재 (870 이하 ) 의 4가지로분류할수있다. 일반금속과도재용으로는저용융도재로백류석 (Leucite) 를첨가하여열팽창계수를높이고강도를증가시켰다. 타이타늄과타이타늄합금에사용되는초저용융도재는열팽창계수가낮고용융온도가낮아제 III, IV형금합금과도사용될수있다 40). 본연구에서 Au-Pd-In 합금에사용된도재는타이타늄에사용되는초저용융도재로도재탈락후표면에존재하는 Si 함량의차이는존재한다. X-ray 회절분석에서주조타이타늄과가공타이타늄에 Au 코팅시형성되는금속간화합물 Au2Ti는 Au 코팅된타이타늄표면에서생성된것에서기인한것으로, 타이타늄표면위의 Ti(O) 고용체의형태와산화를변경시킴으로써도재와타이타늄산화층에영향을주어도재와의결합을용이하게하는것으로보고하였다. 3) 이러한금속-도재간의결합강도를개선하고자하는연구는계속진행되고있으나진정한결합강도를측정할만한일반적인방법은없다. 41) 따라서도재의주성분인 Si을 2축굴곡실험후남아있는함량을정량화하여금속-도재와의결합을평가하는대안으로개발되었고연구가진행되었다. 3,39) 본연구에서주조타이타늄과가공타이타늄에표면처리후도재를축성하고소성하였을때각층의결합양상은표면처리방법에따라유사하게나타났으나, 파절후 Si 함량과분포에서는차이를나타내었다. 주조타이타늄과가공타이타늄에서산화층조절을위해코팅처리한경우에 Au 코팅은도재소 176

성시타이타늄의산화층과새로운화합물인 Au2Ti 를형성하는화학반응을일으켜도재와의결합력을증진시키고, TiN 코팅은도재소성시산소확산의방어막으로작용하여도재와의결합력을증진시킬것으로판단되지만, 2축굴곡실험후주조타이타늄과가공타이타늄표면의도재탈락현상은주로코팅층과모재의결합력저하로인한것으로부착실패 (adhesive failure) 와응집실패 (cohesive failure) 가동시에존재하는것을알수있었다따라서도재전장금관제작시타이타늄주조체에 Au나 TiN 표면코팅한경우도재와의결합력을향상시킬수있는가능성을보여주었다. 임상에서도재전장금관제작시타이타늄을이용하기위해서, 선행되어야할과제는모재와코팅층간의결합력을더욱향상시킬수있는코팅기술개발이선행되어야할것으로사료된다. Ⅴ. 결론주조및가공타이타늄표면처리에따른결합양상을평가하여다음과같은결론을얻을수있었다. 1. 주조타이타늄과가공타이타늄에표면처리 (Au, TiN, Al2O3 sandblasting) 후표면양상은유사하게나타났으며, 저온소성도재의축성후도재와타이타늄단면관찰에서주조타이타늄과가공타이타늄각군에서동일한결합형상을나타내고있었다. 2. 2축굴곡실험전후 Si 성분의원자량에대한변화는 Al2O3 sandblasting한주조타이타늄에서가장큰차이를나타났으며 (28.6at.% 8.3at.%), Au-Pd-In 합금에서변화량이가장작게나타났다 (24.5at.% 19.1at.%). 3. 도재탈락후주조타이타늄과가공타이타늄에 Au와 TiN 표면처리한실험군에서많은양의 Si 성분이다소균일한분포를나타내고있었으며, Al2O3 sandblasting한실험군에서는적은양의 Si 성분이불규칙한분포를나타내었다. 4. 도재탈락후 X-ray 회절분석에서 Au 와 TiN 코팅된실험군에서각각 Au2Ti 화합물과 TiN 코팅층이존재하였으며, 모든실험군에서타이타늄의대표적인산화물인 TiO2가형성되었음을알수 있었다. 5. 2축굴곡실험후주조타이타늄과가공타이타늄표면의도재탈락현상은주로코팅층과모재의결합력저하로인한것으로판단되며, 부착실패 (adhesive failure) 와응집실패 (cohesive failure) 가동시에존재하는것을알수있었다. 참고문헌 1. Cai Z, Bunce N, Nunn ME, Okabe T. Porcelain adherence to dental cast CP titanium: effects of surface modifications. Biomaterials 2001;22:979-986. 2. Abdulaziz Sadeq, Zhuo Cai, Ronald D. Woody, Amp W. Miller. Effects of interfacial variables on ceramic adherence to cast and machined commercially pure titanium. J Prosthet Dent 2003;90:10-17. 3. Lee KM, Cai Z, Griggs JA, Guiatas L, Lee DJ, Okabe T. SEM/EDS Evaluation of Porcelain Adherence to Gold-Coated Cast Titanium. J Biomed Mater Res Part B: Appl Biomater 2004;68B:165-173. 4. De rand T, Herψ H. Bond strength of porcelain on cast vs. wrought titanium. Scand J Dent Res 1992;100:184-188. 5. Saadet A, Semih B. Bond strength of three porcelains to two forms of titanium using two firing atmospheres. J Prosthet Dent 2000;84;567-574. 6. Russell R. Wang, Gerhard E. Welsch, Othon Monteriro. Silicon nitride coating on titanium to enable titanium-ceramic bonding. J Biomed Mater Res 1999;46: 262-270. 7. Taira M, Moser JB, Greener EH. Face coats for dental casting of titanium alloys. J Dent Res 1985;64:317. 8. Bagby M, Marshall SJ, Marshall GW. Metal ceramic compatibility: A review of the literature. J Prosthet Dent 1990;63:21-25. 177

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ABSTRACT THE BOND CHARACTERISTICS OF PORCELAIN FUSED BY TITANIUM SURFACE MODIFICATION Taek-Huw Choi, D.D.S,. Ph.D., Sang-Won Park, D.D.S, Ph.D., Mong-Sook Vang, D.D.S., Ph.D., Hong-So Yang, D.D.S., Ph.D., Ha-Ok Park, D.D.S., Ph.D., Hyun-Pil Lim, D.D.S., M.S.D., Gye-Jeong Oh, B.S., Hyun-Seung Kim, M.S., Kwang-Min Lee, Ph.D*, Kyung-Ku Lee, Ph.D.** Department of Prosthodontics, College of Dentistry, Chonnam National University *Division of Materials Science and Engineering, Research Institute for Functional Surface, Chonnam National University ** R&D Center for Titanium and Special Alloys Statement of problem: Titanium is well known as a proper metal for the dental restorations, because it has an excellent biocompatibility, resistance to corrosion, and mechanical property. However, adhesion between titanium and dental porcelains is related to the diffusion of oxygen to the reaction layers formed on cast-titanium surfaces during porcelain firing and those oxidized layers make the adhesion difficult to be formed. Many studies using mechanical, chemical and physical methods to enhance the titanium-ceramic adhesion have been actively performed. Purpose: This study meant to comparatively analyse the adhesion characteristics depending on different titanium surface coatings after coating the casts and wrought titanium surfaces with Au and TiN. Material and method: In this study, the titanium specimens (CP-Ti, Grade 2, Kobe still Co. Japan) were categorized into cast and wrought titanium. The wrought titanium was cast by using the MgO-based investment(selevest CB, Selec). The cast and wrought titanium were treated with Au coating(paraone, Gold Ion Sputter, Model PS-1200) and TiN coating(atec system, Korea) and the ultra low fusing dental porcelain was fused and fired onto the samples. Biaxial flection test was done on the fired samples and the porcelain was separated. The adhesion characteristics of porcelain and titanium after firing and the specimen surfaces before and after the porcelain fracture test were observed with SEM. The atomic percent of Si on all sample surfaces was comparatively analysed by EDS. In addition, the constituents of specimen surface layers after the porcelain fracture and the formed compound were evaluated by X-ray diffraction diagnosis. 180

Result: The results of this study were obtained as follows : 1. The surface characteristics of cast and wrought titanium after surface treatment(au, TiN, Al2O3 sandblasting) were similar and each cast and wrought titanium showed similar bonding characteristics. 2. Before and after the biaxial flection test, the highest atomic weight change of Si component was found in Al2O3 sandblasted wrought titanium(28.6at.% 8.3at.%). On the other hand, the least change was seen in Au-Pd-In alloy(24.5at.% 19.1at.%). 3. Much amount of Si components was uniformly distributed in Au and TiN coated titanium, but less amount of Si s was unevenly dispersed on Al2O3 sandblasting surfaces. 4. In X-ray diffraction diagnosis after porcelain debonding, we could see Au2Ti compound and TiN coating layers on Au and TiN coated surfaces and TiO2, typical oxide of titanium, on all titanium surfaces. 5. Debonding of porcelain on cast and wrought titanium surface after the biaxial flection is considered as a result of adhesion deterioration between coating layers and titanium surfaces. We found that there are both adhesive failure and cohesive failure at the same time. Conclusion: These results showed that the titanium-ceramic adhesion could be improved by coating cast and wrought titanium surfaces with Au and TiN when making porcelain fused to metal crowns. In order to use porcelain fused to titanium clinically, it is considered that coating technique to enhance the bonding strength between coating kklayers and titanium surfaces should be developed first. Key words : Titanium, Surface treatment(au, TiN, Al2O3 sandblasting), Adhesion 181