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...

<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>

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

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 ...

Intraoral scanners introduce arch distortion in data they collect for dental processes. Our coordinate system extraction protocol provides a tool for evaluating intraoral scanners on the market. It is most important to transform from the arbitrary coordinates of the intraoral scan to the newly created coordinate system using the reverse engineering reference sphere.A technique of the analysis of distortion in the critical part of dental arch in the x, y, and z directions. Which is an improvement over current methods using best-fit alignment. Demonstrating the procedure will be Dan Young Kim, a technician from our laboratory.Work with the physical model to create the master specimen. For this protocol, prepare a mandibular complete arch model. First remove the canines, the second premolars and the second molars for the study.Take the model to a reference scanner to acquire the data necessary to generate the computer model. Next upload the master specimen data to a computer-aided design program. Using reverse engineering software, design cylinders on top of the trimmed teeth each with a radius of two millimeters and a height of seven millimeters.Design the cylinder of the left second molar so that it is inclined 30 degrees medially and the cylinder for the right second molar so it is inclined 30 degrees distally. To define the coordinate system, add three 3.5 millimeter reference spheres posterior to the left second molar cylinder with one sphere on the buccal side. Use this design in a metal 3D printer to manufacture a cobalt chromium alloy phantom model to serve as a patient's dentition.Return to the industrial model scanner with the metal phantom. Use it to obtain a reference scan of the phantom. The next step is to set up the phantom for scanning with an intraoral scanner, When ready, use the intraoral scanner being tested to scan the phantom.Next, within CAD software, create a model of the phantom with the reference scan data. To begin determining the reference coordinate select Reference Geometry then Create then Sphere to choose the Pick Boundary Points command. Select four points on the reference sphere that are as far apart from each other as possible.Click Done to end point selection. The sphere's center will be determined automatically. Repeat this for each sphere.Next choose Reference Geometry, Create, Plane, and Pick Points in order to connect the centers of the three spheres to define a plane. Label this plane as the XY plane. Then create a tangent plane by going to Reference Geometry, Create, Plane, Offset Plane.Place this above the XY plane. Once again, choose Reference Geometry, then Create and Plane to reach the Pick Points command and generate a plane between the created points and the center of the lingual spheres. Go under Inspection, then Dimension, and use the Linear command to measure the distance of the plane from the center of the buccal sphere.With Geometry, followed by Create and Plane, choose Offset Plane to create a parallel plane that passes through the midpoint of the buccal sphere. Label this plane as the YZ plane. The center of the buccal sphere will be the origin of the coordinate system.Assign a line parallel to the line connecting the remaining two spheres as the Y-axis. Assign the line on the XY plane that passes through the origin and is perpendicular to the Y-axis as the X-axis. Create a new coordinate system with Reference Geometry, Create, Coordinate, and the Pick Origin X, Y Direction command.Label the line perpendicular to the XY plane and passing through the origin as the Z-axis. Go on to select Reference Geometry and Bind to Shell to fix the geometries created on top of the scan data. Then, under Reference Geometry, Transform, and Coordinate, find the Align Coordinate command to transition to the newly created coordinate system.Note the coordinate indicator now coincides with one of the buccal spheres. Now, focus on one of the six cylinders in the image. Go to Reference Geometry, Create, Cylinder, and the Pick Boundary Points command.Specify at least ten points on the top boundary of the cylinder. Specify the same number of points on the ellipse to find where the tooth meets the bottom of the cylinder. Click Done to end point selection.Obtain the extracted coordinates of the center of the cylinder top for comparison with the coordinate values from the intraoral scanner. Here are the CAD and 3D printed model. The CAD image has labels for the sites used for comparison.The difference in the coordinates for these sites between the two models demonstrates that the coordinates from the CAD design cannot be used as a reference and an industrial level scanner must be employed. It is most important to transform from the original coordinates of the intraoral scan to the newly created coordinate system using the reverse engineering reference sphere. Since the same type of data is used, this process can be automated through the macrofunctions in the 3D analysis software to repeat each reverse engineering step.This create an accurate way to analyze arch distortion but resists the biggest weakness of color coordination aber of buccal distances and could be used as an ISO standard or a test method.

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

Research

JoVE Journal

Engineering

7.4K vistas.  Yonsei University. Los escáneres intraorales introducen la distorsión de arco en los datos que recopilan para los procesos dentales. Nuestro protocolo de extracción de sistemas de coordenadas proporciona una herramienta para evaluar los escáneres intraorales en el mercado. Es más importante transformar de las coordenadas arbitrarias del escaneo intraoral al sistema de coordenadas recién creado utilizando la esfera de referencia de ingeniería inversa.Una técnica del análisis de la distorsión en ...