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Research Article| Volume 12, ISSUE 1, P9-14, February 2023

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Validity and reliability of three-dimensional modeling of orthodontic dental casts using smartphone-based photogrammetric technology

  • Dhelal Al-Rudainy
    Correspondence
    Corresponding authors: Dhelal Al-Rudainy: University of Baghdad Bab Al-Moadham Campus, College of Dentistry, Iraq. Liu Yang: The Eighth Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong 518003, China.
    Affiliations
    Orthodontic Department, College of Dentistry, University of Baghdad, Baghdad, Iraq
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  • Hadeel Adel Al-Lami
    Affiliations
    Orthodontic Department, College of Dentistry, University of Baghdad, Baghdad, Iraq
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  • Liu Yang
    Correspondence
    Corresponding authors: Dhelal Al-Rudainy: University of Baghdad Bab Al-Moadham Campus, College of Dentistry, Iraq. Liu Yang: The Eighth Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong 518003, China.
    Affiliations
    Departmet of Stomatology, The Eighth Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong, China
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Published:December 16, 2022DOI:https://doi.org/10.1016/j.ejwf.2022.11.002

      Highlights

      • Three-dimensional (3D) modeling of orthodontic dental casts can be accomplished by smartphone-based stereophotogrammetry.
      • The accuracy of virtual orthodontic dental casts produced by smartphone-based stereophotogrammetry was about 0.34 mm, and the error of repeated 3D models using this method was 0.03 mm.
      • Stereophotogrammetry using smartphone devices is a simple and low-cost technology for the 3D modeling of orthodontic dental casts.
      • This method is a helpful low-cost tool for the digital archiving of dental casts, eliminating physical storage shortcomings, such as broken models and space requirements.

      ABSTRACT

      Background

      The development of intraoral scanning technology has effectively enhanced the digital documentation of orthodontic dental casts. Albeit, the expense of this technology is the main limitation.
      The purpose of the present study was to assess the validity and reliability of virtual three-dimensional (3D) models of orthodontic dental casts, which were constructed using smartphone-based 3D photogrammetry.

      Methods

      A smartphone was used to capture a set of two-dimensional images for 30 orthodontic dental casts. The captured images were processed to construct 3D virtual images using Agisoft and 3DF Zephyr software programs. To evaluate the accuracy of the virtual 3D models obtained by the two software programs, the virtual 3D models were compared with cone-beam computed tomography scans of the 30 dental casts. Colored maps were used to express the absolute distances between the points of each compared two surfaces; then, the means of the 100%, 95th, and 90th of the absolute distances were calculated. A Wilcoxon signed-rank test was applied to detect any significant differences.

      Results

      The differences between the constructed 3D images and the cone-beam computed tomography scans were not statistically significant and were accepted clinically. The deviations were mostly in the interproximal areas and in the occlusal details (sharp cusps and deep pits and fissures).

      Conclusions

      This study found that smartphone-based stereophotogrammetry is an accurate and reliable method for 3D modeling of orthodontic dental casts, with errors less than the accepted clinically detectable error of 0.5 mm. Smartphone photogrammetry succeeded in presenting occlusal details, but it was difficult to accurately reproduce interproximal areas.

      Graphical abstract

      Keywords

      1. Introduction

      In orthodontics, dental casts are valuable tools for precise diagnosis, treatment planning, and evaluation of treatment outcomes. The British Orthodontic Society has recommended retaining orthodontic study models for 11 years or until young patients reach 25 years old [
      • Crory PVM.
      British Orthodontic Society's initiative on orthodontic retention, a GDP's perspective.
      ]. However, storage space is an issue [
      • McGuinness NJ
      • Stephens CD.
      Storage of orthodontic study models in hospital units in the U.K.
      ], and virtualization of dental casts has become the most desirable solution [
      • Abizadeh N
      • Moles DR
      • O'Neill J
      • Noar JH
      Digital versus plaster study models: how accurate and reproducible are they?.
      ]. Digital intraoral scanning devices have provided three-dimensional (3D) virtual models of dentition that offer numerous applications in dentistry generally and in orthodontics specifically [
      • Flügge TV
      • Schlager S
      • Nelson K
      • Nahles S
      • Metzger MC.
      Precision of intraoral digital dental impressions with iTero and extraoral digitization with the iTero and a model scanner.
      ,
      • Martin CB
      • Chalmers EV
      • McIntyre GT
      • Cochrane H
      • Mossey PA.
      Orthodontic scanners: what's available?.
      . This innovative technology helps orthodontists in many aspects, such as digital analysis of dental arches, occlusion evaluations, and digital storage of study models. However, this technology is not readily available in every dental clinic because of its high cost; the average expenditures are between £13,000 and £31,000 [
      • Martin CB
      • Chalmers EV
      • McIntyre GT
      • Cochrane H
      • Mossey PA.
      Orthodontic scanners: what's available?.
      ]. Attempts at low-cost virtual dental cast productions using digital cameras have been introduced in the literature [
      • Pojda D
      • Tomaka AA
      • Luchowski L
      • Tarnawski M.
      Integration and application of multimodal measurement techniques: relevance of photogrammetry to orthodontics.
      ,
      • Stuani VT
      • Ferreira R
      • Manfredi GGP
      • Cardoso MV
      • Sant'Ana ACP
      Photogrammetry as an alternative for acquiring digital dental models: a proof of concept.
      ,
      • Zotti F
      • Rosolin L
      • Bersani M
      • Poscolere A
      • Pappalardo D
      • Zerman N.
      Digital dental models: is photogrammetry an alternative to dental extraoral and intraoral scanners?.
      ,
      • Silvester CM
      • Hillson S.
      A critical assessment of the potential for Structure-from-Motion photogrammetry to produce high fidelity 3D dental models.
      ]. It has been concluded that photogrammetry is applicable for the digitization of dental models, and further studies have been suggested to evaluate the clinical application of its methods.
      Smartphone technology has become part of our daily lives and requires no professionality or experience. It has been presented in orthodontic literature for different purposes, such as digital cephalometric analysis [
      • Livas C
      • Delli K
      • Spijkervet FKL
      • Vissink A
      • Dijkstra PU.
      Concurrent validity and reliability of cephalometric analysis using smartphone apps and computer software.
      ,
      • Zamrik OM
      • İşeri H.
      The reliability and reproducibility of an android cephalometric smartphone application in comparison with the conventional method.
      , treatment monitoring systems [
      • Moylan HB
      • Carrico CK
      • Lindauer SJ
      • Tüfekçi E.
      Accuracy of a smartphone-based orthodontic treatment-monitoring application: a pilot study.
      ], and clinical 3D facial scanning [
      • Unkovskiy A
      • Spintzyk S
      • Beuer F
      • Huettig F
      • Röhler A
      • Kraemer-Fernandez P.
      Accuracy of capturing nasal, orbital, and auricular defects with extra- and intraoral optical scanners and smartphone: an in vitro study.
      ,
      • Salazar-Gamarra R
      • Seelaus R
      • da Silva JVL
      • da Silva AM
      • Dib LL.
      Monoscopic photogrammetry to obtain 3D models by a mobile device: a method for making facial prostheses.
      ,
      • Nightingale RC
      • Ross MT
      • Allenby MC
      • Woodruff MA
      • Powell SK.
      A method for economical smartphone-based clinical 3D facial scanning.
      ]. Virtual facial models were created by capturing two-dimensional (2D) images of the face using a smartphone, and, with the aid of software, 3D models of the face were generated [
      • Salazar-Gamarra R
      • Seelaus R
      • da Silva JVL
      • da Silva AM
      • Dib LL.
      Monoscopic photogrammetry to obtain 3D models by a mobile device: a method for making facial prostheses.
      ,
      • Nightingale RC
      • Ross MT
      • Allenby MC
      • Woodruff MA
      • Powell SK.
      A method for economical smartphone-based clinical 3D facial scanning.
      . The technique was noninvasive, and it was considered a low-cost alternative to stereophotogrammetry and 3D scanners. The application of this technology has not been limited to 3D facial construction; it was used by Barbero-García et al. (2019) [
      • Barbero-García I
      • Lerma JL
      • Miranda P
      • Marqués-Mateu Á.
      Smartphone-based photogrammetric 3D modelling assessment by comparison with radiological medical imaging for cranial deformation analysis.
      ] for the production of virtual cranial vaults for 10 children with cranial deformities. Using a smartphone camera, short videos were recorded, and then, a series of 2D images were extracted from the videos to create 3D models of the cranial vaults using PhotoScan (Agisoft) software. The accuracy of the obtained 3D meshes was comparable to medical diagnostic imaging of cranial vaults (magnetic resonance imaging and computed tomography scans) [
      • Barbero-García I
      • Lerma JL
      • Miranda P
      • Marqués-Mateu Á.
      Smartphone-based photogrammetric 3D modelling assessment by comparison with radiological medical imaging for cranial deformation analysis.
      ].
      To the best of our knowledge, in literature, smartphone-based photogrammetry has not yet been used for the creation of 3D virtual models of orthodontic dental casts. This technology can offer orthodontists low-cost production of virtual dental casts that can be used for digital diagnosis, treatment planning, and digital archiving of dental casts where intraoral scanners are not available.
      This study aimed to measure the validity and reliability of virtual 3D orthodontic dental casts produced by smartphone-based 3D photogrammetry.

      2. Material and Methods

      2.1 Sample

      In the study, 30 randomly selected dental casts for different orthodontic cases were selected from an orthodontic clinic. Two staff members volunteered to collect 30 orthodontic casts—15 each—from storing drawers. The casts were accessed and selected separately and by chance and were from orthodontic treatments in 2017, 2018, and 2019.

      2.2 Generating photogrammetric 3D models

      A Samsung Galaxy Note 9 smartphone was used to capture a set of 2D images for each cast with a zoom of × 2.0. The images were captured while the cast was rotated manually on a disk (Fig. 1A), in such a way that the images were taken around the cast in circles at different heights (Fig. 1B ). The number of images ranged from 80 to 120 within each set and were captured within a few minutes.
      Fig 1
      Fig. 1Illustration of 2D image acquisition. A dental cast was placed on a rotatable disk (A), and a set of 80 to 120 2D images with position information was captured by a smartphone (Samsung Galaxy Note 9) with zoom of × 2.0 by surrounding the cast at different heights (B).
      For each dental cast, two virtual 3D images were created using two types of software: Agisoft (Metashape version 1.5.2) and 3DF Zephyr Aerial (version 4.501) (Fig. 2). First, the set of 2D images of each individual dental cast was imported into the two software programs. The process of 3D model production generally consisted of four main steps in both programs: alignment of the images, point cloud production, mesh generation, and finally, texture mapping. The constructed 3D images were exported and saved in obj.file formats.
      Fig 2
      Fig. 23D models of an orthodontic dental cast constructed using Agisoft software (left), 3DF Zephyr software (middle), CBCT (right).
      The 30 casts were scanned using a cone-beam computed tomography (CBCT) device (NewTom GO), and the images from this were exported to STL.file formats. The 3D images of each dental cast from CBCT, Agisoft, and 3DF Zephyr software packages (Fig. 2) were cropped and scaled using Meshmixer 3.5.474 (Autodesk) software and saved in obj.file formats.

      2.3 Measurements

      To measure the accuracy of the obtained stereophotogrammetric 3D images from both programs of an individual cast, they were compared with a CBCT scan of the same cast and with each other (Fig. 3). CloudCompare software (version 2.10.2 Zephyrus) was used to compare pairings of CBCT models and stereophotogrammetric models, and also to compare each pair of stereophotogrammetric models produced by the two programs. The two 3D models of the same dental cast were imported to CloudCompare software and registered manually. Then, an iterative closest point tool was used to approximate the two surfaces of the 3D models to the minimum mean distances. A colored map of the absolute distances between the closest points of the two surfaces was created, and the distances between these points were exported to txt.file format. The means of 100%, 95th, and 90th percentiles of the absolute distances were calculated.
      Fig 3
      Fig. 3Flow chart illustrates the comparison process between virtual dental casts.

      2.4 Error of the method

      New sets of 2D images were captured for 15 randomly selected dental casts of the sample [
      • Almukhtar A
      • Ayoub A
      • Khambay B
      • McDonald J
      • Ju X.
      State-of-the-art three-dimensional analysis of soft tissue changes following Le Fort I maxillary advancement.
      ,
      • Cheung MY
      • Almukhtar A
      • Keeling A
      • et al.
      The accuracy of conformation of a generic surface mesh for the analysis of facial soft tissue changes.
      ,
      • Almukhtar A
      • Khambay B
      • Ju X
      • McDonald J
      • Ayoub A.
      Accuracy of generic mesh conformation: the future of facial morphological analysis.
      ], and stereophotogrammetric images of these casts were repeated using Agioft and 3DF Zephyr software programs after a 1-month interval. The mean differences between the repeated images for each software type were calculated.

      2.5 Statistical analysis

      The distributions of the means of absolute distances between CBCT scans of orthodontic dental casts (the reference) and their 3D models produced by Agisoft and 3DF Zephyr software programs were tested for normality. Normality tests reject the null hypothesis that the means of absolute distances for each program are derived from a standard normal distribution (P ≤ 0.05). A Wilcoxon signed-rank test was applied to determine whether the differences between stereomodels and their CBCT counterparts and between the two programs were significantly different.

      3. Results

      The mean errors of repeated stereophotogrammetric images of dental casts by Agisoft and 3DF Zephyr software programs were 0.03 mm and 0.01 mm, respectively.
      Table 1 shows the differences between each pair of CBCT models and the stereophotogrammetric images of Agisoft and 3DF Zephyr separately. The means of the 100% mesh point differences were 0.55 mm and 0.50 mm for the Agisoft and 3DF Zephyr software programs, respectively. The means of the 95th and 90th percentile differences were 0.44 mm and 0.38 mm for the Agisoft software, which were comparable to those of the 3DF Zephyr software (0.36 mm and 0.32 mm). All differences were not statistically significant.
      Table 1Mean of absolute distances in mm and P-value of Wilcoxon signed ranks test between CBCT scans of orthodontic dental casts (the reference) and their 3D models produced by Agiosft and 3DF Zephyr software
      Agisoft3DF ZephyrP-value
      MeanSDMinMaxMeanSDMinMax
      100% mesh points0.550.540.052.180.500.560.082.550.349
      95th percentile0.440.460.031.860.360.480.052.260.165
      90th percentile0.380.410.051.600.320.410.042.020.098
      3D, three-dimensional; CBCT, cone-beam computed tomography; Max, maximum; Min, minimum.
      Figure 4 shows the means of the 100%, 95th, and 90th percentiles of absolute distances between Agisoft and 3DF Zephyr programs. The differences were 0.02 mm, 0.01 mm, and 0.01 mm, respectively.
      Fig 4
      Fig. 4Box plots and whisker diagrams of the absolute distances between stereophotogrammetric models produced by Agisoft and 3DF Zephyr software. Mean, median, minimum and maximum are presented.

      4. Discussion

      This study showed that 3D modeling of orthodontic dental casts using smartphone technology was applicable. The error of the constructed 3D models was about 0.3 mm in comparison with corresponding CBCT images. The mean difference between the 3D models produced by the two software types was about 0.01 mm.
      The study compared the 3D models constructed by two software programs: Agisoft and 3DF Zephyr. The errors of repeated 3D models of dental casts by software programs were 0.03 mm and 0.01 mm, respectively. Accordingly, both software programs can be considered reliable.
      The generated stereophotogrammetric images of dental casts produced by both software programs were compared with the corresponding CBCT models individually because the latter has been considered the gold standard [
      • Tarazona B
      • Llamas JM
      • Cibrian R
      • Gandia JL
      • Paredes V.
      A comparison between dental measurements taken from CBCT models and those taken from a Digital Method.
      ,
      • Al-Rimawi A
      • Shaheen E
      • Albdour EA
      • Shujaat S
      • Politis C
      • Jacobs R.
      Trueness of cone beam computed tomography versus intra-oral scanner derived three-dimensional digital models: an ex vivo study.
      ,
      • Emara A
      • Sharma N
      • Halbeisen FS
      • Msallem B
      • Thieringer FM.
      Comparative evaluation of digitization of diagnostic dental cast (plaster) models using different scanning technologies.
      ]. The mean of the absolute distances between stereophotogrammetric images and the corresponding CBCT models was about 0.5 mm (Table 1). This difference decreased to about 0.3 mm when calculating the mean of the 95th and 90th percentiles, and the differences were not statistically significant, with errors less than the accepted clinically detectable error of 0.5 mm [
      • Luu NS
      • Nikolcheva LG
      • Retrouvey J-M
      • et al.
      Linear measurements using virtual study models.
      ]. The decrease in the means is reasonable because the outliers had been excluded. Studies that use an iterative closest point tool for surface-based comparison usually apply the mean of the 90th percentile to eliminate the effect of outliers [
      • Khambay B
      • Ullah R.
      Current methods of assessing the accuracy of three-dimensional soft tissue facial predictions: technical and clinical considerations.
      ,
      • Al-Rudainy D
      • Ju X
      • Stanton S
      • Mehendale FV
      • Ayoub A.
      Assessment of regional asymmetry of the face before and after surgical correction of unilateral cleft lip.
      . CloudCompare software was used for the comparison between the surfaces of the 3D models; the accuracy of this software has been proven [
      • Oniga E
      • Florentin A
      • Negrila C.
      The evaluation of Cloudcompare software in the process of TLS the evaluation of Cloudcompare software in the process of TLS point clouds registration.
      ]. In dentistry, it has been used for 3D model comparisons [
      • Nightingale RC
      • Ross MT
      • Allenby MC
      • Woodruff MA
      • Powell SK.
      A method for economical smartphone-based clinical 3D facial scanning.
      ,
      • Nulty A.
      A comparison of trueness and precision of 12 3D printers used in dentistry.
      ,
      • Au J
      • Mei L
      • Bennani F
      • Kang A
      • Farella M.
      Three-dimensional analysis of lip changes in response to simulated maxillary incisor advancement.
      and for dental model comparisons specifically [
      • Silvester CM
      • Hillson S.
      A critical assessment of the potential for Structure-from-Motion photogrammetry to produce high fidelity 3D dental models.
      ,
      • Amaral Vargas EO
      • Otero Amaral Vargas D
      • da Silva Coqueiro R
      • Franzotti Sant'anna E
      • Melo Pithon M
      Impact of orthodontic brackets on intraoral and extraoral scans.
      ,
      • Sharp IG
      • Minick G
      • Carey C
      • Shellhart CW
      • Tilliss T.
      Assessment of simulated vs actual orthodontic tooth movement with a customized fixed lingual appliance using untreated posterior teeth for registration and digital superimposition: a retrospective study.
      ,
      • Piedra-Cascón W
      • Methani MM
      • Quesada-Olmo N
      • Jiménez-Martínez MJ
      • Revilla-León M.
      Scanning accuracy of nondental structured light extraoral scanners compared with that of a dental-specific scanner.
      .
      In this study, the differences from CBCT (0.3 mm) were less than the differences found in the study of Barbero-García et al. (1.72 mm) [
      • Barbero-García I
      • Lerma JL
      • Miranda P
      • Marqués-Mateu Á.
      Smartphone-based photogrammetric 3D modelling assessment by comparison with radiological medical imaging for cranial deformation analysis.
      ], even though the same software (Agisoft) was used in both studies. Barbero-García et al. stated that the higher errors in their study were due to the effect of hair because their images were for head vaults and not dental casts. The errors in their study could also be due to the use of a different method. In their study, the smartphone was rotated around the patients’ heads during imaging, and the 2D images were extracted from videos. In contrast, in this study, the dental cast was on a rotating disk during the imaging process, and the 2D images were directly captured. This method could give more control and reduce errors. Furthermore, the dental cast morphology was more detailed than in the patients’ head vaults; these details can help in the triangulation process and produce more accurate image registrations. The deviations from CBCT in this study were difficult to compare with the study of Stuani et al. [
      • Stuani VT
      • Ferreira R
      • Manfredi GGP
      • Cardoso MV
      • Sant'Ana ACP
      Photogrammetry as an alternative for acquiring digital dental models: a proof of concept.
      ] because theirs was based on the differences between linear measurements of plaster models and their digital models. They reported discrepancies in the posterior regions rather than the anterior regions, which was not the case in this study. The reason for this is not clear, but it could be due to the number of captured images for each cast of their study being less than in this study; their set of images included only 50 photos, whereas in this study, a range of 80 to 120 photos were captured for each cast. Increasing the number of captured images is crucial; an accurate and precise 3D model necessitates more informative data that improve the efficacy of the triangulation algorithm.
      Studies that compared 3D images of dental casts produced by intraoral scanners with their CBCT scans showed that the differences were 0.57 mm and 0.4 mm [
      • Kim J
      • Heo G
      • Lagravère MO.
      Accuracy of laser-scanned models compared to plaster models and cone-beam computed tomography.
      ,
      • Ryan S
      • Kelton S
      • Ghoneima A.
      Three-dimensional analysis of digital models generated from intraoral, extraoral, and CBCT scanning devices.
      . These results were comparable to the mean differences between stereophotogrammetric models and CBCT scans in our study (see Table 1). It is worth noting that these studies were landmark-based and not surface-based studies.
      The color maps of this study showed that, in most of the cases, the deviation of stereophotogrammetric images from CBCT was in the interproximal areas and at occlusal details: sharp cusps, deep pits, and fissures (Fig. 5, left and middle). It has been stated that in CBCT scans, the interproximal contact points are rounded and indistinct, with a lack of detailed cuspal anatomy [
      • Ryan S
      • Kelton S
      • Ghoneima A.
      Three-dimensional analysis of digital models generated from intraoral, extraoral, and CBCT scanning devices.
      ,
      • San José V
      • Bellot-Arcís C
      • Tarazona B
      • Zamora N
      • O Lagravère M
      • Paredes-Gallardo V
      Dental measurements and Bolton index reliability and accuracy obtained from 2D digital, 3D segmented CBCT, and 3d intraoral laser scanner.
      . However, the pattern of deviation between the images produced by the two software programs, in most of the cases, was in the interproximal areas. The absolute distances between the stereophotogrammetric images were less than the distances from CBCT images (Fig. 5, right). Unlike CBCT scans, the software succeeded in presenting occlusal details, but interproximal areas were difficult to reproduce with these programs.
      Fig 5
      Fig. 5Color maps show the differences between the 3D models of orthodontic dental casts. Left: the CBCT scan (the reference) and stereophotogrammetric model of Agisoft software. Middle: CBCT scan and stereophotogrammetric model of 3DF Zephyr software. Right: stereophotogrammetric models of Agisoft and 3DF Zephyr software.
      The mean differences between the two software types (Agisoft and 3DF Zephyr) were minimal, at around 0.01 mm only (Fig. 4). Both programs apply the same steps and principles in 3D image production, which can reduce the errors between them. Practically, there was no difference between the two software types and both were user-friendly. The only difference was that 3D image construction was a one-step process in the 3DF Zephyr software but the steps were performed separately under the user's control in Agisoft.
      Image calibration was not included in the methodology of this study because our aim was to introduce a simple technique, which is applicable to the majority rather than limited to professional dentists [
      • Stuani VT
      • Ferreira R
      • Manfredi GGP
      • Cardoso MV
      • Sant'Ana ACP
      Photogrammetry as an alternative for acquiring digital dental models: a proof of concept.
      ]. Unlike previous studies, dental casts used in this study were from an orthodontic clinic and were selected randomly for different orthodontic cases. The results of this study reflect the clinical application of smartphone-based 3D modeling of orthodontic dental casts for real clinical cases and are not for typodonts or dentures.
      In terms of expenditure, this technique was almost free, and the requirements were feasible. The 2D images could be captured by an available smartphone device of a dental staff member, the rotating disk was inexpensive (around $15), and the 3DF Zephyr program Aerial (version 4.501) was free. In contrast, the annual cost of Agisoft software was $179, which is reasonable. Both programs have been used in the literature [
      • Stuani VT
      • Ferreira R
      • Manfredi GGP
      • Cardoso MV
      • Sant'Ana ACP
      Photogrammetry as an alternative for acquiring digital dental models: a proof of concept.
      ,
      • Silvester CM
      • Hillson S.
      A critical assessment of the potential for Structure-from-Motion photogrammetry to produce high fidelity 3D dental models.
      ,
      • Nightingale RC
      • Ross MT
      • Allenby MC
      • Woodruff MA
      • Powell SK.
      A method for economical smartphone-based clinical 3D facial scanning.
      ,
      • Barbero-García I
      • Lerma JL
      • Miranda P
      • Marqués-Mateu Á.
      Smartphone-based photogrammetric 3D modelling assessment by comparison with radiological medical imaging for cranial deformation analysis.
      , and this study showed no significant differences between the two programs and the user desires to choose the program they prefer. Despite professional digital cameras being used in some studies [
      • Pojda D
      • Tomaka AA
      • Luchowski L
      • Tarnawski M.
      Integration and application of multimodal measurement techniques: relevance of photogrammetry to orthodontics.
      ,
      • Stuani VT
      • Ferreira R
      • Manfredi GGP
      • Cardoso MV
      • Sant'Ana ACP
      Photogrammetry as an alternative for acquiring digital dental models: a proof of concept.
      ,
      • Zotti F
      • Rosolin L
      • Bersani M
      • Poscolere A
      • Pappalardo D
      • Zerman N.
      Digital dental models: is photogrammetry an alternative to dental extraoral and intraoral scanners?.
      ,
      • Silvester CM
      • Hillson S.
      A critical assessment of the potential for Structure-from-Motion photogrammetry to produce high fidelity 3D dental models.
      ], with a minimal cost of $200, this study proved that a smartphone camera is suitable for the generation of 3D models of orthodontic casts and can save unnecessary expenditures.
      The application of this method will help to create virtual dental casts for the digital archiving of dental casts, eliminating physical storage shortcomings, such as broken models and space requirements by capturing 2D images using smartphone technology, where intraoral scanners are not available. Constantly evolving smartphone technology can open the doors to a new era in 3D imaging in dentistry and in orthodontics specifically.

      5. Conclusions

      The clinical application of smartphone-based photogrammetry to produce virtual orthodontic dental casts was simple, low-cost, and with errors less than the accepted clinically detectable error of 0.5 mm. Both Agisoft and 3DF Zephyr software programs were reliable for the generation of 3D models of orthodontic dental casts. Smartphone photogrammetry succeeded in presenting occlusal details, but interproximal areas were difficult to accurately reproduce.

      Acknowledgment

      The authors thank Dr. Abdullah Ahmed Ibrahim for helping with obtaining cone-beam computed tomography scans for the dental casts.

      Author contributions

      D.A. captured the 2D images of dental casts, generated the 3D models, and compared the 3D images produced by both programs. H.A. obtained the CBCT images of dental casts and measured the deviation of 3D models from CBCT images. L.Y. designed the study, performed the computations, conducted the analytic calculation, and wrote the manuscript with input from the first and second authors.

      References

        • Crory PVM.
        British Orthodontic Society's initiative on orthodontic retention, a GDP's perspective.
        Br Dent J. 2018; 224: 481-486
        • McGuinness NJ
        • Stephens CD.
        Storage of orthodontic study models in hospital units in the U.K.
        Br J Orthod. 1992; 19: 227-232
        • Abizadeh N
        • Moles DR
        • O'Neill J
        • Noar JH
        Digital versus plaster study models: how accurate and reproducible are they?.
        J Orthod. 2012; 39: 151-159
        • Flügge TV
        • Schlager S
        • Nelson K
        • Nahles S
        • Metzger MC.
        Precision of intraoral digital dental impressions with iTero and extraoral digitization with the iTero and a model scanner.
        Am J Orthod Dentofacial Orthop. 2013; 144: 471-478
        • Martin CB
        • Chalmers EV
        • McIntyre GT
        • Cochrane H
        • Mossey PA.
        Orthodontic scanners: what's available?.
        J Orthod. 2015; 42: 136-143
        • Pojda D
        • Tomaka AA
        • Luchowski L
        • Tarnawski M.
        Integration and application of multimodal measurement techniques: relevance of photogrammetry to orthodontics.
        Sensors (Basel). 2021; 21: 8026
        • Stuani VT
        • Ferreira R
        • Manfredi GGP
        • Cardoso MV
        • Sant'Ana ACP
        Photogrammetry as an alternative for acquiring digital dental models: a proof of concept.
        Med Hypotheses. 2019; 128: 43-49
        • Zotti F
        • Rosolin L
        • Bersani M
        • Poscolere A
        • Pappalardo D
        • Zerman N.
        Digital dental models: is photogrammetry an alternative to dental extraoral and intraoral scanners?.
        Dent J (Basel). 2022; 10: 1-15
        • Silvester CM
        • Hillson S.
        A critical assessment of the potential for Structure-from-Motion photogrammetry to produce high fidelity 3D dental models.
        Am J Phys Anthropol. 2020; 173: 381-392
        • Livas C
        • Delli K
        • Spijkervet FKL
        • Vissink A
        • Dijkstra PU.
        Concurrent validity and reliability of cephalometric analysis using smartphone apps and computer software.
        Angle Orthod. 2019; 89: 889-896
        • Zamrik OM
        • İşeri H.
        The reliability and reproducibility of an android cephalometric smartphone application in comparison with the conventional method.
        Angle Orthod. 2021; 91: 236-242
        • Moylan HB
        • Carrico CK
        • Lindauer SJ
        • Tüfekçi E.
        Accuracy of a smartphone-based orthodontic treatment-monitoring application: a pilot study.
        Angle Orthod. 2019; 89: 727-733
        • Unkovskiy A
        • Spintzyk S
        • Beuer F
        • Huettig F
        • Röhler A
        • Kraemer-Fernandez P.
        Accuracy of capturing nasal, orbital, and auricular defects with extra- and intraoral optical scanners and smartphone: an in vitro study.
        J Dent. 2022; 117103916
        • Salazar-Gamarra R
        • Seelaus R
        • da Silva JVL
        • da Silva AM
        • Dib LL.
        Monoscopic photogrammetry to obtain 3D models by a mobile device: a method for making facial prostheses.
        J Otolaryngol Head Neck Surg. 2016; 45: 33
        • Nightingale RC
        • Ross MT
        • Allenby MC
        • Woodruff MA
        • Powell SK.
        A method for economical smartphone-based clinical 3D facial scanning.
        J Prosthodont. 2020; 29: 818-825
        • Barbero-García I
        • Lerma JL
        • Miranda P
        • Marqués-Mateu Á.
        Smartphone-based photogrammetric 3D modelling assessment by comparison with radiological medical imaging for cranial deformation analysis.
        Measurement. 2019; 131: 372-379
        • Almukhtar A
        • Ayoub A
        • Khambay B
        • McDonald J
        • Ju X.
        State-of-the-art three-dimensional analysis of soft tissue changes following Le Fort I maxillary advancement.
        Br J Oral Maxillofac Surg. 2016; 54: 812-817
        • Cheung MY
        • Almukhtar A
        • Keeling A
        • et al.
        The accuracy of conformation of a generic surface mesh for the analysis of facial soft tissue changes.
        PLoS One. 2016; 11e0152381
        • Almukhtar A
        • Khambay B
        • Ju X
        • McDonald J
        • Ayoub A.
        Accuracy of generic mesh conformation: the future of facial morphological analysis.
        JPRAS Open. 2017; 14: 39-48
        • Tarazona B
        • Llamas JM
        • Cibrian R
        • Gandia JL
        • Paredes V.
        A comparison between dental measurements taken from CBCT models and those taken from a Digital Method.
        Eur J Orthod. 2013; 35: 1-6
        • Al-Rimawi A
        • Shaheen E
        • Albdour EA
        • Shujaat S
        • Politis C
        • Jacobs R.
        Trueness of cone beam computed tomography versus intra-oral scanner derived three-dimensional digital models: an ex vivo study.
        Clin Oral Implants Res. 2019; 30: 498-504
        • Emara A
        • Sharma N
        • Halbeisen FS
        • Msallem B
        • Thieringer FM.
        Comparative evaluation of digitization of diagnostic dental cast (plaster) models using different scanning technologies.
        Dent J (Basel). 2020; 8: 79
        • Luu NS
        • Nikolcheva LG
        • Retrouvey J-M
        • et al.
        Linear measurements using virtual study models.
        Angle Orthod. 2012; 82: 1098-1106
        • Khambay B
        • Ullah R.
        Current methods of assessing the accuracy of three-dimensional soft tissue facial predictions: technical and clinical considerations.
        Int J Oral Maxillofac Surg. 2015; 44: 132-138
        • Al-Rudainy D
        • Ju X
        • Stanton S
        • Mehendale FV
        • Ayoub A.
        Assessment of regional asymmetry of the face before and after surgical correction of unilateral cleft lip.
        J Craniomaxillofac Surg. 2018; 46: 974-978
        • Oniga E
        • Florentin A
        • Negrila C.
        The evaluation of Cloudcompare software in the process of TLS the evaluation of Cloudcompare software in the process of TLS point clouds registration.
        RevCAD J Geod Cadastar. 2016; 21: 117-124
        • Nulty A.
        A comparison of trueness and precision of 12 3D printers used in dentistry.
        BDJ Open. 2022; 8: 14
        • Au J
        • Mei L
        • Bennani F
        • Kang A
        • Farella M.
        Three-dimensional analysis of lip changes in response to simulated maxillary incisor advancement.
        Angle Orthod. 2020; 90: 118-124
        • Amaral Vargas EO
        • Otero Amaral Vargas D
        • da Silva Coqueiro R
        • Franzotti Sant'anna E
        • Melo Pithon M
        Impact of orthodontic brackets on intraoral and extraoral scans.
        Am J Orthod Dentofac Orthop. 2022; 162: 208-213
        • Sharp IG
        • Minick G
        • Carey C
        • Shellhart CW
        • Tilliss T.
        Assessment of simulated vs actual orthodontic tooth movement with a customized fixed lingual appliance using untreated posterior teeth for registration and digital superimposition: a retrospective study.
        Am J Orthod Dentofacial Orthop. 2022; 161: 272-280
        • Piedra-Cascón W
        • Methani MM
        • Quesada-Olmo N
        • Jiménez-Martínez MJ
        • Revilla-León M.
        Scanning accuracy of nondental structured light extraoral scanners compared with that of a dental-specific scanner.
        J Prosthet Dent. 2021; 126: 110-114
        • Kim J
        • Heo G
        • Lagravère MO.
        Accuracy of laser-scanned models compared to plaster models and cone-beam computed tomography.
        Angle Orthod. 2014; 84: 443-450
        • Ryan S
        • Kelton S
        • Ghoneima A.
        Three-dimensional analysis of digital models generated from intraoral, extraoral, and CBCT scanning devices.
        J Dent Maxillofac Res. 2019; 2: 1-7
        • San José V
        • Bellot-Arcís C
        • Tarazona B
        • Zamora N
        • O Lagravère M
        • Paredes-Gallardo V
        Dental measurements and Bolton index reliability and accuracy obtained from 2D digital, 3D segmented CBCT, and 3d intraoral laser scanner.
        J Clin Exp Dent. 2017; 9: e1466-e1473