THE ROLE OF ADVANCED 3D TECHNOLOGIES AND ADDITIVE MANUFACTURING IN DESIGNING AND MANUFACTURING OF CUSTOMIZED BONE GRAFTS

Transcription

1 DOI: /jtp THE ROLE OF ADVANCED 3D TECHNOLOGIES AND ADDITIVE MANUFACTURING IN DESIGNING AND MANUFACTURING OF CUSTOMIZED BONE GRAFTS Šokac M. 1, Budak I. 1, Mirković S. 2, Santoši Ž. 1,Movrin D. 1, Puškar T. 2 1 Faculty of Technical Science University of Novi Sad, Serbia 2 Medical faculty, University of Novi Sad, Serbia ABSTRACT In this paper applications of advanced 3D technologies used for designing a complex personalized bone grafts, frequently used in the field of oral surgery, will be presented. This applications will be presented through several complex cases of designed and manufactured personalized bone grafts, with a unique functional and visual characteristics suited for each patient individually. The first step of this whole process is the designing stage of 3D models of bone grafts using advanced 3D technologies. The next step is the application of additive manufacturing (AM) technologies for producing of these personalized bone grafts as a verification stage. Key words: Personalized implants, Bone grafts, 3D modelling, Additive manufacturing (AM) technologies. 1. INTRODUCTION Modern field of mechanical engineering finds itself today to be far beyond the scope of traditional engineering. This has aided in its expansion to other fields of science, and especially in the multidisciplinary fields [1 3]. Ability to adapt and integrate into other fields, such as medicine and dentistry, provided the blueprint to emergence of a new field of science under the name of biomedical engineering (BE). This new field of multidisciplinary approach emphasizes the need for cooperation between engineers and doctors in a very tight bond. By doing this, mentioned collaboration enabled that a fast growing field of BE rapidly spreads to a different fields of medicine, but more importantly in the field of dentistry. Dentists have needs for incorporation of better technical aspects of different types of implants that will improve their work with patients * Corresponding author s budaki@uns.ac.rs

2 34 and provide better medical treatments. Significant cooperation is precisely in the field of dental prosthetics, and making dentures and implants [4 6]. The main task of all dental restorations is to fulfil both functional and aesthetic requirements that are presented before them. Application of Reverse Engineering (RE) in the field of dentistry has greatly facilitated the modelling and designing aspects. For the purpose of creating virtual 3D models, many 3D digitizing methods have been developed in the field of RE [7]. With the introduction of AM technologies in the medical field, this has produced a strong bond in combination of these two emerging fields. By designing complex shapes and structures using RE modelling approach, they can be transferred afterwards to be manufactured using AM technologies. This insures that all necessary preliminary steps are taken into account in order to successfully provide adequate medical care to the patients. The paper is organized as follows: Section 2 contains review of the previous research in the field on bases of current literature relevant for this study. The design process using RE approach, as well as the basics of the AM technologies applied for the study in this paper, are presented in Section 3. Section 4 presents results which are obtained using RE and AM technologies for the purposes of precise analysis and surgical planning. Concluding remarks are given in Section PREVIOUS RESEARCH IN THE FIELD There is no doubt that 3D technologies have made a huge impact on the medical field, more importantly on the fields of maxillofacial surgery and dentistry [8]. When it comes to application of 3D technologies in designing of complex shapes, commonly present in the field of dentistry, ability to transform physical objects into accurate virtual 3D model is extremely important. Custom implants, for the purpose of their reconstruction, have gained importance due to their better performance [9]. This advantage is due to more precise insertion and adaptation of the implant, as well as reduced surgical time. With the introduction of CAx and AM technologies the demand for fast and high-precision design and manufacturing of human anatomy has rapidly increased in this field. As a consequence, many authors have dealt with this demand. Budak et al. [10] proposed a new approach for modelling of personalized bone grafts based on advanced CAD technologies. Their approach was based on geometric modelling of bone grafts used for mandible. Based on the application of advanced computer-aided systems and methods, they designed a fully custom geometric form, while minimizing risk of error during design and placement stages. Mirkovic et al. [5] presented implementation of 3D technologies through a real case of personalized bone graft augmentation. The design process was performed and then AM technology was used as a last verification step before surgical implementation of the bone graft into the patient. However, application of 3D technologies spreads to a wider area of oral and maxillofacial surgery, along with their successful combination with AM technologies for further development and improvement of customized implants. When it comes to the maxillofacial area, in [11] is presented a case where CAD and AM technologies were successfully combined throughout the whole process from planning to surgery. In relation to this field, there is a larger number of papers that addressing the application of AM technologies in this field [6,12,18].

3 D TECHNOLOGIES IN DESIGNING OF CUSTOM MADE BONE GRAFTS The application of modern CAD technologies has certainly found its place in modern medicine with the use of different tools for modelling of complex freeform shapes. With the development of medicine, there is a need for more sophisticated and advanced tools that will be able to follow these modern requirements. Today, there are various specialized software used for these purposes, but a key parameter that limits their wider application is certainly their price. The first step in designing of these complex shapes is the generation of reference DICOM (Digital Imaging and Communications in Medicine) images on a CBCT (Cone Beam Computed Tomography) device that will serve as a basis for further designing process. This step presents an important and necessary step because, based on generated DICOM images, functional 3D models of the upper/lower jaw of the patient are generated. Based on these generated 3D models, further analysis and designing of bone grafts is carried out. After generating 3D models of the mandible/maxilla of the patient, engineers, in cooperation with the oral surgeon and prosthetics, localize the area in which the desired graft is to be designed, and define its basic characteristics grafts shape, size, thickness and width (Figure 1). Fig. 1-3D models of mandible and maxilla as a first step in designing of bone graft 3D model After generating a 3D model based on the collected DICOM images from the CBCT device, it is necessary to prepare an area where the bone graft will be designed. This step is important because it is necessary to ensure that the bottom surface of the bone graft and patients bone precisely aligns

4 36 and fits in order to accelerate the recovery and bone grafts osseointegration after the surgical procedure (Figure 2). The tools used for this are mainly based on closing the small holes/gaps, as well as smoothing the surface on the bone where the bone graft will be placed. However, attention should be paid to the application of these surface smoothing tools so that they are not used aggressively. This can result in violation of overall bone geometry, and therefore impact the accuracy of the bone graft fitting and its successful osseointegration on the patient's jaw. a) b) Fig. 2 - Planned site of bone graft modelling a) before and b) after the use of advanced tools for mesh preparation and modification After the preparation of the graft site, the designing stage of bone graft begins. For the purpose of designing of bone grafts surfaces, GOM Inspect software from GOM GmbH was used. This software was chosen due to its simple and intuitive use, free license, and as well as a variety of useful tools that are used to design and modify complex freeform surfaces. Designed 3D model of bone graft must contain, in addition to good mechanical properties, also necessary aestheticallyfunctional properties so that it can be safely fitted into the patient's jaw. The designing process is carried out from the bone grafts base surface moving upwards, however in the literature there are various ways shown on how to model bone graft [9, 13]. The goal is to obtain, using a tool for modification and manipulation of freeform surfaces, a 3D model of bone graft which corresponds to the site of implantation, while retaining all the necessary properties (mechanical and aesthetically-functional) (Figure 3). This procedure is carried out interdisciplinary, with cooperation of engineers and medical personnel. Examples of some 3D models of bone grafts that are designed using this approach are shown in Figure 4. Fig. 3 - Designing workflow of the bone graft 3D model

5 37 Fig. 4 - Examples of designed bone grafts 3D models with the application of 3D technologies After obtaining the desired shape and form of bone grafts 3D model, by following the guidelines and the instructions of the oral surgeon, the generated 3D model of the bone graft is overlapped with the planned site on the jaw virtually, in order to perform its inspection. This step is carried out in the OnDemand3D software, Cybermed Inc. (Figure 5). Within this step dentists and oral surgeons, together with engineers, perform analysis where certain parameters are checked. Those parameters are [5]: 2D cross-section of graft, maximum graft thickness, presence of negative angles on graft, sharp edges. Fig. 5 - Inspection of bone grafts geometrical characteristics and its alignment with the bone

6 38 4. ADDITIVE MANUFACTURING TECHNOLOGIES IN DESIGNING OF CUSTOM MADE BONE GRAFTS The intensive application of AM technology in the field of medicine is inevitable due to the possibility of converting complex digital 3D models into real physical objects for better understanding of functioning of designed implants [14-16]. After the bone graft has been designed, for the purpose of the final evaluation of the graft on the bone site, the application of AM technology enables the production of such implants and their visual inspection by the medical staff. This approach, in addition to allowing additional check in the final stage of graft preparation, also allows surgical planning, with pre-defined graft fixation sites, as well as its positioning. In this way, the potential barriers that can be predicted during the design phase are further eliminated, and the role of AM technology in this domain is irreplaceable. 4.1 Fused Deposition Technologies (FDM) Today, there are different types of 3D printers available on the market which are working on different principles. 3D printers use additive principle, i.e. they create the product by adding material, usually layer by layer. In FDM process initial material is in the form of solid filament (ABS, PLA, PET, Nylon ). This filament is fed into the working head where it is heated to a semi-liquid state and then extruded on the working platform thru the nozzle, where it cools and solidifies, building a layer of future model (Fig. 6a). Some type of printers can provide different type of materials than model material, for the temporary filling of hollow and hanging parts of the object, which is removed upon completion of the work. In this way, it is possible to print complex forms often present in the field of medicine, and in this case bone grafts for the final step of analysing their functionality. For the purpose of verification of 3D model of bone graft, one case was printed and verified using the FDM approach. The Makerbot Replicator 2 3D printer (Figure 6b) is used, where a mandible is printed (Figure 6c) along with and bone grafts (Figure 6d), and its visual and functional inspection was conducted (Figure 6e). The characteristics of the Replicator 2 printer are shown in Table 1. Table 1 Technical characteristics of FDM printer MakerBot Replicator 2 Maker bot Replicator 2 3D printer characteristics Filament type PLA Filament diameter 1.75 mm Nozzle diameter 0.4 mm Dimension of 28.5x15.3x15.5 workspace cm X-Y positioning 11 microns accuracy Z positioning 2.5 microns accuracy

7 39 a) b) c) d) e) Fig. 6 - Showing a) RP technology based on FDM approach[13], b) 3D printer MakerBot Replicator 2 and c) 3D printed model of the mandible, d) 3D printed models of designed custom bone grafts and e) assembly of printed models of mandible with appropriate bone grafts for their inspection

8 Binder 3D printing Monochrome 3D printer Z310 plus (3D systems - former Z corporation) is an example binder 3D printer (Figure 7). The technical characteristics of this 3D printer are given in Table 2. The first step in this process is to convert imported stl 3D model into cross-sections or slices that are 0.1 mm thick. Then, the printer is printing these 2D cross-sections, starting from the bottom to the top, one after another. Inside the printer there are two pistons. Besides pistons there are also the roller and the print assembly. On the printer, the roller and the print assembly are both mounted together on the gantry. This allows horizontal movement across the build area. To begin the 3D printing process, the printer first spreads a layer of powder in the same thickness as defined by the cross-section. The print head then applies a binder solution to the powder, causing the powder particles to bind to one another and to the printed cross-section one level below. The feed piston comes up and the build piston drops one layer of the thickness. The printer then spreads a new layer of powder and repeats the process, and in a short time the entire part is printed. After printing, the part is removed from the powder, depowered in the recycling station, infiltrated with liquid infiltrant and left to dry. The powder used in the experiment was ZP 131, a binder zb90 and a layer thickness of 0.1 mm. After 3D printing, as a result are obtained parts that have low mechanical properties, which are also called green parts. In order to obtain a final physical model with its good mechanical properties, it is necessary to carry out infiltration with an epoxy resin, cyanoacrylate, waxes etc.. Loctite cyanoacrylate was used as an infiltrant in experimental research. The entire process of 3D printing on this printer, through all stages, is given in Figure 8. Table 2 Technical characteristics of SLS printer Z310 plus by ZCorp (3D systems) Fig. 7-3D printer Z310 plus 3D printer characteristics Layer Thickness: mm Build Size (x, y, z): 203x254x203 mm Build Speed: 25 mm/h in z direction Files format STL, VRML, 3DS, PLY Resolution in x-y directions 300 x 450 [dpi] Number of print heads 1

9 41 Fig. 8 The overall 3D printing process of mandible on a 3D printer Z310 plus

10 42 After obtaining the appropriate physical models of bone grafts and maxilla/mandible, their inspection is performed which also represents the final stage in which the surgical planning by the oral surgeon can be carried out (Figure 9). Fig. 9 Different medical objects printed using binder 3D printer including both bone grafts and bone required in the inspection stage of the process 5. CONCLUSIONS This paper shows the application of 3D technologies and AM technologies, and their influence on the rapid product development in the field of dentistry and oral surgery applications. Complex tools used for designing of complex surfaces are without a doubt today a very useful, with different options for their applications. From the initial stage of planning, up to the designing stage, these tools are very intuitive and allow the end user a variety of options to apply them. In combination with AM technologies, these two aspects have become inseparable, where with the use of 3D technologies any shape, no matter what complexity, can be designed and then 3D printed for its further application. Finally, what is the most important, application of these technologies insures decreased operation time, shorter recovering period and better final comfort to the patients. ACKNOWLEDGEMENT This paper presents the results achieved in the framework of the Project no / funded by the Provincial Secretariat for Higher Education and Scientific Research, and within the project TR , funded by the Ministry of Education, Science and Technological Development of Republic of Serbia.

11 43 6. REFERENCES [1] Belhadj, A., Boudjemaa, H.: Recent Advances of Mechanical Engineering Applications in Medicine and Biology, Medical Technologies Journal, Vol. 1, 2017, pp doi: / x-vol1iss3p [2] Milovanović, J. Trajanović, M.: Medical Applications of Rapid Prototyping, Mechanical Engineering, Vol 5, 2007, pp [3] Gonizzi Barsanti, S., Guidi, G., De Luca, L.: Segmentation of 3D Models for Cultural Heritage Structural Analysis Some Critical Issues, ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol, 4, 2017, pp doi: /isprs-annals-iv-2-w [4] Foley, B.D., Thayer, W.P., Honeybrook, A., McKenna, S., Press, S.: Mandibular reconstruction using computer-aided design and computer-aided manufacturing: an analysis of surgical results., Journal of Oral and Maxillofacial Surgery: Official Journal of the American Association of Oral and Maxillofacial Surgeons. Vol. 71, 2013, pp doi: /j.joms [5] Mirković S., Budak I., Puškar T., Tadić A., Šokac M., Santoši Ž., Đurđević Mirković T.: Application Of Modern Computer-Aided Technologies In The Production of Individual Bone Graft. A Case Report, Vojnosanitetski pregled, Vol. 72, 2015, pp doi: /vsp m. [6] Salmi, M., Tuomi, J., Paloheimo, K., Björkstrand, K., Paloheimo, M.,Salo J., Kontio, R., Mesimäki, K., Mäkitie, A.A.: Patient specific reconstruction with 3D modeling and DMLS additive manufacturing, Rapid Prototyping Journal, Vol. 18, 2012, pp doi: / [7] Budak, I., Trifkovic, B., Puskar, T., Vukelic, D.,, Vucaj-cirilovic, V., Hodolic, J.: Comparative Analysis of 3D Digitization Systems in the Field of Dental Prosthetics, Technical Gazette, Vol. 20, 2013, pp [8] Wan, K.H., Chong, K.K.L., Young, A.L.: The Role of Computer-Assisted Technology in Post-Traumatic Orbital Reconstruction: A PRISMA-driven Systematic Review, Scientific Reports, Vol. 5, 2015, pp doi: /srep [9] Parthasarathy, J.: 3D modeling, custom implants and its future perspectives in craniofacial surgery, Annals of Maxillofacial Surgery, Vol. 4, 2014, pp doi: / [10] Budak, I., Mirkovic, S., Sokac, M., Santosi, Z., Puskar, T., Vukelic, D.: An approach to modelling of personalized bone grafts based on advanced technologies, International Journal of Simulation Modelling, Vol. 15, 2016, pp doi: /ijsimm15(4) [11] Peel, S., Eggbeer, D., Sugar, A., Evans, P.L.: Post-traumatic zygomatic osteotomy and orbital floor reconstruction, Rapid Prototyping Journal, Vol. 22, 2016, pp doi: /rpj [12] Cohen, A., Chen, R., Frodis, U., Wu, M., Folk, C.: Microscale metal additive manufacturing of multi component medical devices, Rapid Prototyping Journal, Vol. 16, 2010, pp doi: / [13] Otto, S., Kleye, C., Burian, E., Ehrenfeld, M., Cornelius, C.P.: Custom-milled individual allogeneic bone grafts for alveolar cleft osteoplasty - a technical note, Journal of Cranio- Maxillofacial Surgery, 2017, pp doi: /j.jcms [14] Bagaria, V., Rasalkar, D., Bagaria, S.J., Ilyas, J.: Medical Application Of Rapid Prototyping - A New Horizon, Advanced Applications of Rapid Prototyping Technology In Modern Engineering, 2011, pp

12 44 [15] Movrin, D., Ivanišević, A., Kačmarčik, I., Lainović, T., Spasić, А., Blažić, L.: Influence of Secondary Orography on rapid prototyping tooth model accuracy, Journal for Technology of Plasticity, Vol. 39, 2014, pp [16] Tabaković, S., Zeljković, M., Živković, A., Movrin, D., Grujić, J.: Development of the endoprosthesis of the femur according to the characteristics of a specific patient with using modern methods for product design and rapid prototyping, Journal for Technology of Plasticity, Vol. 37, 2012, pp [17] Pahole, I., Drstvensek, I., Ficko, M., Balic, J.: Rapid prototyping processes give new possibilities to numerical copying techniques, Journal of Materials Processing Technology, 2005, pp doi: /j.jmatprotec [18] Tabaković, S., Konstantinović, V., Radosavljavić, R; Movrin, D.,Hadžistević, M., Hatab, N. Application of Computer-Aided Designing and Rapid Prototyping Technologies in Reconppuction of Blowout Fractures of the Orbital Floor, Journal of Craniofacial Surgery, 2015, Vol. 26, No. 5, pp doi: /SCS

13 45 ULOGA NAPREDNIH 3D TEHNOLOGIJA I ADITIVNE PROIZVODNJE PRI DIZAJNIRANJU I IZRADI PERSONALIZOVANIH KOŠTANIH GRAFTOVA Mario Šokac 1, Igor Budak 1, Siniša Mirković 2, Željko Santoši 1, Dejan Movrin 1, Tatjana Puškar 2 1 Faculty of Technical Science University of Novi Sad, Serbia 2 Medical faculty, University of Novi Sad, Serbia REZIME U ovom radu je predstavljena primena naprednih 3D tehnologija koje se koriste za dizajniranje složenih personalizovanih koštanih graftova u oblasti oralne hirurgije. Primena pomenutih tehnologija je realizovana kroz nekoliko izabranih složenih slučajeva sa dizajniranim i proizvedenim personalizovanim koštanim graftovima sa jedinstvenim funkcionalnim i vizuelnim karakteristikama prilagođenim za konkretne pojedinačne pacijente. Osnovni korak u ovom procesu je faza dizajniranja 3D modela koštanih graftova primenom naprednih RE alata. Korak koji nadopunjuje ovaj proces je primena tehnologja za aditivnu proizvodnju (AM) koje se koriste za izradu ovih personalizovanih koštanih graftova. Pomenutim koracima je posvećena najveća pažnja u okviru ovog rada. Ključne reči: Personalizovani implanti, koštani graftovi, 3D modeliranje, tehnologije aditivne proizvodnje (AM).