Search Results (53)

Background/Objectives: This study aimed to investigate the influence of shade and thickness on the polymerization of SDR^® flow+, a low-viscosity bulk-fill composite, by assessing its degree of conversion (DC). Methods: An in vitro study was conducted using SDR^® flow+ composite resin. Specimens were prepared at two thicknesses (2 mm and 4 mm) and four shades (Universal, A1, A2, A3). Polymerization was performed using a high-intensity LED curing unit. The DC was assessed using Fourier-transform infrared spectroscopy (ATR-FTIR). Results: Both shade and thickness significantly influenced DC. Thicker specimens (4 mm) exhibited reduced polymerization compared to thinner specimens (2 mm). Darker shades, particularly A3, demonstrated the lowest DC values due to their higher chroma, which limits light penetration. In contrast, the Universal shade achieved higher DC values, even at increased depths, likely due to its greater translucency. Conclusions: Shade and thickness play a critical role in the polymerization of bulk-fill composites. Ensuring adequate polymerization is essential for the longevity of pediatric restorations. Further in vivo research is needed to confirm these findings and assess their clinical implications. Full article

Introduction: Successful root canal therapy relies on thorough cleaning and disinfection to eliminate microorganisms and residual pulp tissue. Advanced irrigation activation techniques, including Sonic, Ultrasonic, and Diode Laser activation, have improved cleaning efficacy, bacterial reduction, smear layer removal, and irrigant hydrodynamics. On the other hand, these irrigation activation techniques may lead to a temperature rise that may risk the surrounding periodontal tissue. Thus, this study aimed to investigate the temperature rise during different irrigation activation techniques at various time intervals and evaluate the efficacy of these techniques in removing biofilm-mimicking hydrogel BMH of a simulated root canal system in 3D-printed tooth models. Methods: Ten extracted human mandibular premolars, prepared to size 40/0.04 taper, and a hundred 3D-printed resin premolars with simulated main (0.25 mm) and lateral canals (0.15 mm at 3, 7, 11 mm from apex) were used; 50 of them were filled with biofilm-mimicking hydrogel (BMH). Five irrigation activation techniques were evaluated: Diode Laser, Ultrasonic, Sonic, XP-Finisher, and Control (n = 10). Temperature rises were measured on the extracted premolars after 30 and 60 s of activation using a thermographic camera in a controlled environment (23 ± 2 °C). Irrigant penetration, with and without BMH, was assessed in 3D-printed premolars using a 2.5% sodium hypochlorite-contrast medium mixture, visualized with a CMOS radiographic sensor. Penetration was scored (main canal: 3 points; lateral canals: 0–2 points) and analyzed with non-parametric tests. Results: Diode Laser activation technique resulted in the highest temperature rise on the external root surface, followed by the Ultrasonic, with no statistically significant difference observed among the remaining groups. In terms of efficacy, Ultrasonic and Sonic activation achieved significantly greater irrigant penetration in samples without BMH, and greater BMH removal in samples with BMH, compared to Diode Laser, XP-Finisher, and Control groups. Conclusions: In this in vitro study, Diode Laser caused the highest temperature rise, followed by Ultrasonic, with significant increases from 30 to 60 s. Temperature rise did not significantly affect penetration or BMH removal. Ultrasonic and Sonic irrigation techniques achieved the highest depth of penetration (without BMH) and biofilm-mimicking Hydrogel removal (with BMH) compared to Diode Laser, XP-Finisher, and Control. Full article

This study presents an analytical description of the computed tomography-based volumetric additive manufacturing (VAM) process, with an emphasis on the impact of resin properties on product dimensions. The main issue addressed in this study is the assessment of the dimensional limitation of the objects produced using the VAM process, which is usually reported to be of the order of one centimeter. An analytical model is introduced to predict the product size based on the resin property (penetration depth—D_p), vial size (radius), and the duration of part formation, and the results indicate significant correlations among these parameters. A method of D_p measurement and analysis that is appropriate for the VAM process is also introduced. Mathematical justification is provided along with experimental verification for the effects of the main governing factor, D_p, on the maximum possible product size. Multiple criteria are also introduced for selecting the appropriate size of the resin container (vial) based on the desired object size and the value of D_p. It was found that the D_p is a crucial factor in analysis and experimentation in the VAM process, and its value is fundamentally different from the one obtained in the conventional polymerization AM methods. The product dimension based on the resin property, vial size, and time for the formation of the part is introduced by the analytical model. This model provides valuable insights into the complex interplay of factors influencing VAM outcomes and can facilitate informed decision-making in material selection and process design. Full article

Thiol–epoxy photopolymerization offers exceptional advantages for high-performance protective coatings, yet efficiently curing thick formulations remains a significant challenge due to the limited penetration depth of conventional UV light. Herein, we report a novel near-infrared (NIR) light-activated photopolymerization system for deep-curing applications, strategically integrating upconversion nanoparticles (UCNPs) as NIR-to-UV converters, isopropylthioxanthone (ITX) as a photosensitizer, and a liquid N-phenylglycine-based photobase generator (NPG-TBD) with enhanced resin solubility. Upon 980 nm NIR irradiation, photogenerated TBD efficiently catalyzes thiol–epoxy polymerization through an anionic mechanism, enabling uniform network formation with epoxy and thiol functional group conversions greater than 90% throughout samples exceeding 2.5 cm in thickness. The resulting coatings exhibit excellent mechanical properties including 3H pencil hardness, strong adhesion (0 grade), and good flexibility (2 mm), significantly outperforming conventional UV systems limited to approximately 1.5 mm. Additionally, the cured materials demonstrate multifunctional characteristics including distinctive upconversion luminescence and dual-responsive shape memory behavior. This approach addresses critical limitations in deep-photocuring technology while offering significant potential for applications in protective coatings for marine infrastructure, chemical storage facilities, and smart materials requiring both substantial barrier properties and programmable responsiveness. Full article

The aim of this research was to examine the effect of water-based hydrophobic impregnations on concrete in order to improve its durability, chemical resistance, and physical–mechanical parameters. The purpose of this research was to prevent as much water evaporation as possible during concrete hydration, which resulted in the improvement in concrete properties including strength, durability, resistance of concrete in high-pressure water, water tightness, etc. Water-based hydrophobic impregnations based on silane and siloxane, epoxy resin, and oil were chosen to achieve improvements in concrete parameters. The comparison of water-based hydrophobic impregnations with solvent-based hydrophobic impregnations was also performed using the determination of absorbency, water pressure penetration depth, watertightness, concrete penetration depth, and resistance to aggressive environment. The concrete microstructure was observed using a digital microscope and a scanning electron microscope (SEM). Samples with hydrophobic agents exhibited a higher contact angle, lower absorbency, and higher resistance to aggressive environment, when compared to the untreated surfaces, confirming the water repellency of the water-soluble hydrophobic impregnations. The positive effect of hydrophobic agents in the compressive strength was also recorded. Furthermore, the benefit of the addition of 0.1 wt.% of nanocellulose into the hydrophobic impregnations was observed. Based on the obtained results, it was found that the addition of nanocellulose to water-soluble hydrophobic impregnations reduced the depth of pressurized water seepage and increased the compressive strength of the concrete after 28 days by 2 MPa. Full article

Oral diseases such as dental caries, periodontitis, and oral cancer are prevalent and present significant challenges to global public health. Although these diseases are typically treated through procedures like dental preparation and resin filling, scaling and root planning, or surgical excision, these interventions are often not entirely effective, and postoperative drug therapy is usually required. Traditional drug treatments, however, are limited by factors such as poor drug penetration, significant side effects, and the development of drug resistance. As a result, there is a growing need for novel drug delivery systems that can enhance therapeutic efficacy, reduce side effects, and improve treatment outcomes. In recent years, drug-loaded vesicles, such as liposomes, polymersomes, and extracellular vesicles (EVs), have emerged as promising drug delivery platforms due to their high drug encapsulation efficiency, controlled release properties, and excellent biocompatibility. This review provides an in-depth examination of the characteristics, advantages, and limitations of liposomes, polymersomes, and extracellular vesicles in the context of oral disease treatment. It further explores the reasons for their advantages and limitations and discusses the specific applications, development prospects, and strategies for optimizing these vesicle-based systems for improved clinical outcomes. Full article

This study examines the influence of nanofillers on the ultraviolet (UV) penetration depth of photopolymer resins used in stereolithography (SLA) 3D printing, and their impact on printability. Three nanofillers, multiwalled carbon nanotubes (MWCNT), graphene nanoplatelets (xGNP), and boron nitride nanoparticles (BNNP), were incorporated into a commercially available photopolymer resin to prepare nanocomposite formulations. The UV penetration depth (Dp) was assessed using the Windowpane method, revealing a significant reduction with the addition of nanofillers. At a concentration of 0.25 wt.%, MWCNT showed the highest reduction in Dp (90%), followed by xGNP (65%) and BNNP (33%). SLA 3D printing was performed at varying nanofiller concentrations to evaluate printability. The findings highlight a strong correlation between Dp and the maximum printable nanofiller concentration, with MWCNT limiting printability to 0.05 wt.% due to its low Dp, while BNNP allowed printing up to 1.5 wt.%. Mechanical testing showed substantial improvements in hardness and elastic modulus, even at low nanofiller concentrations, with BNNP outperforming other fillers. Compared to a clear photopolymer, the elastic modulus for 3D printed nanocomposite samples with 0.05 wt.% nanofiller compositions showed an improvement of 43% for MWCNT, 63% for xGNP, and 104% for BNNP. The hardness results showed an improvement of 86% for MWCNT, 103% for xGNP, and 179% for BNNP. These results underscore the importance of Dp in determining the layer thickness and print success in SLA 3D printing. Practical applications include the design of advanced photopolymer nanocomposites for biomedical devices, electronics, and lightweight structural components. This research provides valuable insights for tailoring material properties to meet the demands of high-performance additive manufacturing. Full article

This study evaluated the color change (ΔE₀₀) and penetration depth (PD) of white spot lesions (WSLs) infiltrated with the resin infiltrant (Icon^®) functionalized with methacrylate epigallocatechin-3-gallate (EGCG). To introduce polymerizable double bonds, EGCG was reacted with methacryloyl chloride (EM). Subsequently, the Icon resin infiltrant (I) was loaded with neat EGCG (IE) or EGCG–methacrylate (IEM) at 2 wt% each. WSLs were created on bovine enamel blocks and treated with I, IE, or IEM. Sound and untreated enamel surfaces were used as controls (C). Infiltrant PD (%) was determined by Confocal Laser Scanning Microscopy (CLSM, n = 12) analysis. For color change (ΔE₀₀) determination (n = 14), ΔL, Δa, and Δb, half of each sample was kept sound as a reference area. The color was determined with a spectrophotometer. Data were statistically evaluated (p = 0.05). Surface morphology was obtained as a qualitative response variable using 3D CLSM. PD (%) did not differ statistically for I, IE, and IEM (p = 0.780). Groups I and IEM showed similar performance on color change (ΔE₀₀) compared to the control group, while IE exhibited intermediate results, with no significant difference observed between the untreated, I, and IEM groups (p < 0.001). IEM promoted the masking of the WSL color without interfering with the PD. Full article

This study aimed to evaluate the fracture resistance of root and sealer penetration after obturation using an epoxy resin sealer AH plus (AH+) and two different bioactive endodontic sealers, i.e., Totalfill BC Hiflow (TF BC), and experimental injectable bioactive glass (Exp.BG). A thermo-sensitive injectable sealer was prepared by using a non-ionic triblock copolymer and bioactive glass. The root canals of human extracted teeth were obturated with the respective sealers. The fracture resistance was analyzed at different time intervals, i.e., days 7, 30, and 90. The morphological and elemental analyses of the fractured roots were conducted with a scanning electron microscopy and a electron dispersive spectroscopy. Sealer penetration depth and the percentage of penetrated sealers into the dentinal tubules were assessed with the confocal laser scanning microscope. Statistical analysis was performed using a one-way ANOVA post hoc Tukey’s test. The mean fracture force in AH+ was significantly higher on day 30 (664.08 ± 138.8 N) compared to day 7 (476.07 ± 173.2 N) and day 90 (493.38 ± 120.18 N). There was no statistically significant difference between the TF BC and Exp.BG at different time intervals. The maximum penetration was observed in the middle region compared to coronal and apical for the Exp.BG, followed by the TF BC and AH+ groups; however, a nonsignificant difference in penetration was found over time. It is concluded that the TF BC group showed overall better fracture resistance than AH+ at day 90. Exp.BG showed comparable sealer penetration to those of TF BC and better than those of AH+. Full article

In recent years, self-healing polymers have emerged as a topic of considerable interest owing to their capability to partially restore material properties and thereby extend the product’s lifespan. The main purpose of this study is to investigate the nanoindentation response in terms of hardness, reduced modulus, contact depth, and coefficient of friction of a self-healing resin developed for use in aeronautical and aerospace contexts. To achieve this, the bifunctional epoxy precursor underwent tailored functionalization to improve its toughness, facilitating effective compatibilization with a rubber phase dispersed within the host epoxy resin. This approach aimed to highlight the significant impact of the quantity and distribution of rubber domains within the resin on enhancing its mechanical properties. The main results are that pure resin (EP sample) exhibits a higher hardness (about 36.7% more) and reduced modulus (about 7% more), consequently leading to a lower contact depth and coefficient of friction (11.4% less) compared to other formulations that, conversely, are well-suited for preserving damage from mechanical stresses due to their capabilities in absorbing mechanical energy. Furthermore, finite element method (FEM) simulations of the nanoindentation process were conducted. The numerical results were meticulously compared with experimental data, demonstrating good agreement. The simulation study confirms that the EP sample with higher hardness and reduced modulus shows less penetration depth under the same applied load with respect to the other analyzed samples. Values of 877 nm (close to the experimental result of 876.1 nm) and 1010 nm (close to the experimental result of 1008.8 nm) were calculated for EP and the toughened self-healing sample (EP-R-160-T), respectively. The numerical results of the hardness provide a value of 0.42 GPa and 0.32 GPa for EP and EP-R-160-T, respectively, which match the experimental data of 0.41 GPa and 0.30 GPa. This validation of the FEM model underscores its efficacy in predicting the mechanical behavior of nanocomposite materials under nanoindentation. The proposed investigation aims to contribute knowledge and optimization tips about self-healing resins. Full article

Prestressed pipe piles are common concrete components characterized by dense concrete structures and favorable mechanical properties, and thus, extensively used as coastal soft soil foundations. However, their durability in harsh environments has not been fully clarified. In this study, leachate from an actual landfill site was collected from the east coast of China as the corrosive medium, and the corrosion process was accelerated by electrifying prestressed pipe piles. The results demonstrated that the concentration of chloride ions in the concrete of the prestressed pile increased with the increase in corrosion time. Moreover, the experimental corrosion of these prestressed piles in the drying–wetting cycle proved to be the most severe. However, a protective layer of epoxy resin coating can effectively inhibit the diffusion of chloride ions into the interior of the piles. The final theoretical corrosion amounts of the piles were 1.55 kg, 1.20 kg, and 1.64 kg under immersion, epoxy resin protection, and a drying–wetting cycle environment. The application of epoxy resin reduced chloride penetration by 22.6%, and the drying–wetting cycle increased chloride penetration by 5.8%, respectively, with corresponding corrosion potentials following similar patterns. The actual corrosion depth of the welding seam was 3.20 mm, and there was a large corrosion allowance compared with the requirement (6.53 mm) for the ultimate bending moment. In summary, these prestressed piles exhibited good durability in a leachate environment. Full article

Recently, the feasibility of using bio-materials to reduce or completely replace the use of bitumen in asphalt mixture has gained increasing attention. Amongst others, an interesting solution is represented by the use of wood co-products with mineral or vegetable oils. This research focuses on the development of bio-binders using vegetable resin (VR) in unmodified form and waste olive oil (WOO) as the main components; in order to optimize the rheological properties of the blends, crumb rubber from end-of-life tyres (CR), Styrene-Butadiene-Styrene (SBS) and polyethylene waxes (PEW) are used as additives. In particular, this investigation focuses on studying different oil/rosin ratios and polymer contents to provide a clear framework on this bio-binder solution; conventional bituminous binders are taken as a reference. The alternative binders are characterized in terms of conventional properties such as penetration depth and softening point, as well as rheological response. Finally, two of the bio-binders studied are selected with the aim of assessing the mechanical properties of the resulting sustainable asphalt mixture using the Marshall Stability test and the Indirect Tensile Strength test, comparing the results with the threshold values set by an Italian road agency. Thus, this research represents a preliminary analysis of the potential application of bio-binder mixtures within the specification limits imposed by road agencies. Although this research represents a first attempt, the results are promising and prove to be worthy of further investigations. Full article

This study comprehensively examines the influence of phenol-formaldehyde resin (PF) on the performance of base asphalt and its mixtures for road applications, emphasizing its innovative use in enhancing pavement quality. Optimal PF content was determined through the evaluation of standard indicators and rotational viscosity. In-depth analyses of PF-modified asphalt’s high- and low-temperature rheological properties and viscoelastic behavior were conducted using dynamic shear rheometers and bending beam rheometers. Aging resistance was assessed through short-term aging and performance grade (PG) grading. Moreover, Marshall and water stability tests were performed on PF-modified asphalt mixtures. Findings indicate that the uniform dispersion of PF particles effectively inhibits asphalt flow at high temperatures, impedes oxygen penetration, and delays the transition from elasticity to viscosity. These unique properties enhance the high-temperature stability, rutting resistance, and aging resistance of PF-modified asphalt. However, under extremely low temperatures, PF’s brittleness may impact asphalt flexibility. Nonetheless, the structural advantages of PF-modified asphalt, such as improved mixture density and stability, contribute to enhanced high-temperature performance, water stability, adhesion, and freeze–thaw cycle stability. This research demonstrates the feasibility and effectiveness of using PF to enhance the overall performance of base asphalt and asphalt mixtures for road construction. Full article

Seeking to improve personal armor equipment by providing mobility and resistance to penetration, this research aimed to explore the potential of sustainable materials in order to assess their ability in ballistic applications. Titica vine fibers (TVFs) extracted from aerial roots of Heteropsis flexuosa from the Amazon region were incorporated at 10, 20, 30, and 40 vol% into an epoxy matrix for applications in ballistic multilayered armor systems (MASs) and stand-alone tests for personal protection against high-velocity 7.62 mm ammunition. The back-face signature (BFS) depth measured for composites with 20 and 40 vol% TVFs used as an intermediate layer in MASs was 25.6 and 32.5 mm, respectively, and below the maximum limit of 44 mm set by the international standard. Fracture mechanisms found by scanning electron microscopy (SEM) attested the relevance of increasing the fiber content for applications in MASs. The results of stand-alone tests showed that the control (0 vol%) and samples with 20 vol% TVFs absorbed the highest impact energy (E_abs) (212–176 J), and consequently displayed limit velocity (V_L) values (213–194 m/s), when compared with 40 vol% fiber composites. However, the macroscopic evaluation found that, referring to the control samples, the plain epoxy shattered completely. In addition, for 10 and 20 vol% TVFs, the composites were fragmented or exhibited delamination fractures, which compromised their physical integrity. On the other hand, composites with 30 and 40 vol% TVFs, whose E_abs and V_L varied between 166–130 J and 189–167 m/s, respectively, showed the best physical stability. The SEM images indicated that for composites with 10 and 20 vol% TVFs, the fracture mode was predominantly brittle due to the greater participation of the epoxy resin and the discrete action of the fibers, while for composites with 30 and 40 vol% TVFs, there was activation of more complex mechanisms such as pullout, shearing, and fiber rupture. These results indicate that the TVF composite has great potential for use in bulletproof vests. Full article

Finishing coatings used in the wood-based composite industry play a key role in the final appearance of the finished product. However, the use of such coatings is not only for aesthetic purposes, but also to protect the product against surface damage and moisture or to minimize the emission of harmful substances. The latter is an extremely important factor in terms of safety for both the manufacturer and the user, which is why the emissivity test is one of the most important tests conducted in this case. Carbon-rich materials, such as those remaining from the extraction of birch bark, can fulfill the role of minimizing the emission of harmful substances. In this article, an attempt to create coatings in the form of a film by combining a biopolymer with suberinic acid residues (SARs) was made. Two types of biopolymers were used, polylactide (PLA) and polycaprolactone (PCL), in various polymer–SAR ratios. Suberinic acid as a residue is a raw material that can potentially contribute positively to the fixing of CO₂ from the atmosphere, which creates the possibility for further use. As part of this study, the obtained coatings were tested in terms of scratch resistance, relative hardness, cold liquids, total volatile organic compounds (TVOCs), formaldehyde emission, surface absorption, etc. Differences between the polymers used and the effect of the SAR additive on selected surface properties were demonstrated. The addition of carbon-rich SAR significantly improves gas barrier properties of the PLA- and PCL-based surface finishing materials. The relative hardness and scratch resistance also increased with rising SAR content. However, the increasing content of SAR filler acts as a limiter in the depth of penetration of the deposited surface finishing materials onto the wood surface. It is possible to state that this innovative approach regarding (1) the utilization of biopolymers as a matrix, instead of conventional, crude oil-based resins, and (2) the incorporation of post-processed carbon-rich waste lignocellulosic materials to produce the surface finishing and/or protective films has been confirmed. Full article