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Mounting casts on a mechanical articulator by using digital multisource data: A dental technique
DENTAL TECHNIQUE
Mounting casts on a mechanical articulator by using digital multisource data: A dental technique Jong-Eun Kim, DDS, MSD, PhD,a Su-Jin Kim, DDS,b Dong-Ho Kwon, CDT,c June-Sung Shim, DDS, PhD,d and Jee-Hwan Kim, DDS, MSD, PhDe The facebow transfer and ABSTRACT mounting of a stone cast on a A facebow transfer is typically used for mounting a maxillary gypsum cast in an ideal location in a mechanical articulator are mechanical articulator. However, the facebow transfer procedure is difficult and may cause the reliable techniques for patient patient discomfort. This proposed technique uses a patient’s cone beam computed tomography diagnosis and prosthesis pro(CBCT) data to reproduce the occlusal plane in relation to digital articulator scan data, align the duction.1,2 A facebow is an patient’s gypsum cast or intraoral scan data on the reproduced plane, and then transfer the data to a mechanical articulator. (J Prosthet Dent 2020;-:---) instrument that records the relationships between various required. Another limitation of the module is that an facial landmarks and the occlusal plane and allows for the arbitrary mounting is used with the intraoral scan data mounting of a maxillary gypsum cast in an ideal location 2 because the desired occlusal plane cannot be captured in a mechanical articulator. Despite its usefulness, the before transferring intraoral scan data to the virtual facebow presents several practical problems, including articulator. being difficult and time-consuming to use. Additionally, Cone beam computed tomography (CBCT) has been positioning the instrument in the external auditory canals 3 ,4 used to facilitate the mounting process,5 as well as in can cause discomfort. diagnostic imaging and presurgical imaging for implant The virtual articulator module in a dental computersurgery and dental restorations.6 Digital mounting aided design (CAD) software program (3Shape dental through the CBCT data of the mandible and landmarks system; 3Shape A/S, exocad DentalCAD; exocad GmbH) eliminates the requirement for a facebow transfer. enables a user to digitally produce a prosthesis while However, the technique can only be used for digital incorporating its articulation. However, the module remounting; CBCT data cannot be used for mounting on a quires a specific compatible mechanical articulator mechanical articulator.5 (PROTAR evo 7; KaVo, Artex articulator; Amann GirrData from digitally mounted casts can be transferred bach AG, and so on). In addition, the module works by to a mechanical articulator with a 3D printing technique.7 scanning a cast by using an articulator jig, which is The dental arch data are printed with the location of the provided as an accessory in a model scanner (Generic mounting plate. This technique is useful because it enArticulator Transfer Plates; 3Shape A/S, KAS jig; Medit) ables transferring the locations of digital data to a mewhen transferring scan data to a virtual articulator. With chanical articulator. However, the technique can only use this system, mounting on a mechanical articulator is
Supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF2019R1H1A2039715). J.-E.K. and S.-J.K. contributed equally to this work as first authors. a Clinical Assistant Professor, Department of Prosthodontics, College of Dentistry, Yonsei University, SeodaemunGu, Seoul, Republic of Korea. b Graduate student, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea. c Researcher, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea. d Professor, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea. e Associate Professor, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
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Figure 1. A, Obtaining articulator scanning data by using industrial scanner. B, Scanned mounting plate after attaching landmark structures.
Figure 2. Aligning CBCT data and articulator scan data by using skeletal landmarks. A, Front view. B, Side view. C, Aligning data of maxillary gypsum cast with CBCT data. D, Maxillary and mandibular scan data positioned. CBCT, cone beam computed tomography.
3D resins to produce casts, not gypsum casts from physical impressions. Additionally, the technique can only be used with a specific system such as the Kois Dentofacial Analyzer (Panadent Corp). The purpose of the present technique article was to introduce a digital workflow by using multisource THE JOURNAL OF PROSTHETIC DENTISTRY
data, specifically the scans of a mechanical articulator of a selected type. The scanned data were used to establish a positional relationship between each other by using the CAD software and the gypsum cast and 3D printing cast for mounting on a mechanical articulator. Kim et al
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Figure 3. A, Aligning custom mounting plate data on mandibular mounting plate for mounting gypsum cast. B, Alignment completed. C, Design for space between maxillary scan data and customized mounting plate. D, Completed design data.
Figure 4. Mounting gypsum cast. A, Designed flexible device. B, Maxillary gypsum cast placed on device. C, Mounted cast.
TECHNIQUE Multisource data generation and alignment 1. Scan a mechanical articulator (PROTAR evo 7; KaVo) by using an industrial scanner (Rexcan2; Medit) (Fig. 1A). Attach landmark structures to the mounting plate of the articulator for easier alignment (Fig. 1B). This step only needs to be performed once for each type of articulator. Kim et al
2. Convert the CBCT data of a patient requiring a mounted cast to STL by using a software program (3D Slicer; open source software). 3. Scan the patient’s gypsum cast by using a laboratory scanner (Medit T500; Medit Corp) or scan the arch by using an intraoral scanner (TRIOS 3; 3Shape A/S) to obtain the STL data of the patient’s mandible. 4. Import the scan data of the mechanical articulator and the CBCT data into a CAD software program
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Figure 5. A, Importing and aligning custom mounting plate data to upper part of articulator for mounting intraoral scan data. B, Alignment completed. C, Importing new LEGO brick data to design space between maxillary oral scan data and custom mounting plate. D, Alignment of LEGO brick data and design of integrated cast.
(exocad DentalCAD; exocad GmbH). Locate major landmarks on the CBCT scans to determine the spatial relationship between the CBCT data and articulator scan data (Fig. 2A, 2B). 5. Align the gypsum scan data or intraoral scan data with the dental structure in the CBCT data already aligned with the articulator (Fig. 2C, 2D). Gypsum cast mounting 1. Create a custom mounting plate on the mandibular mounting plate of the mechanical articulator by using a mesh modeling software program (Meshmixer; Autodesk Inc). Design the plate such that there are 6 or 7 textured structures in the uppermost portion. 2. Import the data of a predesigned custom mounting plate to the dental CAD software (exocad DentalCAD; exocad GmbH) and align the data according to the landmarks attached to the mounting plate (Fig. 3A, 3B). 3. Design the empty space between the gypsum cast and custom mounting plate by using the Bite Splint THE JOURNAL OF PROSTHETIC DENTISTRY
module in the dental CAD software (exocad DentalCAD; exocad GmbH) (Fig. 3C, 3D). Design a structure such that the device locks into the textured structures in the upper portion of the custom mounting plate and fixes the gypsum cast. 4. Three-dimensionally print the designed device by using flexible materials (Flexible Resin; Formlabs) (Fig. 4A). 5. Place the printed device on the custom mounting plate, place the maxillary gypsum cast on the device, and then mount the cast. Finally, mount the antagonist gypsum cast by using the conventional method (Fig. 4B, 4C). Mounting of intraoral scan data 1. Design a 3D-printed structure that can be attached to the maxillary mounting plate of the mechanical articulator by using the 3D design software (Meshmixer; Autodesk Inc). Design a custom mounting plate for the maxilla by using LEGO brick data from the LEGO Digital Designer file sharing website (Thingiverse; MakerBot Industries, LLC). Kim et al
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Figure 6. Mounting procedure by using 3D-printed cast from intraoral scan data and LEGO brick data. A, Custom mounting plate by using LEGO brick data. B, Printed cast fixed with LEGO brick. C, Three-dimensionally printed cast mounted.
2. Import the data of a predesigned customized mounting plate and align the data according to the landmarks attached to the mounting plate (Fig. 5A, 5B). 3. Import additional LEGO brick data and align the data with the maxillary intraoral scan data in the empty space between the custom mounting plate and intraoral scan data. Then, merge the LEGO brick data with the maxillary intraoral scan data (Fig. 5C, 5D). 4. Three-dimensionally print the data produced by these steps. Immediately attach a completed LEGO brickecontaining 3D printing cast to the custom mounting plate (Fig. 6A). 5. Position and mount the 3D-printed antagonist cast by using a conventional method (Fig. 6B, 6C). DISCUSSION This technique uses a patient’s CBCT data to reproduce the occlusal plane in relation to the scan data of a mechanical articulator, align the patient’s gypsum cast or intraoral scan data on the reproduced plane, and then transfer the data to a mechanical articulator. This technique has advantages, including mounting a cast on a mechanical articulator without a facebow transfer, for patients who have undergone CBCT for diagnostic reasons or as a planning process for implant surgery or prosthesis production. The technique uses the center of the condyle as a reference point for mounting, which may more accurately replicate the patient’s hinge axis than an arbitrary facebow. Therefore, it may be useful where the occlusal vertical dimension is altered. The technique also allows for the direct mounting of a gypsum cast and thus may be useful for mounting definitive casts for crowns and fixed partial dentures. The custom mounting plate containing LEGO bricks and textured structures can also reduce the 3D-printing material needed because these components can be used as building blocks so that only the remaining components are 3D printed. The technique has limitations including that an entire articulator must be scanned initially by using an industrial scanner. This can be performed by using the scanning services provided by industrial scanning companies Kim et al
or by purchasing expensive industrial scanners. However, the same scans can be used repeatedly for subsequent mounting for other patients. Another limitation is that the technique is not possible for patients where a CBCT is not indicated, such as for straightforward prosthetic procedures. Research on the accuracy and reproducibility of the technique is indicated. SUMMARY A method of cast mounting from CBCT data and the scanned data of the articulator is described. As the positional relationship is set by using the scan data of the articulator to be used, the advantage is that the relationship can be also transferred to the actual mechanical articulator. The technique allows the straightforward mounting of a cast on a mechanical articulator. REFERENCES 1. Brandrup-Wognsen T. The face-bow, its significance and application. J Prosthet Dent 1953;3:618-30. 2. The glossary of prosthodontic terms. Ninth edition. J Prosthet Dent 2017;117(5S):e1-105. 3. Farias-Neto A, Dias A, de Miranda B, de Oliveira A. Face-bow transfer in prosthodontics: a systematic review of the literature. J Oral Rehabil 2013;40: 686-92. 4. Yohn K. The face bow is irrelevant for making prostheses and planning orthognathic surgery. J Am Dent Assoc 2016;147:421-6. 5. Lepidi L, Chen Z, Ravida A, Lan T, Wang HL, Li J. A full-digital technique to mount a maxillary arch scan on a virtual articulator. J Prosthodont 2019;28:335-8. 6. Suomalainen A, Vehmas T, Kortesniemi M, Robinson S, Peltola J. Accuracy of linear measurements using dental cone beam and conventional multislice computed tomography. Dentomaxillofac Radiol 2008;37:10-7. 7. Crockett RJ, Shah KC. Transferring dentofacial analyzer into analog workflow with CAD digitization: a dental technique. J Prosthet Dent 2019;123:45-9. Corresponding author: Dr Jee-Hwan Kim Department of Prosthodontics College of Dentistry Yonsei University 50-1 Yonsei-ro, Seodaemun Gu Seoul, 03722 REPUBLIC OF KOREA Email: [email protected] Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.10.022
THE JOURNAL OF PROSTHETIC DENTISTRY
Mounting casts on a mechanical articulator by using digital multisource data: A dental technique Jong-Eun Kim, DDS, MSD, PhD,a Su-Jin Kim, DDS,b Dong-Ho Kwon, CDT,c June-Sung Shim, DDS, PhD,d and Jee-Hwan Kim, DDS, MSD, PhDe The facebow transfer and ABSTRACT mounting of a stone cast on a A facebow transfer is typically used for mounting a maxillary gypsum cast in an ideal location in a mechanical articulator are mechanical articulator. However, the facebow transfer procedure is difficult and may cause the reliable techniques for patient patient discomfort. This proposed technique uses a patient’s cone beam computed tomography diagnosis and prosthesis pro(CBCT) data to reproduce the occlusal plane in relation to digital articulator scan data, align the duction.1,2 A facebow is an patient’s gypsum cast or intraoral scan data on the reproduced plane, and then transfer the data to a mechanical articulator. (J Prosthet Dent 2020;-:---) instrument that records the relationships between various required. Another limitation of the module is that an facial landmarks and the occlusal plane and allows for the arbitrary mounting is used with the intraoral scan data mounting of a maxillary gypsum cast in an ideal location 2 because the desired occlusal plane cannot be captured in a mechanical articulator. Despite its usefulness, the before transferring intraoral scan data to the virtual facebow presents several practical problems, including articulator. being difficult and time-consuming to use. Additionally, Cone beam computed tomography (CBCT) has been positioning the instrument in the external auditory canals 3 ,4 used to facilitate the mounting process,5 as well as in can cause discomfort. diagnostic imaging and presurgical imaging for implant The virtual articulator module in a dental computersurgery and dental restorations.6 Digital mounting aided design (CAD) software program (3Shape dental through the CBCT data of the mandible and landmarks system; 3Shape A/S, exocad DentalCAD; exocad GmbH) eliminates the requirement for a facebow transfer. enables a user to digitally produce a prosthesis while However, the technique can only be used for digital incorporating its articulation. However, the module remounting; CBCT data cannot be used for mounting on a quires a specific compatible mechanical articulator mechanical articulator.5 (PROTAR evo 7; KaVo, Artex articulator; Amann GirrData from digitally mounted casts can be transferred bach AG, and so on). In addition, the module works by to a mechanical articulator with a 3D printing technique.7 scanning a cast by using an articulator jig, which is The dental arch data are printed with the location of the provided as an accessory in a model scanner (Generic mounting plate. This technique is useful because it enArticulator Transfer Plates; 3Shape A/S, KAS jig; Medit) ables transferring the locations of digital data to a mewhen transferring scan data to a virtual articulator. With chanical articulator. However, the technique can only use this system, mounting on a mechanical articulator is
Supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF2019R1H1A2039715). J.-E.K. and S.-J.K. contributed equally to this work as first authors. a Clinical Assistant Professor, Department of Prosthodontics, College of Dentistry, Yonsei University, SeodaemunGu, Seoul, Republic of Korea. b Graduate student, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea. c Researcher, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea. d Professor, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea. e Associate Professor, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
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Figure 1. A, Obtaining articulator scanning data by using industrial scanner. B, Scanned mounting plate after attaching landmark structures.
Figure 2. Aligning CBCT data and articulator scan data by using skeletal landmarks. A, Front view. B, Side view. C, Aligning data of maxillary gypsum cast with CBCT data. D, Maxillary and mandibular scan data positioned. CBCT, cone beam computed tomography.
3D resins to produce casts, not gypsum casts from physical impressions. Additionally, the technique can only be used with a specific system such as the Kois Dentofacial Analyzer (Panadent Corp). The purpose of the present technique article was to introduce a digital workflow by using multisource THE JOURNAL OF PROSTHETIC DENTISTRY
data, specifically the scans of a mechanical articulator of a selected type. The scanned data were used to establish a positional relationship between each other by using the CAD software and the gypsum cast and 3D printing cast for mounting on a mechanical articulator. Kim et al
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Figure 3. A, Aligning custom mounting plate data on mandibular mounting plate for mounting gypsum cast. B, Alignment completed. C, Design for space between maxillary scan data and customized mounting plate. D, Completed design data.
Figure 4. Mounting gypsum cast. A, Designed flexible device. B, Maxillary gypsum cast placed on device. C, Mounted cast.
TECHNIQUE Multisource data generation and alignment 1. Scan a mechanical articulator (PROTAR evo 7; KaVo) by using an industrial scanner (Rexcan2; Medit) (Fig. 1A). Attach landmark structures to the mounting plate of the articulator for easier alignment (Fig. 1B). This step only needs to be performed once for each type of articulator. Kim et al
2. Convert the CBCT data of a patient requiring a mounted cast to STL by using a software program (3D Slicer; open source software). 3. Scan the patient’s gypsum cast by using a laboratory scanner (Medit T500; Medit Corp) or scan the arch by using an intraoral scanner (TRIOS 3; 3Shape A/S) to obtain the STL data of the patient’s mandible. 4. Import the scan data of the mechanical articulator and the CBCT data into a CAD software program
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Figure 5. A, Importing and aligning custom mounting plate data to upper part of articulator for mounting intraoral scan data. B, Alignment completed. C, Importing new LEGO brick data to design space between maxillary oral scan data and custom mounting plate. D, Alignment of LEGO brick data and design of integrated cast.
(exocad DentalCAD; exocad GmbH). Locate major landmarks on the CBCT scans to determine the spatial relationship between the CBCT data and articulator scan data (Fig. 2A, 2B). 5. Align the gypsum scan data or intraoral scan data with the dental structure in the CBCT data already aligned with the articulator (Fig. 2C, 2D). Gypsum cast mounting 1. Create a custom mounting plate on the mandibular mounting plate of the mechanical articulator by using a mesh modeling software program (Meshmixer; Autodesk Inc). Design the plate such that there are 6 or 7 textured structures in the uppermost portion. 2. Import the data of a predesigned custom mounting plate to the dental CAD software (exocad DentalCAD; exocad GmbH) and align the data according to the landmarks attached to the mounting plate (Fig. 3A, 3B). 3. Design the empty space between the gypsum cast and custom mounting plate by using the Bite Splint THE JOURNAL OF PROSTHETIC DENTISTRY
module in the dental CAD software (exocad DentalCAD; exocad GmbH) (Fig. 3C, 3D). Design a structure such that the device locks into the textured structures in the upper portion of the custom mounting plate and fixes the gypsum cast. 4. Three-dimensionally print the designed device by using flexible materials (Flexible Resin; Formlabs) (Fig. 4A). 5. Place the printed device on the custom mounting plate, place the maxillary gypsum cast on the device, and then mount the cast. Finally, mount the antagonist gypsum cast by using the conventional method (Fig. 4B, 4C). Mounting of intraoral scan data 1. Design a 3D-printed structure that can be attached to the maxillary mounting plate of the mechanical articulator by using the 3D design software (Meshmixer; Autodesk Inc). Design a custom mounting plate for the maxilla by using LEGO brick data from the LEGO Digital Designer file sharing website (Thingiverse; MakerBot Industries, LLC). Kim et al
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Figure 6. Mounting procedure by using 3D-printed cast from intraoral scan data and LEGO brick data. A, Custom mounting plate by using LEGO brick data. B, Printed cast fixed with LEGO brick. C, Three-dimensionally printed cast mounted.
2. Import the data of a predesigned customized mounting plate and align the data according to the landmarks attached to the mounting plate (Fig. 5A, 5B). 3. Import additional LEGO brick data and align the data with the maxillary intraoral scan data in the empty space between the custom mounting plate and intraoral scan data. Then, merge the LEGO brick data with the maxillary intraoral scan data (Fig. 5C, 5D). 4. Three-dimensionally print the data produced by these steps. Immediately attach a completed LEGO brickecontaining 3D printing cast to the custom mounting plate (Fig. 6A). 5. Position and mount the 3D-printed antagonist cast by using a conventional method (Fig. 6B, 6C). DISCUSSION This technique uses a patient’s CBCT data to reproduce the occlusal plane in relation to the scan data of a mechanical articulator, align the patient’s gypsum cast or intraoral scan data on the reproduced plane, and then transfer the data to a mechanical articulator. This technique has advantages, including mounting a cast on a mechanical articulator without a facebow transfer, for patients who have undergone CBCT for diagnostic reasons or as a planning process for implant surgery or prosthesis production. The technique uses the center of the condyle as a reference point for mounting, which may more accurately replicate the patient’s hinge axis than an arbitrary facebow. Therefore, it may be useful where the occlusal vertical dimension is altered. The technique also allows for the direct mounting of a gypsum cast and thus may be useful for mounting definitive casts for crowns and fixed partial dentures. The custom mounting plate containing LEGO bricks and textured structures can also reduce the 3D-printing material needed because these components can be used as building blocks so that only the remaining components are 3D printed. The technique has limitations including that an entire articulator must be scanned initially by using an industrial scanner. This can be performed by using the scanning services provided by industrial scanning companies Kim et al
or by purchasing expensive industrial scanners. However, the same scans can be used repeatedly for subsequent mounting for other patients. Another limitation is that the technique is not possible for patients where a CBCT is not indicated, such as for straightforward prosthetic procedures. Research on the accuracy and reproducibility of the technique is indicated. SUMMARY A method of cast mounting from CBCT data and the scanned data of the articulator is described. As the positional relationship is set by using the scan data of the articulator to be used, the advantage is that the relationship can be also transferred to the actual mechanical articulator. The technique allows the straightforward mounting of a cast on a mechanical articulator. REFERENCES 1. Brandrup-Wognsen T. The face-bow, its significance and application. J Prosthet Dent 1953;3:618-30. 2. The glossary of prosthodontic terms. Ninth edition. J Prosthet Dent 2017;117(5S):e1-105. 3. Farias-Neto A, Dias A, de Miranda B, de Oliveira A. Face-bow transfer in prosthodontics: a systematic review of the literature. J Oral Rehabil 2013;40: 686-92. 4. Yohn K. The face bow is irrelevant for making prostheses and planning orthognathic surgery. J Am Dent Assoc 2016;147:421-6. 5. Lepidi L, Chen Z, Ravida A, Lan T, Wang HL, Li J. A full-digital technique to mount a maxillary arch scan on a virtual articulator. J Prosthodont 2019;28:335-8. 6. Suomalainen A, Vehmas T, Kortesniemi M, Robinson S, Peltola J. Accuracy of linear measurements using dental cone beam and conventional multislice computed tomography. Dentomaxillofac Radiol 2008;37:10-7. 7. Crockett RJ, Shah KC. Transferring dentofacial analyzer into analog workflow with CAD digitization: a dental technique. J Prosthet Dent 2019;123:45-9. Corresponding author: Dr Jee-Hwan Kim Department of Prosthodontics College of Dentistry Yonsei University 50-1 Yonsei-ro, Seodaemun Gu Seoul, 03722 REPUBLIC OF KOREA Email: [email protected] Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.10.022
THE JOURNAL OF PROSTHETIC DENTISTRY