Search Results (27)

This work aimed at replacing per- or poly-fluoroalkyl substance (PFAS)-based food-serving containers with wood-based, oil- and grease-resistant food-serving containers. A novel container was developed by laminating wet cellulose nanofibril (CNF) films to both sides of yellow birch wood veneer using a food-grade polyamide–epichlorohydrin additive (PAE) as an adhesive. CNFs significantly improved the wood veneer container’s mechanical strength and barrier properties. The container’s mechanical testing results showed significant increases in flexural strength and modulus of elasticity (MOE) values in both parallel and perpendicular directions to the grain. All formulations of the container showed excellent oil and grease resistance properties by passing “kit” number 12 based on the TAPPI T 559 cm-12 standard. The water absorption tendency of the formulation treated at higher temperature, pressure, and longer press time showed similar performance to commercial paper plates containing PFASs. The developed composite demonstrates superior flexural strength and barrier properties, presenting a sustainable alternative to PFASs in food-serving containers. Both wood and CNFs stand out for their remarkable eco-friendliness, as they are biodegradable and naturally compostable. This unique characteristic not only helps minimize waste but also promotes a healthier environment. If scaled up, these novel containers may present a solution to the oil/grease resistance of bio-based food containers. Full article

The use of veneer composites as structural components in engineering requires special design. The dimensioning of laminated wood can be optimized by varying the wood species, veneer thickness, orientation, arrangement, number of single layers, and other factors. Composite properties can be calculated using suitable model approaches, such as the classical laminate theory. Thus, an optimization can be achieved. The present study verified the adaptability of the classical laminate theory for veneer composites. Native veneer, adhesive-coated veneer, and solid wood were investigated as raw materials for the plywood layers. Mechanical properties were determined using tensile and shear tests and used as parameters to calculate the composite properties of the plywood. The adhesive coating results in an increase in stiffness and strength compared with the native veneer parameters, which is greater perpendicular to the fiber than in the fiber direction. The increase due to the adhesive decreases with increasing veneer thickness. The plywood was bending tested. The measured Young’s modulus was in the range of 8000–10,700 MPa, the shear modulus was in the range of 500–1100 MPa, and the strength was in the range of 70–100 MPa. The values obtained were compared to the calculations. The best prediction of the plywood properties is obtained by using the properties of the adhesive-coated veneer as a single layer. Full article

Fluorapatite glass-ceramics (FGC) have been widely used in dental ceramics due to their excellent aesthetic properties and biocompatibility. In recent years, new synthesis methods, forming technologies, and the continuous optimization of performance attributes have driven the application of FGC in dental veneers, coatings, composites, and other restorations. This review summarizes the current research and applications of this material in the dental field and looks forward to its future optimization directions. The article focuses on five aspects: the development of preparation techniques for FGC; advances in their application in dental restoration shaping technologies; the performance advantages and limitations of these materials as dental materials; the current application status in veneers, coatings, composites, and other restorations; as well as the challenges in the current applications and prospects. In addition, additive manufacturing technology shows extremely broad application potential in FGC molding and applications. This review is hoped to provide strong guidance for the further application of FGC in the dental field, promoting the integration of related research and industry upgrades better to meet the needs of clinical practice and patients. Full article

In recent years, laminate veneer restorations should be considered as a minimally invasive treatment option for several aesthetic reasons. This study compared direct composite veneers’ and indirect ceramic laminate veneers’ longevity in multiple diastema closures. A total of 28 patients with a mean age of 26 years received 60 direct resin composite (Estelite Asteria; n = 14) and 60 indirect ceramic veneers (IPS e.max Press; n = 14) on the maxillary anterior teeth with diastema closure. Veneers were evaluated at baseline and thereafter every 6 months for up to 2 years using USPHS criteria. Data were analyzed with Fisher’s exact and chi-squared tests, while Kaplan–Meier curve was used to assess time to event. In total, three failures were observed in the form of debonding (n = 1) and fracture (n = 2) in the indirect ceramic veneers. No significant difference was observed between the survival rates of composite and ceramic veneers (Estelite Asteria: 93.4%, IPS e.max Press: 95%; p > 0.05). The overall survival rate was 94.2% (Kaplan–Meier). Staining (n = 11) and roughness (n = 14) were frequently observed for the resin composite veneers up to the final recall. Thereby, the preliminary results from this clinical trial comparing two veneer materials indicated that their survival rates were statistically similar. However, surface quality changes were more frequent in the composite veneer material. Full article

Among the many benefits of implementing numerical analysis on real objects, economic and environmental considerations are likely the most important ones. Nonetheless, it is also crucial to constrain the duration and space necessary for conducting experimental investigations. Although these benefits are clear, the applicability of such models must be appropriately verified. This research subjected validation of numerical models depicting the behavior of unstrengthened and strengthened laminated veneer lumber (LVL) beams. As a reinforcement, a carbon fiber reinforced polymer (CFRP) sheet and laminates were used. Experiments were conducted on full-scale members within the framework of the so-called four-point bending testing method. Numerical simulations were performed using the Abaqus software. Two types of material models were examined for laminated veneer lumber: linearly elastic and linearly elastic–perfectly plastic with Hill’s yield criterion. A distinction was made in the material properties of carbon composites based on their location on the height of the cross-section. The outlined numerical models accurately depict the behavior of real structural elements. The precision of predicting load-bearing capacity amounts to a few percent for strengthened beams and a maximum of eleven percent for unstrengthened beams. The relative deviation between numerical and experimental values of bending stiffness was at a maximum of seven percent. Applying the elastic–plastic model enables accurate representation of the load versus deflection relation and the distribution of stress and deformation of strengthened beams. Based on the findings, directives were provided for further optimization of the positioning of composite reinforcement along the span of the beam. Reinforcement design of existing laminated veneer lumber members can be made using presented methodology. Full article

Anterior teeth restoration represents a challenge for dentists, who often rely on the dental technician’s wax-up. The proposed Stratified Stamp Technique (SST) allows for clinically reproducing the wax-up in a quick and easy way. A patient with fractures and discoloration on the upper central incisors was treated with resin-based composite direct restorations. Using SST, a 1 mm thick thermoformed polyethylene-terephthalate-glycol (PETG) template, based on the technician’s wax-up, was produced. Enamel Selective Area Reduction (SAR) was performed to guarantee adequate space for the restorations, and the fracture margins were rounded and finished. Traditional layering procedures according to the five color dimensions of teeth were performed, except for the final labial layer, which was realized with warm composite loaded inside the template and polymerized through it, in order to ensure accurate tooth morphology reproduction. SST offers a reliable method for transferring technician’s wax-up morphology to direct composite restorations in anterior teeth. Compared with other methods, SST allows for better isolation with a rubber dam and permits traditional layering with multiple composite shades, thus leading to satisfactory esthetic outcomes. Full article

To promote the development of the ‘Bamboo as a Substitute for Steel’ proposal, rotary cut bamboo veneers were applied to prepare a kind of high-strength laminated bamboo composite, which was achieved through the hot press molding method in this study. Orthogonal experiments of L9 (3³) were performed, with hot-pressing temperature, pressure, and time considered as three influencing factors. Physical properties like density and moisture content, and mechanical properties like modulus of rupture (MOR), modulus of elasticity (MOE), shear strength, and compressive strength were tested for the samples. It can be obtained from the results of range analysis and ANOVA that higher density and lower moisture content were correlated with higher mechanical strength. Within the selected range of tested factors, a hot-pressing temperature and time of 150 °C and 10 min can contribute to higher density and lower moisture content, and the combination of 150 °C and 50 MPa can produce greater mechanical strength. In the thickness direction, the laminated bamboo composites displayed a notable compressed structure. Full article

In this paper, the results of dynamic laboratory tests of four laminated veneer lumber (LVL) slabs of different thicknesses, widths, and types were presented. In three of the tested slabs, LVL with all veneers glued lengthwise was used (LVL R). In one LVL slab, a fifth of the veneers were glued crosswise (LVL X). Laminated veneer lumber slabs are engineering wood products with several important performance characteristics, making them a sustainable and preferred solution in civil engineering. To ensure the safe operation of a building with LVL structural elements, it is important to know their dynamic properties. The basic dynamic characteristics of the slabs obtained from experimental tests made it possible to validate the numerical models of the slabs. The slab models were developed in the Abaqus program using the finite element method. The elastic and shear moduli of laminated veneer lumber used in the four slabs were identified through an optimization process in which the error between the analyzed frequencies from the laboratory tests and the numerical analyses was minimized. In the case of slabs that possess the same thickness and are composed of different LVL types, the elastic modulus of LVL R in the longitudinal direction was 1.16 times higher than the elastic modulus of LVL X in the same direction. However, the elastic moduli of LVL R in tangential and radial directions were lower than the elastic moduli of LVL X in the same directions. The above was the result of the fact that the 45 mm LVL X slab had 3 out of 15 veneers glued crosswise. In the case of slabs possessing different thicknesses but the same width and type, the elastic modulus of the thicker panel was 1.13 times higher than that of the thinner panel. After validating the models, the numerical analyses yielded results consistent with the experimental results. The numerical models of the LVL slabs will be used to develop numerical models of composite floors with LVL panels in future research. Such models will allow for the analysis of floor dynamic characteristics and user-generated vibrations, which is required when verifying the serviceability limit state. Full article

Optimization of structural elements via composition of different components is a significant scientific and practical point-of-view problem aimed at obtaining more economical and environmentally friendly solutions. This paper presents the results of a static work analysis of small-size laminated veneer lumber (LVL) beams reinforced by a Carbon Fiber Reinforced Polymer (CFRP) sheet. The nominal dimensions of LVL beams were 45 × 45 × 850 mm, and 0.333- and 0.666-mm thick reinforcement layers were used. The reinforcement was applied on opposite sides of the cross section obtaining a sandwich-type structure. An epoxy resin was used as a bonding layer. The bending tests were conducted in the so-called four-point bending static scheme in edgewise and flatwise conditions. The results of experimental tests confirmed the validity of this combination of materials. The highest load-bearing capacity was obtained for configuration, where CFRP sheets with a thickness of 0.666 mm were placed on the sides of the core, parallel to the direction of loading and the veneer’s grain in the core. The increase in this case was up to a maximum of 57% compared to the core alone. The highest bending stiffness increase, 182% compared to the core alone, involves placing two layers of sheets perpendicular to the direction of loading, i.e., on the upper and lower surfaces. The presented novel sandwich structure can be competitive against traditional steel and reinforced concrete elements in civil engineering and can be utilized as beams or slabs. Full article

This review discusses both preventive measures and clinically implemented therapy procedures that have been developed recently for the prevention and treatment of tooth erosion. Methods: The databases PubMed, Scopus, and Web of Science were used for a thorough search. Studies on the prevention and treatment of dental erosion that were conducted in English and used in vitro were among the inclusion criteria. Results: The search turned up 391 papers in total, with 34 of those publications matching the requirements for inclusion. Varnishes, toothpastes, and solutions containing fluoride and other substances were used as preventive measures. Conclusions: Dental erosion is a significant issue, and taking preventative steps is crucial to lessening the disease’s spread and its effects. Interventions based on fluoride seem to be successful at halting erosion and encouraging remineralization. To effectively address severe tooth erosion, therapeutic methods, including composite restorations, prosthetic crowns, and veneers, are available. Dental erosion causes aesthetic and functional issues that are best addressed with less invasive treatments like direct composite restorations. To improve and broaden the range of available treatments for this common dental issue, additional research and development are required. Full article

This study presents a testing campaign aimed at evaluating the strength and stiffness properties of laminated veneer lumber (LVL) specimens. LVL is an engineered wood product composed of thin glued wood veneers whose use in construction for structural applications has increased due to its sustainability and enhanced mechanical performance. Despite LVL’s growing popularity, there is a lack of comprehensive information regarding stress–strain responses, failure modes, and the full set of strength and stiffness properties. These are particularly essential when LVL is employed in pure timber structures or composite systems such as steel–timber or timber–concrete load-bearing elements. This research aims to bridge this knowledge gap, focusing on crossbanded LVL panels, known as LVL-C, crafted from Scandinavian spruce wood, which is an LVL product with 20% of crossbanded veneers. The study explores LVL-C mechanical behavior in three primary orthogonal directions: longitudinal, tangential, and radial. A series of mechanical tests, including compression, tension, shear, and bending, was conducted to provide a thorough assessment of the material’s performance. In compression tests, different behaviors were observed in the three directions, with the longitudinal direction exhibiting the highest stiffness and strength. Tensile tests revealed unique stress–strain responses in each direction, with gradual tension failures. Shear tests showcased varying shear stress–strain patterns and failure modes, while bending tests exhibited significant strength and stiffness values in flatwise bending parallel to the grain and flatwise bending perpendicular to the grain. This paper summarizes the comprehensive testing results and discusses the obtained strength and stiffness properties of LVL-C panels, providing valuable insights into their mechanical behavior for engineering applications. Full article

Introduction: Currently, there is little clinical evidence to support the medium- and long-term survival and clinical performance of ultraconservative approaches using adhesive restorations in full-mouth restorations. The aim of this case series study was to evaluate the medium-term clinical performance of anterior and posterior adhesive restorations applied with direct and indirect techniques using resin composites and glass-ceramic-based materials. Materials and Methods: The inclusion criteria were an esthetic problem as the main reason for consultation and severe generalized wear of grade 2 to 4 according to the Tooth Wear Evaluation System (TWES 2.0). In addition, at each follow-up appointment, patients were required to submit a clinical-parameter-monitoring record according to the modified United States Public Health Service (USPHS) criteria. Results: Eight patients with severe tooth wear were treated through full rehabilitation in a private dental clinic in Spain by a single operator (AFC). A total of 212 restorations were performed, which were distributed as follows: 66 occlusal veneers, 26 palatal veneers and 120 vestibular veneers. No signs of marginal microleakage or postoperative sensitivity were observed in any occlusal, vestibular and/or palatal restoration after the follow-up period. The estimated survival rate of the 212 restorations was 90.1% over 60 months of observation, with a survival time of 57.6 months. Only 21 restorations had complications, which were mostly resolved with a direct composite resin. The dichotomous variables of the restoration type (posterior veneer, anterior veneer) and the type of restored tooth (anterior, posterior) were the risk predictors with statistically significant influences (p < 0.005) on the survival of the restorations. Conclusion: According to the results of this study, there is a significantly higher risk of restorative complications in posterior teeth compared to anterior teeth. Also, it can be concluded that the indication of adhesive anterior and posterior restorations is justified in the total oral rehabilitation of patients with severe multifactorial tooth wear, as they are associated with a low risk of failure. Full article

This paper presents a study of the deformations of the birch veneer layer of plywood composed of veneer sheets, each with a thickness of 1.4 mm. Displacements in the longitudinal and transverse directions were analyzed in each layer of veneer from the composition of the board. Cutting pressure was applied to the surface equal to the diameter of the water jet, located in the center of the laminated wood board. Finite element analysis (FEA) does not study the breaking of the material or its elastic deformation, but only what happens from a static point of view when maximum pressure acts on the board, which causes detachment of the veneer particles. The results of the finite element analysis indicate maximum values of 0.0012 mm in the longitudinal direction of the board located in the proximity of the application of the maximum force of the water jet. Additionally, in order to analyze the recorded differences between both longitudinal and transversal displacements, estimation of statistical parameters with 95% confidence intervals (CI) was applied. The comparative results indicate that the differences are not significant for the displacements under study. Full article

Pediatric esthetic dentistry is a sensitive technique, as children can be less cooperative; hence, minimal appointments are preferred. The most conservative treatment modality for anterior esthetic rehabilitation is using direct composite veneer restorations. In many instances, esthetic improvements using composite resin are the only possible option until the growth phase of the pediatric patient is complete. In this article, we present three different case scenarios in young teenagers with different treatment needs requiring esthetic restorations. The first case report is a patient with amelogenesis imperfecta, the second is with generalized spacing, and the third is with localized microdontia. All three patients were followed up for six months post direct composite veneering and were highly satisfied with their treatment outcomes, which boosted their self-confidence. Full article

The aim of this study was to compare bond strength resin composites to porcelain laminate veneers in the indirect repair method to composite resins used in the direct repair method for cases of porcelain veneer fracture of zirconia-based fixed dental prostheses. In the study, the groups were formed with different percentages of areas to be repaired to mimic porcelain fractures in the mouth. The experimental group of veneered zirconia were as follows: Group A = 100% Zr surface; Group B = 70% Zr, 30% porcelain surface; Group C = 50% Zr, 50% porcelain surface; Group D = 30% Zr, 70% porcelain surface; Group E = 100% porcelain surface. The repairs of the specimens were made using composite resin systems in half of the groups and using porcelain laminate veneers in the other half. Specimens were embedded in acrylic blocks before surface treatments and repairs were applied. After surface conditioning, laminate veneers were applied to the first half of the groups, and composite repair systems were applied to the second half of the groups. After all specimens were aged by thermal cycling, their bond strength values were measured using a Universal Testing Machine, and the obtained data were recorded. The specimens were examined with a stereomicroscope and classified according to failure types (adhesive/cohesive/mixed). Bond strength values were evaluated based on independent-samples t-test statistics. According to the comparisons among the groups, the bond strength of the indirect repairs made with the laminate material was higher than the bond strength of the repairs made with the composite. There was a statistically significant difference in favor of the indirect repair groups among all groups except for Group C. The highest bond strength was found in Group A in the indirect repair method, while the lowest bond was found in the direct repair method in Group E. Adhesive failure was mostly seen in the groups that were repaired with the composite. Full article