To give a current review of silane adhesion chemistry, applications of silane coupling agents and related surface pretreatment methods in contemporary dentistry.
Silane coupling agents are adhesion ...promoters to chemically unify dissimilar materials used in dentistry. Silanes are very effective in adhesion promotion between resin composites and silica-based or silica-coated indirect restorative materials. It is generally accepted that for non-silica-based restorations, surface pretreatment is a mandatory preliminary step to increase the silica content and then, with help of silane, improve resin bonding. This review discusses the silane-based adhesion chemistry, silane applications in dentistry, surface pretreatment methods, and presents the recent development of silane coupling agents.
A silane coupling agent is considered a reliable, good adhesion promoter to silica-based (or silica-coated) indirect restorations. Surface pre-treatment steps, e.g., acid etching for porcelain and tribo-chemical silica-coating for metal alloys, is used before silanization to attain strong, durable bonding of the substrate to resin composite. In clinical practice, however, the main problem of resin bonding using silanes and other coupling agents is the weakening of the bond (degradation) in the wet oral environment over time.
A silane coupling agent is a justified and popular adhesion promoter (adhesive primer) used in dentistry. The commercial available silane coupling agents can fulfil the requirements in clinical practice for durable bonding. Development of new silane coupling agents, their optimization, and surface treatment methods are in progress to address the long term resin bond durability and are highly important.
This article discusses the issue of “green bonds”. “Green” bonds are relevant and attractive for investors today. The features of “green” bonds are presented and the development practice in Europe is ...studied. The figures show the number of climate-aligned and green bonds worldwide in 2018 by region, the distribution of green bond issuance in Europe in 2019 by type of regional issuers, and the volume of green bond issuance in selected European countries in the first half of 2020.
Abstract Objective An ideal dental adhesive should provide retentive strength, marginal seal, be relatively simple to achieve and demonstrate clinical durability. Future improvements in adhesive ...bonding to tooth structure require in vitro test methods that provide reliable data for materials development and/or evaluation of experimental variables. The objective of this project was to identify a test method that is relatively easy to perform, repeatable and ultimately useful for predicting clinical outcomes. Methods The Academy of Dental Materials initiated a project to develop and distribute guidance documents on laboratory test methods that are useful for the evaluation of dental adhesives and cements, composite resins and ceramics. Results The dental adhesive sub-group has identified the micro-tensile bond strength test, especially after subjecting the specimens to a durability challenge, as currently the best practical surrogate measure of dental composite restoration retention. Conclusion The following μTBS guidance is meant to aid the researcher in conducting the μTBS test. The authors, while recognizing the limitations of a static, strength-based test method, welcome comments and suggestions for improvements of this guidance document in future revisions.
•Anions can interact with Group 14–17 elements as electron-deficient sites.•These interactions are known as tetrel, pnictogen, chalcogen and halogen bonding.•Such noncovalent bonds offer unique ...features for anion recognition.•Diverse receptor architectures and applications have been reported.
Compounds incorporating Group 14–17 elements as electron-deficient sites are capable of attractive, directional interactions with Lewis bases. These noncovalent interactions are known as tetrel, pnictogen, chalcogen and halogen bonding, respectively. When the Lewis base is a negatively charged species, such interactions can be employed as the basis for the development of anion receptors, which are of interest from a fundamental standpoint and in applications ranging from chemical sensing to catalysis and medicinal chemistry. Halogen bonding and related interactions offer intriguing features in this context, including distinctive patterns of anion selectivity and solvent effects, along with unique opportunities for structural variation and synthetic access. This review article summarizes advances in anion recognition using halogen, chalcogen, pnictogen and tetrel bonding, with a focus on examples for which solution-phase thermodynamic data have been obtained.
Starting from the chlorogermyliumylidene chloride salt L(Cl)Ge:Cl (1) (L = 1,1'-methylene-3,3'-di-2,6-diisopropyl-phenylimidazol e-2,2'-diylidene), the chloride ion can be easily substituted by BPh ...sub(4) to yield L(Cl)Ge:BPh sub(4) (3). Reaction of the latter with NaN sub(3) furnishes L(N sub(3))Ge:BPh sub(4) (4). In contrast, the direct reaction of 1 with NaN sub(3) affords exclusively the first azidogermyliumylidene azide salt L(N sub(3))Ge:N sub(3) (2). The latter represents the first isolable diazido Ge(ii) complex with a covalently bonded azido ligand and a weakly coordinating azide anion as the counterion. All new compounds 2, 3, and 4 were fully characterized, including using X-ray diffraction analysis.
MP2/aug-cc-pVTZ calculations were carried out on complexes of ZH sub(4), ZFH sub(3) and ZF sub(4) (Z = C, Si and Ge) molecules with HCN, LiCN and Cl super(-) species acting as Lewis bases through ...nitrogen centre or chlorine ion. Z-Atoms in these complexes usually act as Lewis acid centres forming sigma -hole bonds with Lewis bases. Such noncovalent interactions may adopt a name of tetrel bonds since they concern the elements of the group IV. There are exceptions for complexes of CH sub(4) and CF sub(4), as well as for the F sub(4)Si...NCH complex where the tetrel bond is not formed. The energetic and geometrical parameters of the complexes were analyzed and numerous correlations between them were found. The Quantum Theory of 'Atoms in Molecules' and Natural Bonds Orbital (NBO) method used here should deepen the understanding of the nature of the tetrel bond. An analysis of the electrostatic potential surfaces of the interacting species is performed. The electron charge redistribution, being the result of the tetrel bond formation, is the same as that of the S sub(N)2 reaction. The energetic and geometrical parameters of the complexes analyzed here correspond to different stages of the S sub(N)2 process.
The product of the intermolecular 'frustrated Lewis pair' (FLP) B(C sub(6)F sub(5)) sub(2)(C sub(6)Cl sub(5))/2,2, 6,6-tetramethylpiperidine and H sub(2) has been studied by single-crystal neutron ...diffraction. This is the first structurally characterised example of a geometrically unconstrained dihydrogen (H...H) bond within a hydrogenated FLP system.
Magnetic field induces transition in the distorted Fe2+aFe2+ pairs (quantum dots) from the initial bonding singlet state to the high spin antibonding state providing decay of the pairs for two ...separated Fe2+ ions. Dislocations moving under internal stresses easily overcome separated Fe2+ ions in comparison with Fe2+aFe2+ pairs lying close to the glide plane. Non-monotonous field dependence of dislocation displacements under internal stresses governed by short (100 I14s) impulse of high magnetic fields up to 31 T was revealed in NaCl:Fe crystals. This non-typical dependence is the fingerprint of the LandauaZener non-adiabatic spin transition between singlet and high spin states in quantum dots distorted by mechanical stresses of moving dislocations.
The elastic behaviour of Cr3+ substituted CoaZn ferrites system; Co0.7Zn0.3CrxFe2axO4 where x=0.0 to 0.5 in step of 0.1 were prepared by ceramic method. Ultrasonic Pulse transmission method at room ...temperature was employed to determine the elastic properties of the presently investigated samples. Values of longitudinal and shear wave velocities were increased with an increases in Cr composition x. Using these value of velocities; Young's modulus, rigidity modulus, bulk modulus, longitudinal modulus and Poisson's ratio were calculated. The values of moduli were increased with an increases in Cr composition x. Debye temperature of all sample were calculate using the Anderson equation and it shows increasing trend with an increases in Cr composition x. The behaviour elastic moduli of Co0.7Zn0.3CrxFe2axO4 are interpreted in terms of bonding force between atoms.
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