Three-dimensional (3D) printing know-how in medication is without doubt one of the new and revolutionary know-how for fabricating 3D fashions of advanced anatomical buildings that may be noticed each visually and haptically. Affected person-specific 3D fashions fabricated by way of this course of are at present getting used for numerous functions, together with surgical simulation, coaching, and medical training. Many of the private use/low-end desktop 3D printers which can be turning into widespread are fused deposition modeling (FDM) 3D printers. In comparison with skilled/high-end 3D printers, the worth of the private use/low-end desktop FDM 3D printer itself, filament, and working prices are decrease; it will probably decrease the financial bottleneck for introducing 3D printing know-how into medical follow, similar to surgical simulation. With a desktop FDM 3D printer and a general-purpose PC, anybody can now quickly fabricate 3D fashions on their very own with out having to depend on 3D printing labs and specialised technicians. Nonetheless, additionally it is true that FDM 3D printers, because of their mechanical traits, encounter many difficulties and issues that emerge throughout the 3D printing course of. Information, know-how, and recommendations on FDM 3D printers have been launched in numerous media, and it has turn into straightforward to learn about them worldwide through the Web. Nonetheless, there was no complete technical overview thus far to provide osseous 3D fashions to be used in oral and maxillofacial surgical procedure. On this report, to create 3D fashions in keeping with the traits of maxillofacial and oral surgical procedure, we allow surgeons themselves to create 3D fashions easily by presenting concepts for CT scanning, factors to notice when exporting Digital Imaging and Communications in Drugs (DICOM) picture information, the best way to create optimum stereolithography (STL) fashions, and issues and options for 3D printing.
Introduction
For the reason that late Nineties, anatomical and life-like three-dimensional (3D) fashions have had a particular place in cranio-maxillofacial surgical procedure [1,2]. Extra just lately, advances in 3D printing know-how and the progress and generalization of {hardware} and software program have made it simpler to manufacture full-scale 3D fashions of varied organs and acquire them. At the moment, the sphere of oral and maxillofacial surgical procedure can also be rising the usage of patient-specific anatomical 3D fashions for surgical simulation, coaching, and medical training [3-5]. The function of the 3D mannequin is the power to visualise delicate and complicated anatomical buildings and to look at and contact them from any course. These can present a three-dimensional understanding of anatomical buildings for the surgeon, and the usage of simulation might help enhance the predictability of surgical procedure, which in flip contributes to surgical security.
Round 2010, at about the identical time because the worldwide 3D printer increase, our group developed a 3D printing lab to be used within the area of oral and maxillofacial surgical procedure [6]. This lab can fabricate low-cost 3D fashions with brief supply occasions, with out the necessity for specialised 3D printing labs or skilled technicians. We now have demonstrated that in orthognathic surgical procedure, surgical simulation utilizing fabricated osseous 3D fashions will increase the surgeon’s surgical certainty, decreases intraoperative blood loss, and shortens operative time [7]. These 3D fashions are produced with commercially out there desktop fused deposition modeling (FDM) 3D printers. In comparison with high-end, costly skilled 3D printers, these printers are very cheap, but can produce osseous 3D fashions enough for medical use [8,9].
To manufacture osseous 3D fashions, it’s essential to know the best way to create an optimum 3D computer-aided design (CAD) mannequin information and to grasp the fabrication traits of FDM 3D printers. Nonetheless, till now, there have been no reviews or manuals that particularly cowl the sequence of processes within the 3D mannequin fabrication based mostly on the specifics of oral and maxillofacial surgical procedure, and it has required a variety of time to be taught them. This report presents options discovered from many 3D printing failures and describes methods for FDM 3D printing with diminished failures.The aim is to make this cost-effective 3D printing know-how out there to all fields that require osseous 3D fashions.
Technical Report
Fundamentals and vocabulary
One downside in describing the fabrication of 3D fashions is that it has been very troublesome to unify the assorted phrases used of their related jargon. It’s because the terminology varies from literature to literature, from producer to producer, and from person to person. Many of the 3D printing phrases used on this report are based mostly on the suggestions by the Worldwide Group for Standardization (ISO/ASTM 52900:2021) [10]. Right here, “3D printing” signifies the manufacturing of 3D fashions utilizing a 3D printer; and “fabrication” signifies the whole sequence of processes to create that 3D mannequin, together with segmentation and binarization of Digital Imaging and Communications in Drugs (DICOM) pictures on the medical imaging software program packages, 3D printing with the 3D printer, removing of assist buildings, and remaining ending.
Stereolithography (STL), additionally known as “Normal Triangle Language” or “Normal Tessellation Language” is a generally used information format (.stl) that represents the floor of an object as a mesh of small triangles. It has a protracted historical past and is the de facto normal file format utilized in fields similar to 3D CAD, fast prototyping, and extra just lately, 3D printing. On this report, STL format information can be referred to as “STL information,” and the polygonal mesh fashions created based mostly on these information can be referred to as “STL mannequin”. Within the technique of changing a DICOM picture right into a 3D printable information file, it’s first essential to create intermediate information. These information function an middleman, which interacts with information produced by a variety of 3D CAD software program packages (synonymous with STL mannequin information on this report). The format of the exported file wanted to proceed to the following step is dependent upon the medical imaging software program (DICOM segmentation software program) and/or 3D CAD software program (polygon enhancing software program) used. Lots of them have “saved as STL file” or “exporting to STL” instructions, nevertheless, and it’s common for it to be exported as an information file in STL format. Though the FDM mechanism is at present additionally referred to as the fused filament fabrication (FFF) mechanism, this report will seek advice from it as FDM, following the catalog of 3D printer producers. Determine 1 exhibits the 3D fashions we fabricate and use in medical oral and maxillofacial surgical procedure.
Mechanism, options, and the fabrication technique of the FDM 3D printer
Desktop FDM 3D printers, that are categorised as private and low-end, supply nice benefits by way of compactness, upkeep, and working price. Furthermore, FDM 3D printers are additionally environmentally pleasant as they don’t require any particular supplies similar to resin options, which different sorts of 3D printers do. Moreover, in printing FDM 3D fashions, the filaments are melted at roughly 200 levels Celsius. They are often sterilized with high-pressure steam, as is the case with many medical units. Which means they are often introduced into the working room.
Determine 2 exhibits the mechanism of the FDM 3D printer. The melted resin is extruded by way of a nozzle to kind layers in single strokes, a course of resembling that seen in a soft-serve ice cream machine. The time taken for FDM printing will increase with the scale and/or many 3D fashions required. One other issue to be thought-about is warpage because of heat-induced shrinkage, which will increase with the scale of the mannequin required. The usual filaments used within the FDM 3D printers are polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). Our group makes use of PLA as a result of it has a stiffness just like that of cortical bone and is appropriate for osteotomy simulation, in addition to for ease of availability and price. One downside is that every one these filaments change over time, turning into brittle as they take up moisture. Beneath regular situations of use and storage, nevertheless, it takes a number of months earlier than they’re not usable (Be aware: this doesn’t imply that they’re unusable, however fairly that they often break or plug up in printing). Subsequently, this could not pose an excessive amount of of an issue.
The 3D mannequin fabrication course of workflow is proven in Determine 3. The information exported from medical imaging modalities similar to multidetector-row computed tomography (MDCT) and restricted cone-beam computed tomography (CBCT) within the type of DICOM information can’t be instantly used to manufacture a 3D mannequin. To manufacture a 3D mannequin with a 3D printer, it’s first essential to organize the information that can function the blueprint for the 3D mannequin. Optical 3D scanners are sometimes used for the acquisition of STL information required for the manufacture of handmade merchandise. Within the medical area, DICOM pictures obtained from medical imaging modalities, primarily MDCT, are transformed to STL information and ready after binarization, setting of areas of curiosity, and different processing. Within the binarization course of, which determines whether or not to 3D print or not, the brink worth of voxel depth (equal to the Hounsfield unit in MDCT) enormously impacts the geometric shapes of the STL mannequin. The operator of the medical picture processing software program (DICOM segmentation software program) determines the binarization threshold, which differs from operator to operator. If the brink is just too excessive, the replication of skinny bones can be poor. Alternatively, a low threshold worth would lead to a low-quality STL mannequin with a tough floor as a result of it will embody a voxel depth as excessive as that of the encompassing gentle tissue along with steel artifacts.
The created STL mannequin is exported to the slicing software program (often known as a slicer, this software program generates information (G-code), which mediates between the 3D mannequin and the 3D printer). G-code is probably the most extensively used pc numerical management (CNC) together with FDM 3D printers programming language within the business. It’s generated by the slicing software program and accommodates numerous parameters for working the 3D printer, similar to printing orientation (course of lamination), laminating pitch, infill density, supporting properties (form, infill sample, filling density of helps, overhang angle, z-distance), the temperature of the heated nozzle and construct plate, and print pace. After the 3D printing is accomplished, the assist buildings are faraway from the 3D mannequin, and the 3D mannequin is supplied with ending touch-ups similar to deburring and trimming.
Dimensional accuracy of osseous FDM 3D fashions
To research the dimensional accuracy, 4 mandibular 3D fashions with totally different laminating pitches had been fabricated, and the STL mannequin created by reverse scanning every mannequin was in comparison with the grasp STL mannequin. The form error was measured by evaluating the form with the grasp STL mannequin and the STL mannequin created by reverse scanning. Desk 1 and Desk 2 present the 3D printing parameters and the reverse scanning parameters of the MDCT. The FDM 3D printer used for the fabrication was Value3DMagiX MF-800 (MUTOH Industries Ltd., Tokyo, Japan). A 64-slice MDCT Aquilion (Canon Medical Methods, Otawara, Japan) was used for reverse scanning. 3D CAD comparability and inspection software program package deal SpGauge 2014.1 (Armonicos Co., Ltd., Hamamatsu, Japan) was used to visualise and measure form errors.
The polygon depend of the grasp STL mannequin and every STL mannequin after reverse scanning was about 600,000 and the file dimension was 30 megabytes. Desk 3 and Determine 4 present the outcomes of the 3D mannequin after fabrication, with a shade map picture and a close-up view of the 3D mannequin floor after the grasp STL mannequin and reverse scanned STL mannequin was superimposed. The outcomes confirmed that rising the laminating pitch diminished the 3D printing time, however the floor of the 3D mannequin grew to become rougher and streaky steps had been extra noticeable. Compared with the grasp STL mannequin, some form errors had been noticed within the z-direction (condyle – inferior margin of the mandible course), however they had been virtually inside plus or minus 0.5 mm.
Dialogue
3D fashions reproduce the advanced buildings of the tooth and jaws (e.g., foramen, cavities, processes, ridges, skinny bone), permitting us to substantiate bone thickness, cavity depth, and blind areas which can be troublesome to see instantly. It can be used to simulate lifelike surgical procedure. Many younger surgeons who need to enhance their surgical abilities should be educated in follow fashions. Nonetheless, acquiring these fashions has typically required excessive prices. For them, cheap, patient-specific 3D fashions can be an important assist [11,12].
FDM 3D printers are typically used for private use, similar to for hobbies and crafts. When they’re used to manufacture anatomical 3D fashions and for medical functions similar to surgical simulations, it’s pure to be involved about their 3D printing accuracy. In 2017, George et al. [13] investigated the accuracy and reproducibility of 3D printed medical fashions, by which they reported that the benefit of FDM 3D printers is low price, however that the spatial decision is decrease than that with different modalities. There aren’t any right CT scanning parameters, STL mannequin creation parameters, or 3D printing parameters for fabricating 3D fashions. Subsequently, the protocol adopted on this report follows our earlier reviews [6,14] and the report by Mitsouras et al. [15]. A slight dimensional error occurred between the grasp STL mannequin and the STL mannequin as a result of quantity of laminating pitch, however all had been inside plus or minus 0.5 mm. The explanation for the slight error in dimensional form was assumed to be as a result of individuality of the software program used to transform the DICOM picture to STL information (derived from the binarization algorithm carried out within the software program) and/or the deformation of the filament throughout the 3D printing course of. Nonetheless, the error is the scale of 1 or two voxels of an MDCT picture and is the restrict of the spatial decision of the MDCT used on this research. These outcomes present that dimensional errors brought on by variations in laminating pitch don’t considerably have an effect on sensible operations similar to surgical simulations.
Utilizing the FDM 3D printer is a continuing wrestle towards the instability of the 3D printing course of. We now have skilled quite a few 3D printing failures (Determine 5). They’re often the results of a mixture of two or three interrelated components, and discovering an answer to them is troublesome.
Determine 6 exhibits some issues that may be encountered in FDM 3D printing and their urged options. Right here, these issues have been divided into two main classes: these brought on by poor high quality STL fashions or G-code; and people brought on by the 3D printer or filament. To keep away from 3D printing failures and obtain clean 3D printing, it’s first essential to correctly create the STL mannequin. As an answer to 3D printing failures derived from the standard of the STL mannequin, throughout STL mannequin creation, skinny areas of bone which can be anticipated to be “perforated” by binarization, such because the maxillary sinus wall, condylar, and anterior ramus margin, are compensated by filling or including columnar helps (Determine 7). Desk-shaped helps are additionally typically added, for components which have little contact space with the construct plate. A raft-, brim-, or skirt-shaped further marginal supportive layers could also be used to enhance stability. As an answer to failures brought on by 3D printers and filaments, in our expertise, the commonest downside is the failure to repair the primary layer. Issues brought on by the failure of the primary layer are generally known as “First layer issues” or “First layer points”. That is arguably the largest downside bothering all FDM 3D printer customers [16]. Filaments are susceptible to deformation because of extended publicity to warmth from the construct plate throughout 3D printing, with ABS filaments being notably susceptible to this. Subsequently, decreasing the temperature of the construct plate (Be aware: with some FDM 3D printers, the temperature of the construct plate will be adjusted however not all) or utilizing auxiliary supplies similar to masking tape, hairspray, or glue sticks can enhance fixation and cut back filament warpage. Care should even be taken with the standard of the filament itself. Some filaments usually are not wounded neatly and may turn into entangled throughout the 3D printing course of, rising the chance of failure (Determine 8). Moreover, the properties of the identical model typically differ amongst manufacturing heaps. The 3D printing parameters differ from the standard of the 3D printer and the filament used, however in any case, if they’re improper, it’ll instantly result in the failure of the 3D print. In different phrases, the standard of the G-code determines the result. Within the present scenario, the place 3D printing operator ingenuity is required, one of the best parameters/settings for every 3D printer and filament high quality should be decided based mostly on their very own expertise.
Steel artifacts in DICOM pictures brought on by dental metallic supplies seem as imaging noise and consequently cut back the element of the 3D mannequin. Because of this, they’re eliminated as a lot as attainable throughout the creation of the STL mannequin, however some could stay. We adjusted the place of the pinnacle and jaw and the lean of the gantry to slim the vary of artifacts (particularly, the occlusal airplane needs to be perpendicular to the ground throughout CT scanning) (Determine 9). Moreover, we additionally carried out scanning with the affected person’s mouth saved barely open utilizing a chew block at a stage to facilitate the segmentation of the maxilla and mandible on the STL mannequin. Generally, the standard of the supply information shouldn’t be appropriate for 3D printing. In lots of circumstances, the pictures are exported in thick slices (Determine 10). If the time has handed since scanning and no CT uncooked information have been saved (the values of all detector indicators are measured throughout the scanning; from these information, a CT picture is reconstructed by mathematical strategies; the uncooked information can be utilized later for added planes and pictures reconstruction; as a result of dimension of the information, it’s often saved on a server for a number of weeks after which deleted because of storage capability limitations), the picture can’t be reconstructed and re-exported with a thinner slice thickness. Simply as firms that present surgical guides and stents for dental implant surgical procedure present detailed directions throughout CT scanning and DICOM file exporting, they need to present applicable directions throughout 3D printing.
Desktop FDM 3D printers, even when they’re merely “private” or “low-end,” have important benefits of their economics [7,17,18]. The “one-stop” 3D printing resolution, the place the entire course of from STL mannequin creation to 3D printing will be accomplished in-house, presents many benefits. During the last seven years, our group has used three FDM 3D printers [6,19,20], and every one represented an enchancment on the earlier era of printers, with stability persevering with to extend. Sadly, nevertheless, expertise has proven that the printing stability of FDM 3D printers remains to be not adequate, and plenty of options should be mastered for profitable fabrication. We now have mentioned that there are various variations in 3D printing failures. We now have urged an answer to keep away from these. In our expertise, the success fee of 3D printing is about 75%, i.e., the 3D printer masses the G-code information and finishes constructing with out encountering any issues. Since there isn’t a precedent for this, it’s troublesome to evaluate whether or not this worth is excessive or low, and that is simply our opinion. Nonetheless, which means FDM 3D printing shouldn’t be a straightforward course of.
It is extremely troublesome to foretell the long run, however we count on 3D printing know-how to proceed to evolve and the sophistication and complexity of the information required to extend. Information and methods associated to 3D printing know-how will turn into more and more essential sooner or later. Whereas it might be troublesome to unify opinions on the optimum CT scan parameters and 3D printing parameters, as they range from affected person to affected person and facility to facility, consolidating measures to cut back 3D printing failures can be important for the long run use of 3D fashions in medication. It’s anticipated {that a} system with synthetic intelligence will clear up these issues, similar to mechanically detecting and setting numerous optimum parameters with out human intervention.
Conclusions
It’s no exaggeration to say that the introduction of 3D printing know-how within the area of oral and maxillofacial surgical procedure can present medical advantages to all. From an financial standpoint, the FDM 3D printer specifically may play an essential position. As the marketplace for 3D printers, not simply FDM 3D printers, grows and is used for numerous functions, data of 3D imaging engineering and 3D printing know-how will turn into more and more essential. This information can be much more important if surgeons are to manufacture their 3D fashions. It’s hoped that this report will assist operators that aren’t 3D printing specialists perceive what to be taught and the best way to use 3D printing know-how to create 3D fashions effectively and with out failure.
