Research article ISSN (print) / ISSN (online) 주근단공의조건에따른 Root ZX 의정확성평가 박신영, 이동균, 황호길 *

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1 Research article ISSN (print) / ISSN (online) 주근단공의조건에따른 Root ZX 의정확성평가 박신영, 이동균, 황호길 * 조선대학교치과대학보존학교실 Received October 14, 2011; Revised November 7, 2011; Accepted November 16, Park SY, DDS, PhD student; Lee DK, DDS, PhD student; Hwang HK, DDS, PhD, Professor, Department of Conservative Dentistry, Chosun University School of Dentistry, Gwangju, Korea *Correspondence to Ho-Keel Hwang, DDS, PhD. Professor, Department of Conservative Dentistry, Chosun University School of Dentistry, 375 Seosuk-dong, Dong-gu, Gwangju, Korea TEL, ; FAX, ; , rootcanal@ hanmail.net An evaluation of the accuracy of Root ZX according to the conditions of major apical foramen Shin-Young Park, Dong-Kyun Lee, Ho-Keel Hwang* Department of Conservative Dentistry, Chosun University School of Dentistry, Gwangju, Korea Objectives: The purpose of this study was to assess the accuracy of Root ZX (J. Morita Corp.) according to the location of major foramen and open apex. Materials and Methods: 81 mandibular premolars with mature apices were selected. After access preparation, 27 teeth were instrumented to simulate open apices. 54 teeth were classified according to location of major foramen under surgical microscope (x16). The file was fixed at the location of apical constriction by Root ZX using glass ionomer cement. The apical 4 mm of the apex was exposed and photo was taken and the distance from file tip to the major foramen was measured by calibrating metal ruler on graph paper. The results were statistically analyzed using ANOVA and Scheffe test at p < 0.05 level. Results: Mean distance from file tip to major foramen was mm in Tip foramen group (I), mm in Lateral foramen group (II) and mm in open apex group (III). Root ZX located apical constriction accurately within ± in group I of 85.71%, in group II of 59.09%, and in group III of 33.33%. There was a statistically significant difference between group I and III (p < 0.05). Conclusion: Root ZX located apical constriction accurately regardless of location of major foramen. However, Root ZX couldn t find it in open apex. Clinicians have to use a combination of methods to determine an appropriate working length at open apex. It may be more successful than relying on just electronic apex locator. (Restor Dent Endod 2012;37(2):68-73) Key words: Accuracy; Electronic apex locator; Major foramen; Open apex 서론 근관치료의성공을위해서는감염된치수조직의완벽한제거, 철저한근관계의세정과형성및삼차원적인근관충전이이루어져야하며, 이를위해서는정확한근관장설정이필수적이다. 1 이상적인근관내기구조작과근관충전의한계는근첨협착부로알려져있으며, 근첨협착부까지근관장을설정했을때근관계의세정및형성이쉽고치근단봉쇄를더쉽게얻을수있으며가장적절한창상치유가일어날수있다 년 Suzuki가개의근관내와구강점막사이의전기저항이일정함을발견한이래 1962년 Sunada 가치근첨과구강점막사이에 6.5 kω의직류저항을나타낸다는원리를이용하여최초의전자근관장측정기를개발하였다. 3,4 이러한초창기제품은단순히전기저항을이용했기때문에근관내에습기나혈액등의오염이있을때저항이급격하게떨어져많은오차를발생하였다. 이후 1991년 Kobayasi 이논문은 2007 년도조선대학교학술연구비지원을받아연구되었음. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 68 Copyrights The Korean Academy of Conservative Dentistry.

2 Accuracy of Root ZX according to major foramen 등이두개의주파수를사용했을때나타나는두개의교류저항 (impedence) 을동시에측정하여얻어진두저항값의차이나비율이여러전해질용액에서일정하다는것을실험적으로증명하여발표하였다. 5,6 파일이근첨협착부에가까워질수록저항이증가되다가치주인대와같은치주조직에접촉시저항이급격하게감소되므로이를이용하여근관내파일의위치를나타내도록개발된전자근관장측정기가 Root ZX이다. 기존에전자근관장측정기의정확성에부정적영향을미치는요인으로지목되었던근관내전해질, 수분조건은이러한제3세대전자근관장측정기의개발로해결되었다. 5 치근단형태에대한연구를통해방사선학적근첨과주근단공까지평균거리가, 주근단공에서근첨협착부까지평균거리가 0.5 mm이므로방사선사진상근첨과근첨협착부까지의거리는대략 1 mm로간주할수있다. 7-9 그런데주근단공이치근장축에서편향되어위치하는측방근단공을갖는치아에서전자근관장측정기로임의근관장을설정하고방사선사진으로확인하려고하는경우, 임상에서흔히근관장방사선사진이 짧게 보이는경우가있으며, 실제로파일끝과근첨협착부간의거리가치근단에위치한주근단공과어떠한차이를보이는지의문을갖게된다. 또한열린근단공은미성숙치근단뿐만아니라교정치료또는성숙치근의외흡수로생길수있으며, 치근단공이매우크고근첨협착부가부족하여근관치료하기에상당히어렵다. 10 여러문헌에서치근단공의크기가클수록전자근관장측정기의정확성이떨어진다고보고되었으나, 열린근단공에서의전자근관장측정기의정확성에대한연구는많지않다 따라서본연구에서는주근단공이치근단또는측방에위치할경우와열린근단공을갖는경우에서전자근관장측정기가얼마나정확한지를평가해보고자하였다. 부학적치근첨에위치하는치아를그룹 I, 주근단공이치근장축에서벗어나위치하는치아를그룹 II 로하였으며, 27 개의치아는열린근단공을재현하기위해인위적으로열린근단공의형태를만들어그룹 III 으로분류하였다. 3) 열린근단공모델제작열린근단공을재현하기위해 Hachmeister 등의연구에서의모델제작방법과동일하게치근단 2 mm 를평두열구상버 (FG 559, SSW, Lakewood, NJ, USA) 로절단한뒤, 10 번크기의 K 형파일끝이절단된치근면에비치는지점을실제길이로설정하고, #2 Peeso Reamer (Dentsply Maillefer) 로실제길이까지근관형성을시행하였다. 15 그리고치근단측으로넓은열린근단공의형태를만들기위해.04 경사도의 50 번크기의 K3 파일 (SybronEndo Inc., Orange, CA, USA) 을이용하여 cutting blade (D16) 까지역방향으로형성한뒤방사선사진을촬영하고식염수에보관하였다 (Figure 1). 4) 전자근관장측정구강밖에서전자근관장을측정할수있는실험모델을고안하여내부에는전해질인식염수를채우고치근을볼수없도록플라스틱통의외부를검정테이프로감싼후구강내와유사한조건으로 Root ZX 를사용하여 10 번크기의 K 형파일을근관내로전진하여계기판의근첨에도달한후근첨으로부터제조사가 근첨협착부 로읽는지점 (0.5 Mark) 에위치시켜러버스탑을교합면에고정하고, 파일을광중합형글래스아이오노머시멘트 (GC Fuji II LC, GC Co, Tokyo, Japan) 로치아에고정시키고, 광중합되는동안동일한지점을가리키는지재확인하였다. 16 연구재료및방법 실험재료 #2 Peeso Reamer 교정적이유로발치된단근관의하악소구치중에서치근단공형성이완료되었고치근단의흡수나치근파절을보이지않는총 81 개를실험대상으로하였다. 발치된치아는방사선사진촬영을통해근관의형태를확인하였고실험기간동안생리식염수에보관하였다. D16 실험방법 1) 실험시편의준비실험치아는원형의다이아몬드버 (BR-41, Mani, Utsunomya Tochgi, Japan) 를이용하여치수강을개방하였으며, 교합면을치아의장축에직각으로삭제하고근관의입구로부터치근단공으로의개방성을 8 번크기의 K 형파일 (Dentsply Maillefer, Balleigue, Switzerland) 로확인하였다. Gates-Glidden drill (Dentsply Maillefer) 을사용하여치관부근관형성을시행하였으며식염수로근관을세척하였다. 2) 실험군의분류 54 개의치아를 16 배의수술용현미경 (OPMI Pico, Carl Zeiss Co., Oberkochen, Germany) 하에서주근단공의위치에따라주근단공이해.04/50 K 3 file (a) (b) (c) Figure 1. An open apex model. (a) The canals were instrumented with a #2 Peeso reamer to the actual length; (b) A divergent open apex was prepared by retrograde apical preparation with a.04/50 K3 file inserted to the length of the cutting blade; (c) Simulated open apex model. 69

Park SY et al. 5) 파일고정후파일끝에서주근단공까지의실제거리측정파일끝에서치근단공의외연까지의거리측정을위해원형의다이아몬드버를치근의장축방향으로사용하여 25 배의수술용현미경하에서치근단 4 mm 의치질을파일끝이어느정도노출되도록삭제하고 #15 blade 로잔존치질을조심스럽게삭제하여파일끝을노출시켰다.

통계분석 통계적자료분석은그룹간의평균차이를분석하기위해 ANOVA test 와사후분석을위해 Scheffe post hoc test 를이용하였다. 이상의통계분석은통계프로그램인 SPSS V14.0 (SPSS Inc., Chicago, IL, USA) 을이용하였고통계적유의성여부는유의수준 0.05 를기준으로판단하였다.

통계처리시파일첨과주근단공간의거리에대해그룹간비교를하였을때, 그룹 I 과그룹 III 간에는통계적으로유의한차이를보이지만 (p < 0.05), 그룹 I 과그룹 II, 그룹 II 와그룹 III 사이에는통계적으로유의한차이를보이지않았다 (p > 0.05). major foramen file tip Figure 2.

3 Park SY et al. 5) 파일고정후파일끝에서주근단공까지의실제거리측정파일끝에서치근단공의외연까지의거리측정을위해원형의다이아몬드버를치근의장축방향으로사용하여 25 배의수술용현미경하에서치근단 4 mm 의치질을파일끝이어느정도노출되도록삭제하고 #15 blade 로잔존치질을조심스럽게삭제하여파일끝을노출시켰다. 16 이과정에서파일의위치변화, 치근첨의손상으로 7 개시편이제외되었다. Graph paper 하에서 간격의 metal ruler 를수평, 수직으로고정한뒤치아를위치시키고 25 배의수술용현미경하에서사진을촬영하고거리를측정하였다 (Figures 2-4). 통계분석 통계적자료분석은그룹간의평균차이를분석하기위해 ANOVA test 와사후분석을위해 Scheffe post hoc test 를이용하였다. 이상의통계분석은통계프로그램인 SPSS V14.0 (SPSS Inc., Chicago, IL, USA) 을이용하였고통계적유의성여부는유의수준 0.05 를기준으로판단하였다. 결과 파일끝에서주근단공까지의거리 총 81 개의표본중시편제작시손상된 7 개표본은통계분석시제외하고, 그룹 I 은 28 개, 그룹 II 는 22 개, 그룹 III 은 24 개로분류되었다. 파일끝과주근단공까지의거리는평균적으로그룹 I 은 mm, 그룹 II 는 mm, 그룹 III 은 mm 를보였다 (Table 1). 통계처리시파일첨과주근단공간의거리에대해그룹간비교를하였을때, 그룹 I 과그룹 III 간에는통계적으로유의한차이를보이지만 (p < 0.05), 그룹 I 과그룹 II, 그룹 II 와그룹 III 사이에는통계적으로유의한차이를보이지않았다 (p > 0.05). major foramen file tip Figure 2. Tip foramen (group I), in which major foramen is located at the tip along the main axis of root. File was fixed in the position and the distance from file tip to major foramen was measured (x25). 주근단공으로부터파일끝의위치관계 ± 오차범위에서의정확도는그룹 I 은 85.71%, 그룹 II 는 59.09%, 그룹 III 은 33.33% 를보였으며, ± 1.0 mm 에서의정확도는그룹 I 은 100%, 그룹 II 는 86.36%, 그룹 III 은 62.5% 를보였다 (Table 2). major foramen file tip major foramen file tip Figure 3. Lateral foramen (group II), in which major foramen deviates from the main axis of root. File was fixed in the position and the distance from file tip to major foramen was measured (x25). Figure 4. Simulated open apex (group III). File was fixed in the position and the distance from file tip to major foramen was measured (x25). 70

4 Accuracy of Root ZX according to major foramen Table 1. Distance from file tip to major foramen (mm) * mm No. Minimum Maximum Mean SD Group I Group II Group III * A significant difference was found between group I and group III (p < 0.05). SD, standard deviation. Table 2. Position of file tip relative to major foramen d (mm) group I group II group III n = 28 % n = 22 % n = 24 % d < -0.5* d < 0* d d > * Negative value indicates file tip short from major foramen. d, distance from file tip to major foramen. 총괄및고안 치근단부위의근관형태는생리적이거나병리적인변화, 흡수및새로운경조직형성으로인해계속적으로변형되므로정확한근관장을설정하기는임상적으로어렵다. 7,8,17 부정확한근관장으로인해과도한기구조작을하게되는경우, 기구나충전물질이치근단을벗어나외부조직에가해져염증반응을일으킬수있고, 불충분하게기구조작되는경우에는잔존치수로인해지연된동통반응을일으킬수있어서정확한근관장을설정하는것이근관치료의성공또는실패를좌우한다고볼수있다. 18 근관치료시기구조작과충전의한계점으로제시되는근첨협착부의위치는치근마다다양하여평균적으로치근단공의외측면으로부터 mm에위치하는것으로알려져있으며, Kuttler의연구에의하면치근단백악질의침착으로치근단공이편향되어위치하는비율이 68-80% 라고하였고, 특히구치부에서치근단공이편향되어위치하는비율이전치부보다높다고하였다. 8,9 방사선사진은치근단공의위치에대한정보를제공하지않으므로임상가가편향된치근단공을갖는치아의근관장을결정하기위해방사선사진을촬영하는경우, 실제보다훨씬짧게기구가위치하기때문에근관장결정에혼돈을겪게된다. 19 이에치근단공의위치가전자근관장측정시정확성에영향을미치는지알아보기위하여본연구를계획하였다. 또한외상이나우식, 그외다른치수병소에의해치근성장이불완전하게되는열린근단공의경우, 근관이매우크며, 얇고취약한치근상아질벽을갖고, 발산형의치근첨구조를가지므로정확한근관장을설정하기어렵다. 전자근관장측정기는치근흡수, 수평치근파절, 해부학적구조물과의중첩으로방사선사진상관찰이어려운경우 와같은임상적상황에서근관치료에유용한도구로서특히치근이미완성된열린근단공의경우에서도비교적위치를감지해낸다고하였다 이에열린근단공에서전자근관장측정시정확성을평가해보는것이임상적으로의의가있으리라생각되었다. 본실험에서는Kobayashi와 Suda가제안한생체외실험용전자근관장측정기실험모델을응용하여전해액으로는젤라틴모델대신생리식염수를이용하였다. 23,24 그동안전자근관장측정기의정확도를측정하는방법으로는방사선사진상의길이와측정값을비교하거나, 발치후파일끝과근단공사이의거리를실제로계측하는방법등이있으며, 대개측정치의평균과표준편차를구하고측정치가미리정한허용범위내에들어가는백분율을계산하여정확도를평가하게되어, 본실험에서도이방법을이용하였다. 25 여러문헌에서근첨협착부는단지조직학적인지표이며파일끝은근첨협착부의유무와관계없이주근단공주위에위치하게된다고보고하였다 본실험에서도치근단부를삭제했을때근첨협착부를정확하게인지하거나명확하게찾아내기힘들었다. 따라서근관장측정의정확성을평가하는해부학적기준점으로서보다관찰하기용이한주근단공을선택하였고주근단공에서 ± 를임상적오차범위로간주하였다. 14 열린근단공의형태를재현하기위해본실험에서는 2번크기의 Peeso reamer로얇은치근상아질벽과치근첨근처에서 0.90 mm 직경의근관을만들었다. 또한발산형의근단공형태를재현하기위해.04 taper의 50번크기의 K3 파일을역방향으로 16 mm까지기구조작하여본실험에서열린근단공의형태인발산형의근첨을재현하였다. 그룹 III의평균적인파일첨에서주근단공까지의거리는평균 mm로대략 1 mm로측정되었다 (Table 1). 열린근단공의경우방사선학적근첨보다 2 mm 짧게근관장을설정하는것이추천되어지고있어본실험결과와비교시대략 1 mm 차이가난다. 근관의직경을의도적으로 1.02 mm까지넓히고 10번크기부터 100번크기의파일로전자근관장을측정한결과, 사용된파일에따라대략 1 mm의오차범위를보였다는연구를참고할때, 본실험에서 10번크기의 K형파일을사용하였기때문에 1 mm의차이를보인것으로사료된다. 29 그동안 Root ZX를이용하여여러조건하에서의정확성에대한연구가많이행해져왔으며, 그정확성은 75-97% 로연구방법에따라다소간의차이를보인다. 10,30 본실험에서주근단공의위치에따른전자근관장측정값의거리차이는있으나통계학적으로유의한차이는없었다. 또한본연구는 in vitro상의연구인반면, Pagavino 등은주근단공이측방에위치한그룹이치근단에위치한그룹보다전자근관장측정치의오차가컸다는 SEM 연구를통해전자근관장사용시치근단공의위치를고려해야한다고하였고 Ding 등은파일끝과치근단공간의거리를측정했을때주근단공이측방에위치한그룹이치근단에위치한그룹보다유의하게치근단공에근접한다고하였다. 1,19 그리고이런차이가발생한이유에대해근관의교류저항이저항, 전기용량으로구성된복잡한전기적체계망이며, 근관의저항이근관형태에따라다르다는가능성을제시하였다. 31,32 ± 임상적오차범위에서전자근관장측정기의정확성은치근단근단공인그룹 I 은 85.71%, 측방근단공인그룹 II 는 59.09%, 열린근단공인그룹 III 은 33.33% 로평가되었고특히열린근단공그룹의정확성이매우낮고전자근관장이짧게기록되었다. 이러한이유로나팔총모양의치근첨에서는치수와치주조직간의교류저항 (impedence) 이명확하게경계지어지지않아서전자근관장의정확성 71

5 Park SY et al. 이떨어진다고보고된바있다. 33 여러문헌에의하면치근단공의크기가전자근관장측정기의정확도에영향을미치는것으로보고되는데, Saito 등은 0.62 mm, Huang 등은 0.40 mm 이상인경우정확성이떨어진다고하였고, 이번연구에사용된열린근단공의경우에도치근첨부위직경이 0.90 mm 이상이었기때문에정확성이떨어진것으로사료되었다. 34,35 근관장의측정방법중방사선적방법은전통적으로근관장결정에사용되어왔다. 방사선사진은근관계의해부학적구조물과질환의존재유무를알려주고, 근관장결정의초기지침으로사용될수있는장점이있다. 36 그런데편향된치근단공을갖거나복잡한근관만곡을갖는경우에 3차원적구조물을 2차원의방사선사진만으로판단하기에는한계가있으며, 해부학적구조물과중첩될수있고, 치근단부위의정상적인해부학적변이때문에근관길이를과측정할가능성이있다. 특히주근단공이협측또는설측으로위치하는경우에는다양한각도에서촬영할지라도방사선사진만으로는치근단공의위치를정확히알아내기는매우어렵기때문에 micro CT를활용하는등추가적인연구가요구된다. 결론 본연구결과주근단공의위치가전자근관장측정기의정확도에영향을미치지않았으나전자근관장측정에는물리적, 생물학적측면이전자근관장측정기의능력에영향을미치므로, 앞으로 in vivo 상의연구가필요할것으로생각되며, 근관장 방사선사진상근관장이짧게보이는경우, 전적으로방사선사진에만의존하여근관장을조정한다면과도한기구조작이될가능성이높으므로방사선사진을참고하되전자근관장측정기를재측정하여근관장을결정하는것이방사선노출양을감소시키고치료시간을단축시킬수있는점에서임상적으로효과적이라사료된다. 그리고열린근단공에서는전자근관장측정기의정확도가낮으므로임상가는열린근단공의근관장을결정할때전적으로전자근관장측정기에의존하기보다는방사선학적인방법등을함께사용하여재확인하는과정을거쳐야될것으로사료된다. Conflict of Interest: No potential conflict of interest relevant to this article was reported. References 1. Ding J, Gutmann JL, Fan B, Lu Y, Chen H. Investigation of apex locators and related morphological factors. J Endod 2010;36: Riccuci D, Langeland K. Apical limit of root canal instrumentation and obturation, part 2. a histological study. Int Endod J 1998;31: Suzuki K. Experimental study on iontophoresis. J Jpn Stomatol 1942;16: Sunada I. New method for measuring the length of the root canal. J Dent Res 1962;41: Kobayashi C, Suda H. New electronic canal measuring device based on the ratio method. J Endod 1994;20: Kobayashi C. Electronic canal length measurement. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995; 79: Green D. Stereomicroscopic study of 700 root apices of maxillary and mandibular posterior teeth. Oral Surg Oral Med Oral Pathol 1960;13: Dummer PM, McGinn JH, Rees DG. The position and topography of the apical canal constriction and apical foramen. Int Endod J 1984; 17: Kuttler Y. Microscopic investigation of root apexes. J Am Dent Assoc 1955;50: Torabinejad M, Walton RE. Endodontics: principles and practice. 4th ed. Missouri: Saunders Elsevier; p Herrera M, Abalos C, Planas AJ, Llamas R. Influence of apical constriction diameter on Root ZX apex locator precision. J Endod 2007;33: Stein TJ, Corcoran JF, Zillich RM. Influence of the major and minor foramen diameters on apical electronic probe measurements. J Endod 1990;16: Fouad AF, Rivera EM, Krell KV. Accuracy of the Endex with variations in canal irrigants and foramen size. J Endod 1993;19: Huang L. An experimental study of the principle of electronic root canal measurement. J Endod 1987;13: Hachmeister DR, Schindler WG, Walker WA 3rd, Thomas DD. The sealing ability and retention characteristics of mineral trioxide aggregate in a model of apexification. J Endod 2002;28: Cho JH, Kum KY, Lee SJ. In vitro evaluation of accuracy and consistency of four different electronic apex locators. J Korean Acad Cons Dent 2006;31: Ponce EH, Vilar Fernández JA. The cemento-dentinocanal junction, the apical foramen, and the apical constriction: evaluation by optical microscopy. J Endod 2003;29: Sjögren U, Hägglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod 1990;16: Pagavino G, Pace R, Baccetti T. A SEM study of in vivo accuracy of the Root ZX electronic apex locator. J Endod 1998;24: Goldberg F, De Silvio AC, Manfré S, Nastri N. In vitro measurement accuracy of an electronic apex locator in teeth with simulated apical root resorption. J Endod 2002;28: Nguyen HQ, Kaufman AY, Komorowski RC, Friedman S. Electronic length measurement using small and large files in enlarged canals. Int Endod J 1996;29: Kim BH, Lee YK, Kim YS. A study on the accuracy of the ROOT-ZX in the canal with mechanically formed constriction. J Korean Acad Cons Dent 1999;24: Czerw RJ, Fulkerson MS, Donnelly JC. An in vitro test 72

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대한치과보존학회지 : Vol. 33, No. 1, 종전자근관장측정기의일관성에관한 in vitro 연구 ABSTRACT 황규용 노병덕 김의성 이승종 * 연세대학교치과대학보존학교실 IN VITRO EVALUATION OF THE CONSISTENCY OF TW

대한치과보존학회지 : Vol. 33, No. 1, 종전자근관장측정기의일관성에관한 in vitro 연구 ABSTRACT 황규용 노병덕 김의성 이승종 * 연세대학교치과대학보존학교실 IN VITRO EVALUATION OF THE CONSISTENCY OF TW 대한치과보존학회지 : Vol. 33, No. 1, 2008 ABSTRACT 황규용 노병덕 김의성 이승종 * 연세대학교치과대학보존학교실 IN VITRO EVALUATION OF THE CONSISTENCY OF TWO ELECTRONIC APEX LOCATORS Gyu-Young Hwang, Byoung-Duck Roh, Eui-Sung Kim, Seung-Jong