Finite Element Analysis of Patient-Specific 3D-Printed Cranial Implant Manufactured with PMMA and PEEK: A Mechanical Comparative Study

Bibliometric analysis of additive manufacturing in cranial and craniofacial implant research

Additive manufacturing (AM) offers solutions to complex surgical challenges by enabling the production of medical devices with highly sophisticated and customized designs. As a result, it has significantly advanced the field of implant customization for cranial and craniofacial reconstruction. However, comprehensive insights into the research trends in this area remain limited. This study aims to provide a bibliometric analysis of literature related to AM in cranial and craniofacial implant applications from the Web of Science (WoS) Core Collection. A highly refined search strategy was employed by utilizing an advanced query with specific keywords such as 'additive manufacturing,' 'cranial implants,' '3D printing,' and 'customized'. This search resulted in a total of 408 publications, which were then narrowed down to 331 articles by selection of articles as the publication type. A visualization tool named VOSviewer was employed to analyze trends in publication volume, author collaboration, journal impact, and keyword co-occurrence. The analysis revealed an increasing trend in research publications with a focus on patient-specific implants, 3D bioprinting technologies, and virtual surgical planning. Additionally, the collaborations between institutions in North America, Europe, and Asia are driving the field forward. Despite significant progress since 2000s, there are still challenges related to material optimization, regulatory concerns, and clinical integration.

Cranial Reconstruction for Infiltrative Meningioma Using 68Ga-DOTATATE Positron Emission Tomography/Computed Tomography and Individual Patient Solutions CaseDesigner®: A Case Series

BACKGROUND AND OBJECTIVES

Meningioma with bone involvement presents challenges for complete resection and cranial reconstruction. 68Ga-dodecanetetreaacetic acid tyrosine-3-octreotide (DOTATATE) positron emission tomography (PET)/computed tomography (CT) has emerged as an excellent modality for localizing invasive meningiomas because of molecular interaction with somatostatin receptor-2. We present a novel technique to design 3-dimensional-printed artificial cranioplasty, using combined fine-slice CT, MRI, and 68Ga-DOTATATE PET/CT with Individual Patient Solutions (IPS) CaseDesigner® software. This study's objective was to generate proof-of-concept work for a novel artificial cranioplasty protocol that combines customized cranial implant software and DOTATATE PET/CT.

METHODS

Three patients with invasive bone meningiomas were retrospectively identified. For each patient, the proposed protocol combines CT, MRI, and 68Ga-DOTATATE PET/CT imaging to generate a 3-dimensional cranial reconstruction within the Karl Leibinger Surgical (KLS) Martin-IPS CaseDesigner® software. Subsequently, the virtual rendering is used to manufacture a customized polyetheretherketone (PEEK) implant, along with a guiding component, which ensures precise delineation of surgical borders before craniectomy. Finally, cranioplasty with the customized implant is performed using standard techniques.

RESULTS

The described preoperative cranioplasty design protocol was performed for each patient. Tumor invasion was visualized using 68Ga-DOTATATE PET/CT. Patient 1 presented with a recurrent right frontal meningioma with invasion into anterior skull base. In this case, IPS CaseDesigner® was used to create a mirror image PEEK implant for the left orbit and affected cranium. Patients 2 and 3 had intraosseous meningiomas invading the frontal bone; customized PEEK implants were tailored to the side of the planned craniectomy for both patients and were successfully placed without complication. Postoperatively, all patients remained neurologically intact and were discharged without complications. In all patients, the PEEK implants exhibited appropriate cranial continuity and integrity.

CONCLUSION

68Ga-DOTATATE PET/CT has high sensitivity and specificity for detecting meningiomas during preoperative planning, particularly when the tumor involves bone. IPS CaseDesigner® demonstrates excellent utility for planning and constructing customized cranioplasties tailored to each patient for skull reconstruction.

Mechanical Behavior of PEEK and PMMA Graphene and Ti6Al4V Implant-Supported Frameworks: In Silico Study

A comparative analysis has been carried out between three different dental materials suitable for the prostheses manufacturing. The analysis performed is based on the finite elements method (FEM) and was made to evaluate their performance under three different loading conditions. Three different materials were modeled with 3D CAD geometry, all of them suitable to be simulated by means of a linear elastic model. The materials employed were graphene polymethyl methacrylate (G-PMMA) with 0.25% of graphene, polyether ether ketone (PEEK), and Ti6Al4V. Three loading conditions have been defined: distal, medial, and central. In all cases under study, the load was applied progressively, 5 N by 5 N until a previously fixed threshold of 25 N was reached, which always ensures that work is carried out in the elastic zone. The behavior of G-PMMA and PEEK in the tests performed is similar. Regarding maximum deformations in the model, it has been found that deformations are higher in the G-PMMA models when compared to those made of PEEK. The highest values of maximum stress according to the von Mises criteria are achieved in models made of Ti6Al4V, followed by G-PMMA and PEEK. G-PMMA is more prone to plastic deformations compared to Ti6Al4V. However, due to its relatively higher stiffness compared to other common polymers, G-PMMA is able to withstand moderate stress levels before significant deformation occurs, placing it in the intermediate position between Ti6Al4V and PEEK in terms of stress capacity. It should be noted that there is also a difference in the results obtained depending on the applied load, whether distal, medial, or central, proving that, in all simulations, it is the distal test that offers the worst results in terms of presenting a higher value for both displacement and tension. The results obtained allow us to identify the advantages and limitations of each material in terms of structural strength, mechanical behavior, and adaptability to loading conditions that simulate realistic scenarios.

Comparative Analysis of the Mechanical Properties and Biocompatibility between CAD/CAM and Conventional Polymers Applied in Prosthetic Dentistry

Modern media often portray CAD/CAM technology as widely utilized in the fabrication of dental prosthetics. This study presents a comparative analysis of the mechanical properties and biocompatibility of CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) polymers and conventional polymers commonly utilized in prosthetic dentistry. With the increasing adoption of CAD/CAM technology in dental laboratories and practices, understanding the differences in material properties is crucial for informed decision-making in prosthodontic treatment planning. Through a narrative review of the literature and empirical data, this study evaluates the mechanical strength, durability, esthetics, and biocompatibility of CAD/CAM polymers in comparison to traditional polymers. Furthermore, it examines the implications of these findings on the clinical outcomes and long-term success of prosthetic restorations. The results provide valuable insights into the advantages and limitations of CAD/CAM polymers, informing clinicians and researchers about their suitability for various dental prosthetic applications. This study underscores the considerable advantages of CAD/CAM polymers over conventional ones in terms of mechanical properties, biocompatibility, and esthetics for prosthetic dentistry. CAD/CAM technology offers improved mechanical strength and durability, potentially enhancing the long-term performance of dental prosthetics, while the biocompatibility of these polymers makes them suitable for a broad patient demographic, reducing the risk of adverse reactions. The practical implications of these findings for dental technicians and dentists are significant, as understanding these material differences enables tailored treatment planning to meet individual patient needs and preferences. Integration of CAD/CAM technology into dental practices can lead to more predictable outcomes and heightened patient satisfaction with prosthetic restorations.

Advanced FFF of PEEK: Infill Strategies and Material Characteristics for Rapid Tooling

Traditional vulcanization mold manufacturing is complex, costly, and under pressure due to shorter product lifecycles and diverse variations. Additive manufacturing using Fused Filament Fabrication and high-performance polymers like PEEK offer a promising future in this industry. This study assesses the compressive strength of various infill structures (honeycomb, grid, triangle, cubic, and gyroid) when considering two distinct build directions (Z, XY) to enhance PEEK's economic and resource efficiency in rapid tooling. A comparison with PETG samples shows the behavior of the infill strategies. Additionally, a proof of concept illustrates the application of a PEEK mold in vulcanization. A peak compressive strength of 135.6 MPa was attained in specimens that were 100% solid and subjected to thermal post-treatment. This corresponds to a 20% strength improvement in the Z direction. In terms of time and mechanical properties, the anisotropic grid and isotropic cubic infill have emerged for use in rapid tooling. Furthermore, the study highlights that reducing the layer thickness from 0.15 mm to 0.1 mm can result in a 15% strength increase. The study unveils the successful utilization of a room-temperature FFF-printed PEEK mold in vulcanization injection molding. The parameters and infill strategies identified in this research enable the resource-efficient FFF printing of PEEK without compromising its strength properties. Using PEEK in rapid tooling allows a cost reduction of up to 70% in tool production.

Optimization of Fixations for Additively Manufactured Cranial Implants: Insights from Finite Element Analysis

With the emergence of additive manufacturing technology, patient-specific cranial implants using 3D printing have massively influenced the field. These implants offer improved surgical outcomes and aesthetic preservation. However, as additive manufacturing in cranial implants is still emerging, ongoing research is investigating their reliability and sustainability. The long-term biomechanical performance of these implants is critically influenced by factors such as implant material, anticipated loads, implant-skull interface geometry, and structural constraints, among others. The efficacy of cranial implants involves an intricate interplay of these factors, with fixation playing a pivotal role. This study addresses two critical concerns: determining the ideal number of fixation points for cranial implants and the optimal curvilinear distance between those points, thereby establishing a minimum threshold. Employing finite element analysis, the research incorporates variables such as implant shapes, sizes, materials, the number of fixation points, and their relative positions. The study reveals that the optimal number of fixation points ranges from four to five, accounting for defect size and shape. Moreover, the optimal curvilinear distance between two screws is approximately 40 mm for smaller implants and 60 mm for larger implants. Optimal fixation placement away from the center mitigates higher deflection due to overhangs. Notably, a symmetric screw orientation reduces deflection, enhancing implant stability. The findings offer crucial insights into optimizing fixation strategies for cranial implants, thereby aiding surgical decision-making guidelines.