3D-printed Models Research Articles

How to improve ZMC fracture reconstruction due to severe enophthalmos

Introduction and importanceZygomaticomaxillary (ZMC) fractures are common, often resulting from traffic accidents, and account for 17 % of facial fractures. These fractures can lead to issues such as enophthalmos, flattened cheeks, diplopia, maxillary hypoesthesia. If the reduction is inadequate to restore facial structure, long term-functional and aesthetic complications may arise. In such cases a computed tomography (CT) scan with 3-dimensional (3D) reconstruction is valuable to assessing the fracture and planning surgery, with current technological advancements, 3D printing can now be utilised for this purpose. Presentation of caseA 24-year-old male, after a motorcycle accident and initial surgery for maxillofacial fractures, experienced persistent diplopia and facial numbness. Physical examination showed malpositioning of the right eye, and a CT scan with 3D reconstruction revealed multiple fractures and prior internal fixation. A 3D-printed model was created to plan a second surgery using rib cartilage and a silicone orbital base for orbital rim reconstruction. Post-surgery, the patient reported minimal pain and no diplopia or blurred vision in the primary gaze position. Clinical discussions3D printing is beneficial in facial reconstruction, aiding in surgical planning by allowing precise measurement and design of graft. Rib cartilage can serve as an alternative for orbital rim reconstruction, and 3D printing facilitates accurate harvesting of the rib. ConclusionIn cases of severe ZMC fracture, 3D printing was utilised as a guide during surgical preparation to achieve improved outcomes.

Simulation training for invasive cardiovascular procedures: the Heart-SIMS-1 study

Abstract Introduction Interventional cardiology training has a long learning curve and exposes patients and clinicians to undesirable procedural risks. We aim to assess whether mentored simulation-based training with three dimensional (3D) printed models can improve the procedural skills and safety performance of beginners in coronary diagnostic procedures. Methods Twenty-nine final-year medical students from a single centre were lectured in the basic principles of invasive coronary angiography (ICA) for one-hour, and then randomized to conventional training or simulation training. Conventional training (n=15) consisted in watching a 20-minute video demonstrating all ICA steps in a 3D-printed coronary simulator. Simulation training (n=14) offered the same explanations in a hands-on training session with the 3D-printed model, in pairs, for 20 minutes. The co-primary endpoint was efficacy and safety of performing a simulated ICA in the 3D-printed simulator, installed under sterile drapes, in a conventional angiography suite. Efficacy and safety were graded by a blinded investigator using a pre-specified performance checklist, including the identification of procedural "red flags", graded 0-100%. The secondary endpoint was theoretical knowledge, assessed in a 25-question multiple-choice quiz, graded 0-100%. Results All participants completed the training and evaluation phases. Both elements of the co-primary endpoint were superior in the simulation group: efficacy score of 91.5 ± 3.8 vs 64.6 ± 8.3% and safety score 100.0 (100.0-100.0) vs 62.5 (20.8-79.2) %, p<0.001. The median number of "red flags" were 2 (1-4) in conventional and 0 (0-0) in simulation training recipients (p<0.001). Secondary endpoint was higher in simulation training: 85.7 ± 9.0 vs 76.8 ± 12.7% (p=0.039). Conclusion Mentored simulation-based training of medical students in ICA with 3D-printed models resulted in improved performance regarding efficacy, procedural safety, and theoretical knowledge.ResultsSimulation and evaluation setup

A promising pullulan/PLA composite: Influence of pullulan in the scaffolds morphology constructed by 3D printing

AbstractManufacturing three‐dimensional scaffolds with significant rough and porous structures is advantageous in tissue regeneration approaches influencing cell growth. Thus, this work aims to study the effect of using different Pullulan contents (PULL) in the poly(lactic) acid (PLA) matrix for 3D printing scaffolds. PLA composites filler with PULL (5 and 10% wt.) were prepared in a thermokinetic mixer, extruded in a machine, and then used to print samples using a fused deposition modeling (FDM) 3D printer. The prepared filaments and scaffolds were characterized using Field emission scanning electron microscopy (FESEM), Fourier‐transform infrared spectroscopy (FTIR), thermogravimetry analyses (TGA), water contact angle (WCA), differential scanning calorimetry (DSC), and hardness techniques. The insertion of PULL into the PLA matrix influenced the increase in diameter and roughness, and density reduction of the composite filaments compared to pristine PLA. Furthermore, the filler promoted an increase in thermal stability, shore hardness, and the development of promising morphological characteristics for cell growth because the walls of the scaffolds are more robust and have more regular‐sized holes. The scaffold fabrication reinforced with 10% PULL presented high surface roughness (up to 1022% if compared with pristine PLA), and open pores can be confirmed successfully compared to pristine PLA. Thus, the use of PULL as a filler in a PLA matrix guarantees the development of composite scaffolds with improved morphological and hardness properties, which could allow the possibility of future research into the application of the proposed material (10% wt. PULL) as an ecologically correct and biocompatible alternative for application in tissue engineering.

Comparative analysis of mechanical and drilling properties: Human skull vs. 3D-printed replicas for neurosurgical training

Neurosurgery is one of the most difficult surgical disciplines, making neurosurgical simulation crucial for learners. 3D printing is increasingly used for this simulation due to its accessibility and cost-effectiveness compared to conventional methods. Previous studies have qualitatively evaluated the efficacy of 3D printing models for burr hole and craniotomy simulation using surgeon feedback. This study quantitatively evaluates the mechanical properties of human skulls and compares them with 3D-printed skulls to identify the necessary materials and technologies for accurate replication in neurosurgical training. Vickers hardness, compression, and drilling simulation tests were conducted on human cadaveric skulls and 3D-printed models manufactured using Fused Filament Fabrication (FFF), Stereolithography (SLA), and Material Jetting (MJ) technologies. Uniaxial force during a simulated burr hole procedure was measured as drilling progressed through the outer table (OT), diploë and inner table (IT) of the skull. The results showed that different 3D printing technologies and materials have qualities corresponding to each of the three layers of the human skull. For instance, the White Resin 40 model was the closest match to the OT of human skull, exhibiting the lowest mean difference of drilling modulus of 1.98. The OT of the human skull had a Vickers hardness of 38.6 ± 5 HV0.05. The closest 3D-printed models were SLA White at 16.6 ± 0.3 HV0.05 and Rigid 10K at 65.7 ± 3 HV0.05. In terms of mechanical properties, the human skull demonstrated a compression modulus that closely matched the SkullSTN 2, PC 60, PEEK 40, and PEEK 60, with differences of less than 0.1 GPa. These findings demonstrate the effectiveness of drilling simulation tests in evaluating various materials and infills to refine models before neurosurgeon evaluation, enabling the identification of an optimal 3D-printed training model for simulating burr hole procedures.

Complex left atrial appendage closure using 3D printing system simulation in a patient with mitral prosthetic valve: a case report

Abstract Background Left atrial appendage (LAA) closure (LAAc) has emerged as a safe and effective alternative to oral anticoagulation (OAC) for stroke prevention in patients with atrial fibrillation (AF) and contraindications to OAC. Case Summary A 61-year-old woman with permanent atrial fibrillation (AF) and a history of mitral surgery replacement with mechanical prosthesis was referred to our cardiology department to undergo left atrial appendage (LAA) closure (LAAc). The preoperative computed tomography (CT) revealed that the ostium of the left atrial appendage was close to the mitral prosthesis ring. As a result of the difficult LAA morphology a CT-image based virtual model was created, then a 3D printing model was prepared in our laboratory and procedure simulation was performed with the two different LAA occlusion devices (plug- vs. pacifier like models) to see which one was more suitable for the patient anatomy. Discussion In this case of complex LAAc in a patient with mechanical prosthetic mitral valve with the use of a 3D-printed model has guided prosthesis selection and device sizing reducing procedure time and complications.

The Use of 3D Model Printing for Acute Planning in Oral and Maxillofacial Traumatology

Introduction Due to the complex anatomy of craniomaxillofacial structures, facial reconstruction following high-impact traumas is extremely challenging. Therefore, this study aimed to evaluate the use of biomodels in the surgical planning of complex fractures and the sequelae in the oromaxillofacial region. Materials and Methods This is a cross-sectional, exploratory, descriptive, and quantitative documentary study. It was conducted at the “Dom Luiz Gonzaga Fernandes” Emergency and Trauma Hospital, in the hinterland of the state of Paraíba, in Brazil, based on cases recorded between November 2021 and November 2022. The research instrument utilized was a self-developed questionnaire. Results No statistically significant correlation was observed between the biomodel acquisition time and the length of hospitalization, with a Spearman's correlation coefficient of r = -0.079. Although the need for adjustment of osteosynthesis material was 50% in cases where acrylonitrile butadiene styrene (ABS) models were used, with p (1) = 0.464, in order to be significantly more faithful, it would require a study with a higher sample size. The average length of surgery, in minutes, was 91.25 ± 28.00. The average cost of the materials used to manufacture the biomodels, in Brazilian reais (R$), was R$122.00 ± R$89.09. Conclusion The use of biomodels in the surgical planning of complex fractures and oromaxillofacial sequelae did not increase the length of hospitalization. The material used for the prototype manufacture suggests a potential influence on its faithfulness. The length of surgery was shorter in interventions that utilized biomodels in the planning phase. It was also noted that the average cost of manufacture varies according to the type of material chosen and the quantity required.

3D-printed model is a useful addition in orthopedic resident education for the understanding of tibial plateau fractures

This study aimed to explore the role of the three-dimension (3D) printed models in orthopedic resident training of tibial plateau fractures. A total of 41 residents from our institution were divided into two groups. The intervention group, consisting of 20 residents, had access to 3D-printed models illustrating thirteen tibial plateau fractures. In contrast, the control group, comprising 21 residents, received digital images of thirteen identical tibial plateau fractures. Evaluation of learning outcomes included the accurate identification of tibial plateau fracture patterns, deduction of traumatic mechanisms, preoperative plan, assessment time, and subjective questionnaire responses. The participants with 3D printed models scored significantly higher in both the Schatzker classification and Luo three-column classification compared to those without 3D printed models. Residents in the intervention group performed better in accuracy in deducing traumatic mechanisms compared to the control group. In addition, the sum score of preoperative plan in the intervention group was significantly higher than that in the control group. Specifically, participants with 3D printed models scored higher in surgical approach choice and implants placement than these in the control group. Residents exposed to 3D printed models also spent less time to complete the assessment than those with access only to digital imaging. Subjective assessments indicated that 3D-printed models boosted confidence in fracture identification, improved preoperative plan for fracture management and enhanced the understanding in injury mechanism of tibial plateau fractures. Furthermore, residents agreed that the use of 3D-printed models heightened their interest in learning tibial plateau fractures. Therefore, the addition of 3D printed models significantly contributed to a comprehensive understanding of tibial plateau fractures, the improvement in fracture identification, inferring injury mechanisms and preoperative plan.

Evaluating the efficacy of a cost-effective, fully three-dimensional-printed vertebra model for endoscopic spine surgery training for neurosurgical residents.

A fused deposition modeling three-dimensional (3D)-printed model of the L4-5 vertebra for lumbar discectomy was designed. The model included separately printed dura mater, spinal cord, ligamentum flavum, intervertebral disc (from thermoplastic polyurethane), and bony structures (from polylactic acid), and the material cost approximately US$ 1 per model. A simple plumbing endoscope was used for visualization. Dura mater injury was assessed by painting two layers on the dura mater, which peeled off with trauma. Endoscopic spine surgery is a subject of high interest in neurosurgery given its minimally invasive nature; however, it has a steep learning curve. This study evaluated the effectiveness of a cost-efficient 3D-printed model when teaching this technique to neurosurgery residents. Only a few studies have investigated the efficacy of such a model. Eight residents with >2 years of training participated. Residents performed the procedure bilaterally and twice at 1-week intervals. From the 32 surgeries, four were excluded because of facet removal (as it widened the surgical corridor), leaving 28 surgeries for analysis. Initial surgeries demonstrated a mean operation time of 21 minutes 18 seconds (standard deviation [SD], 2 minutes 32 seconds), which improved to a mean of 6 minutes 45 seconds (SD, 37 seconds) in the fourth surgery (F(3, 17)=19.18, p <0.0001), demonstrating a significant reduction in surgical time over successive surgeries. The median area with the paint removed decreased, from 161.80 (85.55-217.83) to 95.13 mm2 (12.62-160.54), (F(2.072, Inf)=2.04, p =0.128); however, this was not significant. Resident feedback indicated high satisfaction with the educational value of the model. The developed fully 3D-printed model provides a viable and scalable option for neurosurgical training programs, enhancing the learning experience while maintaining low costs. This model may be an excellent stepping stone for learning lumbar spine endoscopy, acclimating to the two-dimensional view, progressing to cadaver models, and, eventually, independent surgery.

Influence of Material, Sterilization, and Disinfection on the Accuracy of Three-Dimensional Printed Surgical Templates: An InVitro Study.

To evaluate the influence of the three-dimensional (3D) printing technology, material, sterilization, and disinfection on the accuracy of guided surgical templates. Fifty printed resin surgical templates were designed and fabricated using a digital light processing 3D printer with a photopolymerizing resin, and 50 printed metal surgical templates were designed and fabricated using a selective laser melting 3D printer with a titanium alloy. Templates from both groups were randomly divided into five subgroups involving different sterilization and disinfection procedures. The group without any sterilization or disinfection procedure served as the control group, whereas the other groups were used as the study groups (hydrogen peroxide gas plasma sterilization, 5% povidone-iodine disinfection, 75% ethyl alcohol disinfection, and steam autoclave sterilization). Implant simulations were performed on the 3D-printed resin models, and postoperative impressions were acquired with scan bodies attached to the implants. All surgical templates were digitally scanned. The root mean square was used to determine and quantify fabrication accuracy and reproducibility, and the definitive and planned implant positions were compared. The printed resin templates exhibited lower fabrication accuracy and reproducibility, as well as higher 3D deviations, after steam autoclave sterilization (p < 0.001); however, the printed metal templates were not affected by the different sterilization or disinfection procedures (p > 0.05). Printed metal surgical templates are viable alternatives for guided implant surgery. Preoperative steam or gas plasma sterilization is recommended, especially for metal templates, as resin templates show deformation and decreased accuracy after steam sterilization. chictr.org.cn number: ChiCTR2400081334.

Integrating 3D technology with the Sampaio classification for enhanced percutaneous nephrolithotomy in complex renal calculi treatment

BackgroundTo investigate the safety and efficacy of percutaneous nephrolithotomy (PCNL) in the treatment of complicated renal calculi by integrating three-dimensional (3D) computed tomography (CT) reconstruction with the Sampaio classification of the renal collecting system.MethodsSixty-four consecutive patients with complex kidney calculi who underwent PCNL between January 2019 and October 2023 were retrospectively analyzed and divided into experimental group (3D printing) and control group (CT imaging) according to their willingness to pay for 3D imaging. Both groups underwent preoperative CT urography. The Digital Imaging and Communications (DICOM) in Medicine data of the experimental group from CT imaging were used for 3D reconstruction and model printing. Then, the Sampaio classification system was used to design the puncture channel and develop a surgical strategy.ResultsThe 3D-printed models of the experimental group successfully displayed the Sampaio classification system. There was no significant difference in the baseline parameters between the groups. Compared with the control group, the experimental group exhibited significant improvements in the puncture time, number of puncture needles, number of puncture channels, target calyx consistency, number of first puncture channels, and stone clearance. There were no significant differences in the total operative time, decrease in the hemoglobin level, length of hospital stay, and postoperative complications between the groups.ConclusionsIntegration of 3D technology with the Sampaio classification of the renal collecting system can enhance the preoperative evaluation and planning of percutaneous renal access. This approach allows a more precise method of PCNL for treating complex renal calculi.

Integrated substrate and adsorbent layer additive manufacturing for asymmetrically operating minichannel adsorbent bed

Adsorption heat pumps (AHP) have conventionally used packed bed design, making their operation sluggish leading to difficulty in using heat for the adsorbent regeneration. While thin adsorbent coatings improve the performance of AHPs when implemented in microscale geometries like minichannels, integrating the adsorbent coating procedure into the scaled-up adsorbent bed manufacturing has been impractical because of the finite time required for the coating process. Meanwhile, separately coated plates manifest sealing issues. This research details an innovative avenue to fabricate a unified adsorbent bed integrated with thin adsorbent coatings. Here, a compact adsorbent bed was fabricated through the integration of additive manufacturing using a fused deposition modeling (FDM) 3D printer for the substrate and resin curing for the MIL-101 (Cr) adsorbent layer. The multi-layered bed was designed to exchange heat between heat transfer fluid (HTF) and the passages through which the refrigerant vapor flows. The vapor channels were coated with a MIL-101 (Cr) adsorbent. The research incorporated both experiments and computational models to evaluate the operation of this adsorbent bed through the measurement of pressure during the adsorption and desorption stages for this component. Various HTF temperatures (80 °C − 90 °C) and flow rates (0.125 kg min−1 – 0.25 kg min -1) were tested. The findings revealed the much-desired asymmetrical operation with long adsorption (75–80 % of the cycle time) and short desorption stages (20 %-25 % of the cycle time), opening the possibility of employing a single bed in adsorption cooling systems to produce a near continuous cooling effect leading to more compact AHPs. The computational model developed for this test setup using MATLAB strongly aligned with experimental findings, with an error margin of 4–12 %.

Exploring the use of atmospheric freeze drying for dehydrating pharmaceutics in vials: Baseline water sublimation investigation

Atmospheric freeze-drying (AFD) is a relatively new freeze-drying technology without the need for a vacuum, making it easy to operate and cost-effective. Although there have been studies using AFD to dehydrate solid foods, there is currently no research on using AFD to dehydrate frozen liquids in pharmaceutical vials. In this study, several approaches were evaluated to enhance the atmospheric sublimation of water in pharmaceutical vials. Using −4 °C impinging jet airflow to dry frozen water samples in the vial, it was found that convective action significantly affected the sublimation rate. On this basis, a 3D-printed air-guide model was designed to improve airflow circulation in the vial, and it was found that the drying rate was highest when airflow energy loss was minimized, and airflow velocity at the sample surface was maximized. Additionally, the geometric characteristics of the vial also influenced the sublimation rate; vials with a larger bottom area and shorter height showed the highest sublimation rate. Increasing the vial’s bottom radius from 11 mm to 13 mm, under atmospheric pressure and using cold air at approximately −5 °C, reduced the drying time of 1 g of frozen water from 8.5 h to 6 h; each 5 mm height increase added 0.5 h to the drying time. Using cold air at −10 °C to dry 1 g of frozen water in a 5 mL vial, the combination of ultrasonic-induced energy (at a frequency of 39.46 kHz) and the air-guide model effectively reduced the sublimation time from 7 h to 5 h, compared to using only the air-guide model. However, this technique may be vulnerable to melting at the vial-transducer contact point, should the transducer be directly attached to the vials.

Surgical Closure of Multiple Muscular Ventricular Septal Defects in Children Using 3D-Printed Models.

Multiple muscular ventricular septal defects (VSDs) are often difficult to visualize and access surgically. The main challenge is identifying all defects intraoperatively, without which residual defects are inevitable. Patient-specific three-dimensional (3D) printed models can help accurately demonstrate intracardiac anatomy. We present our experience using this technology to surgically close multiple muscular VSDs . Data of all patients with multiple VSDs in whom a 3D-printed model was used to aid surgical planning between September 2021 and July 2023 was collected retrospectively. Our approach involved generating a 3D model from a preoperative computerized tomography scan for each patient, which was then used to precisely identify the location of the multiple VSDs and plan surgical intervention. Six patients underwent closure of multiple VSDs using a 3D model. The mean age at surgery was 3.5 years (SD ± 2.8 years). Five (83.3%) patients had previously undergone pulmonary artery banding. The VSDs were approached through the right atrium in three (50%) and the right ventricle in three (50%) patients. Mean cardiopulmonary bypass and myocardial ischemia times were 185.2 min (SD ± 94.8 min) and 147.5 min (SD ± 86 min), respectively. There was no postoperative heart block or a hemodynamically significant residual VSD. All six patients had normal biventricular function at a median follow-up duration of 1.7 months (interquartile range: 1.2-7.4 months). 3D printing to aid closure of multiple VSDs is safe, reliable, and reproducible. We recommend adding 3D printing to surgeons' armamentarium when faced with the challenge of closing multiple muscular VSDs in children.

Clinical application of CAD/CAM technology in 3D printed dental model used for removable splints fabrication in the treatment of traumatized anterior permanent teeth in children

ObjectivesTo evaluate the effectiveness of computer-aided design (CAD)/computer-aided manufacturing (CAM) in designing and manufacturing 3D-printed dental models used to make thermoplastic removable splints for children with traumatized anterior permanent teeth. MethodsA total of 28 patients with dental trauma (subluxation, extrusive luxation, and lateral luxation) were divided into experimental (14 patients) and control groups (14 patients). The experimental group was treated with the removable splint made using a new 3D printed dental model designed with CAD/CAM technology, while the control group received a wire-composite splint. Follow-up was performed at week 2 and 1, 2, 3, 6, 12, 18, and 24 months post-treatment, and every year after that. The traumatized teeth were evaluated according to clinical symptoms, tooth color, mobility, position, percussion pain, abnormal percussion sounds indicating ankylosis or other pathosis, swelling, fistula of gums, vitality test, and radiographic examination. ResultsNo significant difference was found in gender and age between the two groups. The experimental group had 23 traumatic teeth, and the control group had 24 traumatic teeth. Traumatic teeth in the two groups most commonly involved open apex teeth (>90 %). The average follow-up time for the experimental and control group was 35.47±14.23 and 32.92±14.79 months (P > 0.05), respectively. The pulp survival rate and periodontal healing rate in the experimental group (86.96 %, 91.30 %) were higher compared to the control group (62.50 %, 75.00 %) (all P > 0.05). ConclusionA removable splint made by a 3D printed dental model designed with CAD/CAM technology achieved an equivalent treatment effect to a wire-composite splint. Clinical significanceA 3D-printed dental model designed with CAD/CAM technology can be used to fabricate removable splints, which in turn can decrease iatrogenic injuries frequently encountered during the traditional model production process. For example, taking the impression directly from the patient's mouth can cause displacement of a traumatized tooth or even exfoliation. The removable splints produced using a new 3D-printed dental model can meet clinical treatment requirements of traumatized teeth, especially for children and adolescents with occlusal trauma in mixed dentition.

Novel Image-Guided Simulator for Transcervical Intralaryngeal Injection Training.

To assess the impact of a novel 3D-printed simulation model with Brainlab Image Guidance on enhancing otolaryngology residents' skills and confidence in performing transcervical intralaryngeal injection (TII) compared with conventional training methods. Utilizing a 3D-printed larynx model derived from computed tomography (CT) scans, this study involved 16 otolaryngology residents divided into two groups for TII training: one with Brainlab Image Guidance (LMIG) and the other without (LM). Pre- and post-training evaluations measured participants' confidence while the Brainlab system measured the accuracy of their needle placements. After training, participants exhibited a significant increase in confidence with an average rise from 1.56 to 2.75 on a 5-point scale. The LMIG group outperformed the LM group in accuracy achieving statistically significant reductions in target distances after training (3.5 mm right, 3.6 mm left). The LMIG also demonstrated a significantly greater increase in procedural confidence over the LM group after training. The TII laryngeal model with Brainlab Image Guidance significantly improves procedural confidence and accuracy among otolaryngology residents, signifying potential advantage over a more conventional training approach. The model's realistic tactile and live instrument positioning feedback augments the process of surgical skill refinement in a controlled, risk-free, simulation environment. NA Laryngoscope, 2024.

Upcycling end-of-life carbon fiber in high-performance CFRP composites by the material extrusion additive manufacturing process

Each year, a significant amount of waste is produced from carbon fiber polymer composites at the end of its lifecycle due to extensive use across various applications. Utilizing regenerative carbon fiber as a feedstock material offers a promising and sustainable approach to additive manufacturing based on materials. This study proposes the additive manufacturing of recycled carbon fiber with a polyamide-12 polymer composite. Filaments of recycled carbon fiber-reinforced polyamide-12 (rCF-PA12) with different recycled carbon fiber contents (0%, 10%, and 15% by weight) in the polyamide-12 matrix are developed. These filaments are utilized for 3D printing of specimens by using various infill density parameters (80% and 100%) on a fused deposition modeling 3D printer. The study examined how the fiber content and infill densities influenced the flexural performance of the printed specimens. Notably, the part containing 15 wt% recycled carbon fiber (rCF) composites showed a significant improvement in flexural performance due to enhanced interface bonding and effective fiber alignment. The results indicated that reinforcing the printed part with 10% and 15 wt% recycled carbon fiber (rCF) improved the flexural properties by 49.86% and 91.75%, respectively, compared to the unreinforced printed part under the same infill density and printing parameters. The investigation demonstrates that the additive manufacturing-based technique presents a potential approach to use carbon fiber-reinforced polymers waste and manufacture high-performance engineering, economic, and environmentally friendly industrial applications with the complicated design using different polymer matrices.

In Vitro Investigation Using a New Biomechanical Force-Torque Analysis System: Comparison of Conventional and CAD/CAM-Fixed Orthodontic Retainers.

(1) Background: After more than a decade since their first description, Inadvertent Tooth Movements (ITMs) remain an adverse effect of orthodontic retainers without a clear etiology. To further investigate the link between ITMs and the mechanical properties of different retainers, the response upon vertical loading was compared in three retainer types (two stainless steel and one nickel-titanium). The influence of different reference teeth was also considered. (2) Methods: Three retainers (R1, R2, R3) were tested in a newly developed biomechanical analysis system (FRANS). They were bonded to 3D-printed models of the lower anterior jaw and vertically displaced up to 0.3 mm. Developing forces and moments were recorded at the center of force. (3) Results: The vertical displacement caused vertical forces (Fz) and labiolingual moments (My) to arise. These were highest in the lateral incisors (up to 2.35 ± 0.59 N and 9.27 ± 5.86 Nmm for R1; 1.69 ± 1.06 N and 7.42 ± 2.65 Nmm for R2; 3.28 ± 1.73 N and 15.91 ± 9.71 Nmm for R3) for all analyzed retainers and with the R3 retainer for all analyzed reference teeth, while the lowest Fz and My values were recorded with the R1 retainer. (4) Conclusions: Displacements of 0.2 mm and larger provided forces and moments which could be sufficient to cause unwanted torque movements, such as ITMs, in all analyzed retainers. Clinicians must be mindful of these risks and perform post-treatment checkups on patients with retainers of all materials.

A novel 3D printed model for educating medical students on limb fractures: a randomized controlled preliminary study

BackgroundMedical education related to bone fracture must address numerous challenges including complex anatomical characteristics, diverse injury mechanisms, fracture typing, and treatment modalities. Our newly developed 3D printed model comprises components that may be combined or split to simulate various anatomical features, fracture types, and treatment modalities. This study aims to analyze the teaching utility of the new 3D-printed model compared with the traditional solid model.MethodsThis prospective study included 112 students randomly assigned to fracture-related education with a conventional model or the newly developed 3D-printed model. All students received 40 min of lecture, 20 min for femoral neck and 20 min for tibiofibular fractures, and a post-class quiz (10 min each) immediately followed. Scores on tests of fracture-related knowledge and user satisfaction were measured pre and post education for comparison.ResultsThe 3D printing group had an advantage in retention of anatomic knowledge, fracture typing and choice of treatment for the femoral neck fracture (P < 0.05). For the tibiofibular fracture the 3D printing group had an advantage in retention of anatomic knowledge and fracture complications (P < 0.05).Scores on the questionnaire survey also showed increased satisfaction in the 3D-printed model group(P < 0.05).ConclusionsThe proposed 3D-printed model can enhance the teaching effect significantly and has potential for widespread use in medical student education.

Rapid aerodynamic characterization of surface heat exchangers for turbofan aeroengines through optical techniques and additive manufacturing

Surface heat exchangers that use the bypass flow as heat sink are becoming a widely used solution to alleviate the high thermal load of modern aeroengines. Experimental characterization of such heat exchangers in full-scale engine tests is extremely expensive and time-consuming, so carrying out experiments in scaled wind tunnels that can replicate their very challenging flow conditions is highly desirable. However, intrusive instrumentation can affect the actual aerodynamics of the component due to the reduced size of the section and the typical high air velocities of turbofan engines. For this reason, a methodology to characterize a surface heat exchanger designed to work in the turbofan bypass using optical techniques is presented in this work. Additionally, the possibility of replicating the experimental conditions using additively manufactured models of exchangers would allow rapid preliminary characterization of these components. In this investigation, different non-intrusive techniques such as PIV, LDA, Schlieren, or LDV have been applied to determine the heat exchanger aerodynamic performance and vibration response, and a detailed characterization of the flow field has been carried out. Data have been cross-validated using different measurement techniques. A 3D-printed model has also been built to compare with the aluminum heat exchanger, showing almost an identical behavior in terms of velocity distribution downstream of the heat exchanger and pressure drop induced by its fins, as well as corrected frequencies, confirming thus the suitability of additive manufacturing for the aerodynamic characterization of these devices in preliminary stages.

A human-centered intelligent platform for holographic control and management of 3D printers

Under the wave of emerging human-centric concepts such as Industry 5.0 and Human-Centered Intelligent Manufacturing, Mixed Reality (MR) has emerged as a pivotal enabling technology with profound impacts on human–machine interaction. Simultaneously, the affordability of Fused Deposition Modeling (FDM) 3D printers has expanded their accessibility beyond industrial applications to homes and public spaces. However, the operational and management complexities of different 3D printers and their varying human–machine interfaces (HMI) present challenges for users, especially beginners. In this paper, we presented a human-centered intelligent platform for FDM 3D printer control and management enabled by Mixed Reality. A flexible system architecture is developed in the paper with two essential communication protocols, MQTT and WebSocket, for stable data transfer. In addition, a task-oriented HMI is explored on the MR headset to simplify the operation procedure with little training effort and allow parallel supervision of multiple machines. By leveraging the advantages of our architecture, real-time monitoring, failure detection, and hologram visualization were able to be integrated into our platform for intelligent operation and management. Importantly, the flexibility of the architecture via a holographic interface enables our platform to easily expand to various machining operations in the future.