Keywords
Maxillofacial prosthesis, anaplastology, Digital Models, Additive Manufacturing, 3D-Printing
Maxillofacial prosthesis, anaplastology, Digital Models, Additive Manufacturing, 3D-Printing
We clarified some details about printing parameters and statistical analysys; the abstract was better structured; and conclusion is more concise
See the authors' detailed response to the review by Rodrigo de Faria Valle Dornelles
See the authors' detailed response to the review by Dinesh Rokaya
Prosthesis encompasses a wide range of mechanisms for the replacement of body parts, in order to rehabilitate the characteristics of the missing part in function or appearance. Within them, there is a branch known as “maxillofacial prostheses”, among which are nasal, ear, oculo-palpebral prostheses, etc.1 They are generally used by patients who have suffered cancer (52%), deformities due to accidents (17%) and/or congenital diseases (19%), among others.2
Most of the prostheses, being systems that simulate missing body parts, must be personalized for each patient, which tends to raise their costs. Traditional manufacturing methods require a lot of professional and patient time. In addition, in the public health system, when the service exists and is covered, there are patients who wait between 6 months and 2 years for their rehabilitations. Once the appointment is obtained, they can only be served between 30 minutes to 2 hours per appointment due to the shortage of time and high demand. With the method proposed by the NGO “Mais Identidade”, global work times can be reduced by half.3 In the elaboration of a facial prosthesis, three main stages must be carried out4: obtaining the shape of the patient’s anatomy, traditionally cast from a plaster mold; modelling, made from thermoplastic materials for modelling; and fabrication, using a negative version of the sculpture and placing layers of intrinsically characterized medical grade silicones; in addition to the fabrication of the ocular prosthesis,5,6 with the different difficulties that this can entail, which will finally form part of the maxillofacial prosthesis. But, in the manufacturing process of these prostheses, the patient’s self-perception, emotional stability, personality characteristics and social circumstances are the most important factors when treating maxillofacial defects, as well as the rehabilitation process.7,8
With the aim of optimizing the process and making prostheses more accessible and of good quality, both data acquisition and manufacturing, a digital manufacturing process is chosen. Which consists of: Data acquisition, such as digitization through 3D scanning or photogrammetry; Prosthesis design (reverse engineering software) and rapid prototyping (3D printing).9,10 These technologies can offer advantages such as obtaining digital color 3D colour models, which can be modelled using affordable CAD software for printing on biomaterials such as ceramics and polymers for medical applications11 and, in the future, even directly on medical grade silicone.12,13
In this sense, the purpose of this research is to compare additive manufacturing mechanisms, from a 3D model of the oculo-palpebral model for a future maxillofacial prosthesis, obtained from the “Mais Identidade” Methodology. It will be evaluated which of the additive manufacturing mechanisms achieves the best reproduction of the leather details and maintains the desired dimensional properties, according to the original file. To select the manufacturing method, the oculo-palpebral models manufactured in 7 different 3D printing mechanisms were evaluated, according to their economic, physical and aesthetic characteristics.
The structure of this paper is the following: section 2 briefly details the printing techniques used for the testing; section 3 describes the procedure of the experiments; section 4 presents and evaluates the results; section 5 discusses the evaluations and the context in which they were made; section 6 proposes suggestions for future work and research conclusions.
It is the process by which physical objects are generated from 3D digital files. These files, prior to being printed, go through software in which they are divided into thin layers, with the desired printing characteristics (speed, layer thickness, etc.).14 For the “Mais Identidade” method, layer levels in the range of 100 μ to 16 μ are used to obtain a high level of detail.
It is the most used method of 3D printing. This method uses a thermoplastic filament that goes through a heating system where it is heated to a temperature at which it is moldable and extruded to take the desired shape.15 For the present investigation, PLA filament will be used as a material for printing the prototypes due to its printing practicality, low cost and because it is the most used material in this technology.
This method covers liquid resins that go through a photopolymerization process, which exposes them to a specific range of light, with which they undergo a chemical reaction that solidifies them.15 This technology is usually faster and has a higher level of finish than FDM. Within stereolithography, there are variants such as16:
(1) SLA: A UV laser cures the resin point by point in the resin tank using a projector and a set of mirrors.
(2) LCD: An LCD screen projects the UV light and passes through a filter that allows the exposure of light in the necessary points.
(3) DLP: A projector emits light and through a mirror generates the shapes to be printed layer by layer.
The resins used, both in SLA and LCD and DLP, go through the photopolymerization process when interacting with a light range of 405 nm. Generally, each equipment uses its own resin, so basic light curing resins will be used for prototypes.
This method is based on the injection of polymers that are cured by ultraviolet light. This technology stands out for its high speed and high print resolution, as well as being able to reproduce functional models without the need to assemble them.17 For this research, Vero black was used to print the model, and Sup706 was used for the support.
The selection of the ideal additive manufacturing equipment for printing models that are used in the manufacturing process of maxillofacial prostheses by the “Mais Identidade” method is detailed in Figure 1.
The following technologies were used for the tests: FDM, SLA, LCD, DLP and POLYJET. Table 1 specifies the characteristics of the equipment selected for its good resolution and precision.
For the tests, the model to be printed was a clinical case of a 75-year-old patient with an oculo-palpebral trauma. For the input parameters, the best printing options were selected: per layer, material to be used, printing temperature (FDM), exposure times (SLA, LCD, DLP), etc.
For the tests, three impressions per equipment were made, to make an average with the data, based on the Design of Experiments theory. The printed models, as they require supports, must go through a post process that eliminates them to obtain the final model.
For each impression, the data of the printing parameters were taken, to register them and carry out the economic and physical evaluations.
3.4.1 Economic data collection
To carry out the economic evaluations of each equipment, the data shown in Table 2, must be collected from each impression.
Using the previous data, the cost was calculated using the following equations:
Equation 1: Material Cost Calculation.
Source: TRESDE company quotation tables.
Where:
Equation 2: Calculation cost Hour Machine Worked.
Source: TRESDE company quotation tables.
Where:
Taking into consideration that the Machine Hour is calculated as follows:
Equation 3: Calculation of Machine Hour.
Source: TRESDE company quotation tables.
Where:
Equation 4: Cost calculation Man Hour worked.
Source: TRESDE company quotation tables.
Where:
Equation 5: Cost Per Impression Calculation.
Source: TRESDE company quotation tables.
3.4.2 Physical data collection
For physical evaluations, each printed model is digitized and compared to the original digital file. To do this, each model is covered with developer spray to obtain better scans; reference points are placed on the back face of the model; in the ZEISS software it is scanned with the COMET 8M model; the rotary option is selected, with 10 stops and the back and front of the model are scanned, obtaining the results shown in Figure 2.
With help of the reference points, the two shots are coupled to turn it into a single digitized model. Finally, the digitized model is compared with the original digital model and the deviation between both is obtained for each case, as shown in Figure 3.
After registering the previously mentioned necessary data, economic, physical and aesthetic evaluations are made.
The economic evaluation was scored based on the manufacturing cost of each prototype. The physical evaluation, based on the precision obtained according to the average deviation of the models printed by each device. The aesthetic evaluation was carried out by Dr. Rodrigo Salazar, specialist in maxillofacial rehabilitation, according to his appreciation of the prototypes. Each evaluation has a score from 1 to 5, where 5 (five) represents the most economical, precise and aesthetic, respectively; and 1 (one) the lowest.
4.1.1 Mini L
For printing on the MINI L, with FDM technology, the 3DTALK slicer was used and parameters are shown in Table 3. The model is shown in Figure 4.
Filament | Layer thickness | Wall thickness | Printing speed | Infill density | Support density |
---|---|---|---|---|---|
White PLA | 0.1 mm | 0.8 mm | 40 mm/s | 15% | 15% |
The model does not reproduce correctly, as it has complex parts that FDM printers cannot reproduce, resulting in a low-quality print with holes. For this reason, it was decided to leave out the FDM technology in the evaluation.
4.1.2 Photon S
For printing on the Photon S, with LCD technology, the CHITUBOX slicer was used and parameters are shown in Table 4. The model is shown in Figure 4.
Resin | Layer thickness | Number of bottom layers | Bottom layers exposure time | Normal layers exposure time | Support density |
---|---|---|---|---|---|
Basic | 0.02 mm | 3 | 50 s | 8 s | 15% |
4.1.3 DS-200
For printing on the DS-200, with LCD technology, the 3DTALK slicer was used and parameters are shown in Table 5. The model is shown in Figure 4.
Resin | Layer thickness | Number of bottom layers | Bottom layers exposure time | Normal layers exposure time | Support density |
---|---|---|---|---|---|
Modelo | 0.025 mm | 3 | 30 s | 4 s | 15% |
4.1.4 Phrozen Shuffle XL
For printing on the Phrozen Shuffle XL, with LCD technology, the CHITUBOX slicer was used and parameters are shown in Table 6. The model is shown in Figure 4.
Resin | Layer thickness | Number of bottom layers | Bottom layers exposure time | Normal layers exposure time | Support density |
---|---|---|---|---|---|
Modelo | 0.025 mm | 3 | 30 s | 4 s | 15% |
4.1.5 MoonRay S
For printing on the MoonRay S, with DLP technology, the RayWare slicer was used and parameters are shown in Table 7. The model is shown in Figure 4.
Resin | Layer thickness | Support thickness | Support strength |
---|---|---|---|
Model Gray | 0.02 mm | Low | Low |
4.1.6 PRO95
For printing on the PRO95, with DLP technology, the RayWare slicer was used and parameters are shown in Table 8. The model is shown in Figure 4.
Resin | Layer thickness | Support density | Support strength |
---|---|---|---|
Die & Model Tan | 0.05 mm | Low | Low |
4.1.7 Objet500 Connex3
For printing on the Objet500 Connex3, with Polyjet technology, a proprietary slicer was used the parameters are shown in Table 9. The model is shown in Figure 4.
The printing data per piece are shown in Table 10. Values such as: Days per year (Ds), Hours per day (Hr), Design, Specifications, Control and Post Printing Man-Hours are specified in Section 3.4.1.
Using the data obtained and equation 3.1 – 3.5, the printing cost was obtained as shown in Table 11.
As a result of the alignment and boolean cut of the digitized models with the originals, as shown in Figure 5, the deviation between them and the corresponding physical data in Table 12 is obtained.
4.3.1 Economic evaluation
As shown in Table 13, the equipment with the best score and the lowest printing cost is the Photon S. While the equipment with the lowest score and the highest printing cost is the Objet500 Connex3.
Printing cost range ($) | 41 – 50 | 31 – 40 | 21 – 30 | 11 – 20 | 0 – 10 |
Score | 1 | 2 | 3 | 4 | 5 |
Photon S | $ 9.72 | ||||
DS-200 | $ 13.70 | ||||
Phrozen Shuffle XL | $ 12.27 | ||||
MoonRay S | $ 12.80 | ||||
PRO95 | $ 12.42 | ||||
Objet500 Connex3 | $ 39.95 |
4.3.2 Physical evaluation
As shown in Table 14, the devices that are in the range of deviation with the best score are: Photon S, Phrozen Shuffle XL and PRO95, while the devices with the highest deviation are: DS-200 and Objet500 Connex3.
Deviation range | 8-10% | 6-8% | 4-6% | 2-4% | 0-2% |
Score | 1 | 2 | 3 | 4 | 5 |
Photon S | 1.401% | ||||
DS-200 | 5.794% | ||||
Phrozen Shuffle XL | 1.714% | ||||
MoonRay S | 2.861% | ||||
PRO95 | 1.707% | ||||
Objet500 Connex3 | 5.083% |
4.3.3 Aesthetic evaluation
As shown in Table 15, the prints of the PRO95 and Objet500 Connex 3 obtained the best score, while the equipment with the least score was the DS-200 printer.
Deviation range | Low | Regular low | Regular | Regular good | Good |
Score | 1 | 2 | 3 | 4 | 5 |
Photon S | X | ||||
DS-200 | X | ||||
Phrozen Shuffle XL | X | ||||
MoonRay S | X | ||||
PRO95 | X | ||||
Objet500 Connex3 | X |
4.3.4 Multicriteria evaluation
Finally, as shown in Table 16, the equipment with the best combined score were the Photon S and the PRO95, with 4.67 out of 5.
The Photon S, due to its LCD technology, is an economical equipment, with a high level of precision and suitable for using a wide range of resins. The disadvantages of the equipment are its printing volume, 11.5×6.5×16.5 cm, in addition to having components with a short useful life, LCD screen, FEP film, etc.
The PRO95, due to its DLP technology, has an excellent level of precision, its large printing volume, as well as being one of the fastest stereolithography equipment on the market. The disadvantages of the equipment are its high cost, which exceeds $10,000 and its manufacturing cost is almost four times that of the Photon S.
For the choice of equipment to be used in the “Mais Identidade” methodology, the volume of work, acquisition capacity, reliability of the equipment, among other parameters, must be considered.
In the investigation, a standardized methodology was proposed in order to minimize the variation between tests. As in the printing process in LCD and DLP equipment, both in the steps in the use of the slicer and in post printing. In the same way, the sensitivity of the Comet 8M scanner must be taken into account when digitizing, since these equipment, when there is a change in the environment, movements in the work area, high temperatures, among others, can alter the quality of results.
This research shows in detail the process of economic, physical and aesthetic evaluation carried out on 3d models of maxillofacial prostheses by 5 different 3d printing equipment, to finally make a multicriteria analysis. It is worth mentioning that this study is limited to the 3 exposed criteria, since they were considered the most important for the purposes of the +ID workflow, although any other if relevant could be included for better decision making. Likewise, only 5 printers were evaluated for accessibility to them, but the study is easily replicable for any 3D printing equipment.
Previous research on additive manufacturing (3D printing) demonstrates the feasibility of its use for manufacturing processes of maxillofacial prostheses. Unlike these investigations, this one focuses on the equipment within the Peruvian market for the selection of the ideal team for the “Mais Identidade” process, evaluated based on the investigation of the Mais Identidade Institute, in conjunction with Dr. Rodrigo Salazar. Likewise, it was decided to use these seven pieces of equipment in the investigation due to time limits and accessibility to them.
Based on the Multicriteria Analysis, the Photon S and PRO95 had the best score with 4.67 out of 5. While in the economic evaluation the Photon S printer obtained the best score with 9.72 dollars; in the physical evaluation, the Photon S, Phrozen Shuffle XL and PRO95 obtained the same score with a deviation between 0 and 2%; and in the aesthetic evaluation, the PRO95 performed the best prints.
In this way, it is recommended in future research to broaden the spectrum of evaluation with criteria such as: Printing volume, printing speed, volume of work; as well as organizational factors: budget, conditions or workflow As well as expanding the range of technologies and equipment to be evaluated, since with technological advances, equipment may arise that is more suited to the needs of each organization.
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Is the work clearly and accurately presented and does it cite the current literature?
No
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
References
1. Sharma S, Dhiman M, Kalra P, Banga H, et al.: Reverse engineering and CAD/CAM application in the design of maxillofacial prosthesis. International Journal on Interactive Design and Manufacturing (IJIDeM). 2023. Publisher Full TextCompeting Interests: No competing interests were disclosed.
Reviewer Expertise: Additive Manufacturing, Ergonomics, CAD/CAM
Competing Interests: No competing interests were disclosed.
Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
I cannot comment. A qualified statistician is required.
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Plastic Surgery; Cranio-Maxillo-Facial Surgery; 3D researcher
Is the work clearly and accurately presented and does it cite the current literature?
Partly
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Partly
References
1. Rokaya D, Kongkiatkamon S, Heboyan A, Dam V, et al.: 3D-Printed Biomaterials in Biomedical Application. 2022. 319-339 Publisher Full TextCompeting Interests: No competing interests were disclosed.
Reviewer Expertise: Dentistry, Prosthodontics, Maxillofacial Prosthetics, Dental Biomaterials
Alongside their report, reviewers assign a status to the article:
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