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1 대한치과재료학회지 44(1) : , 2017 ISSN: (Print); (Online) Available online at 가속노화효과에의한치과용 3D 프린터출력물의변형도평가 문준모 1, 김정미 2, 배지명 1, 오승한 1* 원광대학교치과대학치과생체재료학교실및생체재료 매식연구소 1, 원광대학교치과대학병원중앙기공실 2 <Abstract> Evaluation of acceleration aging effect on the deformity of dental 3D printer products Joon-Mo Moon 1, Jeong-Mi Kim 2, Ji-Myung Bae 1, SEunghan Oh 1* Department of Dental Biomaterials and the Institute of Biomaterials Implant, Wonkwang University, Iksan, Korea 1, Central Dental Laboratory, Dental Hospital, Wonkwang University. 2 The objective of this study was to estimate the accuracy of 3D printed models and acceleration aging deformity of 3D printed models by calculating the RMS values of original model and 3D printed models with or without acceleration aging. RMS values between original model and four kinds of 3D printed models were μm (Polyjet), μm (DLP), μm (SLA), and μm (FDM) in this order. Also, RMS values between original model and four kinds of 3D printed models treated by acceleration aging were μm (Polyjet), μm (SLA), μm (DLP), and μm (FDM) in this order. Statistical analysis of both tests results that there was significant differences between each experimental group (P<0.05). Comparison test of RMS values of 3D printed model before and after acceleration aging resulted that all experimental groups showed significant difference between before and after acceleration aging (P<0.05). Within the limitation of this study, most 3D printers except FDM type are expected to be acceptable to prepare the model for preparing clear aligner. Also, immediate model preparation by 3D printer at each stage is recommended to ensure accurate orthodontic treatment with clear aligner. Key words: 3D printer, acceleration aging, accuracy, deformity, RMS (Root mean square), clear aligner Ⅰ. 서론 교정치료방법은교정진료지식과경험을데이터화하고그바탕으로교정에필요한새로운브라켓이나교정장치등이개발되었다. 그교정장치중하나로투명교정이있다. 투명교 * Correspondence: 오승한 (ORCID ID: X) (54538) 전북익산시익산대로 460, 원광대학교치과대학치과생체재료학교실 Tel: , Fax: shoh@wku.ac.kr Received: Mar. 8, 2017; Revised: Mar. 20, 2017; Accepted: Mar. 20, 2017 정의경우 CAD/CAM (Computer aided design/computer aided manufacturing) 기술의발달로인해혁신을이루었다 (Wong, 2002). 투명교정장치의제작방법은크게술자가직접손으로제작하는방식과디지털장비를활용하는방식으로나누어진다. 술자가직접제작하는방식은구강에서채득한환자의인상모형을기공용톱이나기공용도구를사용하여모형을성형하여제작하는방법과모형을통해얻어진투명교정장치를열과플라이어 (plier) 를이용하여환자의치아가이동할수있도록성형하여사용하는 Essix 방법이있다 ( 김, 2005). 그리고디지털장비를활용한방법으로는환자의

2 인상을구강스캐너나채득된모형을모형스캐너를활용해 3차원스캔파일을만들고 CAD 상에서투명교정프로그램을이용해디자인한후그파일을치과용 3D 프린터로 3차원교정모형을출력하여제작하는방법이다 (Massimo, 2013; Shalish et al., 2012). 3D 프린터의출력방식에따라크게광경화수지조형방식 (stereo-lithography apparatus; SLA), 마스크투영이미지경화방식 (digital light processing; DLP), 폴리젯방식 (Polyjet), 및압출적층조형방식 (fused deposition modeling; FDM) 등으로나누어진다 (Stampfl과 Liska, 2005). 현재다양한 3D 프린터들이개발, 사용되고있으나디지털치과기공물에대한연구는주로 CAM 장비를통해제작된치과보철물의모형적합도에관련된내용들이었다 (Sachiko, 2005; Kim et al., 2015; de Franca, 2015). 3D 프린터를적용한인상채득이나모형디지털화의치과영역사용가능성은이미많은연구를통해검증되었다 (Quimby et al., 2004; Stevens et al., 2006). 그러나 3D 프린터출력물의장기간보관에따른변형도연구는미비하다고볼수있다. 특히, 3D 프린터출력물들은층간결합이약하고 3D 프린터용고분자소재의특성상장기간보관에따른변형이발생할가능성이높다. 이에본연구에서는투명교정장치제작에필요한여러단계의 3D 프린터출력물을미리제작한후오랜시간이지난뒤활용해도변형없이사용가능한가를평가하기위해 3D 프린터출력물의스캔이미지에대한실효값 (root mean square; RMS) 값을측정하여비교평가하였다. 투명교정장치제작에사용되는 4가지방식의 3D 프린터로제작된교정장치제작용모형과원본모형간의 RMS 값을측정하여정확도를평가하였다. 그리고가속노화전 후출력물간의 RMS 값을측정하여변형도를평가함으로써 3D 프린팅된모형의장기관보관에대한유효성에대해서확인하였다. Ⅱ. 연구재료및방법 1. 4종의 3D 프린터를이용한모형제작본연구에서사용된원본의치모형 (Frasaco ANA-4v CER, Germany; Figure 1) 을교정전용모형스캐너 (R1000, 3shape, Denmark) 로스캔하여원본모형스캔이미지를추출하였다. 추출된원본모형스캔이미지를이용하여 4종의 3D 프린터 (SLA, DLP, polyjet, 및 FDM 방식 ) 로모형복제물을제작하였다 (Table 1). 각실험군당 5개의모형을제작하였고 (Figure 2), 출력된모형을다시교정전용모형스캐너로스캔하여각각의모형스캔이미지를생성하였다. Figure 1. Photo image of denture model used in this study. Table 1. Information about of 3D printers used in the study Operation type (Model NO, Company, Country) SLA(Stereo-Lithography apparatus) (Digitalwax029D, DWS, Italy) DLP(Digital Light Processing) (3Dent, Envision Tec Co. USA) Polyjet (EDEN260V, Startasys Co. Israel) FDM(Fused Deposition Modeling) (VIS-MINI, Vistech Co. Korea) 2. 가속노화시험 Features 1. Min. Layer Thickness: 10 μm 2. Max. build size: 150*150*10 mm 3 1. Min. Layer Thickness: 25 μm 2. Max. build size: 279*184*76 mm 3 1. Min. Layer Thickness: 16 μm 2. Max. build size: 255*252*200 mm 3 1. Min. Layer Thickness: 50 μm 2. Max. build size: 140*140*140 mm 3 4종의 3D 프린터로출력한 20개의모형들을국제표준 ISO , (2006), 및 ASTM F1980(2016) 의규정에맞춰 54

Type 3D printed model Type 3D printed model SLA DLP Polyjet FDM Figure 2. Photo images of 3D printed models (SLA, DLP, Polyjet, and FDM types).

본연구에서는 6개월동안보관하는조건을설정하여 60 C 에서 12일동안가속노화시험을수행하였다. 3. 색지도측정법을이용한원본모형과 3D 프린팅된모형간의정확도분석 색지도측정법은 3차원이미지를중첩하여출력된스캔파일의음영차이를색지도로형상화하여나타내는것이다.

대조군원본모형스캔이미지와 3D 프린팅된출력물스캔이미지의중첩에의한음영차이를나타내는색지도의대표적인예가 Figure 3에나타나있다. 색지도에서녹색은원본과출력물이거의차이가없음을나타내는것이고, 파란색은출력물이원본보다함몰된것이고, 빨간색은출력물이원본보다돌출된것이다. Figure 3. Color map showing volumetric difference between the scanned images of original model and 3D printed model.

3 Type 3D printed model Type 3D printed model SLA DLP Polyjet FDM Figure 2. Photo images of 3D printed models (SLA, DLP, Polyjet, and FDM types). 가속노화시험 (Greenpia Technology, Korea) 을수행하였다. 보관온도 20 C 에서 60 C 로승온하여가속노화시험을수행하게되면가속노화공식에따라 20 C에서 1년에해당하는가속노화기간은 60 C 에서약 23일이소요된다. 본연구에서는 6개월동안보관하는조건을설정하여 60 C 에서 12일동안가속노화시험을수행하였다. 3. 색지도측정법을이용한원본모형과 3D 프린팅된모형간의정확도분석 색지도측정법은 3차원이미지를중첩하여출력된스캔파일의음영차이를색지도로형상화하여나타내는것이다. 색지도를이용한변형도측정법은미국국립표준기술연구소와영국의국립물리연구소에서테스트받았으며독일국립측정연구소 (Physikalisch-Technische Bundesanstalt) 계측기관에서 Class 1 정확도로인증된방법이다 (Lee et al., 2015). 대조군원본모형스캔이미지와 3D 프린팅된출력물스캔이미지의중첩에의한음영차이를나타내는색지도의대표적인예가 Figure 3에나타나있다. 색지도에서녹색은원본과출력물이거의차이가없음을나타내는것이고, 파란색은출력물이원본보다함몰된것이고, 빨간색은출력물이원본보다돌출된것이다. Figure 3. Color map showing volumetric difference between the scanned images of original model and 3D printed model. 4. RMS 값을이용한원본모형과 3D 프린팅된모형간의정확도분석및가속시효전 후모형의변형도분석 가속노화전 후의모형들과원본모형간의정확도를평가하고가속노화전과후의모형간의변형도를확인하기위하여각모형을스캔한이미지를 3차원이미지분석프로그램 (Geomagic control 2014, 3D systems, USA) 을이용하여 RMS 값을계산하였다 (Schaefer et al., 2012). RMS 값계산공식은아래와같다. 55

RMS n n i x i x i x1,i는참고측정지점, x2,i는중첩측정지점, n= 표본측정지점의총수를의미한다. 본공식은치은을포함하지않은치아영역내에서의계산만수행하였다. 5. 통계분석 각시험에서계산된 RMS 값비교는 IBM SPSS Statistics (Ver. 18.0; IBM Co., Armonk, NY, USA) 를이용하였다 (α =0.05).

색지도측정법기반의원본모형과 3D 프린팅된모형간의정확도평가 원본모형스캔이미지와 4종의 3D 프린터로출력된모형스캔이미지를색지도측정법으로중첩시킨이미지가 Figure 4에나타나있다. 색지도측정법으로중첩된이미지들중에서 FDM 방식의모형스캔이미지가원본스캔이미지와의편차가가장컸다.

4 RMS n n i x i x i x1,i는참고측정지점, x2,i는중첩측정지점, n= 표본측정지점의총수를의미한다. 본공식은치은을포함하지않은치아영역내에서의계산만수행하였다. 5. 통계분석 각시험에서계산된 RMS 값비교는 IBM SPSS Statistics (Ver. 18.0; IBM Co., Armonk, NY, USA) 를이용하였다 (α =0.05). 원본모형스캔이미지와 3D 프린팅된모형스캔이미지간의 RMS 값비교는 Kruskal-Wallis test로통계분석하였고, Duncan s multiple range test로사후검정하였다. 가속노화전 후 3D 프린팅모형간변형도를평가하기위한가속노화전과후의모형스캔이미지간의 RMS 값비교는독립표본 t-test로통계분석하였다. Ⅲ. 연구결과 1. 색지도측정법기반의원본모형과 3D 프린팅된모형간의정확도평가 원본모형스캔이미지와 4종의 3D 프린터로출력된모형스캔이미지를색지도측정법으로중첩시킨이미지가 Figure 4에나타나있다. 색지도측정법으로중첩된이미지들중에서 FDM 방식의모형스캔이미지가원본스캔이미지와의편차가가장컸다. 특히회색으로표시된부분은 3D 프린팅된모형에원본모형대비 1 mm이상의심한변형이발생했다는것을의미한다. 2. 원본모형과 3D 프린팅된모형간의 RMS 평가 원본모형스캔이미지와 3D 프린팅된모형의스캔이미지간의 RMS 계산결과를 Table 2에나타내었다. RMS 값은 (A) (B) (C) (D) Figure 4. Color map images showing volumetric differences between the scanned images of original model and printed model of (A) SLA, (B) DLP, (C) Polyjet, and (D) FDM 3D printers. 56

5 Polyjet(41.60 μm ) < DLP(44.52 μm ) < SLA(48.60 μm ) < FDM (55.46 μm ) 순으로, Polyjet 이 4개의실험군에서가장낮은 RMS 값을, FDM이가장높은 RMS 값을각각나타내었다. 또한각실험군간의 RMS 값은모두통계적인유의차를나타내었다 (P<0.05). 따라서색지도측정법을이용한이미지중첩분석결과와 RMS 값을토대로 FDM 방식의 3D 프린터가가장낮은정확도를나타내는것으로확인되었다. 4. 가속노화전과후의 3D 프린팅된모형간의 RMS 평가독립표본 t-test 로통계분석된가속노화전과후의 3D 프린팅된모형스캔이미지간의 RMS 비교결과를 Figure 5에나타내었다. 네가지실험군모두가속노화전과후의 RMS 값이통계적인유의차를나타내었다 (P<0.05). Table 2. Statistical analysis of RMS values calculated from original model and 3D printed model (Kruskal-Wallis test) Type RMS ( μm ) Ranking df Asymptotic P SLA C DLP B Polyjet A FDM D 3. 가속노화시험후, 원본모형과 3D 프린팅된모형간의 RMS 평가 원본모형스캔이미지와가속노화후의 3D 프린팅된모형스캔이미지의 RMS 계산결과를 Table 3에나타내었다. RMS 값은 Polyjet(63.56 μm ) < SLA(68.04 μm ) < DLP(72.10 μm ) < FDM( μm ) 순이었다. 가속노화전모형에대한 RMS 평가결과와유사하게 Polyjet 이 4개의실험군중에서가장낮은 RMS 값을나타냈고, FDM은가장높은 RMS 값을보였고, 실험군간에유의성있는차이를나타내었다 (P<0.05). Table 3. Statistical analysis of RMS values calculated from original model and 3D printed model after acceleration aging test (Kruskal-Wallis test) Type RMS ( μm ) Ranking df Asymptotic P SLA B DLP C Polyjet A FDM D Figure 5. RMS graph of 3D printed models (SLA, DLP, Polyjet, and FDM) before and after accelerating aging. The same lowercase letters were not significantly different among groups before accelerating aging analyzed by Kruskal-Wallis test and Duncan s multiple range test at α=0.05. The same uppercase letters were not significantly different among groups after accelerating aging analyzed by Kruskal-Wallis test and Duncan s multiple range test at α=0.05. Asterisk (*) means that there are significant differences between experimental groups before and after accelerating aging analyzed by t-test (α=0.05). Ⅳ. 고찰 본연구에서는치과교정영역중투명교정에사용할수있는 4가지방식의 3D 프린터 (SLA, DLP, Polyjet, 및 FDM) 출력물들의원본과의정확도를평가하고, 가속노화시험을통하여 3D 프린터출력물의장기간보관에따른안정적형태유지여부를확인하고자하였다. 원본모형스캔이미지와 3D 프린팅된모형 ( 가속노화전 ) 스캔이미지간의 RMS 비교분석결과, Polyjet은다른 3D 프린터에비해가장낮은 RMS 값을나타내었고, FDM이가장높은 RMS 값을나타나 FDM 이가장낮은정확도를나타내는 57

6 것으로확인되었다. 이는 Polyjet 은출력방식의특성상고체시료를사용함으로써광중합시주변재료에미치는빛간섭이액상재료를사용하는 DLP나 SLA보다적기때문이다. 또한, FDM의낮은정확도의큰원인으로는 Table 1에서확인할수있듯이 3D 프린터의출력성능즉최소적층두께의차이로인한영향이가장큰것으로판단된다. 각각의 3D 프린터적층두께를확인해보면, SLA는 10 μm, DLP는 25 μm, Polyjet 는 16 μm이었으나, FDM 은 50 μm이므로이로인하여정확도가상대적으로낮다. 이러한연구결과는 Keating et al(2008) 의연구결과와동일함을확인하였다. 가속노화실험후에도 FDM의 RMS 값이가장크게나타나나머지 3종의 3D 프린터에비해체적안전성이가장낮은것을확인하였다. 특히가속노화실험후 FDM의 RMS 값은 292 μm로일반적인교정장치제작에서의허용오차범위 (250 μm ) 를넘는큰변형률을보이고있다 (Zilberman et al., 2003). 이는FDM 방식 3D 프린터에사용되는열가소성필라멘트수지가온도변화에따른열적팽창과수축이상당히크므로, 장기간보관에있어보관장소의온도변화에주된영향을받을것으로사료된다. 따라서본연구결과를토대로 FDM 방식의 3 D 프린터로출력된모형은장기간보관후사용하는것을권장하지않는다. 본연구에사용된모든 3D 프린팅된모형은가속노화전과후의 RMS 값이통계적유의차가있는것으로확인되었다 (P<0.05). 해당결과를교정장치제작에적용할경우, FDM 방식을제외한 3종의 3D 프린터출력물에서는교정장치제작에사용해도무방한것으로확인되었다 (Hazeveld et al., 2014). 하지만투명교정과정에서치아이동량이 0.2 mm인경우, 3D 프린팅된모형의장시간보관으로인한불규칙적변형이교정력에영향을줄수있을것으로예상되므로투명교정장치제작에필요한 3D 프린팅된모형은한꺼번에출력하여장기간보관하지말고필요시바로출력할것을권장한다. 기존의투명교정장치는석고모형을기반으로수작업으로제작되므로기공사의경험또는숙련도에의해최종결과물에많은차이를나타내기도한다. 또한, 아무리숙련도가높은기공사가투명교정을제작한다하더라도치아의이동량을정확하게조절하는작업은한계가있다. 특히하나의모형을이용해여러단계의투명교정장치를생산하다보면작업오 차가커져환자가장치를사용하지못하는치료실패의원인이되기도하였다. 이에반하여 CAD 작업을통해제작된투명교정장치는치아이동을쉽게측정하여수작업에서생긴오류를최소화하여치료의성공률을높일수있을것이며이로인해환자의내원횟수나진료시간을현저히줄이는것이가능해졌다 (Luthard et al., 2009). 또한모형스캐너로스캔된이미지파일은 전송을통해여러장소에서출력이가능하므로물류의효율성및치과의사-기공사간의커뮤니케이션이원활해질수있다 (Delong et al., 2003). 그러나가속노화실험결과를토대로 3D 프린팅된모형은장기간보관시체적안정성이감소되므로여러단계의교정장치제작용모형들을한꺼번에 3D 프린터로출력하여투명교정진료에반영하기보다는환자의내원일정에맞춰교정장치제작용모형을출력하여사용하는것이정확한투명교정장치제작및사용에도움이될것으로판단된다. Ⅴ. 결론본연구에서는현재치과교정영역에서새롭게도입되고있는 4종 (SLA, DLP, Polyjet 및 FDM 방식 ) 3D 프린터들의원본, 출력물, 및가속노화후의출력물간의 RMS 값을측정하여, 원본과출력물간의정확도및가속노화전 후의출력물간의변형도를비교평가하였다. 1. 원본모형스캔이미지와 4종의 3D 프린터로출력된모형의스캔이미지를색지도측정법으로중첩시킨결과, FDM 방식으로출력된모형의스캔이미지가원본과의편차가가장큰것을확인하였다. 2. 원본모형스캔이미지와 3D 프린팅된모형의스캔이미지간의 RMS 값을계산한결과, Polyjet(41.60 μm ) < DLP(44.52 μm ) < SLA(48.60 μm ) < FDM(55.46 μm ) 순으로확인되었고, 각실험군간의 RMS 값이모두통계적인유의차를나타내었다 (P<0.05). 3. 원본모형스캔이미지와가속노화후의 3D 프린팅된모형의스캔이미지간의 RMS 값을계산한결과, Polyjet(63.56 μm ) < SLA(68.04 μm ) < DLP(72.10 μm ) < 58

7 FDM( μm ) 순으로확인되었고, 각실험군간의 RMS 값이모두통계적인유의차를나타내었다 (P<0.05). 4. 가속노화전 후의 3D 프린팅된모형의스캔이미지간의 RMS 값을계산한결과, 네가지실험군모두가속노화전 후의 RMS 값이모두통계적인유의차를나타내었다 (P<0.05). 이상의결과를토대로 FDM을제외한나머지 3D 프린터들의출력물에대한원본과의정확도는비교적우수하여투명교정장치제작용모형출력에사용해도무방하나, 가속노화시험결과를토대로장기간보관시에는모든 3D 프린터의출력물들의체적안정성이감소되므로 3D 프린팅된투명교정장치제작용모형은한꺼번에출력하여장기관보관하지말고, 사용시점에맞춰모형을출력하여사용하는것이더바람직하다고판단된다. Ⅵ. 참고문헌김태원 (2005). 투명교정장치의이론과실제. 서울 : 명문출판사. P ASTM F (2016). Standard Guide for acceleration Aging of Sterile Barrier Systems for Medical Devices Aletta Hazeveld, James J. R. Huddleston Slater, Yijin Ren (2014). Accuracy and reproducibility of dental replica models reconstructed by different rapid prototyping techniques. Am J Orthod Dentofacial Orthop 145: Beguma Z, Chhedat P (2014). Rapid prototyping--when virtual meets reality. Int J Comput Dent. 17(4): de França DG, Morais MH, das Neves FD, Barbosa GA (2015). Influence of CAD/CAM on the fit accuracy of implant-supported zirconia and cobalt-chromium fixed dental prostheses. Prosthet Dent 113:22-8. Delong R, Heinzen M, Hodges JS, Ko CC, Douglas WH (2003). Accuracy of a system for creating 3D computer models of denal arches. J Dent Res 90: Hazeveld A, Huddleston Slater JJ, Ren Y (2014). Accuracy and reproducibility of dental replica models reconstructed by different rapid Prototyping techniques. Am J Orthod Dentofacial Orthop 145: International Organization for standardization. ISO Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definitions. Geneva: ISO;1994. Availabel at: iso/ store.htm. International Organization for standardization. ISO Packaging for terminally sterilized medical devices Part 1: Requirements for materials, sterile barrier systems and packaging systems. Geneva: ISO;2006. Availabel at: International Organization for standardization. ISO Packaging for terminally sterilized medical devices Part 2: Validation requirements for forming, sealing and assembly processes. Geneva: ISO;2006. Availabel at: Keating AP, Knox J, Bibb R, Zhurov AI (2008). A comparison of plaster, digital and reconstructed study model accuracy. J Orthod 35: Kim Jh, Kim JH, Kim HY (2011). A study on common errors in digital impressions: An example of CEREC AC. J Korean Acad Dent Tech 33: Kim JH. KIim KB, Kim WC1, H (2015). Influence of various gypsum materials on precision of fit of CAD/CAMfabricated zirconia copings. Dental Materials Journal 34: Lee KY, Cho JW, Chang NY, Chae JM (2015). Accuracy of three-dimensional printing for manufacturing replica teeth. Korea J Orthod 2015: Liu Q, Leu MC, Schmitt SM (2006) Rapid prototyping in dentistry: technology and application. Int J Adv Manut Technol 29: Luthardt RG, Koch R, Rudolph H, Walter MH (2006). Qualitative computer aided evaluation of dental 59

8 impressions in vivo. J Dent 22: Masood SH, Rattanawong W, Iovenitti P (2003). A generic algorithm for a best part orientation system for complex parts in rapid prototyping. Journal of Materials Processing Technology 139:110-6, 20. Massimo Martorelli (2013). A comparison between customized clear and removable orthodontic appliances manufactured using RP and CNC techniques. Dent Mater 29:1-10. Quimby Ml, Vig KW, Rashid RG, Firestone AR (2004). The accuracy and reliability of measurements made on computer-based digital models. Angel Orthod 74: R. G. Luthard, A. Weber, H. Rudollph, S. Quaas, and M (2009). Walter Design and production of dental prosthetic restoration: basic research on dental CAD/CAM technology, Int J Comput Dent 5: Sachiko TOMITA (2005). Machining Accuracy of CAD/CAM Ceramic Crowns Fabricated with Repeated Machining Using the Same Diamond Bur. Dental Materials Journal 24: Sang-Ik Bak (2006). The comparison between manual and according to the degree of crowding. Korea University Graduate School of Clinical Dentistry, Department of Orthodontics, Masters degree. Schaefer O, Watts DC, Sigusch BW, Kuepper H, Guentsch A (2012). Marginal and internal fit of pressed lithium disilicate partial crowns in vitro: a threedimensional analysis of accuracy and reproducibility. Dent Mater 28: shalish M, Cooper-Kazaz R, Ivgi I, Canetti L, Tsur B, Bachar E, et al. (2012). Adult patients` adjustablility to orthodontic appliances. Part I: a comparison between Labial, Lingual, and InvisalignTM. Eur J Orthod 34: Singhal SK, Jain PK, Pandey PM (2008). Adaptive slicing for SLS prototyping. Computer-Aided Design and Applications 5: Stampfl J, Liska R (2005). New materials for rapid prototyping applications. Macromol Chem Phys 206: Stevens DR, Flores-Mir C, Nebbe B, Raboud DW, Heo G, Major PW (2006). Validity, reliability,and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements. Am J Orthod Dentofacial Orthop 129: Wong BH (2002). Invisalign A to Z. American Journal of Orthodontics and Dentofacial Orthopedics 121: Zhao, Laperriere L (2000). Adaptive direct slicing of the solid model for rapid prototyping. International Journal of Production Research 38: Zilberman O, Huggare JA, Parikakis KA (2003). Evaluation of the validity of tooth size and arch width measurements using conventional and threedimensional virtual orthodontic models. Angel Orthod 73:

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