도재라미네이트와복합레진수복시치간이개양에따른접착계면의응력분포에관한 3차원유한요소법적연구 홍준배 1 탁승민 2 백승호 1 조병훈 1 * 1 서울대학교치의학대학원치과보존학교실, 2 경상대학교공과대학기계항공학과 ABSTRACT THE EFFECT OF THE AMOUNT OF INTERDENTAL SPACING ON THE STRESS DISTRIBUTION IN MAXILLARY CENTRAL INCISORS RESTORED WITH PORCELAIN LAMINATE VENEER AND COMPOSITE RESIN: A 3D-FINITE ELEMENT ANALYSIS Junbae Hong 1, Seung-Min Tak 2, Seung-Ho Baek 1, Byeong-Hoon Cho 1 * 1 Department of Conservative Dentistry, School of Dentistry, Seoul National University, Seoul, Korea, 2 Mechanical Aerospace Engineering, Gyeongsang National University, Jinju, Korea This study evaluated the influence of the type of restoration and the amount of interdental spacing on the stress distribution in maxillary central incisors restored by means of porcelain laminate veneers and direct composite resin restorations. Three-dimensional finite element models were fabricated to represent different types of restorations. Four clinical situations were considered. Type I, closing diastema using composite resin. Labial border of composite resin was extended just enough to cover the interdental space; Type II, closing diastema using composite resin without reduction of labial surface. Labial border of composite resin was extended distally to cover the half of the total labial surface; Type III, closing diastema using composite resin with reduction of labial surface. Labial border of the preparation and restored composite resin was extended distally twothirds of the total labial surface; Type IV, closing diastema using porcelain laminate veneer with a feathered-edge preparation technique. Four different interdental spaces (1.0, 2.0, 3.0, 4.0 mm) were applied for each type of restorations. For all types of restoration, adding the width of free extension of the porcelain laminate veneer and composite resin increased the stress occurred at the bonding layer. The maximum stress values observed at the bonding layer of Type IV were higher than that of Type I, II and III. However, the increasing rate of maximum stress value of Type IV was lower than that of Type I, II and III. [J Kor Acad Cons Dent 35(1):30-39, 2010] Key words: Three dimensional-finite element analysis, Interdental space, Porcelain laminate veneer, Composite resin, Bonding layer, Stress distribution -Received 2009.12.30., revised 2010.1.4., accepted 2010.1.4.- Ⅰ. 서론 *Corresponding Author: Byeong-Hoon Cho Department of Conservative Dentistry, School of Dentistry, Seoul National University 275-1 Yeongeon-Dong, Jongno-Gu, Seoul, 110-768, Korea Tel: 82-2-2072-3514 Fax: 82-2-2072-3859 E-mail: chobh@snu.ac.kr 전치부치간이개 ( 혹은치간공극 ) 는많은환자에게심미적인문제를일으킬수있다. 치간이개는어떠한연령대에서도발생할수있으며, 다양한원인과치료법이알려져있다. 치간이개의원인, 정도및치아의배열상태에따라그치료방법이달라지겠지만, 복합레진 (composite resin) 1,2) 을이 30
도재라미네이트와복합레진수복시치간이개양에따른접착계면의응력분포에관한 3 차원유한요소법적연구 용한직접수복, 도재라미네이트 (porcelain laminate veneer), 3,4) 도재전장관 (all-ceramic crown) 혹은금속도재전장관 (porcelain-fused to metal crown) 5) 을이용한간접수복, 그리고교정치료 (orthodontic treatment) 6) 를통한치열의재배열등을통해해결이가능하다. 치간이개의치료목적은치아사이공간을폐쇄함으로써심미회복과더불어발음교정및조화롭지못한치아의형태로인해야기된환자의정신적장애를해소하는데있지만, 그목적을달성하기위해서는구강내에서기능력 (functional loading) 을받을때탈락되지않고유지될수있어야한다. 구강내에서의기능시발생하는응력으로인해취약한부분은파절이일어나고, 그로인해수복물의실패가발생한다. 일반적으로도재라미네이트수복물의성공률은 53-91% 7-11) 로다양하게보고되고있다. 치의학영역에서주로사용되었던구조물의계면및내부의응력분포양상을알아볼수있는방법에는광탄성응력분석법 (photoelastic stress analysis), 12,13) 변형게이지측정법 (strain gauge measurement), 14,15) three-dimensional deformation analysis, 16) 유한요소분석법 (finite element analysis) 등여러가지가있지만, 컴퓨터발달에힘입어내부응력의분포양상을분석하기편리하고하중에취약한부위를결정하는데있어서다른방법에비해장점을지니고있어 15,17,18) 유한요소분석법을이용한연구가많아지고있다. 유한요소분석법은전체구조 (structure) 를모델링 (modeling) 과격자형성 (meshing) 을통해개개의요소 (element) 로나눈다음, 일련의컴퓨터연산과정을통해각요소와전체구조의응력 (stress) 과변형 (strain) 을계산해내는방법으로, 일종의컴퓨터시뮬레이션 (simulation) 기법이라할수있다. 이러한구조분석은압력과열변화등을비롯한외부자극에의한변화, 자기장분포영역, 유체유동등기타다른여러방법으로접근할수없는연속적인영역의문제들을관찰할수있게하며, in vivo 혹은 in vitro 측정이불가능한생체재료 (biomaterial) 나인체조직 (human tissue) 의기계적특성을이해하는데이용될수있다. 19) 치의학에서는치아 20-22) 및악골 23,24) 그리고치과재료 25-27) 의응력분포분석에널리이용되고있으며, 1990년대이후로유한요소법을이용한연구경향은점점늘어나고있는추세이다. 유한요소법을구강내전치부에적용한여러연구의경우, 수복된치아및수복물의계면에서발생하는응력분포 (stress distribution) 를분석한사례가많았으며, 주로도재라미네이트의내부및접착계면에서의응력분포가치아삭제형태 (tooth preparation design), 28-31) 변연디자인 (margin design), 32) 하중의방향 (load angle) 33) 그리고사용된재료 34) 에따라어떻게바뀌는지에관해서연구가이루어졌다. 전치부치간이개부위를복합레진혹은세라믹으로수복 할경우에는, 치아의인접면에서부터수복물의최종인접면까지추가된연장부위 (free extension) 가필연적으로생길수밖에없는데, 복합레진및세라믹의취약한인장강도와치질과의접착계면으로인해이부위에서의수복물의파절또는접착계면에서의탈락을쉽게일으킬수있다. 35) 접착계면에서의응력분석을위해 Zarone 등, 29) Seymour 등, 30) Troedson 등 31) 이유한요소분석법을이용하여도재라미네이트의변연디자인및치아삭제형태에따른도재라미네이트하방의접착계면에서발생하는응력분포에관해연구한바있으며, 2009 년에 Chander 등 33) 은전치부치간이개를도재라미네이트로수복한경우에연장부위가커지거나, 하중의크기및적용각도가커지면응력이증가함을유한요소법을통해관찰한바있다. 임상적인상황에서, 부적절한치아의배열상태및변색등의다른문제가없는경우전치부치간이개부위는대개치간이개양에따라치료방법이결정되는경향이있다. 간격이좁은경우에는치질의보존, 인접치아와의자연스러운색조화및모양형성의용이성 36,37) 으로인해일반적으로복합레진으로수복하는경우가많으며, 간격이넓어질경우에는시술시간이길어지고, 구강내에서의직접수복으로조화로운모양을형성하기다소어려운측면뿐아니라, 탈락을방지하기위한유지력을얻고보다넓은접착면적을확보하기위해서도재라미네이트혹은도재전장관등의간접수복을시행하는경향이있다. 특히, 도재라미네이트의경우에는치질의삭제량이적으며, 색조안정성이뛰어나고, 표면처리후치질과의접착성이뛰어나기때문에 38) 1980 년대초반에소개된이후 39) 전치부간접수복에많이쓰이고있다. 그러나이러한수복기준또한치간이개양에따른수복방법의용이성에의한분류이며, 현재까지치간이개양에따른응력의차이에근거한수복재료의선택이나, 와동의형태를포함한수복방법의기준에관한연구는부족하다. 이에, 본연구에서는복합레진및도재라미네이트로전치부치간이개를수복할때, 치간이개의간격과수복방법이수복물의접착계면에서의응력분포에미치는영향을비교하고, 치간이개의양에따른수복방법의기준을제시하고자삼차원유한요소분석법 (3D-FEM three dimensionalfinite element analysis) 을이용하여이를평가하였다. Ⅱ. 연구재료및방법 1. 구조및기하학적형상의정의 (Definition of structure and geometric conditions) 균열이나치아우식이없는사람의발치된상악중절치를 micro CT (SkyScan 1072, SkyScan N.V., Belgium) 를 31
이용하여스캔한다음, 획득된디지털영상을 3D image software (V-works 4.0, Cybermed Inc., Korea) 를이용하여 3 차원으로재구성하였다. 서로다른형태의수복상황을재현하기위해 HyperView Player v9.0 (Hyperwork, Altair, Korea) 을이용하여추가적인형태를부여하여복합레진혹은도재라미네이트로수복된모습의 solid model 을형성하였다 (Figure 1). 모든수복물의치경부쪽경계는백악법랑경계 (cementoenamel junction) 상방 1 mm 까지설정하였으며, 치아의순면삭제가필요한경우는 0.5 mm 로균일한삭제가이루어지게하였다. 레진시멘트와 bonding layer 의두께는각각 100 μm, 30) 20 μm 를부여하였다. 수복형태는다음과같이크게네가지범주를고려하였으며, 유한요소모델의대칭성으로인해편측수복형태만을재연하는것으로가정하였다 (Table 1). Type I. 인접면을최소한으로수복하는경우 : 순면은치간이개를폐쇄할수있을정도로만최소한으로피개하며, 구개면은설측융기 (lingual ridge) 직전까지연장하였다. Type II. 순면의절반까지수복하는경우 : 순면은치간이 개를폐쇄하고원심측으로더연장하여전체순면면적의절반까지피개하며, 구개면은설측융기직전까지연장하였다. Type III. 치아삭제후순면의 2/3 까지수복하는경우 : 복합레진으로피개될최종형태에해당하는순면을근심으로부터원심쪽으로 2/3 까지 0.5 mm 삭제한다음, 치간이개부위를포함하여순면의 2/3 까지피개하였다. 구개면은설측융기직전까지연장하였다. Type IV. 도재라미네이트로수복하는경우 : featherededge preparation technique 으로 0.5 mm 가량순면을삭제하여지대치형성후, 도재라미네이트로치간이개부위를포함하여삭제된순면을피개하였다. 2. 격자형성및사용된재료의물성 (Mesh generation and material properties) 형성된모든 solid model 은 HyperView Player v9.0 을통해격자형성 (mesh generation) 과정을거쳐최종유한 a b c d Figure 1. Finite element models of each type of restorations. a. Type I, b. Type II, c. Type III, d. Type IV. Table 1. Three-dimensional finite element models simulating composite resin and porcelain laminate veneer restorations, with or without tooth preparation, for restoring the interdental spaces ranging from 1 mm to 4 mm Composite Resin* Amount of Up to labial 2/3 with Interdental Space Minimal Up to labial 1/2 tooth reduction Porcelain Laminate* 1 mm Type I-1 Type II-1 Type III-1 Type IV-1 2 mm Type I-2 Type II-2 Type III-2 Type IV-2 3 mm Type I-3 Type II-3 Type III-3 Type IV-3 4 mm Type I-4 Type II-4 Type III-4 Type IV-4 *The tooh model was reduced by 0.5 mm up to 2/3 of labial surface for type III model and up to distal surface for type IV model. Each finite element model was designed as restoring half the space of the amount of interdental space (0.5, 1.0, 1.5, 2.0 mm) because opposite tooth model was under symmetrical condition. 32
도재라미네이트와복합레진수복시치간이개양에따른접착계면의응력분포에관한 3 차원유한요소법적연구 Table 2. Mechanical properties of materials used Materials Elastic modulus Poisson s (GPa) Ratio Enamel 84.1 43) 0.30 44) Dentin 18.6 45) 0.32 46) Pulp 0.002 52) 0.45 52) Periodontal ligament 0.05 49) 0.45 49) Composite Resin (Z100) 20 47) 0.24 44) Bonding layer (adhesive) 2.1 44) 0.30 44) Resin-based Cement (Variolink II) 8.3 48) 0.35 48) Porcelain (IPS Empress) 65 50) 0.19 50) Cortical bone 13.7 51) 0.30 51) Trabecular bone 1.37 51) 0.30 51) Figure 2. Load angulation. 50 N of load was applied at 125 angles (tearing force) with the tooth s longitudinal axis at the palatal surface of the crown. 요소모델로변환되었다. 각유한요소모델은사면체요소 (tetrahedral solid element) 로구성되었다. 이용된모든재료는균질하며 (homogeneous), 선형탄성거동을보이고 (linearly elastic), 등방성의 (isotropic) 성질을가지며, 재료들간의결합은완전결합 (complete bonding) 을하는것으로가정하였다. 29) 각재료들의기계적성질은 Table 2 와같다. 3. 경계조건, 하중조건및데이터처리 (Boundary conditions, loading, and data processing) Overbite 와 Overjet 의평균값 40) 및전치부의생리적교합력을고려하여 50 N 28) 의힘을 Figure 2 와같이적용하였다. 찢김력 (tearing force) 을재연하기위해상악치아의장축에 125 에해당하는방향으로힘을가하였다. 29) 치근은치주인대, lamina dura, 피질골, 해면골로구성된악골에고정시켜생리적동요도를허용하였다. 데이터의후처리 (postprocessing) 는 ABAQUS 6.9 (ABAQUS Inc., Providence, RI) 를통해시행하였으며, 결과는접착계면에서의응력분포패턴으로표시하였다. 응력값으로 von Mises stress 를이용하여응력분포를분석하였으며, 결과는 numerical value 혹은 color coding 으로나타내었다. Ⅲ. 결과 Table 3. Maximum von Mises stress within each model with varying interdental spaces (Unit: MPa) Amount of Interdental Type I Type II Type III Type IV sapce 1 mm 2.95 2.55 2.79 4.31 2 mm 3.50 3.80 3.08 5.17 3 mm 4.15 5.08 5.14 5.93 4 mm 5.69 6.80 6.55 6.98 The maximum values were obtained at the cervical area near the line angle between the labial surface and mesial surface. 치간이개의크기및수복형태에따른접착계면에서의응력분포는 Figure 3 에나타낸바와같다. von Mises stress 에따른전체적인응력분포양상 (pattern of stress distribution) 은모든수복형태 (type of restoration) 에대해유사한분포를보였다. 적용된힘의방향과동일한방향으로접착계면을따라분산되어낮은값으로응력이전달된후치경부에서다시집중되어높게나타났다. 각각의수복형태및치간이개간격에대해치경부에서관찰되는 Maximun von Mises stress 값을 Table 3 에정리하였으며, Figure 4 에그래프로나타내었다. 모든수복형태에서최대응력값은치경부변연을따라인접면과순면이이행되는선각부위에서관찰되었다. 동일한수복형태내에서는치간이개간격이넓어질수록최대응력값이증가하였다. Type I 의경우치간이개량이 1.0, 2.0, 3.0, 4.0 mm 로증가함에따라치경부최대응력은각각 2.95, 3.50, 4.15, 5.69 MPa 을보였으며, Type II 의경우각각 2.55, 3.80, 5.08, 6.80 MPa 을나타내었다. 치간이개량이 1.0 mm 일경우는 Type II 가 Type I 에 33
a b c d Figure 3. von Mises stress distribution patterns of each type of restoration. These figures represent stress distribution at the tooth side of bonding layer. a. Type I with interdental space of 2.0 mm. b. Type II with interdental space of 2.0 mm. c. Type III with interdental space of 2.0 mm. d. Type IV with interdental space of 2.0 mm. 비해낮은최대응력값을보이지만, 그외간격에대해서는 Type II 가 Type I 보다높은최대응력값을나타내었다. Type III 와 Type IV 의경우에도치경부최대응력값은각각 2.79, 3.08, 5.14, 6.55 MPa 및 4.31, 5.17, 5.93, 6.98 MPa 을보여치간이개량이증가함에따라치경부최대응력값이증가하는경향을보였다. Type III 는치간이개량이 1.0, 2.0 mm 일때 Type I 보다낮은최대응력값을보였으나치간이개량이 3.0, 4.0 mm 일때는 Type I 보다높은최대응력값을보였다. Type IV 의경우, 치간이개량에관계없이 Type I, II, III 보다항상높은최대응력값을보였으나, 치간이개간격의증가에따른응력값의증가율은 Type I, II, III 보다낮게 관찰되었다 (Figure 4). Type I, III 의경우각각치간이개간격 3.0, 2.0 mm 이후로최대응력값이크게증가하였으며, Type II 는모든치간이개간격에대해최대응력값이지속적으로높게증가하였다. Ⅳ. 총괄및고찰 본연구에서는복합레진및도재라미네이트로전치부치간이개를수복할때수복물의접착계면에서발생하는응력분포차이를분석하고, 치간이개의양에따른수복방법의기준을제시하고자삼차원유한요소분석법을이용하여이를알아보았다. 유한요소분석법은정확한해석결과를위해 34
도재라미네이트와복합레진수복시치간이개양에따른접착계면의응력분포에관한 3 차원유한요소법적연구 MPa 8 7 6 5 4 3 2 1 0 0.5 mm 1.0 mm 1.5 mm 2.0 mm Type I Type II Type III Type IV Figure 4. Line graphs of maximum von Mises stress values at the cervical area of the tooth side of bonding layer. Horizontal axis means interdental space. Vertical axis means von Mises stress values (MPa). 형성된모델이실제와유사해야하며, 이용된재료의정확한물리적성질및발생가능한모든경계조건을모델에부여할수있어야한다. 그러나치아와같은생체조직은해부학적형태가다양하고, 구강내에서적용되는경계조건들을유한하게한정짓는것이불가능하기때문에결과를해석하는데있어서유한요소분석법이가지는한계를고려해야한다. 다양한인체조직의물성에대한이용가능한자료의한계로인하여모든재료는균질이고, 선형탄성거동을보이며, 등방성인것으로가정하였고, 재료들간에는완전결합된것으로가정하였다. 29) 또한일반적으로격자의형성은육면체요소를사용하나본연구에서는치아및수복형태를재연하는데사면체요소 (tetrahedral solid element) 가사용되었다. 사면체요소는변위에대해서는비교적정확하나응력의측면에서는정확성이떨어지기때문에정확한해석결과가필요한부위에서는사용을피하고격자의크기를변화시키고자하는경우에육면체요소간의연결을위해주로사용된다. 19) 그러나치아의해부학적형태가주로곡면으로이루어져있기때문에사면체요소가형태의재연에더적합하였으며, 사면체와육면체의두가지요소를혼재하여사용하는것은해석결과의정확성을더떨어뜨리기때문에본연구에서는사면체요소를선택하였다. 하중조건에서는, 응력분포를평가하기위해연장부위의특정절점에선택적으로힘을적용하는것이충분할것으로생각되었으나, 이경우힘이적용되는부위에만국부적으로응력이발생하여그분포를평가할수없었으며, 과도한응력으로격자가파괴되어나타나는결과를보였다. 선형으로넓게힘을분산시켜치아및수복물에전체적으로힘이적용되도록한경우적절한응력분포를관찰할수있었고, 또한이경우가실제임상과유사한형태로하중을적용할수있을것으로생각 되어본연구에서는다소넓은범위에걸쳐하중을부여하였다. 치간이개는그정도및치아의배열상태에따라치료법이달라지겠지만, 교정치료 6) 를통한치아의재배열을제외한다면, 일반적으로복합레진 1,2) 혹은도재라미네이트 3,4) 를이용하여공간을수복함으로써해결이가능하다. 복합레진을사용하는경우는대개치아를삭제하지않고치간이개부위에직접복합레진을접착하여수복하거나, 혹은레진으로피개될부위의외형변화가필요한경우에는순면을삭제하여수복하기도한다. 36) 본연구에서는치아를삭제하지않고복합레진으로수복하는경우를재연하기위해치아삭제없이인접면만최소한으로피개하는경우 (Type I) 와, 기계적인결합력을증진시키기위해치아삭제없이원심측으로순면의절반까지복합레진을연장하여피개하는경우 (Type II) 를포함하였다. 또한복합레진으로수복하되치질이손실된경우를재연하기위해치아순면의원심 2/3 까지 0.5 mm 를삭제후수복하는경우 (Type III) 를가정하였다. 치아삭제형태에따른도재라미네이트의파절강도에관해서는다양한견해가있으나상하악의전치부에가해지는약한교합력을고려할때치아삭제형태에관계없이임상적인사용에큰차이가없으며, 14,41) feathered-edge preparation technique 이치질의손실이적고, 심미적이어서도재라미네이트의경우 (Type IV) 는 feathered-edge preparation technique 을이용하여치아를수복하였다. 평가응력의선정은압축응력, 인장응력등의주응력 (principal stress) 으로표현하거나혹은주응력간의차이에대한 root mean square 값인 von Mises stress 로나타낼수있는데, von Mises stress 의경우응력분포패턴을주응력의종류및크기에관계없이종합적으로한눈에알아보기편리하며, 손상이발생할수있는부위를나타내는지표로서현재널리쓰이고있다. 29,42) 이에본연구에서는 von Mises stress 를이용하여접착계면의응력분포를평가하고자하였다. 결과해석에의한응력분포패턴은수복형태에관계없이유사한양상으로나타났는데, 하중의방향과동일한방향으로접착계면을따라응력이전달된다음치경부에서다시집중되어높게나타났다. 접착계면을따라응력이전파되는방향은적용된하중의방향과연관이있는것으로보이며, 치경부에서응력값이높아지는것은레진의두께가줄어들면서응력이분산될수있는매질 (medium) 이줄어들기때문인것으로판단된다. 치간이개의간격이넓어질수록모든수복형태에서최대응력값이증가하는현상을관찰할수있었는데, 이는 Chander 등 33) 에의한이전연구결과와도일치하였다. 최대응력값은인접면과순면이이행되는선각부위에서관찰되었다. Type I 과 Type II 를비교해보면치간이개간격이 35
14 12 10 8 6 4 2 0 0.5 mm 1.0 mm 1.5 mm 2.0 mm Type II - resin Type II - porcelain Figure 5. Maximum von Mises stress values in Type II restoration which was restored with porcelain laminate veneer instead of composite resin. 증가하면서 Type II 가 Type I 에비해높은최대응력값을보였음을알수있다. Type II 에서복합레진의순면피개정도를원심부로연장함으로써기계적인결합면적이늘어난것과더불어하중에대해응력이분산될접착계면이증가하여최대응력값이감소될것으로기대하였으나오히려최대응력값은증가하였다. 2 종지렛대의원리를적용하더라도작용점 ( 치경부최대응력부위 ) 과받침점 ( 레진으로피개된순면의최원심부위 ) 의거리가늘어나면서동일한하중에대해작용점에가해지는응력값이줄어들것으로기대되었다. 그러나본실험에서는찢김력재연을위해상악치아장축에 125 로하중을적용하였을뿐이고, 임상상황에서는구강내에서작용하는힘이보다다양한방향으로적용될수있다. 하중에대한조건이바뀔경우, 효율적으로응력분산에참여하는접착계면영역이달라질수있으며, 이경우응력분포양상및응력값의차이가발생할수있을것으로보인다. 하중의적용위치및적용방향등을바꾸어실험한추가적인연구가더필요할것으로생각된다. Type IV 는모든치간이개간격에대해 Type I, II, III 보다항상높은최대응력값을나타냈다. 수복재료의차이가접착계면에서의응력분포에미치는영향을비교하기위해 Type II 의복합레진을도재의물성으로대체하여동일한해석을시행하였다 (Figure 5). 도재로바꾼경우최대응력값이더크게관찰되었다. 본실험에사용되었던복합레진과도재의탄성계수값은각각 20 GPa, 47) 65 GPa 50) 로서약 3 배정도의차이를보이는데, 도재의경우복합레진에비해높은탄성계수로인해전달된하중이수복재료자체에의해흡수, 분산되지못하고하부의접착계면에더큰응력을발생시킨것으로생각된다. 이는 Type IV 가 Type I, II, III 에비해더큰최대응력값을보인이유로설명될수있다. 그러나치간이개간격의증가에따른응력값의증가율은 Type IV 가 Type I, II, III 보다낮게관찰되었는데, Type I, II, III 의경우치간이개간격이증가하면서응력값의증가율이높아지는경향을보인반면, Type IV 는그래프에서비교적완만한기울기를보였다 (Figure 4). Type IV 의경우, 전체접착계면의면적및하중에대한유효응력분포영역이 Type I, II, III 에비해넓기때문에하중을보다잘분산시켜서응력값이낮게증가하였을것으로생각해볼수있다. 또한 Type IV 는다른수복형태와는달리순면의원심측연장부위경계가순면의일부에서끝나는것이아니라반대측으로연장되어모든순면을덮어주어순면치아를감싸는형태였는데, 이러한구조적차이로인해원심측에서다소의응력분산이발생하여응력을보다효율적으로분산시킬수있었던것으로생각된다. 이와더불어도재라미네이트하방의레진시멘트층의낮은탄성계수로인해다소의응력분산이레진시멘트층에서발생한점도영향을미쳤을것으로보인다. 이러한결과를통해예측해보면, Type IV 가 Type I, II, III 에비해하중의분산에있어서는보다효율적임을알수있다. 이상의결과를종합해보면, 치간이개간격이좁을경우에는복합레진으로수복하는것이응력분포의측면에서효율적이며, 내원횟수감소및치질의보존등을비롯한임상적측면에서도유리할것으로생각된다. 그러나치간이개간격이넓어지면서도재라미네이트와복합레진의접착계면에분포되는최대응력값의격차가줄어들고, 또한최대응력값의증가율이도재라미네이트의경우가복합레진보다낮기때문에, 넓은부위의치간이개부위를수복할경우에는도재라미네이트를이용하는것이응력분포의측면에서유리할것으로생각된다. Ⅴ. 결론 이번연구에서는 3 차원유한요소분석법을이용하여치간이개의간격과수복방법이수복물접착계면에서의응력분포에미치는영향을평가하였다. 이실험의한계내에서다음과같은결론을내릴수있다. 1. 모든수복형태에대해, 치간이개간격이넓어질수록접착계면에서발생하는최대응력값은증가한다. 2. 도재라미네이트로치간이개부위를수복할경우 (Type IV), 복합레진으로수복하는경우 (Type I,II, III) 에비해높은최대응력값을나타낸다. 3. 치간이개간격이넓어질수록도재라미네이트와복합레진에서발생하는최대응력값의차이는감소하며, 치간이개간격의증가에따른최대응력값의증가율은도재라미네이트가복합레진으로수복하는경우보다낮다. 36
도재라미네이트와복합레진수복시치간이개양에따른접착계면의응력분포에관한 3 차원유한요소법적연구 참고문헌 1. Heymann HO, Hershey HG. Use of composite resin for restorative and orthodontic correction of anterior interdental spacing. J Prosthet Dent 53(6):766-771, 1985. 2. Lenhard M. Closing diastemas with resin composite restorations. Eur J Esthet Dent 3(3):258-268, 2008. 3. Pensler AV. Multiple-diastema porcelain laminate veneers: a case study. Compendium 14(11):1470-1478,1993. 4. Nash RW. Closing a large central diastema using a pressed ceramic. Dent Today 22(11):62-65, 2003. 5. Aherne T. Treatment of maxillary anterior diastema using resin-bonded porcelain crown restorations. Pract Proced Aesthet Dent 13(6):443-445, 2001 6. Tanaka OM, Furquim BD, Pascotto RC, Ribeiro GL, B?sio JA, Maruo H. The dilemma of the open gingival embrasure between maxillary central incisors. J Contemp Dent Pract 9(6):92-98, 2008. 7. Dumfahrt H, Schaffer H. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service. Part II. 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국문초록 도재라미네이트와복합레진수복시치간이개양에따른접착계면의응력분포에관한 3 차원유한요소법적연구 홍준배 1 탁승민 2 백승호 1 조병훈 1 * 1 서울대학교치의학대학원치과보존학교실, 2 경상대학교공과대학기계항공학과 본연구에서는, 삼차원유한요소분석법을이용하여복합레진및도재라미네이트로전치부치간이개를폐쇄할때, 치간이개의간격과수복방법이수복물의접착계면에서의응력분포에미치는영향을비교하였다. 복합레진혹은도재라미네이트로수복된모습의유한요소모델을형성하여접착계면에서의 von Mises stress 분포양태를분석하였다. 수복형태는크게네가지범주를고려하였다. Type I, 복합레진으로인접면을최소한으로수복하는경우 ; Type II, 치아삭제없이복합레진으로순면의절반까지수복하는경우 ; Type III, 치아삭제후복합레진으로순면의 2/3 까지수복하는경우 ; Type IV, 도재라미네이트로수복하는경우이실험의한계내에서다음과같은결론을내릴수있었다. 모든수복형태에대해치간이개간격이넓어질수록접착계면에서발생하는최대응력값은증가하였으며, 도재라미네이트로치간이개부위를수복한경우 (Type IV) 가복합레진으로수복한경우 (Type I, II, III) 에비해높은최대응력값을나타내었다. 그러나치간이개간격이넓어질수록도재라미네이트와복합레진에서발생하는최대응력값의차이는감소하였으며, 치간이개간격의증가에따른최대응력값의증가율은도재라미네이트가복합레진으로수복하는경우보다낮았다. 주요단어 : 3 차원유한요소분석법, 치간이개, 도재라미네이트, 복합레진, 접착계면, 응력분포 39