3D modeling, custom implants and its future perspectives in craniofacial surgery

Personalized Rehabilitation of Atrophic Customized Subperiosteal Implants

Severe maxillary atrophy and edentulism can pose a range of challenges in implant planning and oral rehabilitation. Modern dentistry has allowed for a review of the concepts and surgical protocols of subperiosteal implants, presenting them as a solution for the rehabilitation of atrophic maxillary and mandibular bone deficiencies. This study aims to address a series of 3 patients with severe maxillary atrophy, as evidenced by presurgical and postsurgical radiographic images, as well as computer-assisted planning and analysis of patient anatomy for rehabilitation with custom sintered subperiosteal implants. Promising results these clinical cases, highlighting the precise technique, biocompatibility, and durability of these materials. The absence of postoperative complications was evident, with high success rates in procedures and patient reports. Importantly, periodic follow-up is needed to assess the longevity and effectiveness of the technique used.

Developmental three-dimensional examination of the pelvic cavity of Hamdani crossbred sheep fetuses (Ovis aries) in the last two periods of gestation

BACKGROUND

Türkiye is a country in the world ranking in terms of sheep breeding. Hamdani crossbred sheep breed is one of the sheep breeds that can adapt to the difficult conditions in our country. In addition, the sentence may be corrected as 'Especially in the southeastern part of the Türkiye, crossbreeding is preferred by breeders to increase the yield characteristics of sheep'.

OBJECTIVES

In our study, it was aimed to perform a pelvimetric analysis of Hamdani crossbred sheep fetuses in the second and third trimesters by three-dimensional modelling method.

METHODS

For this purpose, a total of 40 second-trimester (10 females, 10 males) and third-trimester (10 females, 10 males) fetuses were used. The pelvises of the fetuses were imaged with CT and 3D models were created. Sixteen pelvimetric measurements were performed from the models. The results obtained were evaluated statistically.

RESULTS

The study found statistically significant differences between male and female fetuses in terms of vertical diameter (VD) and foramen obturatum width (FOW) measurement parameters in the second trimester. In the third trimester, there were statistically significant differences between genders in acetabulum (AC) (p < 0.01), medial ischial tuberosities (MIT), and ischiatic arch (IA) (p < 0.05) parameters. As a result of the correlation analysis, it was determined that the pelvis length (PL) measurement parameter was positively correlated with different parameters in varying degrees in both periods, while the IA parameter did not show significant correlations with the other parameter in the last two periods of pregnancy.

CONCLUSION

In conclusion, the data obtained will be useful in pelvimetric evaluations of human and animal fetuses, anatomy education, zooarchaeology and taxonomy studies.

Simulating the Morphological Changes of Facial Deformities after Using 3D-printed Polyether Ether Ketone Facial Implants

Background

Patient-specific implants (PSIs) have been presented as an effective solution for diseases that require reconstruction. PSIs are designed to precisely fit anatomical defects or deformities in terms of shape and size. In addition to the possibility of predicting the results of surgery regarding soft tissue changes.

Methods

A research sample consisting of 10 patients with facial deformities underwent maxillofacial reconstructive surgery between 2020 and 2021 in the Tishreen University Hospital, Syria. All patients underwent computed tomography scans; then, the design of the required facial implant was carried out, and the three-dimensional soft tissues were reconstructed using the ExoCad 3.0 program based on the computed tomography. The final form of the facial implant was printed from polyether ether ketone, and then surgical work was performed. The patients were followed up after 6 months. Then, a comparison was made between the virtual design and the real result.

Results

The absolute difference between the expected soft tissue changes result and the actual result did not exceed three-tenths for all patients, and only two of 10 patients had measurements higher than 20%.

Conclusions

This technique can be relied upon with the placement of implants to predict the outcome of the surgical procedure in terms of morphological changes in the facial soft tissues covering PSI polyether ether ketone. Therefore, it is possible to make a virtual design based on the cosmetic requirements of the patient.

Advances in Three-Dimensional Printing for Craniomaxillofacial Trauma Reconstruction: A Systematic Review

Craniomaxillofacial (CMF) fractures present significant challenges for plastic surgeons due to their intricate nature. Conventional methods such as autologous bone grafts have limitations, necessitating advancements in reconstructive surgery techniques. This study reviewed the use of three-dimensional printing for CMF trauma reconstruction using human studies. A systematic search of PubMed, EMBASE, and Google Scholar was conducted in February 2024 for case reports, case series, and clinical trials related to CMF trauma reconstruction using three-dimensional printing technology. The authors' systematic review included 20 studies and a total of 170 participants with CMF bone defects. In general, the authors observed low bias risk in analyzed case reports and series, serious bias risk in nonrandomized controlled trials, and moderate bias risk in randomized controlled trials. The printed objects included CMF structure model prototypes, patient-specific implants, and other custom surgical devices. Studies reveal successful outcomes, including restored facial symmetry and function, restored orbital occlusion, resolved enophthalmos and diplopia, achieved cosmetically symmetrical lower face reconstruction, and precise fitting of surgical devices, enhancing patient and surgeon comfort. However, complications such as local infection, implant exposure, and persistent diplopia were reported. Three-dimensional printed devices reduced surgery time but increased preparation time and production costs. In-house production options could mitigate these time and cost expenditures. Three-dimensional printing holds potential in CMF trauma reconstruction, addressing both functional and esthetic restoration. Nevertheless, challenges persist in implementing this advanced technology in resource-limited environments.

Scope of magnesium ceria nanocomposites for mandibular reconstruction: Degradation and biomechanical evaluation using a 3-dimensional finite element analysis approach

Magnesium/Ceria nanocomposites (Mg/xCeO2 NCs (x = 0.5 %, 1 % and 1.5 %)) prepared by using powder metallurgy and microwave sintering method are assessed for their corrosion rate for a period of 28 days. As per the immersion tests results, the addition of ceria nanoparticles to pure Mg, brought about a noteworthy improvement to corrosion resistance. A corrosion rate of approximately 0.84 mm/year for Mg/0.5CeO2 and 0.99 mm/year for Mg/1.0CeO2 nanocomposites were observed. Another aspect of the study involves employing the simulation method i.e. finite element analysis (FEA) to compare the stress distribution in magnesium-ceria nanocomposite based screws and circular bars especially for Mg/0.5CeO2 and Mg/1.0CeO2. Further, the simulation also gives a perception of the impact of masticatory forces, the biting force and shear stress exerted on the Mg/0.5CeO2 and Mg/1.0CeO2 based screws. The simulations results show that the screws showed an acceptable level of stresses for a biting force up to 300 N. The circular bar as well kept its stresses at acceptable levels for the same load of 300N. The shear stress results indicated that a biting force up to 602 N can be safely absorbed by Mg/0.5CeO2 screw. The comprehensive approach allows for a better understanding of the corrosion behavior, stress distribution, and mechanical properties of the Mg/CeO2 nanocomposites, enabling the development of effective temporary implants for craniofacial trauma fixation that can withstand normal physiological forces during mastication. The study reported in this paper aims to target Mg/xCeO2 NCs for temporary implants for craniofacial trauma fixation.

Use of Biomaterials in 3D Printing as a Solution to Microbial Infections in Arthroplasty and Osseous Reconstruction

The incidence of microbial infections in orthopedic prosthetic surgeries is a perennial problem that increases morbidity and mortality, representing one of the major complications of such medical interventions. The emergence of novel technologies, especially 3D printing, represents a promising avenue of development for reducing the risk of such eventualities. There are already a host of biomaterials, suitable for 3D printing, that are being tested for antimicrobial properties when they are coated with bioactive compounds, such as antibiotics, or combined with hydrogels with antimicrobial and antioxidant properties, such as chitosan and metal nanoparticles, among others. The materials discussed in the context of this paper comprise beta-tricalcium phosphate (β-TCP), biphasic calcium phosphate (BCP), hydroxyapatite, lithium disilicate glass, polyetheretherketone (PEEK), poly(propylene fumarate) (PPF), poly(trimethylene carbonate) (PTMC), and zirconia. While the recent research results are promising, further development is required to address the increasing antibiotic resistance exhibited by several common pathogens, the potential for fungal infections, and the potential toxicity of some metal nanoparticles. Other solutions, like the incorporation of phytochemicals, should also be explored. Incorporating artificial intelligence (AI) in the development of certain orthopedic implants and the potential use of AI against bacterial infections might represent viable solutions to these problems. Finally, there are some legal considerations associated with the use of biomaterials and the widespread use of 3D printing, which must be taken into account.

Correlation between low skeletal muscle index and 3D anthropometric data measured by 3D body scanner: screening sarcopenia

Background

The screening tools for sarcopenia are measuring calf circumference, SARC-F or SPPB. However, not all of these tools have high sensitivity, specificity, and low margins of error. This research investigates potential of 3D anthropometry of the lower extremities on screening of sarcopenia.

Methods

From October 2022 to February 2023, we retrospectively analyzed results of 3D body scanner and bio-impedance analysis for patients aged 45 to 85 at risk of sarcopenia. The 3D scanner measured the surface and volume values of both thighs and calves. When skeletal muscle index (SMI) is less than 5.7, patients were classified to Low SMI group, indicative of sarcopenia.

Results

A total six out of 62 patients were classified to Low SMI group, showing significantly lower values of right, left, mean calf volumes and mean calf surface than the other patients (right calf volume 2.62 L vs. 3.34 L, p = 0.033; left calf volume 2.62 L vs. 3.25 L, p = 0.044; mean calf volume 2.62 L vs. 3.29 L, p = 0.029; mean calf surface 0.12 m2 vs. 0.13 m2, p = 0.049). There was no statistical difference in thigh volume and surface. Through AUC-ROC analysis, mean calf volume was the most significant cut-off value (right calf volume 2.80 L, AUC = 0.768; left calf volume 2.75 L, AUC = 0.753; mean calf volume 3.06 L, AUC = 0.774; mean calf surface 0.12 m2, AUC = 0.747).

Conclusion

The calf volume and surface values have significant relationship with low SMI, and the mean calf volume was the most significant cut-off screening value for Low SMI. The 3D scanner demonstrated its value as a new means for screening sarcopenia.

Internal surface modification of additively manufactured macroporous TiAl6V4 biomimetic implants via a calciothermic reaction-based process and osteogenic in vivo responses

Three-dimensional macroporous titanium-aluminum-vanadium (TiAl6V4) implants produced by additive manufacturing (AM) can be grit blasted (GB) to yield microtextured exterior surfaces, with additional micro/nano-scale surface features provided by subsequent acid etching (AE). However, the line-of-sight nature of GB causes the topography of exterior GB + AE-modified surfaces to differ from internal GB-inaccessible surfaces. Previous in vitro studies using dense TiAl6V4 substrates indicated that a nonline-of-sight, calciothermic-reaction (CaR)-based process provided homogeneous osteogenic nanotextures on GB + AE surfaces, suggesting it could be used to achieve a homogeneous nanotopography on external and internal surfaces of macroporous AM constructs. Macroporous TiAl6V4 (3D) constructs were produced by direct laser melting and modified by GB + AE, with the CaR process then applied to 50% of constructs (3DCaR). The CaR process yielded nanoporous/nanorough internal surfaces throughout the macroporous constructs. Skeletally mature, male Sprague-Dawley rats were implanted with these constructs using a cranial on-lay model. Prior to implantation, a Cu++-free click hydrogel was applied to half of the constructs (3D + H, 3DCaR + H) to act as a challenge to osseointegration. Osseointegration was compared between the four implant groups (3D, 3DCaR, 3D + H, 3DCaR + H) at 4w. 3D + H implants exhibited lower bone volume (BV) and percent bone ingrowth (%BI) than the 3D implants. In contrast, osseointegrated 3DCaR + H implants had similar BV and %BI as the 3DCaR implants. Implant pull-off forces correlated with these results. In vitro analyses indicated that human bone marrow stromal cells (MSCs) exhibited enhanced production of osteoblast differentiation markers and factors associated with osteogenesis when grown on CaR-modified 3D substrates relative to control (TCPS) substrates. This work confirms that the CaR process provides osteogenic nanotextures on internal surfaces of macroporous 3D implants, and suggests that CaR-modified surfaces can promote osseointegration in cases where osteogenesis is impaired.

Application of Artificial Intelligence at All Stages of Bone Tissue Engineering

The development of artificial intelligence (AI) has revolutionized medical care in recent years and plays a vital role in a number of areas, such as diagnostics and forecasting. In this review, we discuss the most promising areas of AI application to the field of bone tissue engineering and prosthetics, which can drastically benefit from AI-assisted optimization and patient personalization of implants and scaffolds in ways ranging from visualization and real-time monitoring to the implantation cases prediction, thereby leveraging the compromise between specific architecture decisions, material choice, and synthesis procedure. With the emphasized crucial role of accuracy and robustness of developed AI algorithms, especially in bone tissue engineering, it was shown that rigorous validation and testing, demanding large datasets and extensive clinical trials, are essential, and we discuss how through developing multidisciplinary cooperation among biology, chemistry with materials science, and AI, these challenges can be addressed.

3D Printing Applications for Craniomaxillofacial Reconstruction: A Sweeping Review

The field of craniomaxillofacial (CMF) surgery is rich in pathological diversity and broad in the ages that it treats. Moreover, the CMF skeleton is a complex confluence of sensory organs and hard and soft tissue with load-bearing demands that can change within millimeters. Computer-aided design (CAD) and additive manufacturing (AM) create extraordinary opportunities to repair the infinite array of craniomaxillofacial defects that exist because of the aforementioned circumstances. 3D printed scaffolds have the potential to serve as a comparable if not superior alternative to the "gold standard" autologous graft. In vitro and in vivo studies continue to investigate the optimal 3D printed scaffold design and composition to foster bone regeneration that is suited to the unique biological and mechanical environment of each CMF defect. Furthermore, 3D printed fixation devices serve as a patient-specific alternative to those that are available off-the-shelf with an opportunity to reduce operative time and optimize fit. Similar benefits have been found to apply to 3D printed anatomical models and surgical guides for preoperative or intraoperative use. Creation and implementation of these devices requires extensive preclinical and clinical research, novel manufacturing capabilities, and strict regulatory oversight. Researchers, manufacturers, CMF surgeons, and the United States Food and Drug Administration (FDA) are working in tandem to further the development of such technology within their respective domains, all with a mutual goal to deliver safe, effective, cost-efficient, and patient-specific CMF care. This manuscript reviews FDA regulatory status, 3D printing techniques, biomaterials, and sterilization procedures suitable for 3D printed devices of the craniomaxillofacial skeleton. It also seeks to discuss recent clinical applications, economic feasibility, and future directions of this novel technology. By reviewing the current state of 3D printing in CMF surgery, we hope to gain a better understanding of its impact and in turn identify opportunities to further the development of patient-specific surgical care.

Early Surgical Management of Displaced Orbital Roof Fractures: Prospective Observational Study

This study aimed to evaluate the clinical, radiological and functional outcome of early (within 24 h) surgical intervention of displaced orbital roof fractures. This is a prospective observational study for patients with displaced orbital roof fractures. Six patients underwent early surgical management within hours of admission. The primary outcome variables were functional and aesthetic (evaluated through clinical and radiological assessments). The rate of immediate and delayed complications over a 6-months minimum follow-up period was recorded. All patients were males. The median age at the time of presentation was 23.5 years ranging from 4 to 40 years. The etiology was a high impact traffic accident in all patients. In three patients, the orbital roof fractures were unilateral, and in the other three patients, the fractures were bilateral. All patients were treated via transcranial approach at the same time as the neurosurgery. The median follow-up period was 10 months ranging from 6 to 15 months. During the follow-up period, there were no signs of meningitis, cerebrospinal fluid leakage, facial asymmetry, enophthalmos, exophthalmos, restriction of ocular motility, or blindness. Traumatic optic neuropathy was present in two patients (one unilateral and the other bilateral), of whom, one patient achieved full visual acuity recovery, while the other patient showed a mild decrease in visual acuity which improved within 6 months (OD;20/30, OS;20/25). One patient had mild ptosis and recovered spontaneously within 3 months after surgery. Postoperative CT scans showed a good anatomical reconstruction of orbital roof fracture in all cases. Early definite management of displaced orbital roof fractures secures reliable functional and cosmetic results and reduces the incidences of intracranial and ocular complications.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-04056-x.

The Use of 3D Technology in the Management of Residual Asymmetry following Orthognathic Surgery: A Case Report

The purpose of this case report was to present the aesthetic result of the reconstruction of facial residual asymmetry after orthognathic surgery using a patient-specific three-dimensional (3D) mold and a custom-made polymethyl methacrylate implant. Through computer-aided design (CAD), the healthy contralateral side of the mandible was superimposed onto the side with the defect. Exocad Gallway (exocad GmbH, Darmstadt, Germany) was used to design the patient-specific implants (PSIs) of the right mandibular angle. Next, the implant mold was created using the Meshmixer software (Version 3.5, Autodesk Inc., San Rafael, CA, USA) and fabricated using additive manufacturing. During the surgical procedure, the patient-specific implant (PSI) was cast inside the resin mold using Simplex P bone cement (Stryker, Mahwah, NJ, USA). The implant was fixed using three screws. Combining both indirect (involving the dental laboratory) and direct (with surgical intervention) approaches, this innovative hybrid method, which incorporates both computer-aided design and additive manufacturing (AM), not only enhanced facial aesthetics, functional rehabilitation, and patient quality of life but also mitigated the potential risks linked to conventional grafting methods.

Inflammatory Impact on Tissues Surrounding the Dental Implant of Singular Abutments Bonded onto Titanium Base - A Randomized Controlled Trial

Introduction

In dental implants, the biochemical connection between titanium (ti) and bony tissue has been well established. The properties of dental implants such as osseointegration and stability depend upon composition, design of the implant, connection, and design of the abutment, and additional removal of abutments. Recently, laser-generated micro-grooved surface (LSS) and TI abutments are the main focus of preventing peri-implant inflammation.

Objectives

To assess the inflammatory impact of singular abutments bonded onto titanium bases on tissues surrounding the dental implant.

Methods

Twenty subjects were enrolled. Only those subjects were enrolled who were scheduled to undergo prosthetic rehabilitation of missing teeth. Random division of subjects was done. Group A: Test abutment group and Group B: Control abutment group. The test abutments comprised Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) titanium abutments bonded onto titanium abutments. However, control abutments were customized and only one-piece CAD/CAM titanium abutments were enrolled.On 6 months and 12 months of follow-up, the clinical and radiographic examination was done. Assessment of the bone level changes, clinical variables, and IL-1b levels was assessed.

Results

Mean IL-1b levels in Group A subjects at baseline, 6 months, and 12 months were 1.52 pg/mL, 1.69 pg/mL, and 1.55 pg/mL, respectively. Mean IL-1b levels among the patients of group B at baseline, 6 months, and 12 months were 1.56 pg/mL, 1.71 pg/mL, and 1.54 pg/mL, respectively.

Conclusion

Within the limitation of the study, it can be concluded that the impact on the inflammatory condition of surrounding tissues of dental implant does not vary significantly between single abutments bonded onto Titanium bases and singular abutments.

Modeling Methods in Craniofacial Virtual Surgical Planning

Despite the widespread use of virtual surgical planning (VSP), few papers describe the modeling methods used to generate the digital simulations that underpin VSP. This paper aims to review the modeling methods that are currently available for use in VSP and the implications of their use in clinical practice. A literature review was undertaken of the two broad categories of modeling techniques; contour-based planning-namely mirroring from the contralateral side, templating from a normative database, and extrapolation from surrounding landmarks-and occlusal-based planning (OBP). The indications for each modeling method were discussed, including mandibular/maxillary reconstruction, pediatric craniofacial surgery, and orthognathic, as well as the limitations to the accuracy of modeling types. Unilateral defects of the upper/midface, wherein contour accuracy is paramount, are best reconstructed using mirroring methods, whereas bilateral defects-or cases with asymmetry due to craniofacial dysmorphology-are most suited to normative-data-based methods. Cases involving resection of the alveolar margin, in which functional occlusion is the primary outcome are best managed with OBP. Similarly, orthognathic surgery typically uses OBP, although complex cases involving asymmetry, such as clefts, may benefit from a combination of OBP and normative data methods. The choice of modeling methods is, therefore, largely driven by the defect type and the goals of reconstruction.

Fabrication of Porous Tantalum with Low Elastic Modulus and Tunable Pore Size for Bone Repair

Porous tantalum (Ta) is a potential bone substitute due to its excellent biocompatibility and desirable mechanical properties. In this work, a series of porous Ta materials with interconnected micropores and varying pore sizes from 23 to 210 μm were fabricated using spark plasma sintering. The porous structure was formed by thermal decomposition of ammonium bicarbonate powder premixed in the Ta powder. The pore size and porosity were controlled by the categorized particle size of ammonium bicarbonate. The porous Ta has elastic moduli in the range of 2.1-3.2 GPa and compressive yield strength in the range of 23-34 MPa, which are close to those of human bone. In vitro, as-fabricated porous Ta demonstrates excellent biocompatibility by supporting adhesion and proliferation of preosteoblasts. In vivo studies also validate its bone repair capability after implantation in a rat femur defect model. The study demonstrates a facile strategy to fabricate porous Ta with controllable pore size for bone repair.

The simplified tailor-made workflows for a 3D slicer-based craniofacial implant design

A specific design of craniofacial implant model is vital and urgent for patients with traumatic head injury. The mirror technique is commonly used for modeling these implants, but it requires the presence of a healthy skull region opposite to the defect. To address this limitation, we propose three processing workflows for modeling craniofacial implants: the mirror method, the baffle planner, and the baffle-based mirror guideline. These workflows are based on extension modules on the 3D Slicer platform and were developed to simplify the modeling process for a variety of craniofacial scenarios. To evaluate the effectiveness of these proposed workflows, we investigated craniofacial CT datasets collected from four accidental cases. The designed implant models were created using the three proposed workflows and compared to reference models created by an experienced neurosurgeon. The spatial properties of the models were evaluated using performance metrics. Our results show that the mirror method is suitable for cases where a healthy skull region can be completely reflected to the defect region. The baffle planner module offers a flexible prototype model that can be fit independently to any defect location, but it requires customized refinement of contour and thickness to fill the missing region seamlessly and relies on the user's experience and expertise. The proposed baffle-based mirror guideline method strengthens the baffle planner method by tracing the mirrored surface. Overall, our study suggests that the three proposed workflows for craniofacial implant modeling simplify the process and can be practically applied to a variety of craniofacial scenarios. These findings have the potential to improve the care of patients with traumatic head injuries and could be used by neurosurgeons and other medical professionals.

Design, Analysis, and 3D Printing of a Patient-Specific Polyetheretherketone Implant for the Reconstruction of Zygomatic Deformities

The reconstruction of craniomaxillofacial deformities, especially zygomatic bone repair, can be exigent due to the complex anatomical structure and the sensitivity of the crucial organs involved. The need to reconstruct the zygomatic bone in the most precise way is of crucial importance for enhancing the patient outcomes and health care-related quality of life (HRQL). Autogenous bone grafts, despite being the gold standard, do not match bone forms, have limited donor sites and bone volume, and can induce substantial surgical site morbidity, which may lead to adverse outcomes. The goal of this study is to provide an integrated approach that includes various processes, from patient scanning to implant manufacture, for the restoration of zygomatic bone abnormalities utilizing Polyetheretherketone (PEEK) material, while retaining adequate aesthetic and facial symmetry. This study takes an integrated approach, including computer-aided implant design using the mirror reconstruction technique, investigating the biomechanical behavior of the implant under loading conditions, and carrying out a fitting accuracy analysis of the PEEK implant fabricated using state-of-the-art additive manufacturing technology. The findings of the biomechanical analysis results reveal the largest stress of approximately 0.89 MPa, which is relatively low in contrast to the material's yield strength and tensile strength. A high degree of sturdiness in the implant design is provided by the maximum value of strain and deformation, which is also relatively low at roughly 2.2 × 10^-4 and 14 µm. This emphasizes the implant's capability for load resistance and safety under heavy loading. The 3D-printed PEEK implant observed a maximum deviation of 0.4810 mm in the outside direction, suggesting that the aesthetic result or the fitting precision is adequate. The 3D-printed PEEK implant has the potential to supplant the zygoma bone in cases of severe zygomatic reconstructive deformities, while improving the fit, stability, and strength of the implant.

Biocompatibility and osteointegration capability of β-TCP manufactured by stereolithography 3D printing: In vitro study

Beta-tricalcium phosphate (β-TCP) bioceramics have an inorganic composition similar to the human bone. While conventional methods can only produce ceramic scaffolds with poor controllability, the advancement of 3D-printing, especially stereolithography, made it possible to manufacture controllable, highly precise, micropore ceramic scaffolds. In this study, the stereolithography was applied to produce β-TCP bioceramics, while ZrO₂, Al₂O₃, Ti6Al4V, and polyetheretherketone (PEEK) were used as controls. Phase analysis, water contact angle tests, and Micro-CT were applied to evaluate the surface properties and scaffold. Hemolytic toxicity, cell proliferation, and morphological assessment were performed to evaluate the biocompatibility. Alkaline phosphatase (ALP) level, mineralization, and qRT-PCR were measured to evaluate the osteointegration. During the manufacturing of β-TCP, no evident impurity substance and hemolytic toxicity was found. Cells on β-TCP had good morphologies, and their proliferation capability was similar to Ti6Al4V, which was higher than the other materials. Cells on β-TCP had higher ALP levels than PEEK. The degree of mineralization was significantly higher on β-TCP. The expression of osteogenesis-related genes on β-TCP was similar to Ti6Al4V and higher than the other materials. In this study, the β-TCP produced by stereolithography had no toxicity, high accuracy, and excellent osteointegration capability, thus resulting as a good choice for bone implants.

A Review of Image-Based Simulation Applications in High-Value Manufacturing

Image-Based Simulation (IBSim) is the process by which a digital representation of a real geometry is generated from image data for the purpose of performing a simulation with greater accuracy than with idealised Computer Aided Design (CAD) based simulations. Whilst IBSim originates in the biomedical field, the wider adoption of imaging for non-destructive testing and evaluation (NDT/NDE) within the High-Value Manufacturing (HVM) sector has allowed wider use of IBSim in recent years. IBSim is invaluable in scenarios where there exists a non-negligible variation between the 'as designed' and 'as manufactured' state of parts. It has also been used for characterisation of geometries too complex to accurately draw with CAD. IBSim simulations are unique to the geometry being imaged, therefore it is possible to perform part-specific virtual testing within batches of manufactured parts. This novel review presents the applications of IBSim within HVM, whereby HVM is the value provided by a manufactured part (or conversely the potential cost should the part fail) rather than the actual cost of manufacturing the part itself. Examples include fibre and aggregate composite materials, additive manufacturing, foams, and interface bonding such as welding. This review is divided into the following sections: Material Characterisation; Characterisation of Manufacturing Techniques; Impact of Deviations from Idealised Design Geometry on Product Design and Performance; Customisation and Personalisation of Products; IBSim in Biomimicry. Finally, conclusions are drawn, and observations made on future trends based on the current state of the literature.

Shape differences in the semitendinosus following tendon harvesting for anterior cruciate ligament reconstruction

Following hamstring autograft anterior cruciate ligament reconstruction (ACLR), muscle length, cross-sectional area, and volume are reduced. However, these discrete measures of morphology do not account for complex three-dimensional muscle shape. The primary aim of this study was to determine between-limb semitendinosus (ST) shape and regional morphology differences in young adults following tendon harvest for ACLR and to compare these differences with those in healthy controls. In this cross-sectional study, magnetic resonance imaging was performed on 18 individuals with unilateral ACLR and 18 healthy controls. Bilaterally, ST muscles were segmented, and shape differences assessed between limbs and compared between groups using Jaccard index (0-1) and Hausdorff distance (mm). Length (cm), peak cross-sectional area (cm² ), and volume (cm³ ) were measured for the entire muscle and proximal, middle, and distal regions, and compared between limbs and groups. Compared to healthy controls, the ACLR group had significantly (p < 0.001, Cohen's d = -2.33) lower bilateral ST shape similarity and shape deviation was significantly (p < 0.001, d = 2.12) greater. Shape deviation was greatest within the distal region of the ACLR (Hausdorff: 23.1 ± 8.68 mm). Compared to both the uninjured contralateral limb and healthy controls, deficits in peak cross-sectional area and volume in ACLR group were largest in proximal (p < 0.001, d = -2.52 to -1.28) and middle (p < 0.001, d = -1.81 to -1.04) regions of the ST. Overall, shape analysis provides unique insight into regional adaptations in ST morphology post-ACLR. Findings highlight morphological features in distal ST not identified by traditional discrete morphology measures. Clinical significance: Following ACLR, risk of a secondary knee or primary hamstring injury has been reported to be between 2-to-5 times greater compared to those without ACLR. Change in semitendinosus (ST) shape following ACLR may affect force transmission and distribution within the hamstrings and might contribute to persistent deficits in knee flexor and internal rotator strength.

Automation of Measurements for Personalized Medical Appliances by Means of CAD Software-Application in Robin Sequence Orthodontic Appliances

Measuring the dimensions of personalized devices can provide relevant information for the production of future such devices used in various medical specialties. Difficulties with standardizing such measurement and obtaining high accuracy, alongside cost-intensive measuring methodologies, has dampened interest in this practice. This study presents a methodology for automatized measurements of personalized medical appliances of variable shape, in this case an orthodontic appliance known as Tübingen Palatal Plate (TPP). Parameters such as length, width and angle could help to standardize and improve its future use. A semi-automatic and custom-made program, based on Rhinoceros 7 and Grasshopper, was developed to measure the device (via an extraoral scanner digital file). The program has a user interface that allows the import of the desired part, where the user is able to select the necessary landmarks. From there, the program is able to process the digital file, calculate the necessary dimensions automatically and directly export all measurements into a document for further processing. In this way, a solution for reducing the time for measuring multiple dimensions and parts while reducing human error can be achieved.

Strategies to improve bioactive and antibacterial properties of polyetheretherketone (PEEK) for use as orthopedic implants

Polyetheretherketone (PEEK) has gradually become the mainstream material for preparing orthopedic implants due to its similar elastic modulus to human bone, high strength, excellent wear resistance, radiolucency, and biocompatibility. Since the 1990s, PEEK has increasingly been used in orthopedics. Yet, the widespread application of PEEK is limited by its bio-inertness, hydrophobicity, and susceptibility to microbial infections. Further enhancing the osteogenic properties of PEEK-based implants remains a difficult task. This article reviews some modification methods of PEEK in the last five years, including surface modification of PEEK or incorporating materials into the PEEK matrix. For surface modification, PEEK can be modified by chemical treatment, physical treatment, or surface coating with bioactive substances. For PEEK composite material, adding bioactive filler into PEEK through the melting blending method or 3D printing technology can increase the biological activity of PEEK. In addition, some modification methods such as sulfonation treatment of PEEK or grafting antibacterial substances on PEEK can enhance the antibacterial performance of PEEK. These strategies aim to improve the bioactive and antibacterial properties of the modified PEEK. The researchers believe that these modifications could provide valuable guidance on the future design of PEEK orthopedic implants.

Nasoethmoid orbital fracture reconstruction using a three-dimensional printing-based craniofacial plate

The face is one of the most important parts of the body. Untreated facial fractures can result in deformities that can be harmful to patients. Three-dimensional (3D) printing is a rapidly evolving technology that has recently been widely applied in the medical field as it can potentially improve patient treatment. Although 3D printing technology is mostly used for craniofacial surgery, some studies have proved that it can be used to treat nasoethmoid orbital fractures. In this study, a patient-customized plate was constructed using a 3D printer and applied in a simulated surgery for the treatment of nasoethmoid orbital fracture.

Review on 3D printing in dentistry: conventional to personalized dental care

The CAD (Computer-aided design) and CAM (computer-aided manufacturing) have most applications in the manufacturing of fully automated, personalized dental devices and tailor-made treatment plans. 3D printing is one of the most rapidly expanding and new methods of manufacturing different things because of its on-demand and high productivity within the cost-effective manner which have a variety of applications in healthcare, pharmaceuticals, orthopaedics, engineered tissue models, medical devices, defence industries, automotive and aerospace sectors. Due to its emerging applications in the various sectors, the healthcare, Industries, and academic sectors are attracted towards the 3D printed materials. This review talks about the dental implants, polymers that are employed in concocting dental implants, critical parameters, and challenges which are to be considered while preparing these implants, advantages of 3D printing in the field of dentistry and the current trends. it discusses the variety of applications of 3D printed materials in the field of dentistry. Along with their method of fabrication, their critical process parameters (CPPs) are also discussed.

3D printing of pharmaceuticals: approach from bench scale to commercial development

Background

The three-dimensional (3D) printing is paradigm shift in the healthcare sector. 3D printing is platform technologies in which complex products are developed with less number of additives. The easy development process gives edge over the conventional methods. Every individual needs specific dose treatment. 'One size fits all' is the current traditional approach that can shift to more individual specific in 3D printing. The present review aims to cover different perspectives regarding selection of drug, polymer and technological aspects for 3D printing. With respect to clinical practice, regulatory issue and industrial potential are also discussed in this paper.

Main body

The individualization of medicines with patient centric dosage form will become reality in upcoming future. It provides individual's need of dose by considering genetic profile, physiology and diseased condition. The tailormade dosages with unique drug loading and release profile of different geometrical shapes and sizes can easily deliver therapeutic dose. The technology can fulfill growing demand of efficiency in the dose accuracy for the patient oriented sectors like pediatric, geriatric and also easy to comply with cGMP requirements of regulated market. The clinical practice can focus on prescribing each individual's necessity of dose.

Conclusion

In the year 2015, FDA approved first 3D printed drug product, which is initiator in the new phase of manufacturing of pharmaceuticals. The tailormade formulations can be made in future for personalized medications. Regulatory approval from agencies can bring the 3DP product into the market. In the future, formulators can bring different sector-specific products for personalized need through 3DP pharmaceutical product.

Graphical Abstract

Case report: Reconstruction of a complex maxillofacial gunshot defect using a titanium patient-specific implant in a dog

This report describes the surgical reconstruction of large maxillofacial defect caused by a short-range gunshot injury in a dog using titanium patient-specific implant (PSI). A 3-year-old male Wolf Shepherd was admitted for a large right facial defect with right nasal cavity exposure caused by a gunshot injury. Radiographic examination revealed severe loss of the right maxillary, nasal, and incisive bones, multiple fractures of both left and right palatine bones, and a comminuted fracture of the right mandible. Initial surgical procedure included computed tomography (CT) imaging for three-dimensional (3D) implant design. Open wound management was maintained for 18 days until the fresh granulation tissue fully covered the wound bed. The implant was designed in a “hand grasping shape” to cover the defect, align multiple fractured palatine bones, and make a snap fit function. Multiple holes, including cortical screw holes, were added to the final design. The implant was printed on a titanium alloy. Surgical application of titanium PSI was performed 19 days after the primary surgery. A free sublingual mucosal graft was used to reconstruct the mucosal layer of the right nasal cavity. The mucosa was then covered with collagen membrane to strengthen the structure of the nasal cavity. Blunt dissection of the hard palate mucoperiosteum above the palatine process and palatine bones, soft tissue above the maxilla was performed, and the 3D printed titanium implant was fastened in a preplanned position. The facial soft tissue defect was reconstructed, and the titanium PSI was covered using an angularis oris cutaneous flap. Partial flap necrosis occurred in the rostral aspect, and the wound was managed to heal by a second intension. Flap dehiscence at the junction of the flap and hard palate mucoperiosteum occurred with exposure of the implant 2 days postoperatively. Multiple attempts to close the defect failed, and the owner wanted to stop treatment. Healthy granulated tissue was observed proximal to the implant. The defect no longer increased in size and did not show any noticeable complications related to the defect at 60 days after titanium PSI application, and the dog was discharged. Six months post-operatively, the dog remained active with great appetite, gained weight, and showed acceptable facial symmetry without enlargement of the implant exposure or any implant-related problems.

Guide for starting or optimizing a 3D printing clinical service

Three-dimensional (3D) printing has applications in many fields and has gained substantial traction in medicine as a modality to transform two-dimensional scans into three-dimensional renderings. Patient-specific 3D printed models have direct patient care uses in surgical and procedural specialties, allowing for increased precision and accuracy in developing treatment plans and guiding surgeries. Medical applications include surgical planning, surgical guides, patient and trainee education, and implant fabrication. 3D printing workflow for a laboratory or clinical service that produces anatomic models and guides includes optimizing imaging acquisition and post-processing, segmenting the imaging, and printing the model. Quality assurance considerations include supervising medical imaging expert radiologists' guidance and self-implementing in-house quality control programs. The purpose of this review is to provide a workflow and guide for starting or optimizing laboratories and clinical services that 3D-print anatomic models or guides for clinical use.

Additive Manufacturing of Biomaterials-Design Principles and Their Implementation

Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In the past few decades, several design guidelines have been proposed for creating porous lattice structures, particularly for biomedical applications. Meanwhile, the capabilities of AM to fabricate a wide range of biomaterials, including metals and their alloys, polymers, and ceramics, have been exploited, offering unprecedented benefits to medical professionals and patients alike. In this review article, we provide an overview of the design principles that have been developed and used for the AM of biomaterials as well as those dealing with three major categories of biomaterials, i.e., metals (and their alloys), polymers, and ceramics. The design strategies can be categorised as: library-based design, topology optimisation, bio-inspired design, and meta-biomaterials. Recent developments related to the biomedical applications and fabrication methods of AM aimed at enhancing the quality of final 3D-printed biomaterials and improving their physical, mechanical, and biological characteristics are also highlighted. Finally, examples of 3D-printed biomaterials with tuned properties and functionalities are presented.

Low-Cost Cranioplasty-A Systematic Review of 3D Printing in Medicine

The high cost of biofabricated titanium mesh plates can make them out of reach for hospitals in low-income countries. To increase the availability of cranioplasty, the authors of this work investigated the production of polymer-based endoprostheses. Recently, cheap, popular desktop 3D printers have generated sufficient opportunities to provide patients with on-demand and on-site help. This study also examines the technologies of 3D printing, including SLM, SLS, FFF, DLP, and SLA. The authors focused their interest on the materials in fabrication, which include PLA, ABS, PET-G, PEEK, and PMMA. Three-dimensional printed prostheses are modeled using widely available CAD software with the help of patient-specific DICOM files. Even though the topic is insufficiently researched, it can be perceived as a relatively safe procedure with a minimal complication rate. There have also been some initial studies on the costs and legal regulations. Early case studies provide information on dozens of patients living with self-made prostheses and who are experiencing significant improvements in their quality of life. Budget 3D-printed endoprostheses are reliable and are reported to be significantly cheaper than the popular counterparts manufactured from polypropylene polyester.

Comparison of Bone Segmentation Software over Different Anatomical Parts

Three-dimensional bone shape reconstruction is a fundamental step for any subject-specific musculo-skeletal model. Typically, medical images are processed to reconstruct bone surfaces via slice-by-slice contour identification. Freeware software packages are available, but commercial ones must be used for the necessary certification in clinics. The commercial software packages also imply expensive hardware and demanding training, but offer valuable tools. The aim of the present work is to report the performance of five commercial software packages (Mimics®, AmiraTM, D2PTM, SimplewareTM, and Segment 3D PrintTM), particularly the time to import and to create the model, the number of triangles of the mesh, and the STL file size. DICOM files of three different computed tomography scans from five different human anatomical areas were utilized for bone shape reconstruction by using each of these packages. The same operator and the same hosting hardware were used for these analyses. The computational time was found to be different between the packages analyzed, probably because of the pre-processing implied in this operation. The longer “time-to-import” observed in one software is likely due to the volume rendering during uploading. A similar number of triangles per megabyte (approximately 20 thousand) was observed for the five commercial packages. The present work showed the good performance of these software packages, with the main features being better than those analyzed previously in freeware packages.

Customized alloplastic cranioplasty of large bone defects by 3D-printed prefabricated mold template after posttraumatic decompressive craniectomy: A technical note

Background

Manufacturing of customized three-dimensional (3D)-printed cranioplastic implant after decompressive craniectomy has been introduced to overcome the difficulties of intraoperative implant molding. The authors present and discuss the technique, which consists of the prefabrication of silicone implant mold using additive manufacturing, also known as 3D printing, and polymethyl methacrylate (PMMA) implant casting.

Methods

To reconstruct a large bone defect sustained after decompressive craniectomy due to traumatic brain injury (TBI), a 3D-printed prefabricated mold template was used to create a customized PMMA implant for cranial vault repair in five consecutive patients.

Results

A superb restoration of the symmetrical contours and curvature of the cranium was achieved in all patients. The outcome was clinically and cosmetically favorable in all of them.

Conclusion

Customized alloplastic cranioplasty using 3D-printed prefabricated mold for casting PMMA implant is easy to perform technique for the restoration of cranial vault after a decompressive craniectomy following moderate-to-severe TBI. It is a valuable and modern technique to advance manufacturing of personalized prefabricated cranioplastic implants used for the reconstruction of large skull defects having complex geometry. It is a safe and cost-effective procedure having an excellent cosmetic outcome, which may considerably decrease expenses and time needed for cranial reconstructive surgery.

Craniofacial Reconstruction with Personalized Lightweight Scaffold Fabricated Using Electron-Beam Additive Manufacturing

Implants are the most popular option for restoring the facial anatomy in the event of a mishap. The commercially available craniofacial implants are of standard shapes, which need to be tailored and shaped to accurately fit the patient’s anatomy. The manual shaping of the implant to match the bone contours is conducted during surgical operation, and is a cumbersome and inaccurate process. Recent breakthroughs in computer-aided design, analysis, and additive manufacturing (AM) have allowed the precise and rapid manufacture of bespoke scaffolds for difficult anatomical restoration. The goal of this research is to investigate the use of scaffolds for craniofacial reconstruction and their fabrication using electron-beam additive manufacturing (EBAM). Personalized cheekbone scaffolds are additively fabricated using Ti6Al4V and subjected to compression testing. Finally, the scaffold design with the highest compressive strength is subjected to biomechanical analysis. The biomechanical analysis results indicate that the maximum Von Mises stress (40 MPa) and equivalent strain (0.4 µm) are significantly low in magnitude, thus providing a desirable implant that is both flexible and stable. The custom-designed cheekbone scaffold manufactured with AM technology not only aids in bone-implant ingrowth but also helps in reducing implant weight and ensuring implant stability and long-term effectiveness.

Antibacterial Activity Studies of 3D-Printing Polyetheretherketone Substrates with Surface Growth of 2D TiO2/ZnO Rodlike Arrays

Heterogeneous metal implants have been applied in clinical treatments of skeletal wounds, but their low antibacterial properties and the possibility of a release of metal ions may have harmful influences on the human body. Therefore, a polymer implant with low cost, high safety, an elastic modulus similar to that of human bone, and a good antibacterial property must be produced for orthopedic treatments. In this study, the surface of a 3D-printed polyetheretherketone (PEEK) disk was grown with ZnO/TiO2 rodlike arrays using a chemical bath deposition. X-ray diffraction patterns and transmission electron microscopy images showed that TiO2/ZnO rodlike arrays were deposited onto the PEEK substrate. With the direct absorption of antibiotic agents onto the surface of TiO2/ZnO/PEEK samples, their antibacterial performances greater than the values of minimum inhibitory concentration required to inhibit the growth of 90% of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) remained for around 10 days. The concentration of Zn2+ ions in a buffer solution is reduced with the coating of a TiO2 layer on a ZnO rodlike array. The sample with absorption from a mixture containing ampicillin and vancomycin salts with a weight ratio of 1:1 had the best inhibitory effect on the growth of E. coli and S. aureus.

Biomechanical Analysis of Patient-Specific Temporomandibular Joint Implant and Comparison with Natural Intact Jaw Bone Using Finite Element Method

The purpose of this study is to design a patient-specific TMJ implant and study its behaviour under different loading conditions compared with natural intact TMJ. There are several diseases, which affect the proper growth and function of TMJ, and in some cases, TMJ injury results from accidents. To repair the TMJ, temporomandibular joint replacement or TJR surgery is performed. In this work, CT-scan data of the skull and mandible region with broken condylar head were used to study the biomechanical behaviour of the intact mandible and customized TMJ prostheses in order to design a patient-specific total TMJ implant. The customized TMJ implant was virtually studied under simulated loading conditions using finite element method (FEM) in ANSYS Workbench and then compared to the intact jaw-mandible for the combinations of two different biocompatible material models. It is observed that the natural TMJ has a higher deformation value as compared to the patient-specific TMJ implant due to the lower mechanical strength of bone relative to the Ti-6Al-4V and Co-Cr alloy. Hence, we can conclude that the designed custom TMJ implant is safe for the patient from the point of design perspective.

A critical analysis of research methods and experimental models to study root canal fillings

Canal filling materials and techniques have been one of the most studied topics in Endodontics. A simple search using the mesh term "root canal filling" in PubMed revealed more than 11,000 articles, an impressive number that is much higher than "root canal disinfection" (5,544 articles) or even the popular "root canal preparation" (8,527 articles). The overriding importance attributed to root filling procedures is not merely intuitive. It derived from the appealing relevance given by the appearance of the white lines in common radiographs grounded on retrospective clinical data that had identified the quality of a root filling as one of the major causes of treatment failure (lack of healing). Since the publication of the Washington study, impressive efforts have been made for the release of new materials and techniques, as well as, for the development of a plethora of laboratory methods to assess the quality of root filling procedures. This narrative review aims to address and discuss the most relevant laboratory methods to assess the root canal filling. Since filling quality improvements have not translated into higher success rates, as reported in longitudinal clinical studies, more than to deliver a simple methodology-based review, this paper aims to present an in-depth critical view on the assessment of laboratory methods used to study the filling materials and techniques. Recent data indicate that the long-term dimensional stability/degradation over time of endodontic sealers plays a central role in the treatment outcome. In this context, laboratory methods should be developed focusing on predicting, at least to some degree, the long-term clinical behaviour of root canal fillings, rather than simply ranking different materials or techniques.

Fabrication and Characterization of PCL/HA Filament as a 3D Printing Material Using Thermal Extrusion Technology for Bone Tissue Engineering

The most common three-dimensional (3D) printing method is material extrusion, where a pre-made filament is deposited layer-by-layer. In recent years, low-cost polycaprolactone (PCL) material has increasingly been used in 3D printing, exhibiting a sufficiently high quality for consideration in cranio-maxillofacial reconstructions. To increase osteoconductivity, prefabricated filaments for bone repair based on PCL can be supplemented with hydroxyapatite (HA). However, few reports on PCL/HA composite filaments for material extrusion applications have been documented. In this study, solvent-free fabrication for PCL/HA composite filaments (HA 0%, 5%, 10%, 15%, 20%, and 25% weight/weight PCL) was addressed, and parameters for scaffold fabrication in a desktop 3D printer were confirmed. Filaments and scaffold fabrication temperatures rose with increased HA content. The pore size and porosity of the six groups’ scaffolds were similar to each other, and all had highly interconnected structures. Six groups’ scaffolds were evaluated by measuring the compressive strength, elastic modulus, water contact angle, and morphology. A higher amount of HA increased surface roughness and hydrophilicity compared to PCL scaffolds. The increase in HA content improved the compressive strength and elastic modulus. The obtained data provide the basis for the biological evaluation and future clinical applications of PCL/HA material.

Mandibular shape prediction model using machine learning techniques

OBJECTIVE

To create a mandibular shape prediction model using machine learning techniques and geometric morphometrics.

MATERIALS AND METHODS

Six hundred twenty-nine radiographs were used to select the most appropriate craniomaxillary variables in different craniofacial pattern classifications using a support vector machine. To obtain the three-dimensional mandibular shape, a Procrustes fit was used on 55 tomograms, in which 17 three-dimensional landmarks were digitized. A partial least square regression was employed to find the best covariation between craniomaxillary angles and the symmetric components of mandibular shape. The model was applied to a new sample of six tomograms and evaluated by the mean absolute error. Each mandible predicted was assessed using the Hausdorff distance (HDu) and a color scale. The model was also exploratively applied to six new radiographs.

RESULTS

Covariation was 88.66% with a significance of < 0.0001 explained by twelve craniomaxillary variables. Low differences between the original and predicted models were obtained, with a mean absolute error of 0.0143. The mean distance between meshes ranged from 0.0033 to 0.0059 HDu and each color scale demonstrated general similarity between the surfaces.

CONCLUSIONS

This approach offered promising results in obtaining a mandibular prediction model that enhances shape properties in an economical way and is applicable to a Latin American population. Clinical proof of this method will require further studies with larger samples.

CLINICAL RELEVANCE

This method offers a reliable, economic alternative to traditional mandibular prediction methods and is applicable to the Latin American population.

Deposition of Biocompatible Polymers by 3D Printing (FDM) on Titanium Alloy

Nowadays, the replacement of a hip joint is a standard surgical procedure. However, researchers have continuingly been trying to upgrade endoprostheses and make them more similar to natural joints. The use of 3D printing could be helpful in such cases, since 3D-printed elements could mimic the natural lubrication mechanism of the meniscus. In this paper, we propose a method to deposit plastics directly on titanium alloy using 3D printing (FDM). This procedure allows one to obtain endoprostheses that are more similar to natural joints, easier to manufacture and have fewer components. During the research, biocompatible polymers suitable for 3D FDM printing were used, namely polylactide (PLA) and polyamide (PA). The research included tensile and shear tests of metal–polymer bonds, friction coefficient measurements and microscopic observations. The friction coefficient measurements revealed that only PA was promising for endoprostheses (the friction coefficient for PLA was too high). The strength tests and microscopic observations showed that PLA and PA deposition by 3D FDM printing directly on Ti6Al4V titanium alloy is possible; however, the achieved bonding strength and repeatability of the process were unsatisfactory. Nevertheless, the benefits arising from application of this method mean that it is worthwhile to continue working on this issue.

How 3D Printing Is Reshaping Translational Research

"Translational Research" has traditionally been defined as taking basic scientific findings and developing new diagnostic tools, drugs, devices and treatment options for patients, that are translated into practice, reach the people and populations for whom they are intended and are implemented correctly. The implication is of a unidirectional flow from "the bench to bedside". The rapidly emergent field of additive manufacturing (3D printing) is contributing to a major shift in translational medical research. This includes the concept of bidirectional or reverse translation, early collaboration between clinicians, bio-engineers and basic scientists, and an increasingly entrepreneurial mindset. This coincides with, and is strongly complemented by, the rise of systems biology. The rapid pace at which this type of translational research can occur brings a variety of potential pitfalls and ethical concerns. Regulation surrounding implantable medical devices is struggling to keep up. 3D printing has opened the way for personalization which can make clinical outcomes hard to assess and risks putting the individual before the community. In some instances, novelty and hype has led to loss of transparency of outcomes with dire consequence. Collaboration with commercial partners has potential for conflict of interest. Nevertheless, 3D printing has dramatically changed the landscape of translational research. With early recognition and management of the potential risks, the benefits of reshaping the approach to translational research are enormous. This impact will extend into many other areas of biomedical research, re-establishing that science is more than a body of research. It is a way of thinking.

Applications of 3D-Printed PEEK via Fused Filament Fabrication: A Systematic Review

Polyether ether ketone (PEEK) is an organic polymer that has excellent mechanical, chemical properties and can be additively manufactured (3D-printed) with ease. The use of 3D-printed PEEK has been growing in many fields. This article systematically reviews the current status of 3D-printed PEEK that has been used in various areas, including medical, chemical, aerospace, and electronics. A search of the use of 3D-printed PEEK articles published until September 2021 in various fields was performed using various databases. After reviewing the articles, and those which matched the inclusion criteria set for this systematic review, we found that the printing of PEEK is mainly performed by fused filament fabrication (FFF) or fused deposition modeling (FDM) printers. Based on the results of this systematic review, it was concluded that PEEK is a versatile material, and 3D-printed PEEK is finding applications in numerous industries. However, most of the applications are still in the research phase. Still, given how the research on PEEK is progressing and its additive manufacturing, it will soon be commercialized for many applications in numerous industries.

Prebending of Prefabricated Orbital Implants: Towards Improved Orbital Angle Symmetry Post Craniofacial Trauma Surgery

PURPOSE

Reconstructive surgery after craniofacial trauma aim to restore orbital anatomy for function and aesthetic reasons. The purpose of this study is to improve postoperative orbital symmetry with the use of prebent prefabricated titanium implants.

METHODS

In this retrospective study, patients with combined unilateral medial wall and floor fractures who underwent orbital reconstruction surgery were selected. The angle of inferomedial orbital strut (AIOS) was measured at 3 standard locations on preoperative facial computed tomography guided scans of the nonfractured orbit in the coronal view and used as a guide to bend the prefabricated titanium implants intraoperatively. The corresponding values were measured on the postoperative computed tomography and compared for symmetry.

RESULTS

Out of 83 patients recruited for the study, 54 were in the prebent group while 29 were in the control group. All other demographics were similar among the 2 groups. Anterior AIOS has a difference of 4.9° between 2 orbits in the prebent group whereas a difference of 15.5° was noted in the nonprebent group. For middle AIOS, a difference of 4.7° was noted in the prebent group whereas nonprebent group had a difference of 14.1°. For posterior AIOS, the prebent group had a difference of 3.8° versus 14.1° in the nonprebent group. The difference in AIOS at all 3 points between the prebent and nonprebent group were significant.

CONCLUSIONS

Anatomical prefabricated titanium plates are versatile implants that facilitate orbital reconstruction. Prebending of these implants according to the fellow orbit can achieve better surgical outcomes in a cost-effective manner.

Hydrothermal processing of 3D-printed calcium phosphate scaffolds enhances bone formation in vivo: a comparison with biomimetic treatment

Hydrothermal (H) processes accelerate the hydrolysis reaction of α-tricalcium phosphate (α-TCP) compared to the long-established biomimetic (B) treatments. They are of special interest for patient-specific 3D-printed bone graft substitutes, where the manufacturing time represents a critical constraint. Altering the reaction conditions has implications for the physicochemical properties of the reaction product. However, the impact of the changes produced by the hydrothermal reaction on the in vivo performance was hitherto unknown. The present study compares the bone regeneration potential of 3D-printed α-TCP scaffolds hardened using these two treatments in rabbit condyle monocortical defects. Although both consolidation processes resulted in biocompatible scaffolds with osseointegrative and osteoconductive properties, the amount of newly formed bone increased by one third in the hydrothermal vs the biomimetic samples. B and H scaffolds consisted mostly of high specific surface area calcium-deficient hydroxyapatite (38 and 27 m² g^-1, respectively), with H samples containing also 10 wt.% β-tricalcium phosphate (β-TCP). The shrinkage produced during the consolidation process was shown to be very small in both cases, below 3%, and smaller for H than for B samples. The differences in the in vivo performance were mainly attributed to the distinct crystallisation nanostructures, which proved to have a major impact on permeability and protein adsorption capacity, using BSA as a model protein, with B samples being highly impermeable. Given the crucial role that soluble proteins play in osteogenesis, this is proposed to be a relevant factor behind the distinct in vivo performances observed for the two materials. STATEMENT OF SIGNIFICANCE: The possibility to accelerate the consolidation of self-setting calcium phosphate inks through hydrothermal treatments has aroused great interest due to the associated advantages for the development of 3D-printed personalised bone scaffolds. Understanding the implications of this approach on the in vivo performance of the scaffolds is of paramount importance. This study compares, for the first time, this treatment to the long-established biomimetic setting strategy in terms of osteogenic potential in vivo in a rabbit model, and relates the results obtained to the physicochemical properties of the 3D-printed scaffolds (composition, crystallinity, nanostructure, nanoporosity) and their interaction with soluble proteins.

Towards an agent-based model to simulate osseointegration in powder-bed 3D printed implant-like structures

The orthopedic industry is still searching for an efficient way to replace bone loss due to surgical procedures such as arthroplasty and limb-sparing surgery. Additive manufacturing (AM) presents an opportunity to manufacture affordable patient-specific implants. Optimization of the implant-bone interface to maximize osseointegration (bone ingrowth) has not been appropriately addressed. Mechanobiological models, suited to predict mechanical adaptation of bone, cannot be used to predict osseointegration inside implants as the implant is not exposed to any mechanical loading until it is fully accepted by the host body. Biological models relying on partial differential equations based on continuum approximation are not well-suited to predict the discrete phenomenon of osseointegration. This study proposes an agent-based modeling (ABM) approach for representing the osseointegration process for orthopedic implants produced by powder-bed additive manufacturing processes. Agent-Based Modeling (ABM) is a cellular automata based discrete computing technique that uses rule-based mathematics derived from experimental studies to simulate evolutionary phenomena. In this paper, osseointegration inside a hexagonal closed packing of AM powder particles is modeled using ABM. Cellular agents such as pre-osteoblasts and osteoblasts are realistically modeled as cubic cells. The proposed model underpredicts osseointegration at early stages but predicts osseointegration at around 21 days with sufficient accuracy when compared to the in vitro test conducted by Xue et al. in 2007.

Virtual 3D planning and prediction accuracy in two bimaxillary face transplantations in Helsinki

BACKGROUND

The aim of this study was to describe the 3D planning process used in our two composite face transplantations and to analyze the accuracy of a virtual transplantation in predicting the end-result of face transplantation.

METHODS

The study material consists of two bimaxillary composite face transplantations performed in the Helsinki University Hospital in 2016 and 2018. Computed tomography (CT) scans of the recipient and donor were used to define the osteotomy lines and perform the virtual face transplantation and to 3D print customized osteotomy guides for recipient and donor. Differences between cephalometric linear and angular measurements of the virtually simulated and the actual postoperative face transplantation were calculated.

RESULTS

No changes to the planned osteotomy lines were needed during surgery. The differences in skeletal linear and angular measurements of the virtually simulated predictions and the actual postoperative face transplantations of the two patients varied between 0.1-5.6 mm and 0.7°-4°. The postoperative skeletal relationship between maxilla and mandible in both patients were almost identical in comparison to the predictions.

CONCLUSIONS

3D planning is feasible and provides close to accurate bone reconstruction in face transplantation. Preoperative virtual transplantation assists planning and improves the outcome in bimaxillary face transplantation.

Immediate soft-tissue adhesion and the mechanical properties of the Ti-6Al-4V alloy after long-term acid treatment

Close attachment of soft tissues onto implantable devices inside the body is regarded as an optimal condition for preventing complications (e.g., infections and abscess formation around implants, and the migration of small injectable devices). We have recently reported that an α-type commercially pure Ti (CpTi) film after a long-term acid treatment and air drying showed a remarkable soft tissue adhesiveness immediately (i.e., within a few seconds) after the attachment onto soft tissues. Herein, we conducted acid treatment for (α + β)-type Ti-6Al-4V alloys and compared their mechanical properties and the immediate soft-tissue adhesiveness with α-type CpTi. The acid treatment for Ti-6Al-4V also promoted immediate soft-tissue adhesion, although the treatment was less effective than for CpTi. The tensile strength of acid-treated Ti-6Al-4V was much higher than that of acid-treated CpTi or human skin tissues, although the degree of hydrogen embrittlement was more severe than that for CpTi. These results suggest that the small amount of Al in the major α phase and/or the minor β phase of Ti-6Al-4V has a significant influence not only on the mechanical properties but also on the immediate soft-tissue adhesiveness of Ti-based solid-state adhesives after the acid treatment.

Using 3D Printing and Mirror Image Modeling in Orbital Floor Reconstruction

ABSTRACT

Three-dimensional (3D) modeling and printing technologies are increasingly utilized as tools to assist in complex craniofacial reconstructions. Herein, the authors report the intraoperative use of sterilized 3D models printed in-house to mold a custom resorbable implant in the case of a pediatric patient with a unilateral complex orbital fracture. The imaging was processed with open-source software. Two patient-specific orbital models were 3D-printed (Fig. 2): a life-size print of the patient's preoperative CT scan and a left orbit reconstructed to resemble its uninjured state using mirrored-imaging of the uninjured side. This construct ultimately served as a sterilized template to mold a resorbable implant intraoperatively. Post-operatively, the patient experienced no complications. At the 18-month follow-up, the patient had done well without diplopia, headaches or visual problems. The authors report a case of a successful orbit reconstruction assisted by mirrored-image computer modeling and patient-specific 3D printing.

ADSC-Based Cell Therapies for Musculoskeletal Disorders: A Review of Recent Clinical Trials

Recently published clinical trials involving the use of adipose-derived stem cells (ADSCs) indicated that approximately one-third of the studies were conducted on musculoskeletal disorders (MSD). MSD refers to a wide range of degenerative conditions of joints, bones, and muscles, and these conditions are the most common causes of chronic disability worldwide, being a major burden to the society. Conventional treatment modalities for MSD are not sufficient to correct the underlying structural abnormalities. Hence, ADSC-based cell therapies are being tested as a form of alternative, yet more effective, therapies in the management of MSDs. Therefore, in this review, MSDs subjected to the ADSC-based therapy were further categorized as arthritis, craniomaxillofacial defects, tendon/ligament related disorders, and spine disorders, and their brief characterization as well as the corresponding conventional therapeutic approaches with possible mechanisms with which ADSCs produce regenerative effects in disease-specific microenvironments were discussed to provide an overview of under which circumstances and on what bases the ADSC-based cell therapy was implemented. Providing an overview of the current status of ADSC-based cell therapy on MSDs can help to develop better and optimized strategies of ADSC-based therapeutics for MSDs as well as help to find novel clinical applications of ADSCs in the near future.