Search

In this study, polyurethane dimethacrylate (PUDMA) was synthetized from different components and incorporated into a direct resin composite restoration system with the aim to buffer tooth-resin interfacial stresses and maintain the marginal adaptation. The tensile strength, elongation at fracture (ε), and thermal stability of the PUDMA layer were characterized, showing a tensile strength of 22 MPa, an ε of 112%, and a thermal decomposition temperature of about 282°C. In addition, the degree of conversion, water sorption/solubility, hydrophobicity, microtensile bond strength (μTBS), marginal leakage, and cytotoxicity in vitro were evaluated for the PUDMA layer. The data were analyzed using one-way ANOVA, except for leakage depths (which were analyzed using the Wilcoxon paired-rank test). The level of significance was set at 0.05. Compared with dental adhesives, PUDMA displayed a higher degree of conversion, lower water sorption/solubility, and improved hydrophobicity and biocompatibility in vitro. After thermocycling, the μTBS of the restoration system containing PUDMA had increased compared with the μTBS at 24 h. Restorations containing PUDMA showed lower leakage depths than those which did not contain PUDMA. In conclusion, because of its hydrophobic and elastic nature, the PUDMA layer, when used as an intermediate between tooth and resin restoratives, may buffer interfacial stresses, improve the stability and durability of the bonding interface, and reduce microleakage., (© 2020 Eur J Oral Sci.)

In this study we evaluated dual-cure polyurethanes (PUs) as dental adhesives and investigated their effect on the durability of the resin-dentin bonding interface. Different novel photopolymerizable and moisture-curable PUs based on polyester polyol, polyether polyol, and hydroxyethyl methacrylates (HEMAs) were prepared, and their structural characteristics were evaluated by Fourier transform infrared spectroscopy. The tensile strength, elongation at break, and water sorption/solubility of the PU adhesives and the application for bonding with dentin were evaluated. The water sorption and solubility of the PU adhesives were significantly lower than those of two commercial control groups. The bond strength of the PU adhesives after 30 days of storage increased compared with their immediate bond strength, and the microleakage detection of Class V restorations showed less occurrence of marginal leakage compared with the commercial control groups. Cytotoxicity testing has shown that the PU adhesives have low toxicity to pulp cells. The results of this study may shift the future research focus of composite resin dental restoratives from original rigid bonding of the interface to a flexible bonding based on the use of PU adhesives. This may become a new strategy for decreasing the occurrence of microleakage and improving the durability of the bonding interface.

An interpenetrating polymer network (IPN) structured antibacterial layer was prepared on dental base materials containing quaternary ammonium salt monomers (HMDQAs), polyurethane dimethacrylate oligomers (BIHs) and functionalized SiO2 nanoparticles using a one-step photo-crosslinking method. Scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet near-infrared visible spectrophotometry (UV-3600) and water contact angles were used to study the surface properties of the coatings. SiO2 nanoparticles changed the hydrophilicity of the cationic antimicrobial surface and increased its contact angle. Furthermore, the IPN coatings exhibited highly effective antibacterial activity on the modified dental base material, poly(methyl methacrylate) (PMMA), against Streptococcus mutans, which was evaluated by plate colony counting, optical density (OD), SEM and a live/dead assay. The MTT assay confirmed their biocompatibility. The IPN silicon complexed coating displayed good transparency, excellent antibacterial activity, and no cytotoxicity, which indicated enormous potential for the treatment of denture bases. [ABSTRACT FROM AUTHOR]

In this study, we design and synthesize a novel photosensitive polyurethane material as a functional dielectric layer, which can adjust the crystallization of para-hexaphenyl (p-6P). The novel polymer is synthesized with a new monomer 2,2-bis(hydroxymethyl)butyl 4-cyanobenzoate (HM-4-CB), which contains benzene to provide crystal nucleus sites. The grain size and density of the p-6P crystal can be controlled by the content of HM-4-CB in the polymer structure. Therefore, this method can be used to regulate the grain size of semiconductor crystals and then to change the carrier mobility of the device. The results illustrate that with a suitable grain size of the p-6P semiconductor, excellent performance in terms of charge carrier mobility can be obtained. [ABSTRACT FROM AUTHOR]

Novel polyurethane containing terphenyl groups were designed and synthesized as gate insulators to induce the crystallization of p-sexiphenyl(p-6P) for organic thin-film transistors (OTFTs). Different sizes and shapes of p-6P grains were measured by atomic force microscopy (AFM), and results showed that the large size of p-6P grain can improve the performance of OTFTs. About 900 nm thick films can be easily fabricated by spin-coating under ambient conditions, followed by curing at UV irradiation for 10 min. OTFTs with this film as gate insulator were found to have good processability, a high charge-carrier mobility of 1.1 cm 2 /V s, a threshold voltage of −25 V, and an on/off current ratio >10 5 . The result indicated that this material is a promising candidate for the exploration of devices using OTFTs. [ABSTRACT FROM AUTHOR]

Superhydrophobic coatings were successfully fabricated by photo-crosslinked polyurethane (PU) and organic fluoro group-functionalized SiO 2 nanoparticles (F-SiO 2 NPs), and were introduced for preventing microleakage in a dental composite restoration. The F-SiO 2 NPs possessed low surface energy and the PU can not only improve the mechanical stability but also promote F-SiO 2 NPs to form multiscale structure, which could facilitate the properties of the as-prepared superhydrophobic coating by synergetic effect. The morphology and properties of the resulted superhydrophobic coatings with different PU/F-SiO 2 ratios were studied using 1 H NMR spectrum, fourier transform infrared spectra, scanning electron microscopy, atomic force microscopy and UV–vis spectrophotometry. The results showed that the superhydrophobic coatings with low PU/F-SiO 2 ratio (1:3) possessed excellent hierarchical papillae structure with trapped air pockets, high contact angle (160.1°), low sliding angle (< 1°) and good transparency. Additionally, MTT experiments results certified the prominent cell viability and biocompatibility for clinical application. Based on its fantastically superhydrophobic property, the as-prepared superhydrophobic coatings effectively prevented water permeation in resin composite restoration evaluation. This research may provide an effective method to solve the problem of microleakage and will efficiently increase the success rate of dental composite restorations. [ABSTRACT FROM AUTHOR]