Search Results (188)

This study aimed to develop experimental filler-reinforced resin composites for vat-photopolymerization 3D printing and to evaluate the effects of filler addition on their mechanical, physicochemical, and bonding properties for dental restorative applications. Silanized nano- and/or micro-fillers were incorporated into acrylic resin monomers to formulate photocurable resins suitable for vat-photopolymerization. The rheological behavior of these liquid-state resins was assessed through viscosity measurements. Printed resin composites were fabricated and characterized for mechanical properties—including flexural strength, flexural modulus, and Vickers hardness—both before and after 8 weeks of water immersion. Physicochemical properties, such as water sorption, water solubility, and degree of conversion, were also evaluated. Additionally, shear bond strength to a resin-based luting agent was measured before and after artificial aging via thermocycling. A commercial dental CAD-CAM resin composite served as a reference material. Filler incorporation significantly improved the mechanical properties of the printed composites. The highest performance was observed in the composite containing 60 wt% micro-fillers, with a flexural strength of 168 ± 10 MPa, flexural modulus of 6.3 ± 0.4 GPa, and Vickers hardness of 63 ± 1 VHN, while the commercial CAD-CAM composite showed values of 152 ± 8 MPa, 7.9 ± 0.3 GPa, and 66 ± 2 VHN, respectively. Filler addition did not adversely affect the degree of conversion, although the relatively low conversion led to the elution of unpolymerized monomers and increased water solubility. The shear bond strength of the optimal printed composite remained stable after aging without silanization, demonstrating superior bonding performance compared with the CAD-CAM composite. These findings suggest that the developed 3D-printed resin composite is a promising candidate for dental restorative materials. Full article

Recently, 3D-printed resins have been introduced as materials for definitive indirect restorations. Herein, a comparative assessment of the bond strengths of 3D-printed resins to a resin cement was performed. Methods: four definitive restorative materials were selected, i.e., a Feldspar ceramic (VITA Mark II, VM), a polymer-infiltrated ceramic network (VITA Enamic, VE), a nanohybrid resin composite (Grandio Bloc, GB), and one 3D-printed resin (Crown Permanent, CP). VM and VE were etched and silanized, GB was sandblasted, and CP was glass bead blasted; for one further experimental group, this was followed by sandblasting (CPs). A resin cement (RelyX Unicem) was then used for bonding, and then a notched shear bond strength test (nSBS) was performed. Failure modes were observed and classified as adhesive, cohesive, or mixed, and SEM representative images were taken. Data were statistically analyzed with one-way ANOVA, Tukey, and Chi-square tests. Significant differences were detected in nSBS among materials (p < 0.001). The highest nSBS was found in VM (30.3 ± 1.8 MPa) a, followed by CP^b, GB^bc, CP^bc, and VE^c. Failure modes were significantly different (p < 0.001), and with different prevalent failure modes. The bond strength for 3D-printed permanent resin materials was shown to be lower than that of the felspathic ceramic but comparable to that of the resin block and PICN substrates. Full article

Background/Objectives: The increasing clinical integration of 3D-printed definitive resins requires a comprehensive understanding of their physicochemical properties and adhesive behavior. However, there is limited evidence regarding the optimal surface treatment and bonding strategies for clear aligner composite attachments on these materials. This study aimed to characterize a 3D-printed definitive resin, evaluate the effects of surface treatments on its surface topography, and compare the shear bond strength (SBS) of the bonded attachments using different adhesive systems, both before and after thermocycling. Methods: A total of 120 rectangular specimens were fabricated from a 3D printed dental resin (Crowntec^®, SAREMCO Dental AG—Mexico City, Mexico). For physicochemical characterization, six samples underwent scanning electron microscopy/energy-dispersive spectroscopy, X-ray diffraction, and thermogravimetric analysis. To evaluate surface topography, 42 polished specimens were assigned to three groups: untreated (control), etched with 4% hydrofluoric acid (HFA), or sandblasted with 50 µm Al₂O₃ (AA). Each group was subdivided for SEM observation and surface roughness (Ra) measurement. For SBS testing, 72 additional samples received the same surface treatments and were further subdivided according to the adhesive system: Transbond™ XT Primer (TXT) or Single Bond Universal (SBU). Results: The AA group showed the highest Ra (2.21 ± 0.30 µm), followed by HFA (0.81 ± 0.20 µm) and control (0.07 ± 0.30 µm) (p < 0.001). The highest SBS was observed in the AA + SBU group, followed by AA + TXT. Conclusions: Sandblasting with Al₂O₃ particles, combined with a universal adhesive, significantly improved bond strength, suggesting a viable protocol for 3D printed definitive composites in aligner attachment applications. Full article

Background: Limited data are available regarding the mechanical performance of 3D-printed fixed partial dentures (FPDs) fabricated from different materials and connector geometries. The purpose of this in vitro study was to evaluate the influence of connector size and material type on the fracture resistance of three-unit posterior FPDs fabricated with two commercially available 3D-printable dental resins. Methods: A standardized metal model with two cylindrical abutments was used to design three-unit FPDs. A total of sixty samples were produced, considering three connector sizes (3 × 3 mm, 4 × 4 mm, and 5 × 5 mm) and two different resins: Temp Print (GC Corp., Tokyo, Japan) and V-Print c&b temp (Voco GmbH, Cuxhaven, Germany) (n = 10). Specimens were fabricated with a DLP printer (Asiga MAX UV), post-processed per manufacturer recommendations, and tested for fracture resistance under occlusal loading using a universal testing machine. Data were analyzed using nonparametric tests (Mann–Whitney U and Kruskal–Wallis; α = 0.05). Results: Significant differences were found between material and connector size groups (p < 0.001). Temp Print (GC Corp., Tokyo, Japan) demonstrated higher mean fracture loads (792.34 ± 578.36 N) compared to V-Print c&b temp (Voco GmbH, Cuxhaven, Germany) (359.74 ± 131.64 N), with statistically significant differences at 4 × 4 and 5 × 5 mm connectors. Fracture strength proportionally increased with connector size. FPDs with 5 × 5 mm connectors showed the highest resistance, reaching values above 1500 N. Conclusions: Both connector geometry and material composition significantly affected the fracture resistance of 3D-printed FPDs. Larger connector dimensions and the use of Temp Print (GC Corp., Tokyo, Japan) resin enhanced mechanical performance. Full article

Background/Objectives: The introduction of composite attachments has greatly improved orthodontic aligner therapy, through better force delivery, more predictable movements, and enhanced retention. This in vitro study aims to present and investigate an innovative digital protocol for aligner attachment fabrication incorporating the latest 3D technology used in dentistry. Methods: A virtual attachment measuring 2.5 × 2 × 2 mm was designed using computer-aided design (CAD) software (Meshmixer, Autodesk Inc., San Francisco, CA, USA) and exported as an individual STL file. The attachments were fabricated using a digital light processing (DLP) 3D printer (model: Elegoo 4 DLP, Shenzhen, China) and a dental-grade biocompatible resin. A custom 3D-printed placement guide was used to ensure precise positioning of the attachments on the printed maxillary dental models. A flowable resin was applied to secure the attachments in place. Following attachment placement, the models were scanned using a laboratory desktop scanner (Optical 3D Smart Big, Open Technologies, Milano, Italy) and three intraoral scanners: iTero Element (Align Technology, Tempe, AZ, USA), Aoral 2, and Aoral 3 (Shining 3D, Hangzhou, China). Results: Upon comparison, the scans revealed that the iTero Element exhibited the highest precision, particularly in the attachment, with an RMSE of 0.022 mm and 95.04% of measurements falling within a ±100 µm tolerance. The Aoral 2 scanner showed greater variability, with the highest RMSE (0.041 mm) in the incisor area and wider deviation margins. Despite this, all scanners produced results within clinically acceptable limits. Conclusions: In the future, custom attachments made by 3D printing could be a valid alternative to the traditional composite attachments when it comes to improving aligner attachment production. While these preliminary findings support the potential applicability of such workflows, further in vivo research is necessary to confirm clinical usability. Full article

This study aimed to investigate the bonding strength and durability of titanium alloys bonded to zirconia-based materials produced using subtractive and additive digital methods. Two titanium alloy groups (N = 20) and two zirconia ceramic groups (N = 60) were fabricated using CAD/CAM milling from prefabricated discs (Ti-ML and Zr-ML), and 3D printing via SLM (Ti-3D) and DLP/LCM systems (Zr-3D). The specimens were bonded with dental cement to form four test groups: Zr-ML/Ti-ML, Zr-ML/Ti-3D, Zr-3D/Ti-ML, and Zr-3D/Ti-3D. Half of the specimens in each group underwent thermocycling to assess the effect of aging on bond strength. The density, microhardness, and surface morphology were evaluated, along with the shear bond strength and failure modes of the resin composites. Statistical differences were analyzed using one-way ANOVA and Tukey’s HSD test across all groups. The 3D-printed specimens of both materials exhibited higher microhardness and lower surface roughness than the milled specimens. The shear bond strength (SBS) was the highest in the Ti-ML/Zr-ML combination group before and after thermocycling, which had more cohesive failures, whereas the lowest bond strength was observed in the Ti-3D/Zr-ML group. The adhesion between titanium and zirconia-based materials was the strongest when both were fabricated using subtractive methods, followed by additive and mixed-method combinations. Full article

In this paper, titanium oxide nanoparticles (TiO₂-NPs) with complex surface topologies were obtained for the first time using simple procedures applied in laser sintering. Based on the obtained nanoparticles and polymethyl methacrylate-like photopolymer resin, a composite material (MPR/TiO₂-NPs) for 3D printing was created using the MSLA technology. Products made of the material containing from 0.001 to 0.1% wt. TiO₂-NPs didn’t contain internal defects and were less brittle than the resin without nanoparticles. Products made of the MPR/TiO₂-NPs material were well polished; after polishing, areas with a variation in the surface profile height of less than 10 nm were found on the surfaces. Nanoparticles in the volume of products made of the material are apparently unevenly distributed; there are alternating areas of micrometer sizes with slightly higher and slightly lower concentrations of nanoparticles. Spectroscopy showed that adding the developed nanoparticles promoted better polymerization of the MPR resin. The addition of nanoparticles to the material slightly increased its ability to generate active forms of oxygen and damage biomacromolecules. At the same time, the resulting material exhibits significant antibacterial properties and doen’t affect the growth and reproduction of animal cells. The created material can be a very effective basis for the additive manufacturing of products with improved physical and chemical properties and balanced biological activity. Full article

Background: There are very few studies in literature concerning the bonding between 3D-printed resin posts and the core build-up material. This study aimed to evaluate and compare the adhesion of 3D-printed and milled resin posts to composite resin core build-up material following different surface treatments. Methods: Three types of resin posts were utilized in this study: ready-made glass-reinforced fiber post (3M ESPE, Germany), milled PEEK POST (Bredent, Germany), and 3D-printed resin post (CROWNTEC, Saremco Dental AG, Switzerland). Each type of post was categorized into three groups based on surface treatments: C: untreated surfaces; SB: Air abrasion with 50 μm aluminum oxide particles was applied to the posts’ surfaces.; HO: the posts’ surfaces were immersed in 30% H₂O₂ for 5 min. A dual-cured composite resin (Grandio DC; VOCO) was utilized for core build-up in each group to evaluate adhesion through the push-out bond strength test. The modes of failure were analyzed, and the surface morphology of the post was characterized using SEM. Data were analyzed using a two-way analysis of variance (ANOVA) along with Tukey’s test. Results: The two-way ANOVA indicated a significant effect for surface treatment (F = 583.54, p < 001), post type (F = 79.96, p < 0.001), and their interactions (F = 265.74, p < 0.001). Regarding 3D-printed resin post, 30% H₂O₂ for 5 min recorded the highest statistically significant bond strength value (13.11 ± 1.61) compared to other groups. Regarding the milled PEEK post, the air particle abrasion recorded the highest statistically significant value (23.88 ± 1.66) compared to other groups. Adhesive failure was the predominant failure type, with an occurrence rate of 70.35%. Mixed failure was noted in 24.07% of the cases, with a significant prevalence in the PEEK post within the air particle abrasion group (58.3%). Cohesive failure was noted in 5.54% of cases, with a significant prevalence in the air particle abrasion group, occurring at rates of 16.6% in the resin fiber post group and 33.3% in PEEK posts. Conclusions: Air particle abrasion significantly improved the push-out bond strength of milled PEEK posts, but it did not have a similar effect on the 3D-printed resin posts. The application of 30% H₂O₂ for 5 min to 3D-printed resin post enhanced the adhesion to core build-up material. The manufacturing method of posts, the surface treatments utilized, and their interactions affect the interfacial bond strength between posts and the composite resin core build-up material. Full article

This study evaluated the effect of post-printing polymerization time on residual monomer elution and water sorption in a 3D-printed resin composite. Eighty samples were fabricated and assigned to four groups based on post-curing duration: 0, 20, 40, and 60 min. Each group was subdivided according to two storage conditions (distilled water and 75% ethanol–water solution), and evaluated at 1 and 7 days. High-performance liquid chromatography (HPLC) quantified eluted monomers. Additionally, 40 specimens underwent a 4-month sorption/desorption cycle for water sorption and solubility assessment. Data were statistically analyzed using kernel regression (monomer data) and Welch ANOVA (water sorption and solubility) at a significance level of p < 0.05. BisEMA was the only monomer detected, with significantly higher elution recorded in ethanol-based storage. Increasing post-curing time notably reduced both monomer release and water sorption/solubility (p < 0.001); however, the optimal results were observed at 40 min post-curing. These findings suggest that extending post-curing beyond an optimal threshold does not further improve composite properties, underscoring the importance of identifying precise curing parameters in order to enhance durability and material performance. Full article

Objective: To evaluate the cytotoxicity and endocrine-disrupting potential of materials used in removable orthodontic retainers. Methods: A literature search (2015–2025) covered in vitro cytotoxicity, estrogenicity, in vivo tissue responses, and clinical biomarkers in PMMA plates, thermoplastic foils, 3D-printed resins, PEEK, and fiber-reinforced composites. Results: Thirty-eight in vitro and ten clinical studies met inclusion criteria, identified via a structured literature search of electronic databases (2015–2025). Photopolymer resins demonstrated the highest cytotoxicity, whereas thermoplastics and PMMA exhibited predominantly mild effects, which diminished further following 24 h water storage. Bisphenol-type compound release was reported, but systemic exposure remained below regulatory limits. No statistically significant mucosal alterations or endocrine-related effects were reported in clinical studies. Conclusions: Retainer materials are generally biocompatible, though data on long-term endocrine effects are limited. Standardized biocompatibility assessment protocols are necessary to enable comparative evaluation across diverse orthodontic materials. Single-use thermoplastics contribute to microplastic release and pose end-of-life management challenges, raising concerns regarding environmental sustainability. Full article

This paper is focused on the modification of commercial resin by using biobased fillers during stereolithography (SLA) 3D printing. This research aims to create a composite material with a matrix made of commercially available photosensitive resin modified with a filler based on secondary raw materials and materials formed as by-products in the processing of biological materials. The research determines the effect of different fillers on the tensile properties and hardness of samples printed using SLA 3D printing, and it also investigates their integrity using SEM analysis. This study aims to evaluate the feasibility of using these fillers for producing 3D-printed parts with SLA technology. The results of this study open up new possibilities for designing modified composite materials based on additive SLA 3D-printing technology using biological fillers. Within the framework of research activities, a positive effect on tensile properties and an improved interfacial interface between the matrix and the filler was demonstrated for several tested fillers. Significant increases in tensile strength of up to 22% occurred in composite systems filled with cotton flakes (CF), miscanthus (MS), walnut (WN), spruce tree (SB), wheat (WT) and eggshells (ES). Significant potential for further research activities and added value was shown by most of the tested bio-fillers. A significant contribution of the current research is the demonstration of the improved mechanical performance of photosensitive resin modified with natural fillers. Full article

The growing demand for sustainable materials with tunable thermal and structural properties has driven the development of composites reinforced with natural fibers in additive manufacturing (AM) technologies. This study investigates the thermal and chemical behavior of polymer composites produced via Digital Light Processing (DLP), an AM technique based on vat photopolymerization that stands out for its high resolution, dimensional control, and superior speed compared to methods such as FDM and SLA. Samples were manufactured with a UV-curable acrylate resin reinforced with jute fibers (Corchorus capsularis) in mass fractions of 0%, 2%, 2.5%, and 3% in solid geometries (CS-). TGA indicated a 4% reduction in the initial degradation temperature with increasing fiber content, from 326.3 °C (CS-0) to 313.2 °C (CS-3.0). TMA revealed a reduction of up to 19% in the coefficients of thermal expansion, indicating greater dimensional stability. The DMA indicated a 16.9% decrease in the storage modulus with 3% fibers, evidencing changes in the viscoelastic response. FTIR detected additional bands at 3340 cm⁻¹ and 1030 cm⁻¹, related to O–H and polysaccharides, confirming a fiber–matrix chemical interaction. These results demonstrate the potential of jute as a sustainable reinforcement in photopolymerizable resins, paving the way for ecological and functional applications in 3D-printed composites. Full article

Stereolithography (SLA) is a popular additive manufacturing (AM) method frequently used in research and various industrial sectors. The acrylate resin used in this research is renowned for its flexibility and durability, enabling the creation of flawless 3D-printed parts with exceptional mechanical properties. This study aims to enhance the thermomechanical properties of 3D-printed hollow glass microballoon (HGM)-filled composite materials by adding minimal HGM into the acrylate resin. We investigated the material properties through uniaxial compression tests, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). To validate the results, a numerical investigation and a machine learning (ML) approach were carried out and compared with the experimental results. Adding a small number of microballoons increases compressive strength and stiffness. The viscoelastic behavior of the samples also provides an estimate of resilience at higher temperatures, considering the addition of filler material into the resin. Our study shows that the addition of 0.04% of HGM increased compressive strength by around 99.30% compared to the neat sample, while the stiffness increased by around 31.42% compared to the neat sample at 0.05% of HGM. It can also be estimated that the suitable range of HGM addition for the resin we used exists between 0.04% and 0.05%, where the materials achieve their maximum strength and stiffness. In addition, a predictive machine learning (ML) model, namely Random Forest Regressor (RFR), shows low mean squared error (MSE), mean absolute error (MAE), and excellent R² scores, demonstrating the goodness of the model’s performance. This modern approach can guide us to selecting a suitable filler percentage for the photopolymer resin for 3D printing and making it applicable to different engineering prospects. Full article

This study evaluated the effects of print orientation and thermal aging on the flexural strength (FS) and flexural modulus (FM) of novel permanent three-dimensional (3D)-printed polymethyl methacrylate (PMMA) resins reinforced with nano-zirconia and nano-silica. Bar-shaped specimens (25 × 2 × 2 mm) were fabricated using a digital light processing (DLP) 3D printer (Asiga Max UV, Asiga Inc., Australia) in two orientations (0° and 90°). Specimens underwent three-point bending tests at 24 h and after artificial thermal aging (10,000 and 30,000 cycles) to simulate one and three years of intraoral conditions. Scanning electron microscopy (SEM) was used to analyze fracture patterns. Print orientation did not significantly affect FS or FM (p > 0.05). However, artificial aging significantly reduced FS and FM after 10,000 cycles (p < 0.001), with further deterioration after 30,000 cycles. The micro hybrid resin composite exhibited higher FS than the 3D-printed materials throughout aging. SEM analysis revealed distinct fracture patterns, with 3D-printed resins displaying radial fractures and the micro hybrid composite exhibiting horizontal fractures. These findings indicate that aging plays a more critical role in the long-term mechanical performance of 3D-printed restorative resins than print orientation. This study provides original data on the effects of print orientation and prolonged thermal aging on the mechanical behavior of permanent three-dimensional (3D)-printed dental resins. Furthermore, the comparative evaluation of aging protocols simulating one and three years of intraoral service represents a novel contribution to the existing literature. Further studies are required to optimize the mechanical durability of 3D-printed dental restorations. Full article

This study evaluates the optical properties and mechanical durability of adhesive restorations fabricated using different techniques for the treatment of single-tooth loss in the posterior region after an aging process. Sixty extracted human teeth (thirty molars and thirty premolars) were restored using three different fabrication methods: 3D-printed resin restorations, fiber mesh-reinforced direct composite restorations, and indirect composite restorations. Color stability was assessed using a spectrophotometer, and fracture resistance was measured using a universal testing machine. Finite element stress analysis (FEA) was conducted to validate mechanical test results under simulated intraoral conditions. The fiber-reinforced composite group exhibited the highest fracture resistance (1057.91 MPa), while 3D-printed restorations showed the lowest (p < 0.05). Regarding color stability, the fiber-reinforced group demonstrated the highest ΔE⁰⁰ values (ΔE⁰⁰ = 1.71), differing significantly from the other groups, while the 3D-printed and indirect composite restorations showed no significant difference. Mechanical test results were consistent with FEA findings. These results indicate that fiber reinforcement enhances mechanical durability in high-load-bearing areas, while 3D-printed restorations may not yet be suitable for posterior regions. However, their potential use in anterior restorations, where occlusal forces are lower, warrants further investigation to improve material properties. Full article