This work was partly supported by JSPS KAKENHI Grant Number JP17K11914.

This study was approved by the authors&#39; institutional review board, and written consent forms were completed by all patients.
1. Preparation of Materials
<ol>
	<li>Use a personal computer, computed tomographic (CT) data of facial bone and fibula, conversion software such as InVesalius20, and three-dimensional (3-D) CAD software (e.g., Blender21). 
	NOTE: A maximum thickness of 1 mm slices of CT data is recommended for an accurate design. For the actual surgical simulation, use the patient&#39;s CT data. For research, use free human 3-D data22.</li>
	<li>Use a 3-D printer23, screws, metal plates, and a small saw, to check not only the designs but also real objects and results. 
	NOTE: The present study is experimental. Metal plates, screws, and a small saw can be used for the model surgery. Instead of metal plates, plastic-fixation plates can be also printed by the 3-D printer, together with the surgical guides.</li>
	<li>Transfer the imaging data of both facial bone and fibula into 3-D data (.stl format) using InVesalius20. 
	NOTE: CT data is essentially recorded in the form of two-dimensional (2-D) pictures. Thus, before using the 3-D data, it is necessary to convert the data into 3-D data. Free software is sufficient for this purpose. This report does not explain how to transfer the data into a 3-D file; instructional videos and guides are available elsewhere.</li>
	<li>Import each .stl file into Blender21. 
	NOTE: CAD software usually accepts a .stl-style 3-D format. At first, maxillary and fibular .stl files should be opened in the specific CAD software by importing them.</li>
</ol>
2. Design
<ol>
	<li>Deciding on the area of bone removal and solidifying a bone defect
	<ol>
		<li>Decide on the area to be excised. 
		NOTE: In this experimental simulation surgery, any part of the maxilla can be set as an excised area. Because reconstruction after total maxillectomy is difficult, only a small part of the maxilla will be a choice for beginners. In a clinical setting, otorhinolaryngologists will decide the area according to the cancerous region.</li>
		<li>Make a large plane and place it on the border of the area for removal in the object mode (Figures 1a and 1b). Follow that by placing a second plane (Figures 1b-1d) and continue to do so until the planes surround the whole area for removal. Unite these planes in the object mode.</li>
		<li>Select the vertices of all these planes and connect them to each other by making edges and faces (Figure 1e) in the edit mode to surround the areas for removal. 
		NOTE: The excision planes should be copied and maintained because these original planes are used and discarded when solidifying the excision. In the present study, copying every plane and solid on every occasion is recommended in order to make it possible to reuse them.</li>
		<li>Subtract the resectable solid from the facial bone using a Boolean modifier in the edit mode. This results in a shaved facial bone (Figure 1f), which is the maxillary defect model.</li>
	</ol>
	</li>
	<li>Placing a fibula bone
	<ol>
		<li>Place a fibula into the maxillary defect area (Figure 2a). Place small cubes at two points (8 cm distal from the fibular head and 5 cm proximal from the lateral malleolus) in the fibula as markers (purple small cubes are shown in Figure 2). 
		NOTE: In clinical situations, a fibula can be used between 8 cm distal from the fibular head and 5 cm proximal from the lateral malleolus. By this marking, we can easily understand the areas that can be used.</li>
		<li>Link small cubes to the fibula as a parent setting in the object mode.</li>
		<li>Place small cubes as markers in several points in the maxillary lesion where reconstruction is necessary. With this marking, the visibility of the necessary reproduction points is increased.</li>
		<li>Fit the fibula to the front margin of the alveolar bone in the object mode, if the fibula is placed from the midline.</li>
		<li>Use the previous plane of the midline maxillary osteotomy as a first fibular osteotomy plane (Figure 2b).</li>
		<li>Place a new osteotomy plane where appropriate in the object mode (Figure 2c). Link this new plane to the fibula as a parent setting. 
		NOTE: By setting the parent to the fibula, the relative orientation between this new osteotomy plane and the fibula is always maintained even if the fibula is moved into different places. The area of the fibula that is surrounded by these two cutting planes becomes the first fibular block.</li>
		<li>Copy the fibula and two planes of osteotomy as a parent setting in the object mode. Move this copied fibula, which has the first block area with two cutting planes on both ends, to the second area where reconstruction is necessary (Figure 2e) to plan the second fibula block.</li>
		<li>Place the second cutting plane by adding a new plane in the object mode. 
		NOTE: The first and second cutting plane will become the ends of the second fibula block. If a third block is necessary, similar procedures are added. The appropriate length of the gaps between the adjacent fibular blocks should be maintained. 
		NOTE: The gap between the first and second block is considered to be key to having a comfortable osteotomy. If this gap is wide, the osteotomy will be easy because of the wide working space, but the vascular length is somewhat wasted. By contrast, if the gap is narrow, osteotomy becomes troublesome, but the second or third block can be designed by eliminating the waste of the unused bone.</li>
	</ol>
	</li>
	<li>Designing the fibular cutting guides
	<ol>
		<li>Visualize only the fibula and cutting planes for designing the fibula cutting guide in the object mode (Figure 3a).</li>
		<li>Make each cutting plane smaller to occupy only half the area of the fibula cutting section by sliding vertexes along the edges (Figures 3b-3d) in the edit mode. 
		NOTE: The fitting side of the cutting guide is the lateral aspect of the fibula. Because the feeding vessels are located in the medial aspect, the guide is not designed in the medial aspect.</li>
		<li>Unite two planes of the ends to build a solid in the object mode (Figures 4a-4e). Select the vertexes of all these planes and connect them to each other by making edges and faces in the edit mode to form a rectangular solid.</li>
		<li>Subtract the fibula from this rectangular solid by using a Boolean modifier (Figures 5a-5c). 
		NOTE: The surface of this subtraction completely fits the fibular lateral aspect. The same procedures are repeated in every necessary fibular block.</li>
		<li>Unite each subtracted solid in the object mode.</li>
		<li>Place a cube near the subtracted solids (Figure 5d). Extrude faces to make pillars (Figures 5e-5g). Unite these pillars to the subtracted solids. This is the fibular cutting guide (Figures 5h-5j).</li>
	</ol>
	</li>
	<li>Osteotomy cutting guide for the maxilla 
	NOTE: To cut the maxilla, it is not necessary to design the guide for every cutting surface, because only limited areas are to be reconstructed using the fibula. Usually, two cutting guides, which cover the medial alveolar and lateral zygomatic areas, are designed.
	<ol>
		<li>Prepare the maxillary and zygomatic planes that were the original remaining surface after the maxillary removal. A margin of 1 cm in width is sufficient (Figure 6a).</li>
		<li>Extrude the faces prepared in step 2.4.1 to thicken the plane and to solidify them in the edit mode using the solidify modifier (Figure 6b).</li>
		<li>Delete the thickened solid over the resection planes, which were decided in step 2.1, on both ends; this is how the maxillary cutting guides are designed. 
		&#8203;NOTE: If the fitting surface is jagged, a smaller fitting area is sufficient. If the fitting surface is apt to be flat, a large area is needed to avoid any slippage of the guide.</li>
	</ol>
	</li>
	<li>Fixation guide for the fibular segments 
	NOTE: Fibular segments that are to be transferred to the maxilla are considered to be accurate in size and length, but the location of the transfer can deviate freely if the fixation guide is not used. The fibula and each cutting plane (as made in step 2.2) are used again in this segment.
	<ol>
		<li>Construct each fibular block in the Boolean modifier by taking out the intersection area between the fibula and the solid with cutting planes on both ends (Figures 7a and 7b) in the edit mode.</li>
		<li>Extract half of the superficial surface of each fibular block.</li>
		<li>Unite all of these surfaces in the object mode (Figure 7c).</li>
		<li>Delete small faces in the edit mode by using a knife cut ( Figure 8a) to secure the spaces for fitting the metal plates.</li>
		<li>Thicken the surface by using a solidifying modifier in the edit mode (Figures 8b-8e). 
		NOTE: A minimum 2&#8211;3 mm of thickness is necessary to stabilize the fixation guide and avoid warping. If the wing is designed on both ends, it will help the guide to the maxilla without using any metal plates.</li>
	</ol>
	</li>
</ol>
3. 3-D Printing for Model Surgery and Real Guides
NOTE: The main purpose of this report is to show the method of designing surgical guides; the procedure described below is not necessary if 3-D printing is not needed.
<ol>
	<li>Export the designs of the guides in .stl format, which can be 3-D printed.</li>
	<li>Print all guides and bones. 
	&#8203;NOTE: In printing, rafts are considered to disturb smooth surface printing and lead to a jagged surface and poor fit to the bone, so the plane that needs to be smooth must be pointed upward.</li>
	<li>Perform the model surgery as follows:
	<ol>
		<li>Similar to actual surgery, fit the maxillary cutting guide to the facial bone model first (Figure 9a). Then, cut the facial bone along with the cutting plane using a saw.</li>
		<li>Attach the fibular cutting guide to the fibular bone model and cut it into pieces (Figure 9b). Attach the fibular blocks to the fixation guide (Figures 9c and 9d).</li>
		<li>Fix this fixation guide complex to the maxillary defect using screws and plates (Figure 9e). After fixing the fibular segments to the maxilla in the area where the fixation guide does not attach by using screws and plates, remove the fixation guide. This completes the reconstruction (Figure 9f).</li>
	</ol>
	</li>
	<li>Scan the 3-D-reconstructed image and record it in .stl format using a 3-D scanner24.</li>
	<li>Compare the post-model surgery .stl file and the CAD reconstructed design (Figure 10) using comparison software25. 
	NOTE: By comparing the virtual reconstruction design and the guided reconstruction model, actual accuracy is calculated. Because CAD/CAM accuracy is obtained within a 2.5 mm deviation in the mandibular reconstruction10, a similar precision should be required in this method. If the required accuracy cannot be obtained, redo the virtual design.</li>
</ol>

<ol>
	<li>Hirsch, D. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+computer-aided+design+and+computer-aided+manufacturing+to+produce+orthognathically+ideal+surgical+outcomes:+A+paradigm+shift+in+head+and+neck+reconstruction.">Use of computer-aided design and computer-aided manufacturing to produce orthognathically ideal surgical outcomes: A paradigm shift in head and neck reconstruction.</a> Journal of Oral and Maxillofacial Surgery. 67 (10), 2115-2122 (2009).</li><li>Hanasono, M. M., Skoracki, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer-assisted+design+and+rapid+prototype+modeling+in+microvascular+mandible+reconstruction.">Computer-assisted design and rapid prototype modeling in microvascular mandible reconstruction.</a> The Laryngoscope. 123 (3), 597-604 (2013).</li><li>Roser, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+accuracy+of+virtual+surgical+planning+in+free+fibula+mandibular+reconstruction:+Comparison+of+planned+and+final+results.">The accuracy of virtual surgical planning in free fibula mandibular reconstruction: Comparison of planned and final results.</a> Journal of Oral and Maxillofacial Surgery. 68 (11), 2824-2832 (2010).</li><li>Ayoub, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+computer+assisted+mandibular+reconstruction+with+vascularized+iliac+crest+bone+graft+compared+to+conventional+surgery:+A+randomized+prospective+clinical+trial.">Evaluation of computer assisted mandibular reconstruction with vascularized iliac crest bone graft compared to conventional surgery: A randomized prospective clinical trial.</a> Trials. 15, 114 (2014).</li><li>Stirling, C. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simulated+surgery+and+cutting+guides+enhance+spatial+positioning+in+free+fibular+mandibular+reconstruction.">Simulated surgery and cutting guides enhance spatial positioning in free fibular mandibular reconstruction.</a> Microsurgery. 35 (1), 29-33 (2015).</li><li>Schepers, R. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+fibula+reconstruction+using+patient-specific+CAD/CAM+reconstruction+plates+and+dental+implants:+a+new+modality+for+functional+reconstruction+of+mandibular+defects.">Accuracy of fibula reconstruction using patient-specific CAD/CAM reconstruction plates and dental implants: a new modality for functional reconstruction of mandibular defects.</a> Journal of Cranio-Maxillofacial Surgery. 43 (5), 649-657 (2015).</li><li>Tarsitano, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mandibular+reconstructions+using+computer-aided+design/computer-aided+manufacturing:+a+systematic+review+of+a+defect-based+reconstructive+algorithm.">Mandibular reconstructions using computer-aided design/computer-aided manufacturing: a systematic review of a defect-based reconstructive algorithm.</a> Journal of Cranio-Maxillofacial Surgery. 43 (9), 1785-1791 (2015).</li><li>Wilde, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multicenter+study+on+the+use+of+patient-specific+CAD/CAM+reconstruction+plates+for+mandibular+reconstruction.">Multicenter study on the use of patient-specific CAD/CAM reconstruction plates for mandibular reconstruction.</a> International Journal of Computer Assisted Radiology and Surgery. 10 (12), 2035-2051 (2015).</li><li>Huang, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preliminary+clinic+study+on+computer+assisted+mandibular+reconstruction:+the+positive+role+of+surgical+navigation+technique.">Preliminary clinic study on computer assisted mandibular reconstruction: the positive role of surgical navigation technique.</a> Maxillofacial Plastic and Reconstructive Surgery. 37 (1), 20 (2015).</li><li>Numajiri, T., Nakamura, H., Sowa, Y., Nishino, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-cost+design+and+manufacturing+of+surgical+guides+for+mandibular+reconstruction+using+a+fibula.">Low-cost design and manufacturing of surgical guides for mandibular reconstruction using a fibula.</a> Plastic and Reconstructive Surgery - Global Open. 4 (7), 805 (2016).</li><li>Numajiri, T., Tsujiko, S., Morita, D., Nakamura, H., Sowa, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+fixation+guide+for+the+accurate+insertion+of+fibular+segments+in+mandibular+reconstruction.">A fixation guide for the accurate insertion of fibular segments in mandibular reconstruction.</a> Journal of Plastic, Reconstructive &amp; Aesthetic Surgery. Open. 12 (8), 1-8 (2017).</li><li>Toto, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+operative+efficiency+of+free+fibula+flap+mandible+reconstruction+with+patient+specific,+computer-guided+preoperative+planning.">Improved operative efficiency of free fibula flap mandible reconstruction with patient specific, computer-guided preoperative planning.</a> Head &amp; Neck. 37 (11), 1660-1664 (2015).</li><li>Avraham, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+outcomes+of+virtually+planned+free+fibula+flap+reconstruction+of+the+mandible.">Functional outcomes of virtually planned free fibula flap reconstruction of the mandible.</a> Plastic and Reconstructive Surgery. 134 (628), 634 (2014).</li><li>Sieira, G. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surgical+planning+and+microvascular+reconstruction+of+the+mandible+with+a+fibular+flap+using+computer-aided+design,+rapid+prototype+modeling,+and+precontoured+titanium+reconstruction+plates:+A+prospective+study.">Surgical planning and microvascular reconstruction of the mandible with a fibular flap using computer-aided design, rapid prototype modeling, and precontoured titanium reconstruction plates: A prospective study.</a> British Journal of Oral and Maxillofacial Surgery. 53 (1), 49-55 (2015).</li><li>Seruya, M., Fisher, M., Rodriguez, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer-assisted+versus+conventional+free+fibula+flap+technique+for+craniofacial+reconstruction:+An+outcomes+comparison.">Computer-assisted versus conventional free fibula flap technique for craniofacial reconstruction: An outcomes comparison.</a> Plastic and Reconstructive Surgery. 132 (5), 1219-1225 (2013).</li><li>Metzler, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+virtual+surgery+accuracy+for+free+fibula+mandibular+reconstruction:+Planned+versus+actual+results.">Three-dimensional virtual surgery accuracy for free fibula mandibular reconstruction: Planned versus actual results.</a> Journal of Oral and Maxillofacial Surgery. 72 (12), 2601-2604 (2014).</li><li>Numajiri, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+an+in-house+approach+to+CAD/CAM+reconstruction+of+the+maxilla.">Using an in-house approach to CAD/CAM reconstruction of the maxilla.</a> Journal of Oral and Maxillofacial Surgery. 76 (6), 1361-1369 (2018).</li><li>Bosc, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mandibular+reconstruction+after+cancer:+An+in-house+approach+to+manufacturing+cutting+guides.">Mandibular reconstruction after cancer: An in-house approach to manufacturing cutting guides.</a> International Journal of Oral and Maxillofacial Surgery. 46 (1), 24-29 (2017).</li><li>Ganry, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+surgical+modeling+with+an+open-source+software+protocol:+Study+of+precision+and+reproducibility+in+mandibular+reconstruction+with+the+fibula+free+flap.">Three-dimensional surgical modeling with an open-source software protocol: Study of precision and reproducibility in mandibular reconstruction with the fibula free flap.</a> International Journal of Oral and Maxillofacial Surgery. 46 (8), 946-950 (2017).</li><li>. InVesalius Available from: <a target="_blank" href="https://www.cti.gov.br/en/invesalius">https://www.cti.gov.br/en/invesalius</a> (2018)</li><li>. Blender Available from: <a target="_blank" href="https://www.blender.org/">https://www.blender.org/</a> (2018)</li><li>. Free3D Available from: <a target="_blank" href="https://free3d.com/3d-models/human">https://free3d.com/3d-models/human</a> (2018)</li><li>. MakerBot Replicator+ Available from: <a target="_blank" href="https://www.makerbot.com/replicator/">https://www.makerbot.com/replicator/</a> (2018)</li><li>. Artec Eva Lite Available from: <a target="_blank" href="https://www.artec3d.com/portable-3d-scanners/artec-eva-lite">https://www.artec3d.com/portable-3d-scanners/artec-eva-lite</a> (2018)</li><li>Guerrero-de-Mier, A., Espinosa, M. M., Dominguez, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bricking:+A+new+slicing+method+to+reduce+warping.">Bricking: A new slicing method to reduce warping.</a> Procedia Engineering. 132, 126-131 (2015).</li><li>Petropolis, C., Kozan, D., Sigurdson, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+medical+models+made+by+consumer-grade+fused+deposition+modeling+printers.">Accuracy of medical models made by consumer-grade fused deposition modeling printers.</a> Plastic Surgery. 23 (2), 91-94 (2015).</li><li>Alsoufi, M. S., Elsayed, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Warping+deformation+of+desktop+3D+printed+parts+manufactured+by+open+source+fused+deposition+modeling+(FDM)+system.">Warping deformation of desktop 3D printed parts manufactured by open source fused deposition modeling (FDM) system.</a> International Journal of Mechanical and Mechatronics Engineering (IJMME) - International Journal of Engineering and Sciences (IJENS). 17 (4), 7-16 (2017).</li><li>Maschio, F., Pandya, M., Olszewski, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+validation+of+plastic+mandible+models+produced+by+a+"low-cost"+3-dimensional+fused+deposition+modeling+printer.">Experimental validation of plastic mandible models produced by a "low-cost" 3-dimensional fused deposition modeling printer.</a> Medical Science Monitor. 22, 943-957 (2016).</li><li>Rendon-Medina, M. A., Andrade-Delgado, L., Telich-Tarriba, J. E., Fuente-Del-Campo, A., Altamirano-Arcos, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dimensional+error+in+rapid+prototyping+with+open+source+software+and+low-cost+3D-printer.">Dimensional error in rapid prototyping with open source software and low-cost 3D-printer.</a> Plastic and Reconstructive Surgery - Global Open. 6 (1), 1646 (2018).</li><li>Nizam, A., Gopal, R. N., Naing, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dimensional+accuracy+of+the+skull+models+produced+by+rapid+prototyping+technology+using+stereolithography+apparatus.">Dimensional accuracy of the skull models produced by rapid prototyping technology using stereolithography apparatus.</a> Archives of Orofacial Sciences. 1, 60-66 (2006).</li></ol>

The authors have nothing to declare.

CAD/CAM reconstruction is considered to contribute to the attainment of an accurate osteotomy length, width, and angle in cutting bones while using cutting guides4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19. The transferred arrangements of the bones are also considered to be accurate using a fixation guide11. Because the order, process, cutting plane, and arrangement plan are already decided upon before the actual surgery, time-saving is another advantage2,12,13,14.
Moreover, in addition to these theoretical advantages, a strength of the CAD/CAM technique is that because of the surgical guides, any surgeon can cut in the same place in the same way, thus standardizing the technique. If the guides are very accurate, it is possible that every surgeon can obtain accurate reconstruction results rather than using a free-hand approach where results are rather dependent on expertise. Because this CAD/CAM technique has emerged quite recently, reports similar to this are few. Commercial guides are available in Western countries; however, design methods are not open to the public. As this design method is new, we expect it to be developed and spread widely in the future.
This in-house CAD/CAM approach does not always demonstrate superiority. One clinical problem is that this technique becomes useless when the CT exam data is not made of thin and fine slices or is obtained just before the surgery, and the surgeon either does not decide on the resection area quickly or suddenly changes the resection area intra-operatively.
A design-making problem is that, if the designer does not have sufficient experience to see and learn the surgical procedure, an appropriate surgical guide design cannot be obtained. After all, in that situation, the designer does not know what exact space the actual surgeon would make in order to be free of objects in every surgical situation.
As a cost problem, a 3-D printer is necessary for a beginner designer to create trial-and-error designs to materialize the actual guides. After becoming a well-experienced designer, the materialization of the design is no longer indispensable. Luckily, computers and 3-D printers are becoming cheaper, which means we can design and manufacture surgical guides independently without having to rely on the services of expensive companies. A disadvantage is that we cannot yet 3-D print the metal plates used for the fixation. Plastic is the main material we can use for 3-D printing. Thus, we must pre-bend the metal plates before the surgery. As inexpensive 3-D printers that can handle metals are expected to come into use in the future, fixation plates may also be designed then, and all procedures will be less dependent on free-hand techniques.
Fused deposition modeling (FDM) is one of the most used 3-D printing technologies. 3-D objects are built by extruding thermoplastic polymers through a nozzle. When the thermoplastic materials get cold, internal stresses may generate deformations (warping)26. Acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) are the predominant plastics used for thermoplastic filaments. Petropolis et al.7 mentioned that, because ABS mandible models are particularly prone to warping, ABS plastics are less ideal for surgical models when compared with PLA. Both ABS and PLA plastics are gas sterilizable and sufficiently rigid to serve as a template27. Compared with ABS, PLA is less flexible with a lower melting temperature. Thus, we used PLA and a low-temperature plasma sterilization method under 45 &#176;C in a clinical situation. Because the glass temperature of the PLA we used is 60 &#176;C, we did not use either autoclave sterilization (approximately 121 &#176;C) or ethylene gas oxide sterilization (approximately 60 &#176;C).
Warping deformation remains a possibility. However, previous reports validated the accuracy of FDM-printed models in the field of maxillofacial surgery28. Several articles used a comparative study of the dry human mandible and FDM-printed replica using scanned CT data. These studies showed that consumer-grade FDM-printed models have an acceptable accuracy, similar to the results of industrial selective laser sintering (SLS) printers27,29,30. Nizam et al.1 argued that the quality of the CT scan is also one of the main determinants of dimensional errors, alongside the rapid prototype machine.
Even if the precise guides are designed virtually, the printed guides sometimes do not fit the pre-operative surgical bone models. We considered there to be two reasons for this.
1. The superficial bony shape of the area where the guide is designed to be attached is too flat to be hooked (especially maxilla). If these surfaces are smooth and not uneven, the guide surface is prone to become slippery and has a possibility of mis-fitting to the wrong bony area. To avoid this situation, the attached area should be designed wider and broader to catch the exact bony area. At the same time, if the attached area becomes larger, the undermined area becomes larger, which results in a wider scar.
2. On the other hand, the plastic surgical guide is also difficult to fit if the shape of this surface is too uneven and complicated. Because a rough surface with many small processes of the CAD/CAM guides induces friction resistance when attached to the bone, overly winded and complicated guide surfaces are also prone to mis-fit to the wrong place. To avoid these situations, trial-and-error printing and model surgery prior to the actual surgery are necessary. As a result, outsourcing the 3-D printing is not recommended.
Finally, even if the guide was able to fit in the model surgery, when it does not fit in clinical situations, it should be considered to be a kind of reference guide. This is similar to when commercial guides do not fit. Final decisions in real surgery should be made based upon the recognition of occlusion and facial aesthetics by the surgeon, not by the guide.
Although the apparent cost seems to be cheaper using the in-house CAD/CAM approach than commercial approaches, the real cost, which includes the surgeon&#39;s voluntary work and the time for designing and printing, is always underestimated or neglected. However, even if commercial guides become cheaper, this in-house approach still has a unique advantage, which is that surgeons can directly and easily perform trial-and-error reconstructions in a virtual simulation and realize the location relationship between the facial bone and the fibular segments.
The design of guides is limited to hard tissue such as the bone in this report. However, surgical guides can be designed for soft tissue cutting and fixing such as fat or muscle tissues. Guides are considered to be applicable in surgeries for the purpose of performing 3-D structural reconstruction using soft tissues. Fixation guides will soon be designed for breast reconstructions after cancer ablative surgery in a best-fit reshaping of the transferred adipose tissue from the abdomen to the breast.
In conclusion, by using an in-house approach, CAD/CAM surgical guides can be designed and printed at a hospital. In addition to using an accurate reconstruction by CAD/CAM, these techniques can also be used by surgeons who live outside regions where commercial guides are available. This technique is an option for maxillary reconstructions.

The use of CAD/CAM techniques has recently increased in dental and denture work. Following this evolution of CAD/CAM, osteocutaneous flap transfers using CAD/CAM are now used in the field of mandibular reconstruction after an oncologic wide resection of malignant tumors1,2,3. Several companies in Western countries have begun to supply and sell a CAD/CAM cutting guide for the mandible region. A CAD/CAM reconstruction of the mandible is considered to have an advantage in terms of accuracy4,5,6,7,8,9,10,11. However, a disadvantage is that this technique is available in limited areas worldwide and it is very expensive12. Thus, CAD/CAM reconstruction for maxillary lesions has not yet become popular. The number of the cases of maxillary reconstruction is lower than that for the mandible, and commercial guides are not common.
Because commercial maxillary CAD/CAM guides are not sold in Japan, we have developed CAD/CAM surgical guides using an in-house approach. The clinical effectiveness of the CAD/CAM guides has already been reported13,14,15,16,17,18,19, but there is no report of how to design them. The purpose of the present report is to show the CAD/CAM design method using a low-cost in-house approach.

<table><tbody><tr><td>Information Technology Center, Renato Archer, Campinas, Brazil</td><td>InVesalius</td><td>Free software https://www.cti.gov.br/en/invesalius</td><td></td></tr><tr><td>The Blender Foundation, Amsterdam, Netherlands</td><td>Blender</td><td>Free software https://www.blender.org/</td><td></td></tr><tr><td>TurboSquid, Inc. 935 Gravier St., Suite 1600, New Orleans, LA.</td><td>Free 3D skeletal data file</td><td>Free3D https://free3d.com/3d-models/human</td><td></td></tr><tr><td>MakerBot Industries, LLC One MetroTech Center, 21st Fl, Brooklyn, NY.</td><td>MakerBot Replicator+</td><td>https://www.makerbot.com/replicator/</td><td></td></tr><tr><td>YouTube (Google, Inc.), 901 Cherry Ave. San Bruno, CA</td><td>video sharing website.</td><td>https://www.youtube.com/results?search_query=invesalius+dicom+to+stl</td><td></td></tr><tr><td>Artec 3D, 2, rue Jean Engling, Luxembourg</td><td>Artec Eva Lite</td><td>https://www.artec3d.com/portable-3d-scanners/artec-eva-lite</td><td></td></tr><tr><td>CloudCompare</td><td>CloudCompare</td><td>http://www.danielgm.net/cc/</td><td></td></tr></tbody></table>

designing cad/cam surgical guides for maxillary reconstruction using an in-house approach

Computer-aided design/computer-assisted manufacturing (CAD/CAM) is now being evaluated as a preparative technique for maxillofacial surgery. Because this technique is expensive and available in only limited areas of the world, we developed a novel CAD/CAM surgical guide using an in-house approach. By using the CAD software, the maxillary resection area and cutting planes and the fibular cutting planes and angles are determined. Once the resection area is decided, the necessary faces are extracted using a Boolean modifier. These superficial faces are united to fit the surface of the bones and thickened to stabilize the solids. Not only the cutting guides for the fibula and maxilla but also the location arrangement of the transferred bone segments is defined by thickening the superficial faces. The CAD design is recorded as .stl files and three-dimensionally (3-D) printed as actual surgical guides. To check the accuracy of the guides, model surgery using 3-D-printed facial and fibular models is performed. These methods may be used to assist surgeons where commercial guides are not available.

Using the procedure presented here, the resection area was determined first. Using CAD software, the resection area was completely circumscribed by the faces. This area was subtracted from the facial bone by a Boolean operation. The fibula image was placed on the defect, and fibular cutting faces were placed in the appropriate reconstructed points. All fibular cutting faces were linked to the fibula in a parent setting. These faces were made smaller and were united to make solids. The fibula was subtracted from these solids and then became the fibular cutting guides. The remaining surfaces of the facial bone were also thickened; these became the maxillary cutting guides. The superficial sides of the fibular segments are united and extracted to become a fixation guide. Finally, the fibular cutting guide, the maxillary cutting guide, and the fibular fixation guide were designed in Blender. These designs of the guides were exported in .stl format. They became real plastic objects by 3-D printing (Figures 9a and 9b).
Model surgery was performed (Figures 9c-9f). A maxillary cutting guide and fibular cutting guide were completely fitted to the facial bone and fibular bone models. Cutting the models with a saw and fixing the results with titanium plates and screws were also done. After the fixation, a 3-D-reconstructed image was determined by the 3-D scanner24. The post-model surgery .stl file and the CAD reconstructed design were compared in terms of accuracy of the guides and procedures using comparison software25. The data from the model surgery are shown in Figure 10; the reconstruction can be performed approximately within a 2 mm deviation.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58015/58015fig1.jpg" /> 
Figure 1: Deciding on the area of maxillary resection. (a) The original facial bone .stl file is imported to Blender. (b) The first cutting plane is inserted in the zygomatic lesion. (c) The next cutting plane is placed. (d) The cutting plane of the alveolar area is also set. (e) The cutting planes must be united and surround the excision area completely. (f) By using a Boolean modifier, the maxillectomy area is subtracted from the facial bone. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58015/58015fig2.jpg" /> 
Figure 2: Planning the location of the fibular segments. (a) The fibular .stl file is imported to Blender. The distal portion of the fibula is placed in the alveolar area first. (b) The cutting plane is copied and linked to the fibula as a parent setting. (c) According to the preference of the planning surgeon, the next cutting plane is placed on the fibula. The fibular area that is sandwiched between these two planes becomes the first necessary fibular segment. (d) To determine the location of the next fibular segment, the copied fibula is placed. The next cutting planes are also placed according to the judgment of the surgeon. (e) Finally, three fibular blocks are designed, as in this example. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58015/58015fig3.jpg" /> 
Figure 3: Sliding the vertex along the edge. (a) Three pairs of the cutting planes are linked to the fibula as a parent setting. (b-d) To obtain an appropriate guide design, the vertex of the plane is moved along the edge in the edit mode. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58015/58015fig4.jpg" /> 
Figure 4: Designing the box for preparation to make the fibular cutting guide. (a) This cutting plane is going to be reduced in size to become an appropriate cutting guide size. (b) The final size of the cutting plane is highlighted. (c) The cutting plane is determined by sliding the vertex along the edge, similarly to Figure 3. (d) Both cutting planes are united by adding the new plane in the object mode. (e) Finally, the planes are added to surround the whole surface in the edit mode. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58015/58015fig5.jpg" /> 
Figure 5: Making the fibular cutting guide. (a) Using the procedures shown in Figure 4, three boxes are designed. (b) Each box is shared by the fibula using the subtraction of a Boolean modifier. (c) The opposite surface of each box is completely the same as the fibular surface. (d) To make pillars, a cube is placed near the subtracted solids. (e) A face of this cube is extruded. (f) By repeating this extrude, the main pillar is made. (g) By adding other pillars, attachments to the subtracted solids are made. (h) The pillar and the subtracted solids are united. (i and j) This cutting guide completely fits to the surface of the fibula. Each edge becomes the cutting plane, which guides the cutting saw. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/58015/58015fig6.jpg" /> 
Figure 6: Designing the maxillary cutting guide. (a) The remaining surfaces of the maxilla and the zygoma are prepared just adjacent to the cutting area. (b) These planes are thickened to construct the solid to fit to the zygomatic and maxillary bones, using a solidifying modifier in the edit mode. The edge of this solid becomes the bone saw cutting plane. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/58015/58015fig7.jpg" /> 
Figure 7: Taking out the transfer plane. (a) Each fibular segment is separated using the intersection of a Boolean modifier. (b) In this case, alveolar reconstruction is given priority over the zygomatic prominence. (c) Every superficial face is collected and united to prepare for the construction of the fixation guide. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/58015/58015fig8.jpg" /> 
Figure 8: Designing the fixation guide of the fibular segments. (a) Using a knife tool, the lines are designed to the superficial surface. (b) A small window is made by deleting the vertices and faces. This window is used for the titanium plate fixation. (c) After making several windows, the superficial surface is thickened using a solidifying modifier. (d and e) Only the fixation guide is visualized. On both ends, the wings are added to fix this guide to the remaining facial bone. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/58015/58015fig9.jpg" /> 
Figure 9: Model surgery. (a) Using a 3-D printer, the facial bone, fibular bone, and surgical guides can be realized. (b) The cutting guide is examined to fit to the fibula completely. (c and d) The fibular segments that were cut by using the cutting guide are set to the fixation guide. The fixation guide can completely fit to the cut segments. (e and f) Using the titanium plates and screws, fibular segments are transferred to the maxilla. After removing the fixation guide, additional plates and screws are added for a stronger fixation. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/58015/58015fig10.jpg" /> 
Figure 10: Comparing the model to the plan. The post-surgery model is 3-D scanned and compared to the virtual plan. The scale (millimeter) shows the deviation distance from the virtual plan. The transferred bones mostly have a low deviation (green), while the metal fixation plates have a higher deviation (red). However, the deviation is largely below 2 mm. This image is different from the sample shown in Figure 9. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58015/58015fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Designing CAD/CAM Surgical Guides for Maxillary Reconstruction Using an In-house Approach at JoVE.com

Designing CAD/CAM Surgical Guides for Maxillary Reconstruction Using an In-house Approach

Methods for designing a computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guide are shown. Cutting planes are separated, united, and thickened to easily visualize the necessary bone transfer. These designs can be three-dimensional printed and checked for accuracy.

Computer-aided design/computer-assisted manufacturing (CAD/CAM) is now being evaluated as a preparative technique for maxillofacial surgery. Because this ...

designing-cadcam-surgical-guides-for-maxillary-reconstruction-using

Universidad San Sebastian

Research

JoVE Journal

Medicine

8.9K Views.  Kyoto Prefectural University of Medicine. Methods for designing a computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guide are shown. Cutting planes are separated, united, and thickened to easily visualize the necessary bone transfer. These designs can be three-dimensional printed and checked for accuracy.

Video: Designing CAD/CAM Surgical Guides for Maxillary Reconstruction Using an In-house Approach

Analysis of Expansion Patterns from SARPE Using Finite Element Models

Finite Element Analysis Model for Assessing Expansion Patterns from Surgically Assisted Rapid Palatal Expansion

Surgically assisted rapid palatal expansion (SARPE) was introduced to release bony resistance to facilitate skeletal expansion in skeletally mature patients. However, asymmetric expansion between the left and right sides has been reported in 7.52% of all SARPE patients, of which 12.90% had to undergo a second surgery for correction. The etiologies leading to asymmetric expansion remain unclear. Finite element analysis has been used to evaluate the stress associated with SARPE in the maxillofacial structures. However, as a collision of the bone at the LeFort I osteotomy sites occurs only after a certain amount of expansion, most of the existing models do not truly represent the force distribution, given that the expansion amount of these existing models rarely exceeds 1 mm. Therefore, there is a need to create a novel finite element model of SARPE that could perform a clinically required amount of expander activation for further analysis of the expansion patterns of the hemimaxillae in all three dimensions. A three-dimensional (3D) skull model from cone beam computed tomography (CBCT) was imported into Mimics and converted into mathematical entities to segment the maxillary complex, maxillary first premolars, and maxillary first molars. These structures were transferred into Geomagic for surface smoothing and cancellous bone and periodontal ligament creation. The right half of the maxillary complex was then retained and mirrored to create a perfectly symmetrical model in SolidWorks. A Haas expander was constructed and banded to the maxillary first premolars and first molars. Finite element analysis of various combinations of buccal osteotomies at different angles with 1 mm clearance was performed in Ansys. A convergence test was conducted until the desired amount of expansion on both sides (at least 6 mm in total) was achieved. This study lays the foundation for evaluating how buccal osteotomy angulation influences the expansion patterns of SARPE.

Author Spotlight: Development of a Novel Finite Element Analysis Model for Improved Orthognathic Surgical Techniques 

A set of novel finite element models of surgically assisted rapid palatal expansion (SARPE) that could perform a clinically required amount of expander activation with various angles of buccal osteotomy was created for further analysis of the expansion patterns of the hemimaxillae in all three dimensions.

Surgically assisted rapid palatal expansion (SARPE) was introduced to release bony resistance to facilitate skeletal expansion in skeletally mature ...

Bioengineering

A Postoperative Evaluation Guideline for Computer-Assisted Reconstruction of the Mandible

Valid comparisons of postoperative accuracy results in computer-assisted reconstruction of the mandible are difficult due to heterogeneity in imaging modalities, mandibular defect classification, and evaluation methodologies between studies. This guideline uses a step-by-step approach guiding the process of imaging, classification of mandibular defects and volume assessment of three-dimensional (3D) models, after which a legitimized quantitative accuracy evaluation method can be performed between the postoperative clinical situation and the preoperative virtual plan. The condyles and the vertical and horizontal corners of the mandible are used as bony landmarks to define virtual lines in the computer-assisted surgery (CAS) software. Between these lines the axial, coronal, and both sagittal mandibular angles are calculated on both pre- and postoperative 3D models of the (neo)mandible and subsequently the deviations are calculated. By superimposing the postoperative 3D model to the preoperative virtually planned 3D model, which is fixed to the XYZ axis, the deviation between pre- and postoperative virtually planned dental implant positions can be calculated. This protocol continues and specifies an earlier publication of this evaluation guideline.

Here, we propose a practical, feasible and reproducible evaluation guideline for computer-assisted reconstruction of the mandible in order to create uniformity between studies regarding postoperative accuracy evaluation. This protocol continues and specifies an earlier publication of this evaluation guideline.

Valid comparisons of postoperative accuracy results in computer-assisted reconstruction of the mandible are difficult due to heterogeneity in imaging ...

3D Planning and Printing of Patient Specific Implants for Reconstruction of Bony Defects

We are in the midst of the 3D era in most aspects of life, and especially in medicine. The surgical discipline is one of the major players in the medical field using the constantly developing 3D planning and printing capabilities. Computer-assisted design (CAD) and computer assisted manufacturing (CAM) are used to describe the 3D planning and manufacturing of the product. The planning and manufacturing of 3D surgical guides and reconstruction implants is performed almost exclusively by engineers. As technology advances and software interfaces become more user-friendly, it raises a question regarding the possibility of transferring the planning and manufacturing to the clinician. The reasons for such a shift are clear: the surgeon has the idea of what he wants to design, and he also knows what is feasible and could be used in the operating room. It allows him to be prepared for any scenario/unexpected results during the operation and allows the surgeon to be creative and express his new ideas using the CAD software. The purpose of this method is to provide clinicians with the ability to create their own surgical guides and reconstruction implants. In this manuscript, a detailed protocol will provide a simple method for segmentation using segmentation software and implant planning using a 3D design software. Following the segmentation and stl file production using segmentation software, the clinician could create a simple patient specific reconstruction plate or a more complex plate with a cradle for bone graft positioning. Surgical guides can be created for accurate resection, hole preparation for proper reconstruction plate positioning or for bone graft harvesting and re-contouring. A case of lower jaw reconstruction following plate fracture and nonunion healing of a trauma sustained injury is detailed.

This protocol describes the use of 3D planning and printing for reconstruction of bony defects. We use segmentation tools to create 3D models followed by 3D design software to create patient specific implants for reconstruction purposes concomitant to ablative surgery or as a second stage.

We are in the midst of the 3D era in most aspects of life, and especially in medicine. The surgical discipline is one of the major players in the medical ...

Treatment of Facial Deformities using 3D Planning and Printing of Patient-Specific Implants

Technological advancements in surgical planning and patient-specific implants are constantly evolving. One can either adopt the technology to achieve better results, even in the less experienced hand, or continue without it. As technology develops and becomes more user-friendly, we believe it is time to allow the surgeon the option to plan his/her operations and create his/her own patient-specific surgical guides and fixation plates allowing him full control over the process. We present here a protocol for 3D planning of the operation followed by 3D planning and printing of surgical guides and patient-specific fixation implants. During this process we use two commercial computer-assisted design (CAD) software. We also use a fused deposition&#160;modeling printer for the surgical guides and a selective laser sintering printer for the titanium patient-specific fixation implants. The process includes computed tomography (CT) imaging acquisition, 3D segmentation of the skull and facial bones from the CT, 3D planning of the operations, 3D planning of patient-specific fixation implant according to the final position of the bones, 3D planning of surgical guides for performing an accurate osteotomy and preparing the bone for the fixation plates, and 3D printing of the surgical guides and the patient-specific fixation plates. The advantages of the method include full control over the surgery, planned osteotomies and fixation plates, significant reduction in price, reduction in operation duration, superior performance and highly accurate results. Limitations include the need to master the CAD programs.

As technology develops and becomes more user-friendly, planning of operations and patient-specific surgical guides and fixation plates should be performed by the surgeon. We present a protocol for 3D planning of orthognathic skeletal movements and 3D planning and printing of patient-specific fixation plates and surgical guides.

Technological advancements in surgical planning and patient-specific implants are constantly evolving. One can either adopt the technology to achieve ...

Real-Time Dynamic Navigation System for the Precise Quad-Zygomatic Implant Placement in a Patient with a Severely Atrophic Maxilla

Zygomatic implants (ZIs) are an ideal way to address cases of a severely atrophic edentulous maxilla and maxilla defects because they replace extensive bone augmentation and shorten the treatment cycle. However, there are risks associated with the placement of ZIs, such as penetration of the orbital cavity or infra-temporal fossa. Furthermore, the placement of multiple ZIs makes this surgery risky and more difficult to perform. Potential intraoperative complications are extremely dangerous and may cause irreparable losses. Here, we describe a practical, feasible, and reproducible protocol for a real-time surgical navigation system for precisely placing quad-zygomatic implants in the severely atrophic maxilla of patients with residual bone that does not meet the requirements of conventional implants. Hundreds of patients have received ZIs at our department based on this protocol. The clinical outcomes have been satisfactory, the intraoperative and postoperative complications have been low, and the accuracy indicated by infusion of the designed image and postoperative three-dimensional image has been high. This method should be utilized during the entire surgical procedure to ensure ZI placement safety.

Here, we present a protocol to achieve precise quad-zygomatic implant placement in patients with severely atrophic maxilla using a real-time dynamic navigation system.

Zygomatic implants (ZIs) are an ideal way to address cases of a severely atrophic edentulous maxilla and maxilla defects because they replace extensive ...

Digital Hybrid Model Preparation for Virtual Planning of Reconstructive Dentoalveolar Surgical Procedures

Virtual, hybrid three-dimensional (3D) model acquisition is presented in this article, utilizing the sequence of radiographic image segmentation, spatial registration, and free-form surface modeling. Firstly cone-beam computed tomography datasets were reconstructed with a semi-automatic segmentation method. Alveolar bone and teeth are separated into different segments, allowing 3D morphology, and localization of periodontal intrabony defects to be assessed. The severity, extent, and morphology of acute and chronic alveolar ridge defects are validated concerning adjacent teeth. On virtual complex tissue models, positions of dental implants can be planned in 3D. Utilizing spatial registration of IOS and CBCT data and subsequent free-form surface modeling, realistic 3D hybrid models can be acquired, visualizing alveolar bone, teeth, and soft tissues. With the superimposition of IOS and CBCT soft tissue, thickness above the edentulous ridge can be assessed about the underlying bone dimensions; therefore, flap design and surgical flap management can be determined, and occasional complications may be avoided.

A workflow for creating three-dimensional (3D) virtual hybrid models has been designed based on cone-beam computed tomography dataset and intraoral optical scans utilizing radiographic image segmentation methods and free-form surface modeling. Digital models are used for the virtual planning of reconstructive dentoalveolar surgical procedures.

Virtual, hybrid three-dimensional (3D) model acquisition is presented in this article, utilizing the sequence of radiographic image segmentation, spatial ...

Guided Endodontics: Three-Dimensional Planning and Template-Aided Preparation of Endodontic Access Cavities

Pulp canal obliterations (PCO) are often a consequence of dental trauma, such as luxation injuries. Even though dentin apposition is a sign of vital pulp, pulpitis or apical periodontitis may develop in the long term. Root canal treatment of teeth with severe PCO and pulpal or periapical pathosis is challenging for general practitioners and even for well-equipped endodontic specialists. To ensure detection of the calcified root canal and avoid excessive loss of tooth structure or root perforation, static navigation using templates ("Guided Endodontics") was introduced a few years ago. The general workflow includes three-dimensional imaging using cone-beam computed tomography (CBCT), a digital surface scan, and superimposition of both in a planning software. This is followed by virtual planning of the access cavity and the design of a template that will guide the drill to the desired target point. To do this, a true-to-scale virtual image of the drill must be placed in a way that the tip of the drill reaches the orifice of the calcified root canal. Once the template has been fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM) or a 3D printer, guided preparation of the access cavity can be performed clinically. For research purposes, a postoperative CBCT image can be used to quantify the accuracy of the access cavity performed. This work aims to present the technique of static guided endodontics from imaging to clinical implementation.

Guided endodontics describes a template-aided approach for access cavity preparation. The procedure requires cone-beam computed tomography and a surface scan to produce a template. An incorporated sleeve guides the drill to the target point. This allows the preparation of minimally invasive endodontic access cavities in calcified teeth.

Pulp canal obliterations (PCO) are often a consequence of dental trauma, such as luxation injuries. Even though dentin apposition is a sign of vital pulp, ...

A Murine Maxillary Orthodontic Model Guide to Bone Remodeling Analysis

The Establishment of a Murine Maxillary Orthodontic Model

Due to the lack of reproducible protocols for establishing a murine maxillary orthodontic model, we present a reliable and reproducible protocol to provide researchers with a feasible tool to analyze mechanical loading-associated bone remodeling. This study presents a detailed flowchart in addition to different types of schematic diagrams, operation photos, and videos. We performed this protocol on 11 adult wide-type C57/B6J mice and harvested samples on postoperative days 3, 8, and 14. The micro-CT and histopathological data have proven the success of tooth movements coupled with bone remodeling using this protocol. Furthermore, according to the micro-CT results on days 3, 8, and 14, we have divided bone modeling into three stages: preparation stage, bone resorption stage, and bone formation stage. These stages are expected to help researchers concerned with different stages to set sample collection time reasonably. This protocol can equip researchers with a tool to carry out regenerative analysis of bone remodeling.

Author Spotlight: Insights into an Efficient Murine Maxillary Orthodontic Model Protocol

Here we demonstrate step-by-step a manageable, orthodontic tooth movement protocol operated on a murine maxillary model. With the explicit explanation of each step and visual demonstration, researchers can master this model and apply it to their experimental needs with a few modifications.

Due to the lack of reproducible protocols for establishing a murine maxillary orthodontic model, we present a reliable and reproducible protocol to ...

A Finite Element Approach for Locating the Center of Resistance of Maxillary Teeth

The center of resistance (CRES) is regarded as the fundamental reference point for predictable tooth movement. The methods used to estimate the CRES of teeth range from traditional radiographic and physical measurements to in vitro analysis on models or cadaver specimens. Techniques involving finite element analysis of high-dose micro-CT scans of models and single teeth have shown a lot of promise, but little has been done with newer, low-dose, and low resolution cone beam computed tomography (CBCT) images. Also, the CRES for only a few select teeth (i.e., maxillary central incisor, canine, and first molar) have been described; the rest have been largely ignored. There is also a need to describe the methodology of determining the CRES in detail, so that it becomes easy to replicate and build upon.
This study used routine CBCT patient images for developing tools and a workflow to obtain finite element models for locating the CRES of maxillary teeth. The CBCT volume images were manipulated to extract three-dimensional (3D) biological structures relevant in determining the CRES of the maxillary teeth by segmentation. The segmented objects were cleaned and converted into a virtual mesh made up tetrahedral (tet4) triangles having a maximum edge length of 1 mm with 3matic software. The models were further converted into a solid volumetric mesh of tetrahedrons with a maximum edge length of 1 mm for use in finite element analysis. The engineering software, Abaqus, was used to preprocess the models to create an assembly and set material properties, interaction conditions, boundary conditions, and load applications. The loads, when analyzed, simulated the stresses and strains on the system, aiding in locating the CRES. This study is the first step in accurate prediction of tooth movement.

This study outlines the necessary tools for utilizing low-dose three-dimensional cone beam-based patient images of the maxilla and maxillary teeth to obtain finite element models. These patient models are then used to accurately locate the CRES of all the maxillary teeth.

The center of resistance (CRES) is regarded as the fundamental reference point for predictable tooth movement. The methods used to estimate the CRES of ...

Biology

Evaluation of Maxillary Posterior Tooth Movement Using Digital Superimposition

Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition

Since the introduction of Invisalign by Align Technology, Inc. in 1999, questions and debates have persisted regarding the precision of Invisalign (clear aligner) therapy, particularly when compared to the use of traditional fixed appliances. This becomes particularly significant in cases involving anteroposterior, vertical, and transverse corrections, where precise comparisons are of paramount importance. To address these inquiries, this study introduces a meticulously devised protocol, placing a primary emphasis on digitally superimposing the movement of maxillary posterior teeth to facilitate accurate analysis. The sample included 25 patients who had completed their first series of Invisalign (clear) aligners. Four maxillary digital models (pre-treatment, post-treatment, ClinCheck-initial, and final models) were digitally superimposed using the palate rugae and dentitions as stable references. A software combination was used for model superimposition and tooth segmentation. Transformation matrices then expressed the differences between the achieved and predicted tooth positions. Thresholds for clinically relevant differences were at &plusmn;0.25 mm for linear displacement and &plusmn;2&#176; for rotation. Differences were assessed using Hotelling's T-squared tests with Bonferroni correction. The mean differences in rotation (2.036&#176; &plusmn; 4.217&#176;) and torque (-2.913&#176; &plusmn; 3.263&#176;) were significant statistically and clinically, with p-values of 0.023 and 0.0003 respectively. De-rotation of premolars and torque control for all posterior teeth were less predictable. All mean differences for the linear measurements were statistically and clinically insignificant, except that the first molars seemed slightly (0.256 mm) more intruded than their predicted position. The clear aligner system appears to meet its prediction for most translational tooth movements and mesial-distal tipping in maxillary posterior teeth for non-extraction cases with mild to moderate malocclusions.

Author Spotlight: 3D Movement Assessment of Maxillary Posterior Teeth in Clear Aligner Treatment

This manuscript presents a comprehensive protocol to evaluate the three-dimensional (3D) movement of maxillary posterior teeth with clear aligners using digital model superimposition, an invaluable tool in orthodontics and dentofacial orthopedics.

Since the introduction of Invisalign by Align Technology, Inc. in 1999, questions and debates have persisted regarding the precision of Invisalign (clear ...