Analysis of polymerization behavior of dental dimethacrylate monomers by differential scanning calorimetry

Urethane dimethacrylate-based photopolymerizable resins for stereolithography 3D printing: A physicochemical characterisation and biocompatibility evaluation

Vat photopolymerisation (VP) three-dimensional printing (3DP) has attracted great attention in many different fields, such as electronics, pharmaceuticals, biomedical devices and tissue engineering. Due to the low availability of biocompatible photocurable resins, its application in the healthcare sector is still limited. In this work, we formulate photocurable resins based on urethane dimethacrylate (UDMA) combined with three different difunctional methacrylic diluents named ethylene glycol dimethacrylate (EGDMA), di(ethylene glycol) dimethacrylate (DEGDMA) or tri(ethylene glycol) dimethacrylate (TEGDMA). The resins were tested for viscosity, thermal behaviour and printability. After printing, the 3D printed specimens were measured with a digital calliper in order to investigate their accuracy to the digital model and tested with FT-IR, TGA and DSC. Their mechanical properties, contact angle, water sorption and biocompatibility were also evaluated. The photopolymerizable formulations investigated in this work achieved promising properties so as to be suitable for tissue engineering and other biomedical applications.

Methacrylate Polymers With “Flipped External” Ester Groups: A Review

Current resin composites have favorable handling and upon polymerization initial physical properties that allow for efficient material replacement of removed carious tooth structure. Dental resin composites have long term durability limitations due to the hydrolysis of ester bonds within the methacrylate based polymer matrix. This article outlines the importance of ester bonds positioned internal to the carbon-carbon double bond in current methacrylate monomers. Water and promiscuous salivary/bacterial esterase activity can initiate ester bond hydrolysis that can sever the polymer backbone throughout the material. Recent studies have custom synthesized, with the latest advances in modern organic chemical synthesis, a novel molecule named ethylene glycol bis (ethyl methacrylate) (EGEMA). EGEMA was designed to retain the reactive acrylate units. Upon intermolecular polymerization of vinyl groups, EGEMA ester groups are positioned outside the backbone of the polymer chain. This review highlights investigation into the degradation resistance of EGEMA using buffer, esterase, and microbial storage assays. Material samples of EGEMA had superior final physical and mechanical properties than traditional ethylene glycol dimethacrylate (EGDMA) in all degradation assays. Integrating bioinformatics-based biodegradation predictions to the experimental results of storage media analyzed by LC/GC-MS revealed that hydrolysis of EGEMA generated small amounts of ethanol while preserving the strength bearing polymer backbone. Prior studies support investigation into additional custom synthesized methacrylate polymers with “flipped external” ester groups. The long term goal is to improve clinical durability compared to current methacrylates while retaining inherent advantages of acrylic based chemistry, which may ease implementation of these novel methacrylates into clinical practice.

Experimental Investigation of Compression Properties of Composites with Printed Braiding Structure

A kind of composite was designed and additive manufacturing (AM) technology was utilized in the braiding structure fabrication. The printed polylactic acid (PLA) braiding structures were integrated with two types of resins (Epon 828 resin and urethane dimethacrylate/triethylene glycol dimethacrylate (UDMA/TEDGMA) resin) used as the matrix to make composite specimens. The compression test of the composite specimens showed that the printed PLA braiding structures had the effect of varying the compression properties of pure resins: it decreased the compression properties of Epon 828 resin, but increased those of UDMA/TEGDMA resin. Observing scanning electron microscope (SEM) images, it was noted that the decreasing and increasing in the compression properties of the specimens were related to the bonding compactness between the printed braiding structure and resins. Our results may suggest a new methods for the fast manufacturing of AM-based composites, further research directions, and potential applications of this kind of composites.

Thermoanalytical study of sweetener myo-inositol: α and β polymorphs

This work investigates the thermal behavior of α and β myo-inositol polymorphs. The inositol is a natural compound widely used in the food industry due to its presence in carbohydrate metabolism and its sweet taste. The occurrence of polymorphism could change some physico-chemical properties, such as melting and sublimation temperatures, and solubility. Therefore, the thermal study of polymorphism is important to ensure better conditions for synthesis, storage, and transportation of food that contains the myo-inositol. Simultaneous Termogravimetry-Differential Thermal Analysis, Photovisual Differential Scanning Calorimetry, Polarized Light Thermomicroscopy, and Powder X-ray Diffraction were used in investigation. The data show a new thermal event associated to β myo-inositol melting at 221.43°C, suggesting that the solid-solid transition at 185.68°C was incomplete. The kinetics data made it possible to determine the transition lifetime of myo-inositol to occur 5% of solid-solid transition at 20°C and 37°C: 126 and 8years, respectively.

Analysis of photopolymerization behavior of UDMA/TEGDMA resin mixture and its composite by differential scanning calorimetry

The aim of this study was to investigate the extent of polymerization (Ep) in terms of polymerization rate of UDMA/TEGDMA resin mixtures and its composite resin, by using a differential scanning calorimeter (DSC) technique employing a photopolymerization apparatus. The resin mixtures used in this study consisted of urethane dimethacrylate (UDMA) as a base monomer and triethyleneglycol dimethacrylate (TEGDMA) as a low viscosity monomer. The concentration of TEGDMA in the mixed monomer was varied to 0, 20, 40, 60, 80, and 100 mol %. Additionally, using a base monomer consisting of 60 mol % UDMA and 40 mol % TEGDMA, four kinds of composites with silica filler of 0, 20, 40, 60, and 70 wt %, were prepared in this study. The general reaction profile and Ep values were obtained from the DSC curves. Increasing the concentration of TEGDMA resulted in a decrease in the viscosity of the UDMA/TEGDMA mixture, a delay in the time to maximum polymerization rate, and an increase in the Ep values of the resin mixtures. Furthermore, Ep values decreased with increasing filler content between 0 and 60 wt % but did not decrease further between 60 and 70 wt %.