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Precision of intraoral digital dental impressions with iTero and extraoral digitization with the iTero and a model scanner

      Introduction

      Digital impression devices are used alternatively to conventional impression techniques and materials. The aims of this study were to evaluate the precision of digital intraoral scanning under clinical conditions (iTero; Align Technologies, San Jose, Calif) and to compare it with the precision of extraoral digitization.

      Methods

      One patient received 10 full-arch intraoral scans with the iTero and conventional impressions with a polyether impression material (Impregum Penta; 3M ESPE, Seefeld, Germany). Stone cast models manufactured from the impressions were digitized 10 times with an extraoral scanner (D250; 3Shape, Copenhagen, Denmark) and 10 times with the iTero. Virtual models provided by each method were roughly aligned, and the model edges were trimmed with cutting planes to create common borders (Rapidform XOR; Inus Technologies, Seoul, Korea). A second model alignment was then performed along the closest distances of the surfaces (Artec Studio software; Artec Group, Luxembourg, Luxembourg). To assess precision, deviations between corresponding models were compared. Repeated intraoral scanning was evaluated in group 1, repeated extraoral model scanning with the iTero was assessed in group 2, and repeated model scanning with the D250 was assessed in group 3. Deviations between models were measured and expressed as maximums, means, medians, and root mean square errors for quantitative analysis. Color-coded displays of the deviations allowed qualitative visualization of the deviations.

      Results

      The greatest deviations and therefore the lowest precision were in group 1, with mean deviations of 50 μm, median deviations of 37 μm, and root mean square errors of 73 μm. Group 2 showed a higher precision, with mean deviations of 25 μm, median deviations of 18 μm, and root mean square errors of 51 μm. Scanning with the D250 had the highest precision, with mean deviations of 10 μm, median deviations of 5 μm, and root mean square errors of 20 μm. Intraoral and extraoral scanning with the iTero resulted in deviations at the facial surfaces of the anterior teeth and the buccal molar surfaces.

      Conclusions

      Scanning with the iTero is less accurate than scanning with the D250. Intraoral scanning with the iTero is less accurate than model scanning with the iTero, suggesting that the intraoral conditions (saliva, limited spacing) contribute to the inaccuracy of a scan. For treatment planning and manufacturing of tooth-supported appliances, virtual models created with the iTero can be used. An extended scanning protocol could improve the scanning results in some regions.
      For the introduction of computer-aided design and computer-aided manufacturing technologies in dentistry, virtual models of teeth are required. Digital processes are applied for prosthetic-driven backward planning of implant surgery,
      • Morris J.B.
      CAD/CAM options in dental implant treatment planning.
      • Patel N.
      Integrating three-dimensional digital technologies for comprehensive implant dentistry.
      orthodontic measurements, and treatment planning
      • Boldt F.
      • Weinzierl C.
      • Hertrich K.
      • Hirschfelder U.
      Comparison of the spatial landmark scatter of various 3D digitalization methods.
      • Asquith J.A.
      • McIntyre G.T.
      Dental arch relationships on three-dimensional digital study models and conventional plaster study models for patients with unilateral cleft lip and palate.
      • Sjogren A.P.
      • Lindgren J.E.
      • Huggare J.A.
      Orthodontic study cast analysis—reproducibility of recordings and agreement between conventional and 3D virtual measurements.
      • Mullen S.R.
      • Martin C.A.
      • Ngan P.
      • Gladwin M.
      Accuracy of space analysis with emodels and plaster models.
      combined with surgical planning.
      • Metzger M.C.
      • Hohlweg-Majert B.
      • Schwarz U.
      • Teschner M.
      • Hammer B.
      • Schmelzeisen R.
      Manufacturing splints for orthognathic surgery using a three-dimensional printer.
      Data acquired by intraoral scanning, computed tomography, cone-beam computed tomography, and extraoral surface scanning can be fused.
      • Morris J.B.
      CAD/CAM options in dental implant treatment planning.
      • Patel N.
      Integrating three-dimensional digital technologies for comprehensive implant dentistry.
      • Metzger M.C.
      • Hohlweg-Majert B.
      • Schwarz U.
      • Teschner M.
      • Hammer B.
      • Schmelzeisen R.
      Manufacturing splints for orthognathic surgery using a three-dimensional printer.
      For the acquisition of digital images of teeth, different procedures have been described: digitization of plaster casts,
      • Boldt F.
      • Weinzierl C.
      • Hertrich K.
      • Hirschfelder U.
      Comparison of the spatial landmark scatter of various 3D digitalization methods.
      • Sjogren A.P.
      • Lindgren J.E.
      • Huggare J.A.
      Orthodontic study cast analysis—reproducibility of recordings and agreement between conventional and 3D virtual measurements.
      • Persson A.S.
      • Odén A.
      • Andersson M.
      • Sandborgh-Englund G.
      Digitization of simulated clinical dental impressions: virtual three-dimensional analysis of exactness.
      • Dalstra M.
      • Melsen B.
      From alginate impressions to digital virtual models: accuracy and reproducibility.
      • Chandran D.T.
      • Jagger D.C.
      • Jagger R.G.
      • Barbour M.E.
      Two- and three-dimensional accuracy of dental impression materials: effects of storage time and moisture contamination.
      • Luthardt R.G.
      • Walter M.H.
      • Quaas S.
      • Koch R.
      • Rudolph H.
      Comparison of the three-dimensional correctness of impression techniques: a randomized controlled trial.
      • Luthardt R.G.
      • Kühmstedt P.
      • Walter M.H.
      A new method for the computer-aided evaluation of three-dimensional changes in gypsum materials.
      digitization of impressions,
      • Persson A.S.
      • Odén A.
      • Andersson M.
      • Sandborgh-Englund G.
      Digitization of simulated clinical dental impressions: virtual three-dimensional analysis of exactness.
      • Kurbad A.
      Impression-free production techniques.
      and intraoral digital impressions.
      • Kurbad A.
      Impression-free production techniques.
      • Kachalia P.R.
      • Geissberger M.J.
      Dentistry a la carte: in-office CAD/CAM technology.
      The accuracy of the different image acquisition methods and systems has been examined with extraoral reference models.
      • Dalstra M.
      • Melsen B.
      From alginate impressions to digital virtual models: accuracy and reproducibility.
      • Luthardt R.G.
      • Kühmstedt P.
      • Walter M.H.
      A new method for the computer-aided evaluation of three-dimensional changes in gypsum materials.
      • Rudolph H.
      • Luthardt R.
      • Walter M.
      Computer-aided analysis of the influence of digitizing and surfacing on the accuracy in dental CAD/CAM technology.
      • Del Corso M.
      • Abà G.
      • Vazquez L.
      • Dargaud J.
      • Dohan Ehrenfest D.M.
      Optical three-dimensional scanning acquisition of the position of osseointegrated implants: an in vitro study to determine method accuracy and operational feasibility.
      • DeLong R.
      • Heinzen M.
      • Hodges J.S.
      • Ko C.C.
      • Douglas W.H.
      Accuracy of a system for creating 3D computer models of dental arches.
      • Ender A.
      • Mehl A.
      Full arch scans: conventional versus digital impressions—an in-vitro study.
      However, to date, no studies concerning the practical application and precision of digital scanning in vivo have been done.
      Digital work flow has been proposed to improve treatment planning, give higher efficiency, and allow new methods of production and new treatment concepts.
      • Stevens D.R.
      • Flores-Mir C.
      • Nebbe B.
      • Raboud D.W.
      • Heo G.
      • Major P.W.
      Validity, reliability, and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements.
      • Beuer F.
      • Schweiger J.
      • Edelhoff D.
      Digital dentistry: an overview of recent developments for CAD/CAM generated restorations.
      • Al Mortadi N.
      • Eggbeer D.
      • Lewis J.
      • Williams R.J.
      CAD/CAM/AM applications in the manufacture of dental appliances.
      Data storage and reproducibility are facilitated,
      • Dalstra M.
      • Melsen B.
      From alginate impressions to digital virtual models: accuracy and reproducibility.
      • Stevens D.R.
      • Flores-Mir C.
      • Nebbe B.
      • Raboud D.W.
      • Heo G.
      • Major P.W.
      Validity, reliability, and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements.
      and treatment documentation and communication between professionals as well as between dentists and patients have become more convenient.
      • Hajeer M.Y.
      • Millett D.T.
      • Ayoub A.F.
      • Siebert J.P.
      Applications of 3D imaging in orthodontics: part II.
      Currently, there are a few major digital impression devices: iTero (Align Technologies, San Jose, Calif), Lava COS (3M ESPE, Seefeld, Germany), and Trios (3Shape, Copenhagen, Denmark) for image acquisition; and CEREC AC (Sirona, Bensheim, Germany) and E4D (D4D Technologies, Richardson, Tex) for digital imaging and in-office manufacturing.
      • Kachalia P.R.
      • Geissberger M.J.
      Dentistry a la carte: in-office CAD/CAM technology.
      Excluding the iTero and the Trios, all scanning devices need drying and powdering of intraoral surfaces (CEREC, E4D, Lava COS). This limits their practicability and accuracy because powder application can add to the measuring error.
      • Meyer B.J.
      • Mormann W.H.
      • Lutz F.
      Optimization of the powder application in the Cerec method with environment-friendly propellant systems.
      With all devices mentioned, digital impressions are acquired without contact to the gingival tissues.
      The precision of intraoral and extraoral scanning with the iTero as well as extraoral scanning with a model scanner was examined in this study.

      Material and methods

      Impressions were acquired according to the study protocol that was approved by the ethics committee of the medical faculty of Freiburg University, after we received written consent from the study participant. One participant with a Class I occlusion and full dentition was examined.
      In-vivo (intraoral) scans (group 1) and ex-vivo (extraoral) scans of 1 patient and the patient’s models were made with 2 laser scanners (group 2, iTero; group 3, D250; Fig 1).
      Figure thumbnail gr1
      Fig 1Synopsis of model manufacturing and virtual model generation.
      According to the study protocol, the data acquisition for group 1 was based on 10 intraoral scans with the iTero of the maxilla and the mandible of 1 patient (n = 20).
      For groups 2 and 3, a unique model was used. The model fabrication for the extraoral scans was performed as follows.
      Using the same patient as in group 1, polyether impressions of the maxilla and the mandible were taken using a monophase polyether material (Impregum Penta; 3M ESPE) and stainless steel impression trays (M+W-Rim-Lock; M+W Dental, Büdingen, Germany). The impressions were disinfected and poured with type IV stone (picodent U 180; Picodent, Wipperfürth, Germany) after a setting time of 4 hours. The first impression was used for the production of the stone casts, independently of the subjective assessment of the quality. One stone cast of the maxilla and 1 stone cast of the mandible were made.
      The stone casts were scanned with the iTero using the same scanning protocol as for the intraoral scans. The scans of each stone cast model (maxilla and mandible) were repeated 10 times and produced the data set for group 2 (n = 20).
      The virtual models for group 3 (n = 20) were collected by repeated scanning (10 times) of the stone casts with a model scanner (D250).
      All scans with the iTero were recorded by the same examiner (T.V.F.) in a predetermined order. Scanning started with the most distal tooth in the third quadrant continuing to the anterior teeth (Figs 2 and 3). Next, the fourth quadrant was scanned, again beginning with the most distal tooth. Scanning of the maxilla started with the most distal tooth in the first quadrant and ended at the central incisor. The second quadrant was recorded starting with the most distal tooth. Each tooth was scanned from its buccal and lingual sides by placing the camera at an angle of 45° to the tooth axis. Images of each tooth showed neighboring parts of adjacent teeth. These served to overlap the pictures to create a model of the whole arch from single images. All models were exported in a Standard Tesselation Language (STL; 3D Systems, Rock Hill, SC) format and were used for evaluation, independently of the subjective assessment.
      Figure thumbnail gr2
      Fig 2Intraoral scanning and the iTero-rendered stereolithographic model of the scanned jaw.
      Figure thumbnail gr3
      Fig 3Extraoral scanning of a stone cast and the iTero-rendered stereolithographic model of the cast.
      For digitization, the stone casts were placed into the D250 scanner next to a laser source and 2 high-resolution cameras. During the scanning process, the platform moves the model; therefore, the laser reaches the model from multiple angles. Light planes are projected onto the model, and the cameras capture their reflections from the surface (Fig 4).
      Figure thumbnail gr4
      Fig 4Scanning of a plaster cast with the D250 and rendered stereolithographic model of the cast.
      The principle of triangulation was used for the creation of a 3-dimensional model, available as a stereolithographic data set.
      All stereolithographic data sets of 1 dental arch and 1 scanning method (n = 10) were imported in a common coordinate system and aligned by a procedure with the closest distance between 2 surfaces (Rapidform XOR; Inus Technologies, Seoul, South Korea). The models were orientated toward the occlusal plane to fit a view for drawing the cutting planes. A first cutting plane running through the deepest point of the gingival sulcus of the canines and the second molars in the maxilla and the canines and the first molars in the mandible was created. A second cutting plane was created running through the transverse fissure of both second molars. All surfaces were cut with the common cutting planes to create equal basal and posterior borders (Fig 5).
      Figure thumbnail gr5
      Fig 5Stereolithographic data set obtained from scanning with reference planes (reference planes 1 to 3) for cutting, displayed with Rapidform XOR.
      For quantitative analysis of precision, deviations between the vertices of the surfaces were measured. Operated scan data were imported into Artec Studio software (version 0.7.3.39; Artec Group, Luxembourg, Luxembourg) to perform a pairwise rigid body registration. Corresponding models for each comparison were roughly aligned manually and then registered onto another using the implemented surface mapping algorithm.
      Deviations between aligned models were analyzed using the software package Morpho, version 0.25 (based on R; created by Stefan Schlager, Freiburg, Germany).

      Schlager S. Morpho: calculations and visualizations related to geometric morphometrics. 2012.

      To estimate the differences between the surfaces, each vertex on the test surface was projected to the closest point on the corresponding control surface, and the Euclidean distance was recorded. The model rendered from the first scan served as the control surface for the consecutively acquired models in each group.

      Statistical analysis

      Further statistical analysis was performed with the software R.
      • R Development Core Team R
      R: a language and environment for statistical computing.
      For testing differences between the groups’ distributions of averaged distances, the Kolmogorov-Smirnov test—a distribution free and nonparametric procedure—was applied. The level of significance was set at 0.05.
      For the assessment of error, maximum, mean, and median deviations were calculated for each group based on the averaged errors of each observation. The distances between the vertices of the corresponding models were displayed with color maps, so that areas of high and low agreement could be identified.

      Results

      In group 1, the virtual models, rendered from serial intraoral scans of the maxilla and the mandible with the iTero, were compared. The mean deviation was 50 μm (median, 37 μm). Deviations in the maxilla were on average 57 μm (median, 43 μm); the mandible deviated on average 43 μm (median, 31 μm). Maximum deviations were on average 1.137 mm in the maxilla and 717 μm in the mandible. Deviations of the mandible were significantly lower than deviations in the maxilla. Deviations between models are displayed in Figure 6.
      Figure thumbnail gr6
      Fig 6Colored presentation of the deviations between surfaces in group 1.
      The highest deviations were observed at the palatal borders, the facial surfaces of the anterior teeth, and the molars on both sides of the maxilla. In the mandible, the highest deviations were at the buccal side of the molars and the facial side of the anterior teeth. There were also deviations above average in the interdental spaces.
      In group 2, the virtual models acquired with the repeated scans of the stone casts with the iTero were compared. Deviations from the test surface were on average 25 μm (median, 18 μm). The maxillae had a mean deviation of 30 μm (median, 18 μm), whereas the mandibles had a mean deviation of 21 μm (median, 17 μm). The color-coded deviations are depicted in Figure 7.
      Figure thumbnail gr7
      Fig 7Colored presentation of the deviations between surfaces in group 2.
      The highest deviations in the maxilla were found at the facial surfaces of the anterior teeth in the left maxilla and at the palatal borders of the models. The maximum deviation was 1.79 mm in the maxilla. The mandible had lower deviations and a homogenous distribution with above-average values in the molar region and the gingival sulcus. The maximum deviation averaged 423 μm. Deviations in the mandible were significantly lower than in the maxilla.
      In group 3, the deviations between the virtual models rendered from repeated model scanning with the D250 were compared. Models deviated on average 10 μm (median, 6 μm). Average deviations were 11 μm in the maxilla and 9 μm in the mandible. The maximum deviation was 460 μm for the maxilla and the mandible. The color-coded values of the deviations are shown in Figure 8.
      Figure thumbnail gr8
      Fig 8Colored presentation of the deviations between surfaces in group 3.
      Deviations in group 3 were lower than deviations in groups 1 and 2. The areas of deviations showed similar patterns in the maxilla and the mandible. The interdental spaces had the greatest deviations between the virtual models. Deviations in the mandible were significantly lower than those in the maxilla. The color scale (Fig 9) shows the deviations in Fig 6, Fig 7, Fig 8. The mean deviations in all groups are displayed in the Table.
      Figure thumbnail gr9
      Fig 9Colored scale for the deviations shown in Fig 6, Fig 7, Fig 8 (mm).
      TableMean deviation of each method (μm)
      iTero intraoraliTero extraoralD250
      Mean deviation502510
      The Kolmogorov-Smirnov test showed that the overall deviations were significantly different for every method.
      In Figure 10, the boxplot diagram shows the distribution of the deviations for all methods.
      Figure thumbnail gr10
      Fig 10Boxplot of the deviations for every method (outliers are hidden).

      Discussion

      The reason for the use of intraoral digital impression systems is adequate accuracy and precision compared with conventional techniques and extraoral digitization of stone casts. Ender and Mehl
      • Ender A.
      • Mehl A.
      Full arch scans: conventional versus digital impressions—an in-vitro study.
      defined accuracy as a deviation from the original object and precision as the accuracy of repeated measurements.
      The precision of intraoral scanning was evaluated in this study and compared with extraoral digitization of stone casts with the iTero and a model scanner (D250). The accuracy of the different work flows to create a virtual model was not our objective. The systematic errors caused by impression taking and model manufacturing are neither included nor relevant for the present data.
      Polyether-based stone casts served as an extraoral reference. All scans were conducted with the same model. Scanning with the model scanner D250 has a different image acquisition technique compared with intraoral scanners. The model is continuously captured with the projection of laser planes and the recording of their reflections. With all intraoral scanning techniques, image acquisition is done incrementally. The iTero system produces single images of every tooth, which are assembled for a virtual model of the whole jaw. This process, called stitching, might produce a systematic error.
      • Galovska M.
      • Petz M.
      • Tutsch R.
      Unsicherheit bei der datenfusion dimensioneller messungen.
      Mehl et al
      • Mehl A.
      • Ender A.
      • Mormann W.
      • Attin T.
      Accuracy testing of a new intraoral 3D camera.
      found lower accuracy of quadrant digitization compared to single-tooth digitization with the CEREC system. Because the stitching algorithm of the iTero system is unknown, its contribution to the error in precision cannot be explained. However, lower precision of the iTero compared with the D250 was observed in this study.
      Loss of information at model edges, especially in the maxilla, was observed with the iTero system. This resulted in high deviation values. According to the scanning protocol, a fixed number of pictures is acquired of every tooth. The image section of the camera covers the tooth and, depending on its anatomy, a variable portion of the gingiva. The scans show that the image acquisition of the marginal gingiva could not be precisely reproduced in the maxilla. An extended protocol, resulting in a longer scanning time, might be necessary to obtain complete information.
      The facial surfaces of the anterior teeth were imprecisely captured with the iTero in intraoral and extraoral digitizations (Figs 6 and 7). Although they appear to be easily accessible with the scanning wand, the steep-angled anterior surface might require additional scans from different angles, as Mehl et al
      • Mehl A.
      • Ender A.
      • Mormann W.
      • Attin T.
      Accuracy testing of a new intraoral 3D camera.
      have already suggested for steep areas.
      The imprecise digitization of the molar areas with the iTero in extraoral use was more pronounced for intraoral use. This might be caused by the complex angled surfaces of the molars and the undercut surfaces of the neighboring teeth. This theory is supported by Rudolph et al,
      • Rudolph H.
      • Luthardt R.
      • Walter M.
      Computer-aided analysis of the influence of digitizing and surfacing on the accuracy in dental CAD/CAM technology.
      who used different methods for digitization of an extraoral reference model to show that tooth shape was a dominating factor for precision and that large deviations occurred in areas with strong changes of curvature. The precision of extraoral model scanning with the D250 was not lower in areas of high curvature and undercuts. The continuous image acquisition with laser planes captures all areas of the model precisely, except for interdental spaces, that accounted for the overall imprecision. The deviations of the group 3 models were on average 10 μm. This agrees with the study of Persson et al.
      • Persson A.
      • Andersson M.
      • Oden A.
      • Sandborgh-Englund G.
      A three-dimensional evaluation of a laser scanner and a touch-probe scanner.
      Despite the identical scanning protocol, the precision for extraoral scanning with the iTero (25 μm) was higher than for intraoral scanning with the iTero (50 μm). This might be due to patient movement, limited intraoral space, intraoral humidity, and saliva flow. High deviations in intraoral scans of the molar areas indicate that patient-related factors had a strong influence on scanning quality. In comparison, the reduced values obtained with the extraoral iTero scanning might result from greater freedom of placement of the scanning wand next to the model teeth.
      Numerous in-vitro studies have shown that prerequisites for clinical use of intraoral and extraoral scanning devices are met.
      • Dalstra M.
      • Melsen B.
      From alginate impressions to digital virtual models: accuracy and reproducibility.
      • Luthardt R.G.
      • Kühmstedt P.
      • Walter M.H.
      A new method for the computer-aided evaluation of three-dimensional changes in gypsum materials.
      • Rudolph H.
      • Luthardt R.
      • Walter M.
      Computer-aided analysis of the influence of digitizing and surfacing on the accuracy in dental CAD/CAM technology.
      • Del Corso M.
      • Abà G.
      • Vazquez L.
      • Dargaud J.
      • Dohan Ehrenfest D.M.
      Optical three-dimensional scanning acquisition of the position of osseointegrated implants: an in vitro study to determine method accuracy and operational feasibility.
      • DeLong R.
      • Heinzen M.
      • Hodges J.S.
      • Ko C.C.
      • Douglas W.H.
      Accuracy of a system for creating 3D computer models of dental arches.
      However, the precision of scanning devices under intraoral conditions has not been documented to date. This study shows that the iTero system in vivo and ex vivo can be used to create virtual models for diagnostics and treatment planning in orthodontics. To manufacture orthodontic appliances on the basis of the virtual models, not only the scanning process but also the production process must be considered. Computer-aided design and computer-aided manufacturing on the basis of virtual models created with data from the iTero intraoral scans are accompanied by inaccuracies, especially when the depiction of facial surfaces of anterior teeth and molars or marginal soft tissues is important for the appliance (eg, aligners, customized brackets). Extraoral scanning techniques show higher precision and therefore allow higher accuracy of applicances built with computer-aided design and computer-aided manufacturing. However, the inaccuracies of the impression must be added to all laser scanning data acquired ex vivo.
      We showed that intraoral scanning with the iTero was less precise than extraoral scanning and digitization with the D250, which is still the most precise digitization method currently available. The precision of the intraoral iTero scan is similar to the values documented in the literature with conventional polyether impressions (61.3 ± 17.9 μm) for reproduction of the intraoral situation. The in-vitro precision for the CEREC (30.9 ± 7.1 μm) was comparable with that of the iTero under extraoral conditions (25 μm) in our study.
      • Ender A.
      • Mehl A.
      Full arch scans: conventional versus digital impressions—an in-vitro study.
      The in-vitro precision of the Lava-COS system (60.1 ± 31.3 μm) was lower than the in-vitro and in-vivo precision of the iTero.
      • Ender A.
      • Mehl A.
      Full arch scans: conventional versus digital impressions—an in-vitro study.
      With CEREC and iTero, the images are recorded in a static position relative to the tooth, whereas the Lava COS captures images while the scanning wand is constantly moving; this might result in lower precision for this technique.
      Our results indicate that the positions of teeth and their surfaces can be reproduced in a virtual model, but soft-tissue reproduction was imprecise.
      The image acquisition technique of the iTero does not require the application of a scanning powder. The precision of the iTero might be higher compared with the CEREC and the Lava-COS, since powder application, necessary for these systems, produces a layer of variable thickness.
      • Meyer B.J.
      • Mormann W.H.
      • Lutz F.
      Optimization of the powder application in the Cerec method with environment-friendly propellant systems.

      Conclusions

      Intraoral scanning with the iTero is less precise than model scanning with it. Therefore, patient-related factors influence the scanning process. Scanning of the maxilla is less accurate than scanning of the mandible. An extended scanning protocol might improve the scanning results in the maxilla. Because of its technical features, extraoral scanning has the highest precision. For treatment planning and manufacturing of tooth-supported appliances, virtual models created with the iTero can be used.

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