Shrinkage Of Resin Research Articles

Digital Dentures- The Future of Complete Dentures in Oral Rehabilitation

The conventional method of fabricating Complete Dentures (CDs) consists of many clinical and laboratory steps, making it more susceptible to certain problems and inevitable errors. With the advances in the field of technology, these errors can be avoided or minimised. Digital technology making use of computers for designing and or manufacturing CDs is referred to as digital dentures. In this, entire dentures are made by machining the denture’s bases using Computer-Aided Design and Manufacturing (CAD/ CAM). Technology’s quick development in the form of CAD/CAM has had a significant impact on all areas of dentistry, but notably prosthodontics and restorative dentistry. This system has not only simplified the process of fabrication of CDs but also reduced the clinical chairside time, number of dental appointments and helped to deliver error free dentures. It also helps to store the data in digital form which can be utilised further for fabricating other sets of dentures for that particular patient. The most important advantage over conventional denture is that, it lacks polymerisation shrinkage of the acrylic resin and exhibit high strength. Furthermore, it also eliminates laboratory work time. The provision of prosthodontic treatment requires the patient, a qualified physician, and competent laboratory personnel on various levels. The goal of the current review article was to demonstrate how modern technology may replace the traditional approach not only by making labour easier but, also by enabling precise full denture production.

Cytotoksyczność i biokompatybilność kompozytowych, światłoutwardzalnych żywic stomatologicznych

The physical, chemical, and biological properties of restorative dental materials influence the clinical outcome of dental treatment. Methacrylate-based resins are extensively used in everyday dental practice, but accumulating records point to their toxicity. This article reviews the most important experimental data on cell-induced cytotoxicity of composite dental resins, methacrylates and epoxy compounds used to induce polymerization and reduce resin shrinkage. Methacrylate monomers produce reactive oxygen species, induce apoptosis and/or genotoxicity, and affect cell proliferation in culture. There is a need for awareness about the biological risks of these materials. New sensitive methods introduced to the preclinical testing of dental resins may help to highlight specific mechanisms, quantify the biological risk and guide the dentist to select the right biomaterial for dental applications.

Temperature Dependence of Electrical Resistance in Carbon Nanotube Composite Film during Curing Process.

Carbon nanotube (CNT) film possesses excellent mechanical and piezoresistivity, which may act as a sensor for process monitoring and reinforcement of the final composite. This paper prepared CNT/epoxy composite film via the solution dipping method and investigated the electrical resistance variation (ΔR/R0) of CNT/epoxy composite film during the curing process. The temperature dependence of electrical resistance was found to be closely related to resin rheological properties, thermal expansion, and curing shrinkage. The results show that two opposing effects on electrical resistivity occur at the initial heating stage, including thermal expansion and condensation caused by the wetting tension of the liquid resin. The lower resin content causes more apparent secondary impregnation and electrical resistivity change. When the resin viscosity remains steady during the heating stage, the electrical resistance increases with an increase in temperature due to thermal expansion. Approaching gel time, the electrical resistance drops due to the crosslink shrinkage of epoxy resin. The internal stress caused by curing shrinkage at the high-temperature platform results in an increase in electrical resistance. The temperature coefficient of resistance becomes larger with an increase in resin content. At the isothermal stage, an increase in ΔR/R0 value becomes less obvious with a decrease in resin content, and ΔR/R0 even shows a decreasing tendency.

Evaluation of the polymerization shrinkage of different resin cements under the zirconia crowns, using stereomicroscope and Scanning electron microscope

The goal of this in vitro investigation was to assess the microleakage caused by polymerization shrinkage of four different resin cements, which were used for cementation of monolithic zirconia crown on prepared maxillary and mandibular first premolar extracted for orthodontic purpose. The microleakage was analysed by dye staining, followed by evaluation via optical method using stereomicroscope and scanning electron microscope. Following statistical analysis of the results, it was discovered that all of the tested luting cements exhibit a sizable degree of polymerization shrinkage. The depth of dye penetration also showed high degree of correlation with polymerization shrinkage. However, the magnitude of correlation varied among the different groups.

Preparation of isotropic tensile photosensitive resins for digital light processing 3D printing using orthogonal thiol-ene and thiol-epoxy dual-cured strategies

Poor layer interface adhesion leads to increasing anisotropic properties and weakening tensile properties of 3D printed parts. In order to reduce anisotropic properties and enhance the tensile properties of thiol-ene light-sensitive resins for Digital light processing (DLP) 3D printing, thiol-ene-epoxy hybrid resins containing a radical initiator (TPO) and photobase generator (TBD-HBPh4/ITX) were prepared to reduce the anisotropy and enhance the tensile properties of thiol-ene light-sensitive resins for digital light processing (DLP) 3D Printing. Real-time Fourier transform infrared spectroscopy (RT-FTIR) indicated that the CC bond conversion of resins exceeded 60%, and the thiol conversion was approximately 50%. The volumetric shrinkage of the thiol-ene resins increased to an extent with thermal treatment, indicating that these resins had undergone postcuring. Dynamic mechanical analysis showed that the glass temperature (Tg) increased from 20.8 °C to 34.1 °C. The tensile strength of the 3D printed part increased by approximately 500% with each printed orientation, and the degree of anisotropy with each orientation reduced by less than 5%. It was confirmed that the superior isotropic properties of the thiol-ene photosensitive resins for DLP 3D Printing were obtained using orthogonal thiol-ene and thiol-epoxy dual-curing strategies.

Additive manufacturing low shrinkage Si-based composite ceramics with SiCO microsphere/polyvinyl silicon acetylene slurry

In this paper, SiCO microsphere/polyvinyl silicon acetylene slurry was prepared for the first time with low viscosity and good rheological behavior. The dispersion of microspheres in the precursor resin and the UV-light curing performance of the slurry were investigated. After pyrolysis at 1000 °C, the properties of the three-dimensional (3D) printed samples were characterized. The introduction of SiCO microspheres reduced the specimen shrinkage of the pure precursor photosensitive resin used for additive manufacturing and improved their mechanical properties. When the addition of SiCO powder increased from 0 wt% to 10 wt%, the linear shrinkage decreased from 33 % to 26 %, and the flexural strength increased from 43.9 MPa to 79.8 MPa. This study realizes the preparation of Si-based composite materials through low-cost LCD additive manufacturing technology. It confirms the great potential of low-cost light-curing additive manufacturing to fabricate complex functional composite ceramic materials.

A Digital Workflow for the Fabrication of a Milled Removable Partial Denture.

Complete dentures fabricated with the additive or subtractive method have been widely used and proven to be clinically acceptable. However, fabrication of removable partial dentures (RPDs) using computer-aided design and computer-aided manufacturing is limited by its technique sensitivity as the pink resin, which encases part of metal framework, cannot be fabricated digitally. This article introduces a digital workflow to fabricate an RPD with the subtractive method. A complex structure of the offset metal framework and denture base with teeth sockets was milled with this technique. Artificial teeth were milled with a resin disk according to the computer-aided design data, resulting in the customized occlusal surface. This digital technique can be an alternative to the analog fabrication method as the RPD was fabricated digitally, keeping the original structures and reducing resin shrinkage on the intaglio surface.

Magnetic fiber enabled curing electrogram: Real-time process monitoring for thermosetting polymer materials

The curing behavior of thermosetting polymer materials is crucial to the quality and performance of their composite products, which promotes the development of the curing process monitoring. A novel strategy for real-time monitoring of the curing process of thermosetting resin using magnetic fiber (MF) with sensitive stress impedance effect is proposed. Differential scanning calorimetry and dynamical mechanical analysis are performed to obtain the curing degree, modulus, and glass transition temperature (Tg) as a calibration curve to establish a relationship with the impedance of MF embedded in resin during the curing cycle, which is determined by the internal stresses around the MF mainly induced by the crosslinking reaction and cooling shrinkage of resin. The dynamic physical properties of epoxy resin during curing process can be effectively and continuously monitored in real-time through the curing electrogram from the integrated MF sensor signal output, which can digitalize the evolution of resin crosslinking reaction and capture the gelation point, Tg and local mechanical state. The MF sensors for curing process monitoring is a promising technology to be developed into a life-cycle structural health monitoring of polymer composites and instrumental to their smart manufacturing advancement.

Using a Fiber Bragg Grating Sensor to Measure Residual Strain in the Vacuum-Assisted Resin Transfer Molding Process

Vinyl ester (VE) resin has strong environmental tolerance and is the matrix commonly used in the composite materials of fiber-reinforced plastics (FRP). VE resin is often combined with glass fiber in different maritime structures, such as wind turbine blades, spinner cases, and nacelle cases. However, VE resin exhibits exothermic reactions and shrinkage during curing, which often generates residual strain in large structures and those with a high stacking number. This study explored the exothermic reaction and shrinkage of VE resin and glass fiber during the vacuum-assisted resin transfer molding process, as measured using a fiber Bragg grating sensor. The experiment results verified the relationship between the stacking number and residual strain shrinkage. In addition, the symmetric laminate method was used to prevent the bending–twisting coupling effect and subsequent warping deformation of the FRP laminated plate during curing. The experiment results also verified that the bottom layers of the FRP laminated plates produced using VE resin were closer to the mold, and exhibited more shrinkage as the stacking number increased. In addition, this study discovered that during the experiment, the symmetry layer of the FRP laminated plate had a higher exothermic temperature than the bottom layer as a result of the symmetry layer’s ineffective heat dissipation. Therefore, the curing shrinkage of the symmetry layer resin was measured. The experiment results indicated that if the stacking number was between 10 and 30, the residual strain shrinkage of the symmetry layer was greater than that of the surface layer. However, because of the symmetric laminate, the residual strain of the symmetry layer did not increase when the temperature increased. Therefore, the greatest residual strain occurred at the surface of the bottom layer of the laminated plate with a stacking number of 40.

Understanding the Origin of the Low Cure Shrinkage of Polybenzoxazine Resin by Computational Simulation

Thermoset resin-based composite materials are widely used in the aerospace industry, mainly due to their high stiffness-to-weight and strength-to-weight ratios. A major issue with the use of thermoset resins in fiber composites is the process-induced residual stresses that are formed from resin chemical shrinkage during the curing process. These residual stresses within the composite material ultimately result in reduced durability and residual deformations of the final product. Polybenzoxazine (PBZ) polymer resins have demonstrated near-zero volumetric shrinkage during the curing process. Although the low shrinkage of PBZ is promising in terms of reduced process-induced residual stresses, little is known about the physical causes. In this work, Molecular Dynamics (MD) simulations are performed with a reactive force field to predict physical properties (gelation point, evolution of network, mass density, volumetric shrinkage) and mechanical properties (Bulk modulus, Shear modulus, Young's modulus, Poisson's ratio, Yield strength) as a function of crosslinking density. The MD modeling procedure is validated herein using experimental measurements of the modeled PBZ resin. The results of this study are used to provide a physical understanding of the zero-shrinkage phenomenon of PBZ. This information is also a critical input to future process modeling efforts for PBZ composites.

Potential and pitfalls of XRF-CS analysis of ion-exchange resins in environmental studies

Detecting clandestine, intermittent release of heavy metal pollution into natural and man-made water ways is challenging. Conventional chemical methods are both labor intensive and expensive. A recent approach combining ion-exchange resins with the capabilities of X-ray fluorescence core scanners (XRF-CS) therefore is of great interest. In short, ion-exchange resin is deployed in the water using small sachets, the resin is then collected, dried, filled into sample holders and scanned using XRF-CS. Ion-exchange resins take up heavy metals in proportion to the concentration in the ambient water, with a correlation coefficient (R2) between concentration and XRF-CS counts better than 0.96 for most elements. However, a number of parameters influence the measurements. Different drying methods introduce differences in the XRF counts because of lattice bound water, resin shrinkage, and disaggregation of the resin particles. Furthermore, the newly developed sample carrier, which was constructed using 3D printed polymers, contains trace amounts of elements that may influence the sample measurements through edge effects and secondary fluorescence. In the tested sample carrier materials, substantial levels of Cr, Fe, Co, and Zn were detected, while Ca, Ti, Ni, Cu, Ga showed variable levels. Ba, Tl and Bi show very low levels, and Pb is only of importance in the PLA carrier. It is therefore necessary to streamline the analysis-process to ensure that the variations in sample treatment and drying and filling methods are minimized. It is also recommended that only spectra from the center of the compartments are used for the evaluation to avoid edge effects caused by secondary fluorescence of metals in the compartment walls. Although the technique of using ion-exchange resin sachets and XRF-CS analysis is only semi-quantitative, it is a cost effective and fast way to monitor large areas for environmental pollution, and the new sample carrier greatly contributes to make the process faster and less error prone.

THE EFFECT OF TRIACRYLATE MONOMER STRUCTURE ON VOLUME SHRINKAGE AND TENSILE PROPERTIES OF VAT POLYMERIZATION RESINS

This study investigates the influence of triacrylate monomer structure on volume shrinkage, tensile properties, and viscosity of vat polymerization (VP) resins. The amount of triacrylate monomer kept constant as 20%wt. to prevent excessive volume shrinkage effect. Results indicated that ethoxylated and propoxylated triacrylate structures are beneficial to reduce the volume shrinkage of VP resins. However, these flexible chain structures led to a reduction in tensile properties and the elastic modulus of VP resins deteriorated up to 35% compared to trimethylolpropane triacrylate (TMPTA). There is no significant effect observed on VP resin reactivity according to the triacrylate type. Besides, ethoxylated triacrylate presented the best dilution effect on VP resin.

Parametric appraisal of collapsibility and core shrinkage of phenol binded unbaked casting moulds using Taguchi-Sunflower optimization algorithm

When compared to green sand moulds, resin bound sand moulds and cores have higher mechanical characteristics and create more dimensionally exact castings, and are thus increasingly preferred for near net form metal components. The effect of catalyst %, sand particle size and no. of strokes for compression on collapsibility and core shrinkage of no-bake resin bonded mould core was studied in this study using lab testing. Their collapsibility were discovered to decrease and core shrinkage increase with the addition of catalyst amount and bigger grain size. Microscopic study of cross-linked resin bridges between sand grains also supports this. To get the best blend of mould characteristics, the results were optimized using the Taguchi technique and Sunflower optimization algorithm. Tests were used to successfully validate the model and its findings. It was reported that the Sunflower optimization algorithm made more precise prediction than Taguchi method in maximization of collapsibility and minimization of core shrinkage. This study lays the groundwork for optimizing the moulding parameters of resin reinforced sand mould cores in order to achieve the best quality.

Quality Evaluation of Epoxy Pore Casts Using Silicon Micromodels: Application to Confocal Imaging of Carbonate Samples

Pore casting refers to filling the void spaces of porous materials with an extraneous fluid, usually epoxy resin, to obtain a high-strength composite material, stabilize a fragile porous structure, produce a three-dimensional replica of the pore space, or provide imaging contrast. Epoxy pore casting may be accompanied by additional procedures, such as etching, in which the material matrix is dissolved, leaving a clean cast. Moreover, an epoxy resin may be mixed with fluorophore substances to allow fluorescence imaging. Our work aims to investigate and optimize the epoxy pore casting procedure parameters, for example, impregnation pressure. We use silicon micromodels as a reference to validate the key parameters of high-pressure resin impregnation. We demonstrate possible artifacts and defects that might develop during impregnation with resin, e.g., resin shrinkage and gas trapping. In the end, we developed an optimized protocol to produce high-quality resin pore casts for high-resolution 3D imaging and the description of microporosity in micritic carbonates. In our applications, the high-quality pore casts were acid-etched to remove the non-transparent carbonate material, making the pore casts suitable for imaging with Confocal Laser Scanning Microscopy (CLSM). In addition, we evaluate the quality of our etching procedure using micro-computed tomography (micro-CT) scans of the pre- and post-etched samples and demonstrate that the etched epoxy pore casts represent the pore space of microporous carbonate rock samples with high fidelity.

Effect of micron-scale manufacturing flaws on the tensile response of centimeter sized two-photon polymerization microlattices

Two-photon polymerization (TPP) is a unique fabrication technique that enables sub-micron scale resolution. Herein, we report on uniaxial tensile tests on millimeter-sized TPP log-pile structures that were fabricated using a recently developed interdigitated stitching strategy. As expected, the Young’s modulus increased with laser intensity, however elastic modulus, ultimate strength and strain-at-failure varied widely, even for nominally identical samples. Post-mortem analysis revealed a series of print defects resulting from various sources including misalignments, resin shrinkage, laser beam shadowing, and local depletion of the oxygen inhibitor. While some of the defects can be eliminated, such as misalignments due to insufficient precision of the mechanical stage, others are more intrinsic to TPP and thus more difficult to address.

In-Situ Investigation of Resin Shrinkage in the Composite Manufacturing Environment

Cure shrinkage of the polymer matrix during the composite manufacturing process leads to residual stresses, which can adversely affect the structural integrity and dimensional stability of composite structures. In this paper, a novel approach is developed for measuring the resin shrinkage and strain evolution of an epoxy resin (EPON-862) in the composite manufacturing environment. The resin is cured in a custom designed autoclave with borosilicate viewports, while digital image correlation (DIC) is used to analyze the strain evolution throughout the cure cycle. These processing induced strains are correlated to the cure-state using differential scanning calorimetery (DSC). The different mechanisms involved in the polymer strain evolution during composite processing are discussed.

Crack spatial distributions and dynamic thermomechanical properties of 3D braided composites during thermal oxygen ageing

Thermal oxygen ageing behaviors of polymer matrix composites depend on resin and preform architecture. This paper concerns effects of braided architectures on thermo-oxidative ageing, including inner and surface crack initiations and propagations in 3D braided carbon fiber/epoxy composites. The ageing behaviors of unidirectional (UD) was also tested for comparison. Attenuated total reflectance Fourier transform infrared spectroscopy, two-dimensional infrared correlation spectrum, and micro-computer tomography technique have been used to characterize ageing behaviors. Aromatic formation was found ether on the surface of epoxy resin appeared prior to peroxide. The resin shrinkage could appear on the surface, and the changes of shrinkage rate of the UD composites and the 3D braided composites were consistent with cracks volume fraction. In addition, the cracks in the 3D braided composites initiated later and propagated slower than those in the UD composites. The 3D braided structure was beneficial for retaining the stiffness and damping properties after ageing.

Thiol‐terminated hyperbranched polymer for DLP 3D printing: Performance evaluation of a low shrinkage photosensitive resin

AbstractIn order to lower the volume shrinkage of the DLP 3D printing photosensitive resins during printing, a thiol‐terminated hyperbranched polymer (T‐HBP) was synthesized and introduced into the bisphenol A epoxy acrylate (EA) based photosensitive resin system. The obtained T‐HBP was characterized by FTIR and 1H NMR spectra, and the grafting rate of sulfhydryl was determined. The mechanical properties of the photosensitive resins were measured by tensile and impact strength measurement. The glass transition temperature of the photosensitive resins was analyzed by DSC and the impact fracture surface was observed by SEM. T‐HBP exhibited a much lower viscosity than its linear counterparts, and the addition of thiol improved the curing speed of the photosensitive resins. When the amount of T‐HBP added was 20 wt%, the shrinkage of the photosensitive resins was reduced by about 45.5% and the impact strength increased by 33.9% compared with the control. The macromolecular spherical structure of T‐HBP effectively reduced the functional group density of the photosensitive resins. In addition, the thiol‐acrylate photopolymerization introduced by T‐HBP further reduced the volume shrinkage of the photosensitive resins.

Effect of volumetric shrinkage of restorative materials on tooth structure: A finite element analysis.

Post-treatment coronal hermetic seal of the root canal opening prevents the food or saliva which assist to achieve successful endodontic treatment. Gutta-percha is filled in the inner canal, that is, from cervical third to apical third. Gutta-percha does not provide the hermetic seal because it does not bound with dentine walls. Various new restorative materials have been developed in the last 6-7 decade but drawback related to the polymerization shrinkage of the composite resin remains a clinical problem. In general, dental composites having volumetric shrinkage of the material depends on its formulation and curing conditions. In this article, the effect of this polymerization shrinkage on the tooth structure has been studied.

Physical and Mechanical Properties of Resins Blends Containing a Monomethacrylate with Low-polymerization Shrinkage.

Objectives The aim of this study was to evaluate the Knoop hardness (KH), cross-link density (CLD), water sorption (WS), water solubility (WSB), and volumetric shrinkage (VS) of experimental resins blends containing a monomethacrylate with low-polymerization shrinkage. Materials and Methods A blend of bisphenol glycidyl methacrylate (BisGMA) as base monomer was formulated with (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA), Bis-GMA/isobornyl methacrylate (IBOMA), or Bis-GMA/TEGDMA/IBOMA in different concentrations (40, 50, or 60 wt%). The camphorquinone (CQ)/2-(dimethylamino) ethyl methacrylate (DMAEMA) was used as the photoinitiator system. The KH and CLD were measured at the top surface using an indenter. For WS and WSB, the volume of the samples was calculated in mm 3 . The samples were transferred to desiccators until a constant mass was obtained (m1) and were subsequently immersed in distilled water until no alteration in mass was detected (m2). The samples were reconditioned to constant mass in desiccators (m3). WS and WSB were determined using the equations m2 − m3/V and m1 − m3/V, respectively. VS results were calculated with the density parameters before and after curing. Statistical Analysis Data were submitted to ANOVA and Tukey’s test (α = 0.05). Results The resins containing IBOMA showed lower VS results. TEGDMA 40% and TEGDMA/IBOMA 20/20 wt% showed higher KH values. The IBOMA groups showed lower CLD, while TEGDMA groups had higher values of CLD. The BisGMA/TEGDMA resin presented the highest values of WS, and for WSB, all groups showed no significant differences among themselves. Conclusion The monomethacrylate with low-polymerization shrinkage IBOMA used alone or in combination with TEGDMA may decrease VS, WS, and CLD values.