This study was supported by a grant of the Korea Health Technology R&#38;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &#38; Welfare (grant number: HI18C0435).

1. Master specimen preparation
<ol>
	<li>Model preparation
	<ol>
		<li>Remove the artificial teeth (left and right canines, second premolar, and the second molar) on the mandibular complete-arch model with only 1/5 of the cervical portion left.</li>
	</ol>
	</li>
	<li>CAD design
	<ol>
		<li>Acquire the data of the master specimen with a reference scanner.</li>
		<li>Design the cylinders (with a top diameter of 2 mm and a cylinder height of 7 mm) on top of the trimmed six teeth with the reverse engineering software.</li>
		<li>Add three reference spheres (3.5 mm in diameter) posterior to the left second molar for the purpose of defining the reference 3D coordinate system from the reverse engineering software.</li>
		<li>Locate one sphere on the distal side of the distal and buccal side of the cylinder on the left second molar so that the coordinates of all the cylinders have positive values.</li>
		<li>Design the left second molar cylinder so that it is inclined 30&#176; medially and the right second molar cylinder so that it is tilted 30&#176; distally. Set the other cylinders at right angles from the model.</li>
	</ol>
	</li>
	<li>Metal 3D printing
	<ol>
		<li>Manufacture a phantom model with CoCr alloy by a metal 3D printer to serve as a patient&#8217;s dentition (Figure 1).</li>
	</ol>
	</li>
</ol>
2. Reference data acquisition and software analysis
<ol>
	<li>Scan the phantom with the testing intraoral scanner.
	<ol>
		<li>Obtain the reference image by scanning the metal phantom model with the industrial-level model scanner.</li>
	</ol>
	</li>
	<li>Establish a coordinate system by extracting points from reference spheres.
	<ol>
		<li>Load the reference image to the reverse engineering analysis software to calculate the reference coordinates of each cylinder position.</li>
		<li>Extract the sphere by selecting the Ref. geometry | Create | Sphere | Pick boundary points command and picking the four points on the surface of the reference sphere that are furthest apart from each other (Supplemental Figure 1 and Supplemental Figure 2).</li>
		<li>Calculate the center of three reference spheres.</li>
		<li>Use the Ref. geometry | Create | Plane | Pick points command to connect the centers of three spheres and create a plane (Supplemental Figure 3).</li>
		<li>Set the formed plane as XY plane.</li>
		<li>Select the Ref. geometry | Create | Plane | Offset plane command to create a tangent plane above the xy plane (Supplemental Figure 4).</li>
		<li>Create points where the tangent plane and two lingual spheres meet by choosing the Ref. geometry | Create | Point | Project on ref. plane command (Supplemental Figure 5).</li>
		<li>Generate a plane between the points created and the center of the two lingual spheres by using the Ref. geometry | Create | Plane | Pick points command (Supplemental Figure 6).</li>
		<li>Measure the distance from this plane to the center of the buccal sphere with the Inspection | Dimension | Linear command (Supplemental Figure 7).</li>
		<li>Create a parallel plane that passes through the midpoint of the buccal sphere with the Geometry | Create | Plane | Offset Plane command (Supplemental Figure 8).</li>
		<li>Set the formed plane as YZ plane (Supplemental Figure 9).</li>
	</ol>
	</li>
	<li>Set the x, y, and z axes.
	<ol>
		<li>Set the center of the buccal sphere as the &#8216;origin&#8217; of the coordinate system.</li>
		<li>Set a line parallel to the line connecting the center points of the remaining two spheres while traveling in the forward and backward direction of the model through the origin as the Y-axis.</li>
		<li>Set the line on the xy plane that passes the origin and is perpendicular to the y axis as the X-axis.</li>
		<li>Use the Ref. geometry | Create | Coordinate | Pick origin &#38; X, Y direction command to create a new coordinate system with the buccal sphere center as the origin (Supplemental Figure 10).</li>
		<li>Set the line perpendicular to the xy plane and passing through the origin as the Z-axis (Supplemental Figure 11).</li>
	</ol>
	</li>
	<li>Transfer this detail from the scan coordinate system to the newly established coordinate system.
	<ol>
		<li>Use the Ref. geometry | Bind to shell command to fix the geometries created during this process on top of the scan data (Supplemental Figure 12).</li>
		<li>Execute the Ref. geometry | Transform | Coordinate | Align coordinate command to transit from the basic coordinate system to the newly created coordinate system (Supplemental Figure 13).</li>
		<li>In this way, assign a coordinate system to the metal master specimen with reference to the three reference spheres (Supplemental Figure 14).</li>
	</ol>
	</li>
	<li>Extract the measurement points from the cylinders at the main area.
	<ol>
		<li>Extract the x, y, and z coordinates for the upper circle centers of six cylinders to be analyzed for the distortion of the specified regions by the reverse engineering process.</li>
		<li>For this, use the Ref. geometry | Create | Cylinder | Pick boundary points command and specify at least 10 points on the top border of the cylinder and designate the same amount of points on the ellipse that meets the tooth at the bottom of the cylinder (Supplemental Figure 15, Supplemental Figure 16, and Supplemental Figure 17).</li>
		<li>Obtain the extracted coordinates of the cylinder top center. Evaluate the 3D deformation at each position by comparing it with the coordinate values of the same cylinder of the digital impression acquired by the intraoral scanner to be evaluated.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>McLean, J. W., von Fraunhofer, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+estimation+of+cement+film+thickness+by+an+in+vivo+technique.">The estimation of cement film thickness by an in vivo technique.</a> British Dental Journal. 131 (3), 107-111 (1971).</li><li>Park, J. M., Hong, Y. S., Park, E. J., Heo, S. J., Oh, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+evaluations+of+cast+gold+alloy,+machinable+zirconia,+and+semiprecious+alloy+crowns:+A+multicenter+study.">Clinical evaluations of cast gold alloy, machinable zirconia, and semiprecious alloy crowns: A multicenter study.</a> Journal of Prosthetic Dentistry. 115 (6), 684-691 (2016).</li><li>Keul, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fit+of+4-unit+FDPs+made+of+zirconia+and+CoCr-alloy+after+chairside+and+labside+digitalization--a+laboratory+study.">Fit of 4-unit FDPs made of zirconia and CoCr-alloy after chairside and labside digitalization--a laboratory study.</a> Dental Materials. 30 (4), 400-407 (2014).</li><li>Ritter, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+chairside-milled+CAD/CAM+drill+guides+for+dental+implants.">Accuracy of chairside-milled CAD/CAM drill guides for dental implants.</a> International Journal of Computerized Dentistry. 17 (2), 115-124 (2014).</li><li>Grunheid, T., McCarthy, S. D., Larson, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+use+of+a+direct+chairside+oral+scanner:+an+assessment+of+accuracy,+time,+and+patient+acceptance.">Clinical use of a direct chairside oral scanner: an assessment of accuracy, time, and patient acceptance.</a> American Journal of Orthodontics and Dentofacial Orthopedics. 146 (5), 673-682 (2014).</li><li>Penarrocha-Oltra, D., Agustin-Panadero, R., Bagan, L., Gimenez, B., Penarrocha, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impression+of+multiple+implants+using+photogrammetry:+description+of+technique+and+case+presentation.">Impression of multiple implants using photogrammetry: description of technique and case presentation.</a> Medicina Oral, Patolodia Oral y Cirugia Bucal. 19 (4), e366-e371 (2014).</li><li>Kattadiyil, M. T., Mursic, Z., AlRumaih, H., Goodacre, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoral+scanning+of+hard+and+soft+tissues+for+partial+removable+dental+prosthesis+fabrication.">Intraoral scanning of hard and soft tissues for partial removable dental prosthesis fabrication.</a> Journal of Prosthetic Dentistry. 112 (3), 444-448 (2014).</li><li>Kim, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+experience+curves+between+two+3-dimensional+intraoral+scanners.">Comparison of experience curves between two 3-dimensional intraoral scanners.</a> Journal of Prosthetic Dentistry. 116 (2), 221-230 (2016).</li><li>Lim, J. H., Park, J. M., Kim, M., Heo, S. J., Myung, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+digital+intraoral+scanner+reproducibility+and+image+trueness+considering+repetitive+experience.">Comparison of digital intraoral scanner reproducibility and image trueness considering repetitive experience.</a> Journal of Prosthetic Dentistry. 119 (2), 225-232 (2018).</li><li>Muhlemann, S., Greter, E. A., Park, J. M., Hammerle, C. H. F., Thoma, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precision+of+digital+implant+models+compared+to+conventional+implant+models+for+posterior+single+implant+crowns:+A+within-subject+comparison.">Precision of digital implant models compared to conventional implant models for posterior single implant crowns: A within-subject comparison.</a> Clinical Oral Implants Research. 29 (9), 931-936 (2018).</li><li>Park, J. M., Hammerle, C. H. F., Benic, G. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Digital+technique+for+in+vivo+assessment+of+internal+and+marginal+fit+of+fixed+dental+prostheses.">Digital technique for in vivo assessment of internal and marginal fit of fixed dental prostheses.</a> Journal of Prosthetic Dentistry. 118 (4), 452-454 (2017).</li><li>Ender, A., Zimmermann, M., Attin, T., Mehl, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+precision+of+conventional+and+digital+methods+for+obtaining+quadrant+dental+impressions.">In vivo precision of conventional and digital methods for obtaining quadrant dental impressions.</a> Clinical Oral Investigations. 20 (7), 1495-1504 (2016).</li><li>Kim, R. J., Park, J. M., Shim, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+9+intraoral+scanners+for+complete-arch+image+acquisition:+A+qualitative+and+quantitative+evaluation.">Accuracy of 9 intraoral scanners for complete-arch image acquisition: A qualitative and quantitative evaluation.</a> Journal of Prosthetic Dentistry. 120 (6), 895-903 (2018).</li><li>Ender, A., Mehl, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+in+dental+medicine,+a+new+way+to+measure+trueness+and+precision.">Accuracy in dental medicine, a new way to measure trueness and precision.</a> Journal of Visualized Experiments. (86), e51374 (2014).</li><li>Ender, A., Mehl, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-vitro+evaluation+of+the+accuracy+of+conventional+and+digital+methods+of+obtaining+full-arch+dental+impressions.">In-vitro evaluation of the accuracy of conventional and digital methods of obtaining full-arch dental impressions.</a> Quintessence International. 46 (1), 9-17 (2015).</li><li>Ajioka, H., Kihara, H., Odaira, C., Kobayashi, T., Kondo, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Examination+of+the+Position+Accuracy+of+Implant+Abutments+Reproduced+by+Intra-Oral+Optical+Impression.">Examination of the Position Accuracy of Implant Abutments Reproduced by Intra-Oral Optical Impression.</a> PLOS ONE. 11 (10), e0164048 (2016).</li><li>Patzelt, S. B., Lamprinos, C., Stampf, S., Att, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+time+efficiency+of+intraoral+scanners:+an+in+vitro+comparative+study.">The time efficiency of intraoral scanners: an in vitro comparative study.</a> Journal of Americal Dental Association. 145 (6), 542-551 (2014).</li><li>Gan, N., Xiong, Y., Jiao, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+Intraoral+Digital+Impressions+for+Whole+Upper+Jaws,+Including+Full+Dentitions+and+Palatal+Soft+Tissues.">Accuracy of Intraoral Digital Impressions for Whole Upper Jaws, Including Full Dentitions and Palatal Soft Tissues.</a> PLOS ONE. 11 (7), e0158800 (2016).</li><li>Rehmann, P., Sichwardt, V., Wostmann, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoral+Scanning+Systems:+Need+for+Maintenance.">Intraoral Scanning Systems: Need for Maintenance.</a> International Journal of Prosthodontics. 30 (1), 27-29 (2017).</li><li>Patzelt, S. B., Emmanouilidi, A., Stampf, S., Strub, J. R., Att, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+full-arch+scans+using+intraoral+scanners.">Accuracy of full-arch scans using intraoral scanners.</a> Clinical Oral Investigations. 18 (6), 1687-1694 (2014).</li><li>Muallah, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+full-arch+scans+using+intraoral+and+extraoral+scanners:+an+in+vitro+study+using+a+new+method+of+evaluation.">Accuracy of full-arch scans using intraoral and extraoral scanners: an in vitro study using a new method of evaluation.</a> International Journal of Computerized Dentistry. 20 (2), 151-164 (2017).</li><li>Treesh, J. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complete-arch+accuracy+of+intraoral+scanners.">Complete-arch accuracy of intraoral scanners.</a> Journal of Prosthetic Dentistry. 120 (3), 382-388 (2018).</li><li>Patzelt, S. B., Vonau, S., Stampf, S., Att, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+the+feasibility+and+accuracy+of+digitizing+edentulous+jaws.">Assessing the feasibility and accuracy of digitizing edentulous jaws.</a> Journal of Americal Dental Association. 144 (8), 914-920 (2013).</li><li>Andriessen, F. S., Rijkens, D. R., van der Meer, W. J., Wismeijer, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applicability+and+accuracy+of+an+intraoral+scanner+for+scanning+multiple+implants+in+edentulous+mandibles:+a+pilot+study.">Applicability and accuracy of an intraoral scanner for scanning multiple implants in edentulous mandibles: a pilot study.</a> Journal of Prosthetic Dentistry. 111 (3), 186-194 (2014).</li><li>Gimenez, B., Ozcan, M., Martinez-Rus, F., Pradies, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+a+digital+impression+system+based+on+parallel+confocal+laser+technology+for+implants+with+consideration+of+operator+experience+and+implant+angulation+and+depth.">Accuracy of a digital impression system based on parallel confocal laser technology for implants with consideration of operator experience and implant angulation and depth.</a> International Journal of Oral and Maxillofacial Implants. 29 (4), 853-862 (2014).</li><li>Gimenez, B., Ozcan, M., Martinez-Rus, F., Pradies, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+a+digital+impression+system+based+on+active+wavefront+sampling+technology+for+implants+considering+operator+experience,+implant+angulation,+and+depth.">Accuracy of a digital impression system based on active wavefront sampling technology for implants considering operator experience, implant angulation, and depth.</a> Clinical Implant Dentistry and Related Research. 17 Suppl 1, e54-e64 (2015).</li><li>Papaspyridakos, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Digital+versus+conventional+implant+impressions+for+edentulous+patients:+accuracy+outcomes.">Digital versus conventional implant impressions for edentulous patients: accuracy outcomes.</a> Clinical Oral Implants Research. 27 (4), 465-472 (2016).</li><li>Flugge, T. V., Att, W., Metzger, M. C., Nelson, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precision+of+Dental+Implant+Digitization+Using+Intraoral+Scanners.">Precision of Dental Implant Digitization Using Intraoral Scanners.</a> International Journal of Prosthodontics. 29 (3), 277-283 (2016).</li><li>Kim, S. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+dies+captured+by+an+intraoral+digital+impression+system+using+parallel+confocal+imaging.">Accuracy of dies captured by an intraoral digital impression system using parallel confocal imaging.</a> International Journal of Prosthodontics. 26 (2), 161-163 (2013).</li><li>Ender, A., Mehl, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+scanning+strategies+on+the+accuracy+of+digital+intraoral+scanning+systems.">Influence of scanning strategies on the accuracy of digital intraoral scanning systems.</a> International Journal of Computerized Dentistry. 16 (1), 11-21 (2013).</li></ol>

The authors have nothing to disclose.

Among the studies evaluating the accuracy of the intraoral scanner by evaluating the resultant digital impression body, the most common method is to superimpose the digital impression data on the reference image and calculate the shell-to-shell deviation12,13,14,15,20,23. However, this method is limited to calculating the dev...

In the traditional dental treatment process, a fixed restoration or a removable denture is made on a model made of gypsum and impregnated with a silicone or irreversible hydrocolloid material. Because an indirectly made prosthesis is delivered in the oral cavity, a lot of research has been done to overcome the errors caused by a series of such manufacturing processes1,2. Recently, a digital method is used to fabricate a prosthesis through the CAD process by manipulating models in the virtual space after acquiring 3D images instead of making impressions3. In the early days, such an optical impression method was used in a limited range such as a dental caries treatment of one or a small number of teeth. However, as the base technology of the 3D scanner was developed, a digital impression for the complete arch is now used for the fabrication of large-scale fixed restorations, removable restorations such as a partial or full denture, orthodontic appliances, and implant surgical guides4,5,6,7. The accuracy of the digital impression is satisfactory in a short region such as the unilateral arch. However, since the intraoral scanner is a handheld device that completes the entire dentition by stitching together the image obtained through a narrow optical window, the distortion of the model can be seen after completing the U-shaped dental arch. Thus, an appliance of a large range made on this model might not fit well in the patient&#39;s mouth and require a lot of adjustment.
Various studies have been reported on the accuracy of the virtual impression body obtained with an intraoral scanner, and there are various research models and measurement methods. Depending on the research subject, it can be divided into clinical research8,9,10,11,12 for actual patients and in vitro studies13,14,15,16 conducted in models separately produced for research. Clinical studies have the advantage of being able to evaluate the conditions of an actual clinical setting, but it is difficult to control the variables and increase the number of clinical cases indefinitely. The number of clinical studies is not large because there is a limit to being able to evaluate the desired variables. On the other hand, many in vitro studies that evaluate the basic performance of the intraoral scanner by controlling variables have been reported17. The research model also includes a partial or complete arch of natural teeth18,19,20,21,22 and a fully edentulous jaw with all teeth lost23, or the case where the dental implant is installed and spaced apart at a certain interval24,25,26,27, or a form in which the majority of the teeth remain and only a part of a tooth is missing16,28. However, studies on the distortion of the virtual impression body made by a handheld intraoral scanner have been limited to the qualitative evaluation of deviations through a color map created by superimposing it with reference data and expressed as one numerical value per data. It is difficult to accurately measure the 3D distortion of the complete arch because most studies only examine the localized portion of the dental arch with a nondirectional distance deviation.
In this study, the distortion of the dental arch during optical impression with an intraoral scanner is investigated by using a standard model with a coordinate system. The aim of this study is to provide information on a method for evaluating the accuracy performance of the intraoral scanners which exhibit various characteristics by the difference in optical hardware and processing software.

<table>
	<tbody>
		<tr>
			<td>EOS CobaltChrome SP2</td>
			<td>Electro Oprical Systems</td>
			<td>H051601</td>
			<td>Powder type metal alloy for 3D printing</td>
		</tr>
		<tr>
			<td>Geomagic Verify</td>
			<td>3D Systems</td>
			<td>2015.2.0</td>
			<td>3D inspection software</td>
		</tr>
		<tr>
			<td>Prosthetic Restoration Jaw Model</td>
			<td>Nissin Dental Products Inc.</td>
			<td></td>
			<td>Mandibular complete-arch model</td>
		</tr>
		<tr>
			<td>Rapidform</td>
			<td>Inus technology</td>
			<td>RF90600-10004-010000</td>
			<td>Reverse engineering software</td>
		</tr>
		<tr>
			<td>stereoSCAN R8</td>
			<td>AICON 3D Systems GmbH</td>
			<td></td>
			<td>Industrial-level model scanner</td>
		</tr>
	</tbody>
</table>

measuring the complete-arch distortion of an optical dental impression

Digital workflows have actively been used to produce dental restorations or oral appliances since dentists started to make digital impressions by acquiring 3D images with an intraoral scanner. Because of the nature of scanning the oral cavity in the patient&#39;s mouth, the intraoral scanner is a handheld device with a small optical window, stitching together small data to complete the entire image. During the complete-arch impression procedure, a deformation of the impression body can occur and affect the fit of the restoration or appliance. In order to measure these distortions, a master specimen was designed and produced with a metal 3D printer. Designed reference geometries allow setting independent coordinate systems for each impression and measure x, y, and z displacements of the cylinder top circle center where the distortion of the impression can be evaluated. In order to evaluate the reliability of this method, the coordinate values of the cylinder are calculated and compared between the original computer-aided design (CAD) data and the reference data acquired with the industrial scanner. The coordinate differences between the two groups were mostly less than 50 &#181;m, but the deviations were high due to the tolerance of 3D printing in the z coordinates of the obliquely designed cylinder on the molar. However, since the printed model sets a new standard, it does not affect the results of the test evaluation. The reproducibility of the reference scanner is 11.0 &#177; 1.8 &#181;m. This test method can be used to identify and improve upon the intrinsic problems of an intraoral scanner or to establish a scanning strategy by measuring the degree of distortion at each part of the complete-arch digital impression.

The coordinates of each cylinder calculated from the originally designed CAD data and the reference scan image of the 3D-printed metal master specimen scanned by the industrial-level model scanner are shown in Table 1. The difference between the two showed a value of lower than 50 &#181;m, but the z coordinate value of the right second molar cylinder from the 3D-printed master specimen was low. Although the metal phantom was produced from a high-end industrial 3D...

Watch this Scientific Journal Video about Measuring the Complete-arch Distortion of an Optical Dental Impression at JoVE.com

Measuring the Complete-arch Distortion of an Optical Dental Impression

光学歯科印象の完全アーチ歪みを測定する

Here, we present a protocol to measure the degree of distortion at each part of the compete-arch digital impression acquired from an intraoral scanner with 3D-printed metal phantom with standard geometries.

Digital workflows have actively been used to produce dental restorations or oral appliances since dentists started to make digital impressions by ...

measuring-the-complete-arch-distortion-of-an-optical-dental-impression

Research

JoVE Journal

Engineering

7.4K ビュー.  Yonsei University. イントララルスキャナーは、歯科プロセスのために収集するデータにアーチの歪みを導入します。当社の座標系抽出プロトコルは、市場での口腔内スキャナーを評価するためのツールを提供します。リバースエンジニアリング参照球を使用して、イントララルスキャンの任意の座標から新しく作成された座標系に変換することが最も重要です。x、y、z方向の歯科ア?...

ビデオ: Measuring the Complete-arch Distortion of an Optical Dental Impression

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

リチウムイオン電池のコイン細胞の構築とテスト

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

工学

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

ファイバー描画法を用いたメタマテリアルの作製

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

ナノ粒子の光トラッピング

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

We demonstrate how optical tweezers may provide a sensitive tool to analyze the fluidic vibrations generated by the movement of small aquatic organisms. A single gold nanoparticle held by an optical tweezer is used as a sensor to quantify the rhythmic motion of a Nauplius larva (Artemia salina) in a water sample. This is achieved by monitoring the time dependent displacement of the trapped nanoparticle as a consequence of the Nauplius activity. A Fourier analysis of the nanoparticle&#39;s position then yields a frequency spectrum that is characteristic to the motion of the observed species. This experiment demonstrates the capability of this method to measure and characterize the activity of small aquatic larvae without the requirement to observe them directly and to gain information about the position of the larvae with respect to the trapped particle. Overall, this approach could give an insight on the vitality of certain species found in an aquatic ecosystem and could expand the range of conventional methods for analyzing water samples.

Analyzing the Movement of the Nauplius &#039;Artemia salina&#039; by Optical Tracking of Plasmonic Nanoparticles

We use optical tracking of plasmonic nanoparticles to probe and characterize the frequency movements of aquatic organisms.

「ノープリウスの動きを分析する<em&gt;アルテミア·サリナ</em&gt; &#39;プラズモニックナノ粒子の光学追跡することによって、

We demonstrate how optical tweezers may provide a sensitive tool to analyze the fluidic vibrations generated by the movement of small aquatic organisms. A ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

光可飽和遷移を経由してパターニング - 作製と特性評価

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

圧電支援摩擦計と光プロフィルを用いた超音波潤滑の実験

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid cooling, to prepare the desired cryogenic temperature phase. Microliter to picoliter size drops are cooled by projection into a liquid nitrogen-argon (N2-Ar) mixture. The cryogenic temperature phase of the drop is evaluated using a visual assay that correlates with X-ray diffraction measurements. The density of the liquid N2-Ar mixture is adjusted by adding N2 or Ar until the drop becomes neutrally buoyant. The density of this mixture and thus of the drop is determined using a test mass and Archimedes principle. With appropriate care in drop preparation, management of gas above the liquid cryogen mixture to minimize icing, and regular mixing of the cryogenic mixture to prevent density stratification and phase separation, densities accurate to &#60;0.5% of drops as small as 50 pL can readily be determined. Measurements on aqueous cryoprotectant mixtures provide insight into cryoprotectant action, and provide quantitative data to facilitate thermal contraction matching in biological cryopreservation.

A protocol for determining the vitreous phase densities of micro- to pico-liter size drops of aqueous mixtures at cryogenic temperatures is described.

低温での水性ガラスの密度の測定

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid ...

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy (ATOM)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the main trend in the advanced development of flow cytometry. Notably, adding high-resolution imaging capabilities allows for the complex morphological analysis of cellular/sub-cellular structures. This is not possible with standard flow cytometers. However, it is valuable for advancing our knowledge of cellular functions and can benefit life science research, clinical diagnostics, and environmental monitoring. Incorporating imaging capabilities into flow cytometry compromises the assay throughput, primarily due to the limitations on speed and sensitivity in the camera technologies. To overcome this speed or throughput challenge facing imaging flow cytometry while preserving the image quality, asymmetric-detection time-stretch optical microscopy (ATOM) has been demonstrated to enable high-contrast, single-cell imaging with sub-cellular resolution, at an imaging throughput as high as 100,000 cells/s. Based on the imaging concept of conventional time-stretch imaging, which relies on all-optical image encoding and retrieval through the use of ultrafast broadband laser pulses, ATOM further advances imaging performance by enhancing the image contrast of unlabeled/unstained cells. This is achieved by accessing the phase-gradient information of the cells, which is spectrally encoded into single-shot broadband pulses. Hence, ATOM is particularly advantageous in high-throughput measurements of single-cell morphology and texture &#8211; information indicative of cell types, states, and even functions. Ultimately, this could become a powerful imaging flow cytometry platform for the biophysical phenotyping of cells, complementing the current state-of-the-art biochemical-marker-based cellular assay. This work describes a protocol to establish the key modules of an ATOM system (from optical frontend to data processing and visualization backend), as well as the workflow of imaging flow cytometry based on ATOM, using human cells and micro-algae as the examples.

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM

This protocol describes the implementation of an asymmetric-detection time-stretch optical microscopy system for single-cell imaging in ultrafast microfluidic flow and its applications in imaging flow cytometry.

非対称検出時間ストレッチ光学顕微鏡（ATOM）によるマイクロ流体イメージングフローサイトメトリー

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the ...

Design and Fabrication of an Optical Fiber Made of Water

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with solid-cladding devices, capillary oscillations are not restricted, allowing the fiber walls to move and vibrate. The fiber is constructed by a high direct current (DC) voltage of several thousand volts (kV) between two water reservoirs that creates a floating water thread, known as a water bridge. Through the choice of micropipettes, it is possible to control the maximal diameter and length of the fiber. Optical fiber couplers, at both sides of the bridge, activate it as an optical waveguide, allowing researchers to monitor the water fiber capillary body waves through transmission modulation and, therefore, deducing changes in surface tension.
Co-confining two important wave types, capillary and electromagnetic, opens a new path of research in the interactions between light and liquid-wall devices. Water-walled microdevices are a million times softer than their solid counterparts, accordingly improving the response to minute forces.

This protocol describes the design and manufacture of a water bridge and its activation as a water fiber. The experiment demonstrates that capillary resonances of the water fiber modulate its optical transmission.

水の光ファイバーの設計と製作

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with ...

Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, with its peak locomotion speed reaching 150 cm/s. First of all, we observed the microstructure and hierarchy of water strider legs using the scanning electron microscope. On the basis of the observed morphology of the legs, a theoretical model of the detachment from water surface was established, which explained water striders' capability to slide on water surface effortlessly in terms of energy reduction. Secondly, a dynamic force measurement system was devised using the PVDF film sensor with excellent sensitivity, which could detect the whole interaction process. Subsequently, a single leg in contact with water was pulled upward at different speeds, and the adhesion force was measured at the same time. The results of the departing experiment suggested a deep understanding of the fast jumping of water striders.

The protocol here is dedicated to investigating the free and quick maneuvering of water strider on water surface. The protocol includes observing the microstructure of legs and measuring the adhesion force when departing from water surface at different speeds.

PVDF 膜センサーによる上方ジャンプ アメンボの脚に行動力の測定

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, ...