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Superimposition of a cone beam computed tomography (CBCT) scan and a photograph: A dental technique
DENTAL TECHNIQUE
Superimposition of a cone beam computed tomography (CBCT) scan and a photograph: A dental technique Soo Young Lee, DMD, PhD,a Heechul Kim, DDS, PhD,b Doyun Lee, DDS, PhD,c and Chan Park, DDS, PhDd Communication between ABSTRACT dentists and dental techniVarious methods of combining facial and intraoral information have been described. However, cians is essential to achieve overlapping errors lead to errors. This article describes a 3D face model that uses an ultraviolet optimal esthetic and func(UV) mapping technique. The combination of soft-tissue information extracted from cone beam tional outcomes.1 However, in computed tomography (CBCT) and a straightforward facial photograph provides more accurate clinical practice, it is difficult data than with conventional methods. (J Prosthet Dent 2020;-:---) for dental technicians to TECHNIQUE participate actively, and dentists should provide them with as much patient information as possible. 1. Photograph the patient’s face from the front, left, Advances in digital technology have improved the and right and edit the 3 photographs into a single collection of patient data,2 with facial and intraoral image by using an image-editing software program scans being used to transmit and integrate facial (Photoshop CS6; Adobe System Inc) (Fig. 1). First, information.3 However, accurate overlapping of set a vertical line on the frontal view and rotate it so facial and intraoral scan information is problematic as that the left and right eyes are symmetrical. Then, facial soft tissue changes with every scan. A current make horizontal reference lines through the eyes, method4 combines 2 scan data sets by using an mouth, and chin. The structure of the left view occlusal device as a reference point. It requires an (eyes, nose, mouth) can then be adjusted to fit the additional analog method (by using the occlusal horizontal reference line (Fig. 1D). After the device) but has the disadvantage of not evaluating the adjustment is complete, use the software’s masking smile line. function to link the 2 images. The right view is made Cone beam computed tomography (CBCT) can be in the same way, completing the combined image used to improve the current overlapping method of data (Fig. 1E). facial and intraoral scan data. In this method, a normal 2. Acquire a CBCT image of the patient. Convert the facial photograph is converted into an image by using CT soft-tissue data into a standard tessellation the soft tissue faintly included in the CBCT data and language (STL) file by using a medical visualization mapped on the CBCT. This enables the intraoral and software program (InVesalius; CTI). Select “Skin CBCT data of patients to be overlapped into a Tissue (Adult) and create surface at Set redefined combined facial image.
Supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2019R1G1A1006708) and a grant (BCRI19013) of Chonnam National University Hospital Biomedical Research Institute. a Private practice, Obokmanse Dental Clinic, Guro-gu, Seoul, Republic of Korea. b Private practice, W White Dental Clinic, Gangnam-gu, Seoul, Republic of Korea. c Private practice, Doctorplant Dental Clinic, Yeogdeungpo-gu, Seoul, Republic of Korea. d Assistant Professor, Department of Prosthodontics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea.
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Figure 1. Facial photograph. A, Frontal view. B, Left view. C, Right view. D, Processing of frontal and left view superimposition. E, Three photographs superimposed and synthesized with image-editing software.
threshold” to import the CT Digital Imaging and Communications in Medicine (DICOM) file. Then, perform image segmentation and mesh refinement (repairing, smoothing, appending) to the STL file by using the software program procedure.5 The software uses a mesh control program (Netfebb studio Basic; Netfabb GmbH) to reduce the file size (about 3 megabytes) for a fast computer-aided design (CAD) operation (Fig. 2). THE JOURNAL OF PROSTHETIC DENTISTRY
3. Combine the soft-tissue data extracted from CBCT and the facial photograph data by using a 3D modeling software program (Modo; Foundry) to create a new 3D face model through a planar projection (Fig. 3). Import the image file created in Photoshop CS6 by selecting the “shading tap” and “add layer” in the CT data of the Modo software (Fig. 3A). Change the image to a 2D image in Photoshop CS6 and express it as a UV map.5 Adjust Lee et al
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Figure 2. CBCT soft-tissue data acquisition and conversion. CBCT softtissue data acquired on STL files. The file size reduced from 439 to 3 megabytes by using mesh control for fast computer-aided design operation. CBCT, cone-beam computed tomography; STL, standard tessellation language.
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Figure 4. Superimposed intraoral tooth scan data and new manufacturing face model data by using dental CAD software. CAD, computer-aided design.
Figure 3. Three-dimensional face model fabrication by using superimposed facial photograph data and CBCT soft-tissue data through planar projection by using 3D modeling software. A, Import of the CBCT soft-tissue file with Modo software. B, Ultraviolet mapping process for superimposing soft-tissue and photographic image data. C, Rendering output data view. D, Completed facial 3D model file for importing into dental CAD software. CAD, computer-aided design; CBCT, cone beam computed tomography.
the UV map using “UV map editing” in the Modo software for accurate superimposition of the CT soft tissue and photographic image (Fig. 3B). When Lee et al
repositioning is complete, save the image via “render output” (Fig. 3C) to complete the final file (Fig. 3D). If overlapping is not performed in a single THE JOURNAL OF PROSTHETIC DENTISTRY
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attempt, characteristic parts of the face (eyes, nose, mouth) can be overlapped separately, and, subsequently, the whole face can be overlapped. 4. Import the oral data acquired from an intraoral scanner and the facial scan data into a dental CAD software program (Exocad DentalCAD; Exocad GmbH) by superimposition (Fig. 4). DISCUSSION To date, the superimposition of facial and intraoral scan data has been performed by using optical scanning techniques, which are more straightforward than the method described in this article and have the advantage of no radiation exposure. However, because of the changing form of the soft tissues, the overlap is inaccurate, with reduced reliability of the soft-tissue information. The method presented in this article has the advantage of precise soft-tissue information, although there is radiation exposure because of the CBCT. As CT scans are performed at a single time, accurate soft-tissue data can be obtained compared with multiple facial scans. A perfect smile line and anatomic indicators such as the Camper plane can be observed. Moreover, the method of using superimposition data after acquiring intraoral and facial scan data suggests that the average surface distance (ASD) is not constant because of softtissue movement.5 However, this article describes the UV mapping technique, which colors a 3D file in the photograph image and does not cause ASD.6,7 Also, it has the advantage of generating data with straightforward photography and without specialized facial scanners. A similar UV mapping technique has been described for the photograph overlay method.8 While this method is straightforward, it is not accurate because it overlaps a virtual image file. In contrast, the present technique makes a virtual image by using a patient’s CT soft-tissue data, after which the photographic image is superimposed. This method applies color texture data to the soft-tissue surface data included in the CT. Therefore, UV mapping using the CT soft-tissue data can provide
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natural facial data by accurately overlapping the intraoral and extraoral data. The present digital technique can be applied to the existing dental CAD software for universal application. SUMMARY This article introduces a digital technique that superimposes a facial photograph on the soft-tissue data extracted from a CBCT to generate complete information for a patient’s intraoral and extraoral regions. CT data include soft and hard tissue, but the color texture data of soft tissue are not recorded. Superimposing facial photographic images with CT soft-tissue data by using the UV mapping technique will allow for better esthetic and functional treatment planning. REFERENCES 1. Joda T, Zarone F, Ferrari M. The complete digital workflow in fixed prosthodontics: a systematic review. BMC Oral Health 2017;17:124. 2. Schoenbaum TR. Dentistry in the digital age: an update. Dent Today 2012;31. 108, 110, 112-113. 3. Joda T, Bragger U, Gallucci G. Systematic literature review of digital threedimensional superimposition techniques to create virtual dental patients. Int J Oral Maxillofac Implants 2015;30:330-7. 4. Revilla-León M, Raney L, Piedra-Cascón W, Barrington J, Zandinejad A, Özcan M. Digital workflow for an esthetic rehabilitation using a facial and intraoral scanner and an additive manufactured silicone index: a dental technique. J Prosthet Dent 26 July 2019. doi: 10.1016/j.prosdent.2019.03.014. [Epub ahead of print]. 5. Bücking TM, Hill ER, Robertson JL, Maneas E, Plumb AA, Nikitichev DI. From medical imaging data to 3D printed anatomical models. PLoS One 2017;12: e0178540. 6. Levine MD, Yu Y. State-of-the-art of 3D facial reconstruction methods for face recognition based on a single 2D training image per person. Pattern Recogn Lett 2009;30:908-13. 7. Panozzo D, Diamanti O, Paris S, Tarini M, Sorkine E, Sorkine-Hornung O, et al. Texture mapping real-world objects with hydrographics. Comput Graph Forum 2015;34:65-75. 8. Kurbad A, Kurbad S. Cerec smile design–a software tool for the enhancement of restorations in the esthetic zone. Int J Comput Dent 2013;16:255-69. Corresponding author: Dr Chan Park Department of Prosthodontics School of Dentistry Chonnam National University 33 Yongbong-ro, Buk-gu, Gwangju 61186 REPUBLIC OF KOREA Email: [email protected] Copyright © 2020 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2020.01.008
Lee et al
Superimposition of a cone beam computed tomography (CBCT) scan and a photograph: A dental technique Soo Young Lee, DMD, PhD,a Heechul Kim, DDS, PhD,b Doyun Lee, DDS, PhD,c and Chan Park, DDS, PhDd Communication between ABSTRACT dentists and dental techniVarious methods of combining facial and intraoral information have been described. However, cians is essential to achieve overlapping errors lead to errors. This article describes a 3D face model that uses an ultraviolet optimal esthetic and func(UV) mapping technique. The combination of soft-tissue information extracted from cone beam tional outcomes.1 However, in computed tomography (CBCT) and a straightforward facial photograph provides more accurate clinical practice, it is difficult data than with conventional methods. (J Prosthet Dent 2020;-:---) for dental technicians to TECHNIQUE participate actively, and dentists should provide them with as much patient information as possible. 1. Photograph the patient’s face from the front, left, Advances in digital technology have improved the and right and edit the 3 photographs into a single collection of patient data,2 with facial and intraoral image by using an image-editing software program scans being used to transmit and integrate facial (Photoshop CS6; Adobe System Inc) (Fig. 1). First, information.3 However, accurate overlapping of set a vertical line on the frontal view and rotate it so facial and intraoral scan information is problematic as that the left and right eyes are symmetrical. Then, facial soft tissue changes with every scan. A current make horizontal reference lines through the eyes, method4 combines 2 scan data sets by using an mouth, and chin. The structure of the left view occlusal device as a reference point. It requires an (eyes, nose, mouth) can then be adjusted to fit the additional analog method (by using the occlusal horizontal reference line (Fig. 1D). After the device) but has the disadvantage of not evaluating the adjustment is complete, use the software’s masking smile line. function to link the 2 images. The right view is made Cone beam computed tomography (CBCT) can be in the same way, completing the combined image used to improve the current overlapping method of data (Fig. 1E). facial and intraoral scan data. In this method, a normal 2. Acquire a CBCT image of the patient. Convert the facial photograph is converted into an image by using CT soft-tissue data into a standard tessellation the soft tissue faintly included in the CBCT data and language (STL) file by using a medical visualization mapped on the CBCT. This enables the intraoral and software program (InVesalius; CTI). Select “Skin CBCT data of patients to be overlapped into a Tissue (Adult) and create surface at Set redefined combined facial image.
Supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2019R1G1A1006708) and a grant (BCRI19013) of Chonnam National University Hospital Biomedical Research Institute. a Private practice, Obokmanse Dental Clinic, Guro-gu, Seoul, Republic of Korea. b Private practice, W White Dental Clinic, Gangnam-gu, Seoul, Republic of Korea. c Private practice, Doctorplant Dental Clinic, Yeogdeungpo-gu, Seoul, Republic of Korea. d Assistant Professor, Department of Prosthodontics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea.
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Figure 1. Facial photograph. A, Frontal view. B, Left view. C, Right view. D, Processing of frontal and left view superimposition. E, Three photographs superimposed and synthesized with image-editing software.
threshold” to import the CT Digital Imaging and Communications in Medicine (DICOM) file. Then, perform image segmentation and mesh refinement (repairing, smoothing, appending) to the STL file by using the software program procedure.5 The software uses a mesh control program (Netfebb studio Basic; Netfabb GmbH) to reduce the file size (about 3 megabytes) for a fast computer-aided design (CAD) operation (Fig. 2). THE JOURNAL OF PROSTHETIC DENTISTRY
3. Combine the soft-tissue data extracted from CBCT and the facial photograph data by using a 3D modeling software program (Modo; Foundry) to create a new 3D face model through a planar projection (Fig. 3). Import the image file created in Photoshop CS6 by selecting the “shading tap” and “add layer” in the CT data of the Modo software (Fig. 3A). Change the image to a 2D image in Photoshop CS6 and express it as a UV map.5 Adjust Lee et al
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2020
Figure 2. CBCT soft-tissue data acquisition and conversion. CBCT softtissue data acquired on STL files. The file size reduced from 439 to 3 megabytes by using mesh control for fast computer-aided design operation. CBCT, cone-beam computed tomography; STL, standard tessellation language.
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Figure 4. Superimposed intraoral tooth scan data and new manufacturing face model data by using dental CAD software. CAD, computer-aided design.
Figure 3. Three-dimensional face model fabrication by using superimposed facial photograph data and CBCT soft-tissue data through planar projection by using 3D modeling software. A, Import of the CBCT soft-tissue file with Modo software. B, Ultraviolet mapping process for superimposing soft-tissue and photographic image data. C, Rendering output data view. D, Completed facial 3D model file for importing into dental CAD software. CAD, computer-aided design; CBCT, cone beam computed tomography.
the UV map using “UV map editing” in the Modo software for accurate superimposition of the CT soft tissue and photographic image (Fig. 3B). When Lee et al
repositioning is complete, save the image via “render output” (Fig. 3C) to complete the final file (Fig. 3D). If overlapping is not performed in a single THE JOURNAL OF PROSTHETIC DENTISTRY
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attempt, characteristic parts of the face (eyes, nose, mouth) can be overlapped separately, and, subsequently, the whole face can be overlapped. 4. Import the oral data acquired from an intraoral scanner and the facial scan data into a dental CAD software program (Exocad DentalCAD; Exocad GmbH) by superimposition (Fig. 4). DISCUSSION To date, the superimposition of facial and intraoral scan data has been performed by using optical scanning techniques, which are more straightforward than the method described in this article and have the advantage of no radiation exposure. However, because of the changing form of the soft tissues, the overlap is inaccurate, with reduced reliability of the soft-tissue information. The method presented in this article has the advantage of precise soft-tissue information, although there is radiation exposure because of the CBCT. As CT scans are performed at a single time, accurate soft-tissue data can be obtained compared with multiple facial scans. A perfect smile line and anatomic indicators such as the Camper plane can be observed. Moreover, the method of using superimposition data after acquiring intraoral and facial scan data suggests that the average surface distance (ASD) is not constant because of softtissue movement.5 However, this article describes the UV mapping technique, which colors a 3D file in the photograph image and does not cause ASD.6,7 Also, it has the advantage of generating data with straightforward photography and without specialized facial scanners. A similar UV mapping technique has been described for the photograph overlay method.8 While this method is straightforward, it is not accurate because it overlaps a virtual image file. In contrast, the present technique makes a virtual image by using a patient’s CT soft-tissue data, after which the photographic image is superimposed. This method applies color texture data to the soft-tissue surface data included in the CT. Therefore, UV mapping using the CT soft-tissue data can provide
THE JOURNAL OF PROSTHETIC DENTISTRY
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natural facial data by accurately overlapping the intraoral and extraoral data. The present digital technique can be applied to the existing dental CAD software for universal application. SUMMARY This article introduces a digital technique that superimposes a facial photograph on the soft-tissue data extracted from a CBCT to generate complete information for a patient’s intraoral and extraoral regions. CT data include soft and hard tissue, but the color texture data of soft tissue are not recorded. Superimposing facial photographic images with CT soft-tissue data by using the UV mapping technique will allow for better esthetic and functional treatment planning. REFERENCES 1. Joda T, Zarone F, Ferrari M. The complete digital workflow in fixed prosthodontics: a systematic review. BMC Oral Health 2017;17:124. 2. Schoenbaum TR. Dentistry in the digital age: an update. Dent Today 2012;31. 108, 110, 112-113. 3. Joda T, Bragger U, Gallucci G. Systematic literature review of digital threedimensional superimposition techniques to create virtual dental patients. Int J Oral Maxillofac Implants 2015;30:330-7. 4. Revilla-León M, Raney L, Piedra-Cascón W, Barrington J, Zandinejad A, Özcan M. Digital workflow for an esthetic rehabilitation using a facial and intraoral scanner and an additive manufactured silicone index: a dental technique. J Prosthet Dent 26 July 2019. doi: 10.1016/j.prosdent.2019.03.014. [Epub ahead of print]. 5. Bücking TM, Hill ER, Robertson JL, Maneas E, Plumb AA, Nikitichev DI. From medical imaging data to 3D printed anatomical models. PLoS One 2017;12: e0178540. 6. Levine MD, Yu Y. State-of-the-art of 3D facial reconstruction methods for face recognition based on a single 2D training image per person. Pattern Recogn Lett 2009;30:908-13. 7. Panozzo D, Diamanti O, Paris S, Tarini M, Sorkine E, Sorkine-Hornung O, et al. Texture mapping real-world objects with hydrographics. Comput Graph Forum 2015;34:65-75. 8. Kurbad A, Kurbad S. Cerec smile design–a software tool for the enhancement of restorations in the esthetic zone. Int J Comput Dent 2013;16:255-69. Corresponding author: Dr Chan Park Department of Prosthodontics School of Dentistry Chonnam National University 33 Yongbong-ro, Buk-gu, Gwangju 61186 REPUBLIC OF KOREA Email: [email protected] Copyright © 2020 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2020.01.008
Lee et al