Comparative analysis on reproducibility among 5 intraoral scanners: sectional analysis according to restoration type and preparation outline form

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1 J Adv Prosthodont 2016;8: Comparative analysis on reproduibility among 5 intraoral sanners: setional analysis aording to restoration type and preparation outline form Ji-Man Park* Department of Prosthodontis, Seoul National University Gwanak Dental Hospital, Seoul, Republi of Korea PURPOSE. The trueness and preision of aquired images of intraoral digital sanners ould be influened by restoration type, preparation outline form, sanning tehnology and the appliation of power. The aim of this study is to perform the omparative evaluation of the 3-dimensional reproduibility of intraoral sanners (IOSs). MATERIALS AND METHODS. The phantom ontaining five prepared teeth was sanned by the referene sanner (Dental Wings) and 5 test IOSs (E4D dentist, Fastsan, itero, Trios and Zfx Intrasan). The aquired images of the sanner groups were ompared with the image from the referene sanner (trueness) and within eah sanner groups (preision). Statistial analysis was performed using independent two-samples t-test and analysis of variane (α=.05). RESULTS. The average deviations of trueness and preision of Fastsan, itero and Trios were signifiantly lower than the other sanners. Aording to the restoration type, signifiantly higher trueness was observed in rown and inlay than in bridge. However, no signifiant differene was observed among four sites of preparation outline form. If ompared by the harateristis of IOS, high trueness was observed in the group adopting the ative triangulation and using powder. However, there was no signifiant differene between the still image aquisition and video aquisition groups. CONCLUSION. Exept for two intraoral sanners, Fastsan, itero and Trios displayed omparable levels of trueness and preision values in tested phantom model. Differene in trueness was observed depending on the restoration type, the preparation outline form and harateristis of IOS, whih should be taken into onsideration when the intraoral sanning data are utilized. [J Adv Prosthodont 2016;8:354-62] KEYWORDS: Intraoral sanner; Digital impression; Reproduibility of intraoral sanner; Trueness; Preision INTRODUCTION Corresponding author: Ji-Man Park Department of Prosthodontis, Seoul National University Gwanak Dental Hospital, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republi of Korea Tel : , jimarn@snu.a.kr Reeived February 5, 2016 / Last Revision June 24, 2016 / Aepted August 8, The Korean Aademy of Prosthodontis This is an Open Aess artile distributed under the terms of the Creative Commons Attribution Non-Commerial Liense ( org/lienses/by-n/3.0) whih permits unrestrited non-ommerial use, distribution, and reprodution in any medium, provided the original work is properly ited. This work was supported by the Basi Siene Researh Program through the National Researh Foundation of Korea (NRF) funded by the Ministry of Siene, ICT & Future Planning (NRF-2013R1A1A ). 354 With the reent aeleration of the appliation of digital tehnology in the dental mediine, various intraoral sanners (IOSs) that an aquire intraoral images without using the impression material have been introdued in addition to the existing CAD/CAM system. 1 Aording to Nedelu et al. and Shaefer et al., 2,3 IOS an be lassified into the still image aquisition and video aquisition methods aording to the image reombination. Of the IOS distributed urrently in use, CEREC AC Blueam, E4D dentist and itero (first generation) adopted the former method while the latter is adopted by E4D NEVO, Fastsan, Lava COS, Trios and Zfx Intrasan. Due to its nature that the sanner itself has to move in the narrow oral avity as ompared with the desktop sanner, there are various sanning tehnologies. For instane, E4D is operated by optial oherene tomography. Also, ative triangulation is applied for CEREC AC Blueam, Fastsan and Lava COS while onfoal mirosopi tehnology is adopted in itero, Trios and Zfx Intrasan. The depth of field depends pissn , eissn

2 Comparative analysis on reproduibility among 5 intraoral sanners: setional analysis aording to restoration type and preparation outline form on these sanning tehnologies and has an influene on the learning urve of the devie. The powder is used to enhane sanner s reognition rate and shorten san time by reduing refletion on the tooth surfae with various materials. CEREC AC Blueam, Fastsan and Lava COS always require powder. On the other hand, E4D dentist does not require powder in most ases and itero, PlanSan, Trios and Zfx Intrasan do not require the appliation of refletive agent. 4 The literatures omparing the auray of IOSs largely onerned two subjets; the measurement of the internal gap of fabriated rowns and the measurement of the deviations after superposition of two images. There are various studies on these. In partiular, the former internal gap study inludes Seelbah et al. s studyon the single rown and Shaefer et al. s on the partial rown while the latter image superposition study inludes Nedelu et al. s study on simplified and standardized san body, Ender et al. s on full arh, and Patzelt et al. s on edentulous jaws. 2,3,5-10 Papaspyridakos and Wismeijer reported the investigation on the auray of digital implant impressions with IOS In the study on the measurement of the gap of rowns, there is a limitation in determining the performane of the sanner itself due to the unontrollable fators ourring in the fabriation of rowns while the image superposition study suggests neither the relationship with the atual rown nor the data for the speifi important sites suh as margins sine this is a mere omparison of images. If the data on eah setion of the avity form aording to various restorations are measured and ompared, it will be possible to ompare the 3-dimensional reprodution apability of digital IOSs that expresses the ruial parts of the abutment affeting the fits of rowns. The aim of this study is to perform the omparative evaluation of the 3-dimensional reproduibility of several intraoral sanners (IOS) by the restoration type. For this purpose, eah intraoral sanner s preision and trueness were investigated by superposing 3-dimensioanl images and measuring the deviation at the main sites of the abutment in eah setion. Additionally, the differenes depending on the sanning tehnology and harateristis of the sanner were ompared and analyzed. The primary null hypothesis was that the 3-dimensional reproduibility of intraoral sanners did not differ by the restoration type and preparation loation. The seondary null hypothesis was that the trueness of 3-dimensional images were not influened by the sanning tehnology and harateristis of the sanners. MATERIALS AND METHODS In this study, a phantom model ontaining prefabriated abutment teeth was prepared. Right maxillary inisor and anine were seleted as abutment teeth for a 3-unit fixed dental prosthesis. Right maxillary seond molar was designated as an abutment for MO inlay, and the right mandibular seond molar as that for a rown. Artifiial tooth with an ideal shape were arranged at the left dentition for the olusal stability during the digital bual bite registration (Fig. 1). In order to obtain standardized preparations and to avoid an arbitrary preparation by a pratitioner, the abutment teeth that had been prepared in preision proessing by the manufaturer (A50H-set Prepared teeth assortment; Nissin) were used. To keep the refletivity similar to the natural tooth, the metal tooth was not used. The setsrews whih fixate the individual teeth were tightened firmly and yanoarylate ement was applied to prevent unwanted srew loosening. The tooth on the phantom was not removed or added and no external fore was applied during the experiment. All the experiments were arried out at 23 ± 1 C and 50 ± 5% relative humidity. In order to obtain the referene STL file, a desktop sanner (7 Series; Dental Wings In.) with the trueness of 15 µm was used. This sanner uses a laser light soure with 5 axes of freedom, and thus is favorable for reprodution of an underut or ompliated shapes. Also, it has a high sanning apaity ( mm), whih enables sanning of a full arh restoration. 5 types of IOSs were used in this study: itero (1st generation; ALIGN TECHNOLOGY, INC.), E4D dentist (initial version; E4D Tehnologies), Zfx Intrasan (Zfx GmhH), Trios (2 nd generation; 3shape A/S) and Fastsan (IOS Tehnologies, In.). These were lassified by the sanning tehnology suh as Fastsan with the ative triangulation, itero, Trios and Zfx Intrasan with the onfoal mirosopy tehnology, and E4D dentist with the optial oherene tomography (Table 1). Fig. 1. Dental models with various preparation designs. Right maxillary inisor and anine (#11, 13); 3-unit fixed dental prosthesis, right maxillary seond molar (#17); MO inlay, and right mandibular seond molar (#47); rown. The Journal of Advaned Prosthodontis 355

3 J Adv Prosthodont 2016;8: Table 1. Charateristis of intraoral sanners System Manufaturer Sanner tehnology Light soure Aquisition Neessity of oating E4D dentist (initial version) D4D Tehnologies Optial oherene tomography Laser Still imaging None but oasionally Fastsan IOS Tehnologies Ative triangulation and Sheimpflug priniple Laser Still imaging Yes itero (1 st generation) Align Tehnologies Parallel onfoal mirosopy Red laser Still imaging None Trios (2 nd generation) 3shape A/S Confoal mirosopy Not dislosed Video None Zfx Intrasan ZFX GmbH Confoal mirosopy and Moiree effet detetion Laser Video None A phantom ontaining prepared teeth was sanned using 5 different IOSs, and the respetive test group was sanned 4 times. Sanning was performed aording to the instrution of eah manufaturer. In itero and E4D groups, sanning was guided aording to software instrutions and abutment san was finished first, followed by remaining teeth sanning. When sanning with Zfx Intrasan and Trios, olusal sweep was done first and was followed by bual and lingual sweeps in ase of upper arh. Bual and lingual sweeps were hanged for lower arh san. In ase of Fastsan, posterior setions on both sides and anterior setion were sanned separately and stithed together afterwards. Sine Fastsan required the use of spray, its san was performed at the last turn. 4 pairs of 3D data were aquired for eah IOS. Data were obtained diretly from the sanner of Fastsan and Zfx Intrasan while files were obtained from the manufaturer of E4D dentist, itero and Trios. Aording to ISO 12836, the deviation of measurements between the referene model and the intraoral san model was termed the trueness of impression tehnique, and the deviation of measurements between digital models of the same intraoral sanner was preision of impression tehnique. For the image superposition, a reverse engineering program (Rapidform; INUS Tehnology In.) was used. The referene STL file and intraoral san STL files were superposed. Superposition was performed as follows: three points A, B and C were spotted on images, and while mathing these, the two data were moved loser to eah other, then, automerging was performed by omputation using a ommand fine (Fig. 2A). After superposition, the tooth model was divided in the mesiodistal, buolingual, and right and left diagonal diretions into a total of 8 setions. For the trueness investigation, the distane between the referene data and intraoral san data were measured at 4 points (marginal, axial, line-angle, olusal) on eah setion (Fig. 2B). In ase of preision measurement, the distane between two intraoral sans within the same group at the aforementioned points on eah setion. For the mesiodistal and buolingual omparison, mesial, diatal, bual, and lingual setions were investigated and diagonal setions were exluded in the measurement. The inlay was measured likewise. After superposition, setion was reated in the mesiodistal and buolingual diretion of the tooth model, and the distane between the two data were measured at the orresponding 4 points in A B C D Fig. 2. Illustration of the setioning of the superposed datasets and seleted sites from preparation ouline form. (A) setion lines of rown and bridge groups (setions 1, 3, 5, and 7 were investigated for the mesiodistal and buolingual omparison). (B) measured sites for rown and bridge groups. (C) setion line of inlay group (setions a and b were inspeted for the box and non-box omparision). (D) sites from preparation outline form for inlay group. 356

4 Comparative analysis on reproduibility among 5 intraoral sanners: setional analysis aording to restoration type and preparation outline form these setions. For the omparison of box and non-box regions, setions in the mesiodistal diretions were investigated (Fig. 2C and Fig. 2D). The differene in trueness and preision of intraoral sanners, and trueness aording to preparation design, preparation site, and sanning tehnology were verified by analysis of variane (ANOVA). When the differene was signifiant, Tukey HSD test was used in multiple omparisons. In addition, independent two-samples t-test was used to ompare the trueness aording to image aquisition and neessity of oating. Data were analyzed using a statistial program IBM SPSS version 18.0 (IBM Corporation). The signifiane level was set at P =.05. RESULTS Eah sanner had a different resolution, leading to the differene in the details of the model, and the number of polygones were in the order of itero (42,687), Trios (28,280), Fastsan (20,210), E4D dentist (17,607), and Zfx intrasan (10,432) (Fig. 3). Sanners used in this study showed the deviations in trueness and preision of 70.1 μm and 58.9 μm on average, respetively. The average deviations in trueness and preision of Fastsan, itero and Trios were in the range of 40 to 60 μm and 10 to 30 μm, respetively, while those of Zfx Intrasan and E4D dentist were in the range of 80 to 120 μm and 90 to 140 μm, respetively, whih were signifiantly higher than the other three sanners (Table 2 and Fig. 4). In omparison by the restoration type, signifiantly higher trueness was observed in rown and inlay than in bridge irrespetive of intraoral sanners. While no signifiant differene in overall mean trueness was observed among margin, axial wall, line-angle, and olusal site, the trueness at line-angle was higher than those at the others in E4D dentist group. In omparison by the setion, the mesiodistal diretion showed signifiantly higher devia- E4D dentist Fastsan itero Trios Zfx Intrasan Fig. 3. Number of polygons for seleted maxillary inisor for the omparison of the eah IOS s resolution. Table 2. Trueness and preision of eah intraoral sanner Sanner Trueness Mean value ± SD (µm) Preision Mean value ± SD (µm) E4D dentist ± 80.7 a 97.6 ± b Fastsan 45.2 ± ± 24.4 itero 52.1 ± ± 22.5 Trios 49.7 ± ± 12.1 d Zfx Intrasan 89.4 ± 64.2 b ± a Overall mean 70.1 ± ± 89.2 Dental wings (referene sanner) Not determined ( 15 manufaturer) 35.3 ± 42.4 F 132.3** 339.7** P value Multiple omparison: a > b >, P <.01: **, P <.05: * The Journal of Advaned Prosthodontis 357

5 J Adv Prosthodont 2016;8: Trueness Preision E4D dentist a a Fastsan itero Trios Zfx Intrasan b d b µm Fig. 4. Illustration of absolute mean trueness and preision values of intraoral sanners. Same letters denote signifiant differenes in between the groups at the 5% signifiane level. tion than the buolingual diretion. Also, while the trueness is lower in the box overall, there was no signifiant differene in the trueness between the box and the non-box with Fastsan and itero (Table 3 and Table 4). Trueness was observed to be in the inreasing order of Fastsan with the ative triangulation, itero, Trios and Zfx Intrasan with the parallel onfoal tehnology, and E4D dentist with the optial oherene tomography. In addition, the group using powder displayed lower trueness whih means higher auray. On the other hand, no signifiant differene in trueness was observed between the still image aquisition and the video aquisition groups (Table 5). DISCUSSION The trueness and preision of IOS are among the most fundamental evaluation elements for the linial appliation of the digital impression method. Although the evaluation method via image superposition has a fundamental error and limitation in the seletion and superposition of random points on the program, and does not neessarily suggest the relationship with the atual restoration, it an still play an important role in the omparative evaluation of eah IOS. In this in vitro study, the first null hypothesis was rejeted beause in general, the intraoral sanner had lower trueness Table 3. Trueness aording to the preparation design Sanner Crown Inlay Bridge F P value E4D dentist 95.7 ± 67.4 b 95.2 ± 62.6 b ± 89.0 a 11.8**.000 Fastsan 39.0 ± 26.6b 32.9 ± 19.3b 52.8 ± 32.3 a 21.9**.000 itero 38.1 ± 21.4b 35.3 ± 25.5b 65.3 ± 44.5 a 36.9**.000 Trios 28.2 ± 19.3b 50.8 ± 42.2 a 60.0 ± 36.5 a 37.2**.000 Zfx Intrasan 70.3 ± 50.3b 94.5 ± 57.2 a 97.1 ± 70.8 a 8.0**.000 Overall mean 54.3 ± 48.4 b 61.7 ± 52.5 b 81.2 ± 65.5a 50.6**.000 Multiple omparison: a > b, P <.01: **, P <.05: * 358

6 Comparative analysis on reproduibility among 5 intraoral sanners: setional analysis aording to restoration type and preparation outline form Table 4. Trueness aording to the preparation site and in the inlay box Sanner Margin Axial wall Line-angle Olusal P value Mesio distal Buo lingual P-value Box Non-box P-value E4D dentist ± 82.4 b ± 69.8 b ± 97.6 a 95.9 ± 62.6 b.000** ** ± 97.5 a ± 60.7 b ** ± 59.5 a ± 23.7 b Fastsan 45.1 ± ± ± ± ± 41.7 a 39.0 ± 19.9 b.000** 39.3 ± ± itero 54.5 ± ± ± ± ± 53.5 a 48.0 ± 27.2 b.000** 31.0 ± ± Trios 54.5 ± ± ± ± ± 46.3 a 40.0 ± 22.9 b.000** ** ± 34.6 a ± 7.8 b Zfx Intrasan 93.1 ± ± ± ± ± ± ± 54.4 a 65.9 ± 25.6 b.016* Overall mean 72.0 ± ± ± ± ± 72.4 a 59.7 ± 47.3 b.000** ** ± 51.5 a ± 26.4 b Multiple omparison: a > b, P <.01: **, P <.05: * Table 5. Trueness aording to the harateristis of IOS Charate ristis Mean Trueness Image aquisition Neessity of oating P value Still image Video Coating None P value Confoal mirosopy Sanning tehnology Ative triangulation Optial oherene tomography P value 70.5 ± ± ± 29.8 b 76.3 ± 64.0 a.000** 63.7 ± 51.5 b 45.2 ± ± 80.7 a.000** Multiple omparison: a > b >, P <.01: **, P <.05: * in the inlay box, and it is onsidered that this was potentially aused by the limitation in the san depth of IOS and the adjaent teeth underut that hampered the image aquisition. For the trueness depending on the sanning tehnology and harateristis of sanners, the seond null hypothesis was rejeted beause the aquired image displayed deviations in trueness by the sanning tehnology and harateristis of sanners. A desktop sanner, Dental Wings 3D sanner, was used as a referene sanner as in previous studies, and the reason that an IOS was not seleted as a referene sanner was that the aumulation of errors aused by sudden ations during sanning due to the high degree of freedom ould lead to the bending of the model. A trueness of up to 15 μm was reported on the referene sanner for a single measurement ase of the plaster model, 18 and it was shown that the internal and marginal gaps of the rown on the experimental model fabriated using this sanner were up to the range of to μm. 19 In this study, the preision of this referene sanner was measured, whih was 35.3 ± 13.9 μm. There have been many studies whih evaluated the performane of intraoral sanners by measuring fit of restoration or superimposing san data. Seelbah et al. fabriated a single rown using CEREC, itero and Lava COS, and measured the internal gap and marginal fit, whih were 29 to 88 μm and 30 to 41 μm, respetively, in agreement with the values measured on the rown fabriated by the onventional method. 5 In a study of van der Meer et al. using the implant san body, the distane errors between the san bodies measured by CEREC, itero and Lava COS were 79.6 to 81.6 μm um, 61.1 to 70.5 μm and 14.6 to 23.5 μm, respetively. 13 Mehl et al. analyzed the auray by superposing the model data aquired from a desktop sanner and CEREC AC Blueam, and reported that the deviation was 19.2 μm for a single tooth and 35 μm for a quadrant. 20 Kim et al. sanned a polyurethane model fabriated by milling proess using san data of itero and a traditional plaster model with a desktop sanner, and ompared the data. 21 They reported that the deviation was 23.9 ± 17.6 μm for a single tooth and the model fabriated using IOS showed a signifiantly higher deviation than the traditionally fabriat- The Journal of Advaned Prosthodontis 359

7 J Adv Prosthodont 2016;8: ed model, whih, however, was linially aeptable. Ender et al. reported that a deviation of 58.6 μm was observed in the omparison of auray in the full arh models between CEREC AC system and a referene sanner, and a deviation of 32.4 μm was observed in the analysis of preision by omparing between the CEREC data. 22 They onluded that this had a signifiantly lower auray than the traditional method. In their further study, it was reported that the deviations in auray and preision for CEREC Blueam, itero, Lava COS and Omniam were up to 29.4 to 44.9 μm um and 19.5 to 63.0 μm, respetively, 8 whih leads to a onlusion that these IOSs ould be applied to full mouth san ases within the limitations of in-vitro study. Patzelt et al. also reported studies on the auray of full arh san and fully edentulous jaw digitization. 9,10 As the intraoral sanner is a handheld devie, the image stithing error from the uneven and abrupt movement of sanner wand might ause the deformation of san data. These studies have a great signifiane beause they were foused on the deformation of entire arh. This study was onduted to investigate another harateristi of intraoral sanner. The depth of field is related to not only the diffiulty of sanning but also the auray of san data. Learning urve of intraoral sanners with narrow depth of field is very long beause the operator has to keep distane from patient s teeth while wathing omputer display. When the maximum range that intraoral sanner an reah is short, the image aquisition ould not be possible at the long tooth with deep preparation enlosed by tall adjaent teeth. In this study, the auray of various intraoral sanners was evaluated at the mirosopi level of the abutment teeth by setioning and piking up the anatomi strutures whih might be ritial for the adaptation of restorations. In studies that ompared the auray of IOSs, Nedelu et al. analyzed the auray and preision of 4 IOSs by the superposition method based on a desktop sanner as a referene, showing that the auray and preision of CEREC were better than those of E4D dentist. 2 They suggested that this was beause E4D dentist did not have suffiient transition area that was relatively learly defined, and muh noise appeared on the surfae. In this study, itero displayed better results ompared to E4D dentist and Zfx Intrasan, whih was in agreement with previous studies. Shaefer et al. reported that marginal disrepany of a partial rown (MOD inlay) fabriated using itero was up to 90 μm, while An et al. analyzed the marginal fits of zironia oping fabriated using itero by a replia tehnique, whih was shown to be up to μm for a single tooth. 3,23 Also, Keul et al. performed experiments similarly and reported that the marginal opening of 4-unit zironia framework was up to μm. 24 In our study, an abutment sanned by itero displayed higher deviations in the inreasing order of the inlay, rown and bridge, and this trend is onsistent with preeding studies. Also, in general, the trueness of IOS was lower in the fixed dental prosthesis, whih an be attributed to the errors in the image aquisition and stithing proesses due to the presene of the glossy ponti spae with less surfae harateristis. Brawek et al. measured the fits of the rown fabriated using Lava COS and CEREC AC, and showed that the internal gap was larger than the marginal gap. 25 They suggested that this larger internal gap ould be attributed to the fat that there was a lower limit in the size of the milling tool for proessing of the interior of the restoration, and thus the software relief had to be made to proess the angled orner of the interior of the restoration, whih was ompounded by the errors in replia tehnique. 26 In this study, the deviations between the marginal and internal gaps did not show any signifiant differene unlike previous studies, whih an be attributed to the differene in the experimental method sine this study only ompared the abutment forms observed on the san data. Also, in omparison of setions, the trueness in the mesiodistal setion was lower than in the buolingual setion, and it is onsidered that this was beause multiple sans were neessary at the mesiodistal site due to the underut by adjaent teeth, and subsequently the amount of data to be stithed was larger. There are various fators that affet the reproduibility of an IOS, inluding the sanning tehnology, data proessing algorithm, whether or not to use powder and image aquisition method. Ative triangulation is a traditional sanning tehnology and has been frequently applied in the desktop sanner, whih offers the highest trueness if the ondition is right. In omparison, the parallel onfoal tehnology does not require a ertain distane for fousing, and thus images an be aquired regardless of whether the sanner tip is attahed to the teeth when the oral avity is sanned. On the other hand, the optial oherene tomography has a high resolution that an reate an image of the miromorphology of the abutment by ombining the optial interferene phenomenon and the onfoal mirosopy tehnology. In this study, the deviations in trueness and preision inreased in the order of Fastsan with the ative triangulation tehnology, itero, Trios and Zfx Intrasan with the parallel onfoal tehnology, and E4D dentist with the optial oherene tomography tehnology. In a study of Nedelu et al. on CEREC, E4D dentist, itero and Lava COS, the better result was obtained in the order of the ative triangulation, onfoal mirosopy and optial oherene tomography, onsistent with this study. 2 However, Ender et al. and Seelbah et al. studied using CEREC, itero and Lava COS, and reported no notable differene between the ative triangulation and parallel onfoal sanners, 5,7 while Shaefer et al. suggested that the onfoal mirosopy displayed higher auray than the ative triangulation. 3 These latter studies are in disagreement with our study, and thus yet another different result may be expeted in the atual linial setting, whih warrants further studies on this matter. In studies of Ender et al. and Seelbah et al., similar auray was observed regardless of the use of powder while Shaefer et al. observed a signifiant higher auray 360

8 Comparative analysis on reproduibility among 5 intraoral sanners: setional analysis aording to restoration type and preparation outline form in the powder free group. 3,5,7 In ontrast, Nedelu et al. suggested that the group using powder showed higher auray, in onsistent with our study. 2 In addition, they prepared an experimental group with exessive spray oating, and investigated its impat on the auray, whih yielded no signifiant differene. Rupf et al. reported that of fine and ultrafine partiles were aumulated per minute on average under onventional dental sution if sanning spray was applied, and reommended high volume evauation for the prevention of the exposure to fine or ultrafine partiles. 27 Although the use of powder an inrease the sanning speed and the ease of san, inonveniene to patients may be aused during the appliation and removal proess of powder, and the powder remaining in the oral avity may exert a harmful effet on the body. Shaefer et al. and Nedelu et al. lassified IOSs largely into video aquisition and still image aquisition types depending on the sanning method, 2,3 and Ender et al. analyzed the auray of Blueam and Lava COS by superposing images from these sanners with those of the referene sanner, whih showed that there was no signifiant differene in the deviations between the video aquisition and still image aquisition methods. 6 Their further study on CEREC Blueam, CEREC Omniam, itero and Lava COS showed similar results. 7,8 Also, the studies of Shaefer et al. and Seelbah et al. did not show any signifiant differene in the auray between the video aquisition and still image aquisition types. 3,5 Likewise, in this study, a signifiant differene in trueness between the two sanning methods was not observed. However, the video aquisition method has a lear advantage that sanning is onvenient and images an be monitored during sanning. A limitation of this study is that the data on the restoration itself fabriated using IOSs ould not be provided. Also, as atual sanning onditions were not taken into onsideration in this study, the lower trueness is expeted in the atual linial setting than in this study due to the level of patient s ompliane, the skill of a pratitioner, the presene of saliva during sanning, refletivity of the tooth and the intraoral struture. Therefore, it is onsidered that further study using the final restoration in the linial setting is neessary. CONCLUSION Exept for 2 intraoral sanners, Fastsan, itero and Trios displayed omparable levels of trueness and preision values in tested phantom model. The differene in trueness was observed depending on the restoration type, the preparation out line form, the sanning tehnology and the appliation of power. ORCID Ji-Man Park REFERENCES 1. Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. 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