Search Results (294)

The purpose of this in vitro study was to evaluate the mechanical performance, dimensional accuracy, and bonding behavior of fused filament fabrication (FFF)-printed provisional restorations made from polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET), and compare them with digital light processing (DLP)-printed and computer-aided numerical control (CNC)-milled ones. Occlusal veneers (OV), posterior crowns (PC), and anterior crowns (AC) (n = 30) were fabricated using FFF (PMMA, PET), DLP (acrylate), and CNC (PMMA) to assess initial fracture load (IFL). To determine reproducibility three restorations of each group were scanned and compared with each other; to determine printing accuracy the scanned restorations were compared with the STL generated for manufacturing. For shear bond strength (SBS) testing, 72 PMMA (FFF) specimens were conditioned with either Monobond Plus (MP) or Visiolink (VL) and bonded with acrylic cylinders using a dual-cure luting composite (Variolink Esthetic DC). Half of each group underwent thermocycling (10,000 cycles, 5 °C/55 °C, 30 s dwell time); the remainder was tested initially. Additionally, 48 FFF-printed PC were fabricated from PET and PMMA to investigate the fracture load in relation to the adhesive material (FL). PMMA crowns were conditioned with MP (n = 16) or VL (n = 16) and bonded with Variolink Esthetic DC. PET crowns were cemented with either Meron (ME) or Ketac Cem Plus (KE). Half of the PMMA and all PET crowns were subjected to masticatory simulation (1,200,000 cycles, 5 N, 5 °C/55 °C, 60 s dwell). Data were analyzed using Kolmogorov–Smirnov, Kruskal–Wallis, and Mann–Whitney U tests, including IFL, SBS and FL parametric tests, and comparisons were carried out using an independent t-test ($\alpha$ = 0.05). FFF-fabricated restorations showed the lowest fracture load values and CNC-fabricated the highest (p < 0.001). OV fabricated via DLP and CNC exhibited the highest fracture load (p < 0.001). For FFF, PC demonstrated the highest values (p < 0.028), whereas AC showed the lowest fracture load values (p < 0.001). VL showed higher initial SBS than MP (p < 0.001) and no impact on aging (p < 0.608). All MP samples showed debonding after thermocycling. Within PET and PMMA, no impact of luting/cement material on fracture load was observed (p = 0.116–0.282). The fracture load decreased after masticatory simulation (MP-PMMA: p < 0.001, VL-PMMA: p = 0.27). DLP-fabricated restorations showed the highest reproducibility and printing accuracy. CNC and FFF-PET showed comparable values. FFF-PMMA showed the greatest deviations. CNC-fabricated provisional restorations exhibited the highest fracture load. AC presented the lowest fracture load values. DLP provided the highest reproducibility and accuracy. VL achieved superior bonding to PMMA surfaces. Thermomechanical aging significantly reduced fracture load in both PET and PMMA restorations, regardless of luting material. Full article

The increasing prevalence of cardiovascular diseases highlights the need to develop vascular grafts that match the mechanics of native vascular tissue and offer functional adaptability. This study reports the development and systematic optimization of a shape-memory polyurethane acrylate (PUA)-based photocurable resin for digital light processing (DLP)-based four-dimensional printing (4DP) applications. Resin formulations were designed by controlling hard/soft segment ratios, reactive diluent content, and crosslink density to position the glass transition temperature (T_g) within the physiological range (25–40 °C). Thermomechanical characterization was performed via dynamic mechanical analysis (DMA) and tensile testing, while a full-factorial Design of Experiments (DoE) approach was applied to optimize DLP process parameters—namely layer thickness, exposure time, and post-curing time. The developed resin formulation yielded a T_g of 38 °C as determined by DMA. Following process optimization, regression models showed high statistical fit (R² > 99%), and experimental validation under optimal conditions (layer thickness: 82.83 µm, exposure time: 11 s, post-curing: 2 min) resulted in an elongation at break of 64.0 ± 3.4%, a Young’s modulus of 10.9 ± 0.1 MPa, and a tensile strength of 6.2 ± 0.3 MPa. The optimized system exhibited thermally triggerable shape memory behavior at near-body temperature, with mechanical properties consistent with natural arterial tissue benchmarks. These findings demonstrate a promising material design strategy for DLP-based 4D-printed vascular structures. Full article

Post-processing remains a major bottleneck in the fabrication of microfluidic devices using Digital Light Processing Stereolithography (DLP-SLA) 3D printing, where unpolymerized resin trapped within internal structures must be removed without damaging delicate features such as thin membranes, valves, and pumps. Manual flushing is slow, inconsistent, and prone to structural failure, especially as device complexity and port counts increase. Here, we present the first fully automated flushing system for DLP-SLA microfluidic devices, enabled by a standardized chip-to-chip (C2C) interconnect architecture and an electronically controlled pneumatic routing platform. A reusable 32-port flushing interface chip provides alignment, sealing, and modular coupling to arbitrary device chips through integrated microgaskets, while a network of electronic pressure controllers, differential pressure sensors, and multi-port rotary valves enable precise, programmable application of pressure, vacuum, and solvent conditions. We introduce a fluidic-circuit model of the system that relates applied pressure to the pressure drop across device structures and experimentally validate this model using channels with varying fluidic resistances. Using this platform, we demonstrate robust flushing of both passive (straight and serpentine channels) and active (valves, pumps) microfluidic elements, as well as application-specific devices including mixers and concentration-gradient generators. Our system eliminates manual handling, improves valve membrane survival, and provides repeatable flushing across a broad range of device geometries. This work establishes a scalable foundation for automated post-processing in 3D-printed microfluidics and significantly advances the practicality of DLP-SLA fabrication for complex, multi-layered microfluidic devices. Full article

The development of filled photopolymer composites for Digital Light Processing (DLP) additive manufacturing requires optimizing processing parameters to achieve the desired mechanical properties. Traditional experimental approaches are time-intensive, while physics-based models often struggle to capture the complex interactions among parameters. This study presents a physics-informed machine learning framework that combines Random Forest with Bayesian optimization (RF-BO) to predict the ultimate tensile strength in recycled thermoset resin composites manufactured via DLP. A validation dataset of 19 systematically varied formulations (each with n = 5 measurement replicates for reliability) was generated and augmented with 1500 physics-informed synthetic samples to enable robust model training. The limited experimental dataset, while insufficient for traditional statistical inference, provided critical validation of physical trends, including non-monotonic particle-size effects and optimal processing windows. Six machine learning algorithms were evaluated, with RF-BO achieving superior performance (R² = 0.9125, MSE = 1.07 MPa). The framework identified optimal processing conditions of 59–64 μm particle size, 5.0 ± 0.5 wt.% concentration, and 60 min cure time, predicting a maximum UTS of 43.84 MPa with a prediction error of less than 1.0 MPa. Feature importance analysis revealed that cure time was the dominant parameter (40%), followed by particle size (30%), validating the physical interpretability. This approach demonstrates significant potential for accelerating materials design in composite additive manufacturing while maintaining physically meaningful predictions. Full article

Additive manufacturing enables the fabrication of patient-specific zirconia devices with integrated surface features; however, the biological effects of meso-scale topographies remain insufficiently understood. This in vitro study evaluated the influence of defined meso-scale surface modifications on osteoblast behavior using Digital Light Processing (DLP)-fabricated 3Y tetragonal zirconia polycrystal (3Y-TZP) and 5Y partially stabilized zirconia (5Y-PSZ). Planar control specimens and surfaces incorporating regularly distributed columnar structures (height: 100 µm; width: 40 µm; center-to-center spacing: 80, 120, and 160 µm; Mod-80, Mod-120, Mod-160) were fabricated and characterized after sintering. Cytotoxicity was assessed by elution testing and showed cell viability >98% for all groups. Osteoblast adhesion and proliferation (hFOB 1.19) were quantified using metabolic assays. Meso-scale modifications significantly increased early cell adhesion compared to planar controls (p < 0.05), with the strongest effect observed for Mod-160. No significant differences in proliferation rates were detected between groups (p > 0.05). Osteogenic differentiation was evaluated by RT-qPCR (RUNX2, ALPL, COL1A1, BGLAP), revealing material- and geometry-dependent responses. On 3Y-TZP, meso-scale structures, particularly Mod-160, were associated with sustained upregulation of BGLAP, whereas 5Y-PSZ exhibited less pronounced effects. Within the limitations of this in vitro study, meso-scale surface structuring of additively manufactured zirconia enhances early osteoblast adhesion without affecting proliferation and may influence osteogenic differentiation in a material-dependent manner. Full article

3D printing represents a promising fabrication technology for silica-based ceramic cores, which are essential components in the casting of turbine blades, but it is faced with poor high-temperature dimensional stability. Herein, alumina nanopowder was utilized as a modifier agent in digital light processing (DLP) 3D printing of silica-based ceramic cores, and systematic investigations were conducted on the microstructure and properties of ceramic cores throughout sintering and casting dependent on the content of alumina nanopowder (0–1.0 wt.%). Alumina nanopowder increased the sintering barrier of fused silica, significantly reducing the shrinkage in sintering and simulated casting, while improving high-temperature dimensional stability. Even though the alumina nanopowder led to decreased room-temperature and high-temperature flexural strengths attributed to inhibited densification and crystallization, the strengths met investment casting requirements after PVA solution strengthening. Excessive alumina nanopowder (0.8–1.0 wt.%) resulted in poor interlayer bonding and particle spalling, unfavorable to the structural integrity in casting. The optimal alumina content was 0.6 wt.%, which balanced sintering shrinkage of 1.86%, shrinkage of 4.41% after simulated casting, room-temperature flexural strength of 11.13 MPa, high-temperature flexural strength of 31.29 MPa, high-temperature creep deformation of 0.55 mm, and surface roughness of 1.815 μm. This research proposes an effective strategy for the optimization of 3D-printed silica-based ceramic cores in the manufacture of complex hollow turbine blades. Full article

Three-dimensional (3D) printing, also known as additive manufacturing (AM), has become increasingly integrated into dentistry because of its high precision, efficiency, and ability to fabricate patient-specific devices. This review comprehensively discusses the historical development of 3D printing and outlines the fundamental principles of the most widely used technologies in dentistry, including stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD). These technologies enable the accurate and efficient fabrication of dental models, crowns, bridges, dentures, surgical guides, orthodontic appliances, and tissue engineering scaffolds. Current clinical applications are systematically summarized across major dental disciplines, including prosthodontics, orthodontics, oral and maxillofacial surgery, endodontics, periodontics, and pediatric dentistry. Despite existing challenges, such as limited long-term clinical data for certain materials, high initial equipment costs, and post-processing requirements, 3D printing offers substantial advantages in terms of customization, workflow efficiency, and clinical predictability of the final product. Future developments in advanced biomaterials, artificial intelligence-assisted workflows, bioprinting, and four-dimensional (4D) printing are expected to further expand the role of additive manufacturing in personalized and regenerative dentistry. Full article

The increasing adoption of digital light processing (DLP) three-dimensional (3D) printing in prosthodontics has enabled the rapid fabrication of denture bases with improved dimensional accuracy and reproducibility. However, the mechanical performance and surface characteristics of 3D-printed denture base resins remain inferior to those of conventional heat-polymerized polymethyl methacrylate (PMMA), limiting their long-term clinical reliability. This study aimed to investigate the effect of incorporating zinc oxide (ZnO) and samarium oxide (Sm₂O₃) nanoparticles, individually and as hybrid nanofiller systems, on the mechanical and wettability properties of a DLP 3D-printed denture base resin. ZnO and Sm₂O₃ nanoparticles were incorporated into a photopolymerizable denture base resin at concentrations of 1 and 2 wt.%, producing seven experimental formulations, including a control group. A total of 280 specimens were fabricated using a DLP 3D printer and subjected to standardized post-processing. Nanoparticle dispersion and morphology were examined using field-emission scanning electron microscopy (FE-SEM), while Fourier-transform infrared spectroscopy (FTIR) was employed to assess possible chemical interactions between the nanofillers and the polymer matrix. Mechanical performance was evaluated through impact strength, transverse strength, and flexural strength tests, and surface wettability was assessed using static water contact angle measurements. Statistical analysis was conducted using one-way ANOVA followed by Tukey’s post hoc test (α = 0.05). The results demonstrated that all nanoparticle-reinforced groups exhibited significantly enhanced mechanical properties compared with the unmodified control resin. The incorporation of 1 wt.% nanofillers yielded the most pronounced improvements, with the 1 wt.% ZnO group achieving the highest transverse strength and the 1 wt.% ZnO–Sm₂O₃ hybrid group exhibiting the maximum flexural strength. Increasing the nanofiller concentration to 2 wt.% resulted in partial reductions in impact and flexural strength, which were attributed to nanoparticle agglomeration and increased light scattering during photopolymerization. FTIR analysis revealed no evidence of chemical bonding between the resin matrix and the nanofillers, indicating that the observed enhancements were primarily governed by physical reinforcement mechanisms. Wettability analysis showed that Sm₂O₃-containing formulations significantly reduced the water contact angle, indicating increased surface hydrophilicity, whereas ZnO incorporation produced more hydrophobic surfaces. Within the limitations of this in vitro study, the findings suggest that low-concentration incorporation of ZnO and Sm₂O₃ nanoparticles represents an effective strategy to enhance the mechanical integrity and tailor the surface properties of DLP 3D-printed denture base resins. These results suggest potential clinical relevance of nanoparticle-reinforced printed denture bases, emphasizing the importance of optimized filler loading to avoid agglomeration-induced performance degradation. Full article

This study aimed to develop dissolving microneedles (MNs) for the buccal delivery of cannabidiol (CBD). CBD is a non-psychotomimetic phytocannabinoid with anti-inflammatory and anxiolytic properties. The MN arrays were produced using micromolding, which has the ability of scalability. However, this approach lacks the ability to customize needle geometry; thus, additive manufacturing was implemented in the study. Digital Light Processing (DLP) printing is a promising way to produce molds with customized MN architecture. In the present study, molds were fabricated from 3D-printed MN arrays to prepare dissolving MNs for buccal administration. Polymeric needles based on Eudragit L100-55 and Eudragit RSPO were produced from reverse molds and they were evaluated regarding their physiochemical and mechanical properties, followed by in vitro and ex vivo studies using porcine buccal mucosa. Visualization studies were conducted using confocal scanning laser microscopy, whereas the membrane integrity of the porcine mucosa upon application of the MNs was assessed by histological evaluation. Our results suggest that the needles can be effectively inserted into the buccal tissue and release the active pharmaceutical ingredient (API) in a controlled manner. This approach offers a patient-friendly alternative to oral CBD delivery, bypassing first-pass metabolism. Full article

Dimensional accuracy of 3D-printed implant models is essential for precise implant-supported restorations. The objective of this study was to evaluate the influence of printing orientation and model base design on the accuracy of implant position transfer. A standardized maxillary model with four implants was scanned using an intraoral scanner. Solid and hollow models were designed and printed using digital light processing (DLP) technology at orientations of 0°, 45°, and 90° (n = 10 per group). All models were digitized with a high-precision industrial scanner, and implant position deviations were determined by comparing corresponding reference points with the master model. Data were analyzed using two-way analysis of variance and post hoc tests (α = 0.05). Printing orientation significantly affected accuracy (p < 0.001). Models printed at 45° showed the highest deviations, whereas those printed at 0° and 90° exhibited comparable and superior accuracy. Model design (solid vs. hollow) had no significant influence at 0° and 90°, but hollow models were more accurate at 45° (p < 0.001). Mean deviations ranged from 131 μm to 382 μm. Printing at 0° or 90° is recommended, while 45° orientations should be avoided. Model design showed minimal effect on accuracy. Full article

Digital Light Processing (DLP), which operates through a layer-by-layer deposition, has proven to be a promising technique for obtaining complex and customized architectures. However, there are still numerous unresolved challenges in ceramics additive manufacturing, among which is delamination due to suboptimal adhesion between the layers, which threatens the structural integrity and properties of samples. According to recent findings, excess surface hydroxyl groups were identified as being responsible for this defect; a suitable calcination pre-treatment of the ceramic powder could be effective in significantly mitigating delamination flaws in mullite DLP printed bodies. Therefore, in addition to optimizing the printable slurry formulation and printing parameters (mainly in terms of curing energy and layer resolution), this work aimed at investigating the influence of the calcination of a commercial mullite powder (added with magnesium nitrate hexahydrate, as a precursor of the sintering aid MgO) as a simple and effective treatment to additively shape ceramic bodies with limited flaws and enhanced density. The surface characteristics evolution of the mullite powder was investigated, specifically comparing samples after magnesium nitrate hexahydrate addition and ball-milling in water (labeled as BM), and after an additional calcination (BMC). In particular, the effect of the superficial -OH groups detected by FTIR analysis in the BM powder, but not in the BMC sample, was studied and correlated to the properties of the respective ceramic slurry in terms of rheological behavior and curing depth. The hydrophilicity of BM powders, due to superficial hydroxyls groups, affects ceramic powder dispersion and wettability by the resin, causing a weak interface. At the same time, it promotes photopolymerization of the light-sensitive resin, thus inducing the as-printed matrix embrittlement. Anyhow, its photopolymerization degree, equal to 67% and 55% for BM and BMC, respectively, was enough to guarantee the printability of both slurries. However, the use of BMC significantly reduced flaw occurrence in the as-printed bodies and the final density of the samples sintered at 1450 °C (without an isothermal step) was increased (approx. 60% and 50% of the theoretical value for BMC and BM, respectively). Thus, the target porosity of the ceramic bodies was guaranteed, and their structural integrity achieved without any increase in sintering temperature but with a simple powder treatment. Full article

This in vitro study aimed to evaluate the effects of resin type, layer thickness, and printing orientation on the surface and mechanical properties of 3D-printed occlusal splints fabricated using digital light processing (DLP) technology. Three commercially available splint resins (KeySplint Hard, Freeprint Splint 2.0, and V-Print Splint) were used to fabricate 180 rectangular specimens with two-layer thicknesses (50 µm and 100 µm) and three printing orientations (0°, 45°, 90°). Surface roughness (Ra, Rz), gloss, microhardness, flexural strength, and elastic modulus were measured. Statistical analysis was performed using robust ANOVA with Bonferroni correction. Resin type and printing orientation significantly influenced all surface and mechanical properties (p < 0.001), while layer thickness had a limited effect. Keystone resin exhibited the smoothest surface and highest gloss, whereas Freeprint resin showed the highest microhardness and elastic modulus. Printing at 45° generally enhanced flexural strength and provided more balanced mechanical performance. SEM analysis confirmed that surface morphology varied with orientation, correlating with profilometric and gloss measurements. Resin composition and printing orientation are critical determinants of the mechanical and surface performance of 3D-printed occlusal splints. Optimizing these parameters can improve durability, esthetics, and clinical functionality. All tested materials achieved clinically acceptable surface smoothness, supporting their suitability for intraoral use. Full article

This work explores the mechanical responses of 3D-printed periodic arch-inspired structures (PASs) and PASs doped with NdFeB powder to advance their application in lightweight structural load-bearing and future structure–function integration. Three PAS configurations were fabricated via digital light processing (DLP), and magnetic PASs (MPASs) were produced by dispersing NdFeB powder (1–3 g/200 mL) into photosensitive resin. Under quasi-static compression, key mechanical properties—Young’s modulus (E), yield strength (σ_y), and compressive strength (σ_c)—of non-magnetic PASs increase linearly with relative density (ρ* = 0.18–0.48): for PAS22, E rises from 68.1 to 200.3 MPa (+194%), σ_y from 2.18 to 6.75 MPa (+210%), and σ_c from 2.98 to 9.07 MPa (+204%). Under dynamic impact (~100 s⁻¹), mechanical enhancement is even more pronounced: E of PAS22 surges to 814.8 MPa (3.2× higher than quasi-static), and σ_c reaches 11.54 MPa. Finite element simulations reveal that the Ideal Plastic Model best predicts quasi-static brittle fracture, whereas the Hardening Function Model captures dynamic behavior most accurately. Stress and plastic strain concentrate at the straight–arc junctions—identified as critical weak points. MPASs exhibit higher stiffness and yield strength (e.g., E of MPAS22 up to 896.5 MPa under impact) but lower compressive strength (e.g., 11.01 MPa vs. 11.54 MPa for NMPAS22), attributed to NdFeB-induced brittleness that shifts the failure mode from “local damage accumulation” to “rapid overall failure”. This study establishes quantitative doping–structure–property correlations, providing design guidelines for next-generation functional arch-inspired metamaterials toward magnetically responsive, load-bearing applications. Full article

Background/Objectives: The purpose of this in vitro study is to evaluate the effect varying palatal vault depths have on the accuracy of complete maxillary denture bases fabricated using additive manufacturing technology. Methods: One hundred complete maxillary denture bases were manufactured on two different digital light processing (DLP) dental 3D printers at five different palatal depths. After manufacturing, the denture bases were post-cured, scanned, and then analyzed in metrology software. Statistically significant differences were determined using two-way ANOVA tests for normally distributed data and the Kruskal–Wallis test for non-normally distributed data. Color deviation maps were used to give clinical relevance to the results. Results: Significant differences were found for both printers among some groups for the different palatal depths. In relation to the negative mean deviation, the data revealed that the NextDent printers were the least accurate (0.047 ± 0.004) in the group with the deepest palate. The positive mean deviation revealed the most deviation (0.077 ± 0.009) in the group with the deepest palate, which was also mirrored in the Asiga printer (0.050 ± 0.002). The color deviation maps revealed areas of positive and negative average deviation in all groups. The effect of the printer model (p = 0.007) and palatal depth (p = 0.04) on negative average deviation was significant. The effect of the interaction of printer and palatal depth was also significant (p = 0.001). Conclusion: Deeper palatal vaults are associated with higher deviation in DLP 3D-printed complete maxillary denture bases manufactured through additive manufacturing. Full article

Shape memory polymers (SMPs) represent an innovative class of materials that possess programmed, reversible shape-changing capabilities in response to external stimuli. The recent emergence of SMPs’ advanced manufacturing, specifically 4D printing, has created exceptional opportunities for use in biomedical engineering. This review presents a critical synthesis of the latest advances in the chemistry, biomedical applications, manufacturing strategies, and clinical translation of SMPs, highlighting vat photopolymerization techniques, such as stereolithography (SLA) and digital light processing (DLP). Notably, 4D-printed SMPs can promote spatiotemporally controlled architectures, and applications include minimally invasive implants, dynamic tissue scaffolds, and multifunctional drug delivery. This paper focuses on recent advances in resin design, multi-responsive and nanocomposite resins, AI-guided material discovery, and emerging biocompatible and biodegradable formulations, while outlining current roadblocks to clinical implementation, including cytotoxicity, sterilization, regulatory compliance, and device shelf-life. Our goal is to elucidate the relationship between material design, processing, and biomedical performance to inform researchers of potential future directions for 4D-printed SMPs and next-generation, patient-centered medical devices. Full article