Search Results (3,700)

Background: Given their intraoral service for clinically relevant periods, it is important to clarify whether additive manufacturing parameters influence the surface characteristics of 3D-printed provisional restorations and thereby affect microbial colonization. Methods: This study evaluated the effects of printing orientation and layer thickness on surface roughness, wettability, and Streptococcus mutans biofilm formation of LCD-printed provisional restorations. Disk-shaped specimens were fabricated from a methacrylate-based provisional resin at two orientations (0° and 90°) and two layer thicknesses (50 and 100 µm) (n = 7 per group). Surface roughness (Ra) was measured by contact profilometry, wettability by sessile-drop contact angle analysis, and biofilm formation by crystal violet staining after 72 h. Results: Data were analyzed by two-way ANOVA, aligned rank transform (ART) ANOVA, and correlation analysis (α = 0.05). Orientation alone did not affect Ra (p = 0.992), whereas layer thickness (p = 0.012) and the orientation × layer thickness interaction (p = 0.002, η² = 0.339) were significant. At 50 µm, 90° oriented specimens showed higher Ra than 0° (p = 0.021); this pattern reversed at 100 µm (p = 0.020). Neither parameter significantly affected contact angle or biofilm formation (p > 0.05). Conclusions: Both printing orientation and layer thickness altered the surface microtopography of the specimens; however, no significant differences were observed in short-term S. mutans biofilm formation among the tested groups. Within the limitations of the present single-species 72 h in vitro model, the findings suggest that material-related characteristics may have contributed more prominently to the observed biofilm behavior than the printing-induced surface differences evaluated in this study. Full article

The advancement of modern regenerative medicine is closely associated with additive technologies that enable the creation of tissue-engineered constructs and personalized bioprostheses. Three-dimensional bioprinting allows precise modeling of tissue architecture and extracellular matrix microstructures. Recent studies demonstrate rapid growth in the use of 3D bioprinting for biomedical applications including regenerative medicine, pharmaceutical research, and biotechnology. Special attention is given to the development of bioinks that combine biological and structural functions and maintain cell viability during printing. Modern technologies allow the fabrication of skin, bone, vascular, and cartilage tissues with high structural accuracy. The technology is also actively used in reconstructive surgery for the production of personalized implants. However, challenges remain related to vascularization, standardization of materials, and ethical aspects of clinical use. This review summarizes the main principles of 3D bioprinting, technological approaches, biomedical applications, and future perspectives of additive technologies in regenerative medicine. Full article

Sustainable production in dental and orthodontic 3D printing has gained increasing attention due to environmental concerns and the need for cost-effective and resource-saving solutions. This study presents a proof of concept for using recycled polymers and fused granular fabrication (FGF) in a closed-loop 3D printing approach, omitting intermediate filament manufacturing. A desktop 3D printer served as the kinematic platform and was modified with a pellet-based extruder to directly process recycled polyethylene terephthalate glycol (PETG) flakes, obtained by shredding previously printed PETG parts, into dental models. Dimensional accuracy was evaluated using optical 3D scanning analysis. The results indicate that models produced from recycled PETG are, in principle, suitable for dental and orthodontic applications within the investigated scope. This technical note provides initial evidence supporting the integration of recycled thermoplastics into dental and orthodontic model fabrication as part of sustainable additive manufacturing workflows. Potential pathways for workflow integration in clinical and laboratory environments, as well as directions for future research, are outlined, including the optimization of printing parameters and process stability. The main technical challenges were unreliable feedstock flow, causing bridging and jamming, while thermal creep from insufficient inlet cooling promoted premature softening of the flakes, causing torque spikes and unstable feeding. Full article

Bone tissue engineering requires biomimetic materials; however, pure polylactic acid (PLA) exhibits limited osteoinductivity and produces acidic byproducts upon degradation. To address these limitations, this study fabricated PLA scaffolds using fused-deposition modeling (FDM) with four distinct lattice structures (rectangular, triangular, gyroid, and 3D honeycomb) and incorporated hydroxyapatite (HA) at 0, 10, 20, and 30 wt% via injection molding. Mechanical properties were evaluated via compression, three-point bending, and tensile testing. The results revealed that increasing HA content significantly reduced structural strength and increased brittleness across all test modes. Specifically, specimens with 30 wt% HA exhibited a 70.8% reduction in bending strength relative to pure PLA (from 58.60 MPa to 17.07 MPa), while tensile strength decreased by 46.1% at just 10 wt% HA (from 37.54 MPa to 20.23 MPa). Although the triangular lattice achieved the highest absolute compressive load, the rectangular lattice provided a superior load-to-weight ratio and greater plastic deformation capacity before fracture. Consequently, these findings indicate that the rectangular pattern at 70% infill density combined with HA addition limited to ≤10 wt% represents the most mechanically balanced design for bone defect repair applications. Based on the mechanical characterization performed in this study, and drawing on published evidence regarding the biological properties of PLA/HA composites, these scaffolds represent a mechanically promising candidate for further evaluation in bone tissue regeneration. Biological validation through in vitro and in vivo studies is required before clinical relevance can be established. Full article

Understanding the anisotropy in the physical and mechanical properties of layered rocks is essential for predicting and preventing instability in layered rock masses. However, in-situ sampling is often hindered by the difficulty of obtaining specimens with controlled bedding orientations. Cement-based 3D printing (3DP) offers an efficient approach for fabricating rock analogues, yet the inherent anisotropy induced by the layer-by-layer deposition process has not been well characterized, hindering its broader application. The objectives of this study are (i) to systematically evaluate the intrinsic anisotropy of cement-based 3DP rocks and (ii) to compare the mechanical anisotropy and failure modes of 3DP layered rocks with those of natural layered sandstone. The key findings are as follows: (1) The uniaxial compressive strength (UCS), P-wave velocity, and computed tomography (CT) number of the 3DP rock vary by less than 6% among the X-, Y-, and Z-directions, indicating lower intrinsic anisotropy compared to typical sandstones and several other natural rocks. (2) The UCS, elastic modulus, and secant modulus of the 3DP layered rocks all decrease initially and then increase with bedding dip angle, reaching a minimum at 60°. (3) The main fracture characteristics of the 3DP layered rocks are similar to those of layered sandstone; notably, the 3DP layered soft rock exhibits the most pronounced shear failure features. This study quantifies the low intrinsic anisotropy of cement-based 3DP rocks and validates their similarity to natural layered sandstone in both mechanical anisotropy and failure modes. It thereby provides a reliable, reproducible basis for physical modeling of layered rock masses using 3DP, offering a new approach for laboratory-scale investigations of layered rocks. Full article

Background: Endovascular aortic aneurysm repair (EVAR) is considered the gold standard for the treatment of abdominal aortic aneurysms. However, the performance of stent-grafts used during this procedure may be affected by their structural design, particularly in anatomically challenging, tortuous iliac arteries. This study aimed to evaluate the hemodynamic performance of different stent-graft limb designs in an in vitro EVAR simulation using compliant three-dimensional (3D)-printed iliac artery models with controlled angulations. Methods: Four commercially available stent-grafts (Anaconda^®, Endurant II^®, Treo^®, Zenith Spiral-Z^®) representing different stent-strut configurations (including O-ring, Z-stent, and spiral designs) were deployed in compliant 3D-printed vascular phantoms simulating severe iliac angulations of 75°, 90°, and 105°. The models were incorporated into a pulsatile flow circuit, and pressure and flow velocity were measured proximally and distally to the angulated segment. Results: Across all tested angulations, the O-ring-based design demonstrated the most favorable hemodynamic performance. In particular, the Anaconda stent-graft showed the smallest pressure loss and the lowest increase in distal flow velocity, especially in the 90° and 105° models. These findings suggest that O-ring-supported structures provide greater flexibility and conformability in severely angulated iliac segments. Conclusions: In this controlled in vitro setting, stent-grafts with O-ring strut morphology better preserved flow conditions than other tested configurations in tortuous anatomy. These results suggest that stent-graft structural design may influence device behavior in challenging iliac anatomy under controlled in vitro conditions. These findings should be considered hypothesis-generating bench data and do not represent direct evidence for clinical device selection. Full article

Introduction: Simulation-based training is a key component of surgical education; however, existing models, such as dry-laboratory and virtual reality simulators, have limitations in terms of realism and accessibility. The use of human cadaveric material is also challenging because of its high cost and limited availability. Objectives: To evaluate the effectiveness of biological models based on large animal cadaveric material, specifically cattle and pigs, for practicing head and neck surgical skills. Materials and Methods: The study included 100 third- and fourth-year students, who were divided into a study group and a comparison group, with 50 participants in each group. The study group practiced surgical skills using animal cadaveric material: a porcine mandible for bone graft harvesting and a bovine head for resection craniotomy. The comparison group practiced using 3D-printed models. The results were assessed using an anonymous 8-item Likert-scale questionnaire, followed by statistical analysis using the Mann–Whitney U test. Results: In the study group, statistically significant increases were observed in satisfaction with participation, fulfillment of expectations, perceived subjective acquisition of manual skills, and overall satisfaction with the training process (p < 0.001; median scores: 38.0 and 34.0, respectively). The greatest differences were observed in satisfaction with participation, where 54% of participants rated it as “Excellent” compared with 6% in the comparison group, and in perceived subjective acquisition of manual skills, reported by 80% of participants in the study group compared with 24% in the comparison group. Conclusions. The use of cadaveric specimens from large animals is associated with higher satisfaction and represents an accessible alternative for practicing basic and commonly performed head and neck surgical procedures that do not require fine dissection of neurovascular bundles. This model provides a high degree of tactile realism and anatomical context and is subjectively preferred over non-anthropomorphic simulators. Full article

The use of parts made of polymeric materials has occasionally highlighted the need for them to possess the best possible mechanical properties. One of the currently widely used processes for manufacturing parts from polymeric materials is fused deposition modeling. This process allows for variations in the magnitudes defining the mechanical properties of polymeric materials to be obtained through an appropriate selection of the process input factor values. The analysis of the process has highlighted the primary factors capable of affecting the values of parameters corresponding to the mechanical properties of polymeric materials. The opinions formulated by various researchers regarding the influence of fused deposition modeling application conditions on some of the mechanical properties of polymeric materials have been synthetically and systematically presented. In terms of mechanical properties, tensile strength, compression strength, elongation at break, flexural strength, torsional strength, impact strength, fatigue resistance, and hardness were taken into consideration. Some modeling and optimization solutions for the influence exerted by the 3D printing process input factors on the values of the parameters defining the mechanical properties of polymeric materials in parts manufactured via the FDM process were also highlighted. Full article

Additive manufacturing (AM) techniques are becoming key factors for repairing and replacing damaged bone. These techniques enable the customization of implants, which can be tailored to the specific area to be treated or healed. Additionally, the combination of absorbable and osteoconductive biomaterials with 3D printing could eliminate second surgeries to remove implants, which is particularly relevant in pediatric and geriatric patients. The capabilities of AM in this context affect not only the external shape but also the internal microarchitecture, where the arrangement of struts to develop complex infills enhances relevant properties such as specific strength, degradation rate, and vascularization. In this study, auxetic scaffold structures made of both polylactic acid (PLA) and a PLA-hydroxyapatite (PLA-HA) composite with 40 wt% of hydroxyapatite (HA) are designed and produced using Fused Filament Fabrication (FFF). Samples of PLA and PLA-HA were 3D printed in dense samples and with auxetic infills. In dense samples, the characterization is performed by X-ray diffraction (XRD), Raman spectroscopy, wettability tests, nanoindentation, and tribological assessments. Two auxetic cellular models have been tested after degradation in PBS media, and their microstructural, structural, and mechanical properties are analyzed. Results show that the addition of hydroxyapatite (HA) significantly improves the hydrophilicity of the PLA matrix, as evidenced by a decrease in water contact angle from 73.4 ± 4.4° to 52.6 ± 2.8° (≈28% reduction), while also enhancing its mechanical and tribological properties, with hardness increasing from 207 ± 30 MPa to 241 ± 28 MPa (≈15%) and Young’s modulus from 4.08 ± 0.55 GPa to 6.24 ± 0.61 GPa (≈53%). Additionally, biodegradation of PLA-HA composites reveals a significant reduction in mechanical properties after 15 days, while the auxetic re-entrant structures mostly retain their shape during compression testing. Full article

Electrical monitoring of brain activity can be performed discreetly and continuously over long periods of time using intra-auricular electroencephalography (intra-auricular EEG), a promising technique suitable for subjects who are difficult to monitor, such as newborns or patients with neurological conditions requiring discreet but long-term neurophysiological assessment. The concept of intra-aural EEG can be realized through the development of systems that include wearable sensors, whose performance critically depends on the development of biocompatible electrode materials that exhibit low impedance and can maintain and provide stable contact between the electrode and the epithelial tissue. Based on our previous work on carbon nanotube (CNT)-based hydrogel composites for intra-aural EEG electrodes, this study focuses on the electrochemical characterization of hydrogels initially prepared from gelatin methacrylate (GelMA)/2-hydroxyethyl methacrylate (HEMA) doped with varying concentrations of CNTs (0–3 wt%). In the present study, the materials obtained in the first stage were evaluated using electrochemical impedance spectroscopy (EIS) under both liquid and dry conditions, supplemented by measurements of hydration capacity. The results show that the composite with 3% CNT content exhibits suitable properties, making the material making the 3 wt% CNT formulation a promising platform for the further development of 3D-printable hydrogel electrodes for intra-aural EEG applications. Equivalent circuit modeling reveals improved ionic and electronic conductivity compared to the undoped hydrogel, attributed to better CNT dispersion and polymer crosslinking. This work provides insights into the structure–property relationships of CNT–hydrogel composites and lays the foundation for the further development of a 3D-printed and in vitro/in vivo validated prototype of intra-aural EEG sensors. Full article

Unsupported and weakly supported overhang features remain a critical challenge in laser powder bed fusion (LPBF) due to their strong susceptibility to geometric degradation, residual stress accumulation, and part distortion. In this study, bridge-shaped structures with four different arch sizes are fabricated to systematically investigate geometry-dependent macroscopic forming quality, stress evolution, and distortion behavior. Experimental results show that increasing arch size leads to progressive thickness reduction at the arch bottom and eventual overhang closure loss, indicating a monotonic deterioration in geometric fidelity. A thermo-mechanically coupled finite element model is developed and calibrated using 3D scanning measurements of warpage, achieving a maximum deviation below 0.03 mm between predicted and measured displacements. Numerical analyses reveal that larger arch sizes promote local heat accumulation and reduced cooling rates beneath the arch, which reduce the instantaneous load-bearing capacity of the material and increase its susceptibility to downward deformation. Meanwhile, arch size significantly influences the establishment of structural continuity and stress transfer during printing; incomplete closure in large arches interrupts load-bearing paths and alters stress redistribution at intermediate stages, whereas similar stress evolution trends are observed once geometric continuity is achieved. These findings demonstrate that arch closure acts as a key structural transition controlling stress transmission and distortion development during LPBF, thereby providing mechanistic insight into geometry-induced defects and offering quantitative guidance for the design of unsupported features in additively manufactured components. Full article

Quantitative characterization of internal stress fields in fracture-dominated geological materials remains a significant challenge due to the limitations of conventional measurement techniques. This study presents the first quantitative full-field stress analysis of slightly sandy dolomite (Level I sandification) using an enhanced CT-3D printing–photoelasticity workflow. Five transparent physical models were fabricated from CT-scanned dolomite specimens to replicate the natural fracture-matrix structure and tested under diametrical compression (800 N) using ten-step phase-shifting digital photoelasticity. To overcome the severe optical noise generated by dense fracture networks, a robust phase unwrapping procedure (CPULSI) was incorporated into the data processing pipeline, enabling continuous stress parameter retrieval where conventional unwrapping methods fail. The recovered full-field principal stress-difference maps reveal that the internal stress field is dominated by meso-scale fracture geometry: Stress concentrations localize at fracture tips and narrow intact matrix bridges, reaching 3–5 times the far-field stress, while the macro-scale loading pattern becomes progressively obscured as fracture complexity increases across the five models. Quantitative validation against CT-based finite element simulations (RFPA-3D) demonstrates good agreement in intact matrix regions, with mean relative errors of 9–18%. These results provide new experimental evidence for the meso-scale stress distribution mechanisms governing the mechanical behavior of sandy dolomite—a geomaterial of significant engineering relevance in Southwest China—and establish a validated experimental pathway for investigating stress fields in other fracture-dominated geomaterials. Full article

Background: Objective performance assessment is essential in surgical skill training, yet current methods are labor-intensive and focus on observing the trainee rather than the end-product of the procedure. Machine learning (ML) methods offer reproducible feedback but have mainly relied on kinematic or video data, often reducing assessment to binary or ternary classification. Our objective was to compare ML regression models predicting expert-assigned scores of vascular anastomoses from computational fluid dynamics (CFD) features of the final product. Additionally, we aimed to assess biomechanical plausibility of predictions. Methods: A total of 146 participants performed 419 end-to-side anastomoses on case-specific three-dimensional (3D) printed simulators. Anastomoses were digitized via 3D scanning, ranked by experts, and characterized using CFD-derived hemodynamic features. These served as input for linear models (Ridge, Partial Least Squares), support vector machines, and tree-based ensembles (Random Forest, Extremely Randomized Trees, and Extreme Gradient Boosting [XGBoost]), evaluated using 10-fold nested cross-validation with genetic hyperparameter optimization. Results: Inter-rater reliability of expert indicated strong agreement (intraclass correlation coefficient ICC3k = 0.846). XGBoost achieved the lowest mean root mean squared error of 0.758 (95% bootstrap CI: 0.722–0.799) and a coefficient of determination (R²) of 0.673 (0.617–0.725), with the most stable performance across folds. Shapley additive explanations (SHAP) identified the wall shear stress gradient, transverse wall shear stress, and maximum pressure as the most influential features—variables associated with intimal hyperplasia and atherosclerotic remodeling. Conclusions: Tree-based ensemble methods, particularly XGBoost, effectively modeled biomechanical properties against expert scores. Combining CFD and ML can provide reproducible, mechanistically relevant feedback in vascular surgical skill training. Full article

3D printed concrete technology has demonstrated great potential in transforming construction methods, improving efficiency, and reducing environmental impacts. However, the current quality control and identification of 3D printed concrete mainly rely on manual experience and traditional non-real-time measurements, enabling the printed quality to face major challenges. Although an increasing number of studies have investigated automated quality monitoring and defect detection in 3D printed concrete, a dedicated review that systematically synthesizes these methods is still lacking. This paper provides a comprehensive review of automated quality monitoring methods for 3D printed concrete, focusing on current techniques, challenges, and future applications. Optical image processing and machine learning have been successfully used to detect defects in 3D printed concrete, although these methods have limitations in real-time performance, automation, and data quality. Further, deep learning-based methods have shown great potential in improving the accuracy and automation of defect detection, although data annotation, model generalization, large-scale construction projects, and real-time integration still face challenges. Finally, the integration of quality monitoring with building information modeling and further developments in multi-source data fusion, data augmentation, real-time adaptive control, and active quality control are recommended to address current challenges. Full article

Aim: This literature review presents the biological evaluation of light-curing 3D printing materials containing methacrylic and acrylic resin in dentistry. The sample was 42 articles published between 2008 and 2025, available on PubMed, Scopus, Cochrane, and Google Scholar. The articles were analyzed following the assessment requirements of ISO 10993-2018 (Endpoint) regarding the biological evaluation of each Medical Device. The first selection criterion of the articles was based on the PRISMA schema, concerned with the application of these materials in various fields of dentistry used in 3D printing (e.g., material for crowns and bridges, night, and surgical guide, orthodontic, and denture base). The second criterion included the composition of materials (e.g., catalysts, methacrylic resins, and stabilizers) and the post-curing process. Results: The topics discussed in the literature included: (a) estrogenic interactions, sensitization, and the zebra fish model to determine acute toxicity; (b) the main post-processes affecting biocompatibility, i.e., alcohol washing and polymerization in light ovens; and (c) the modification of 3D resins using various types of nanomaterials. Conclusions: 3D resins can be used safely in dentistry to make various types of restorations, provided that the polymerization, washing with alcohol and post-polymerization in a light oven follow the manufacturer’s specifications. Full article