Amorphous Elastomeric Ultra-High Molar Mass Polypropylene in High Yield by Half-Titanocene Catalysts.

Propylene polymerizations with different ketimide-modified half-titanocene catalysts, Cp'TiCl(N=CBu) [Cp' = CH (), CMe (), MeSiCH ()], with MAO as a cocatalyst, were investigated. The obtained polymers were studied in detail by determining their microstructure, molar masses, thermal, and mechanical properties. The Cp*-ketimide, (CMe)TiCl(N=CBu) (), exhibited higher catalytic activities than Cp'TiCl(N=CBu) (,), yielding higher molar mass polymers, up to 1400 Kg/mol.

Maxillary Anterior Teeth Dimensions and Relative Width Proportions: A Narrative Literature Review.

Predictable results in the aesthetic treatment of anterior teeth can be obtained by resorting to the concept of dental aesthetics and, in particular, defining the ideal tooth dimensions and proportions to obtain a harmonious smile. Considering the great variety of articles dealing with the topic, and the lack of updated reviews, this narrative literature review aims to evaluate current knowledge on anterior teeth dimensions and to verify the existence and the potential applications of the anterior teeth proportioning theories (Golden Proportion, Golden Percentage, RED Proportion, and Golden Rectangle). PubMed, Embase, Cochrane Library, and Google Scholar databases were comprehensively searched using different keywords and term combinations.

Flexible Polyurethane Foams from Bio-Based Polyols: Prepolymer Synthesis and Characterization.

Bio-polyols (BPOs), characterized by a hydroxyl number up to around 90 mg KOH/g, narrow polydispersity index and relatively low molecular mass up to 2000 g/mol, were synthetized from partially and completely epoxidized soybean and linseed oils and caprylic acid or 3-phenyl butyric acid. These BPOs were used in the presence of toluene diisocyanate to produce polyurethane (PU) foams by using a quasi-prepolymer method involving a two-step reaction. A detailed structural investigation of the prepolymers from toluene diisocyanate and both BPOs and polypropylene glycol was conducted by SEC and solution NMR.

High-Glass-Transition Polyesters Produced with Phthalic Anhydride and Epoxides by Ring-Opening Copolymerization (ROCOP).

Polyesters with a high glass transition temperature above 130 °C were obtained from limonene oxide (LO) or vinylcyclohexene oxide (VCHO) and phthalic anhydride (PA) in the presence of commercial salen-type complexes with different metals-Cr, Al, and Mn-as catalysts in combination with 4-(dimethylamino) pyridine (DMAP), bis-(triphenylphosphorydine) ammonium chloride (PPNCl), and bis-(triphenylphosphoranylidene)ammonium azide (PPNN) as cocatalysts via alternating ring-opening copolymerization (ROCOP). The effects of the time of precontact between the catalyst and cocatalyst and the polymerization time on the productivity, molar mass (), and glass transition temperature () were evaluated. The polyesters were characterized by a molar mass () of up to 14.

Biocomposite Foams with Multimodal Cellular Structures Based on Cork Granulates and Microwave Processed Egg White Proteins.

In an effort to reduce greenhouse gas emission, reduce the consumption of natural resources, and increase the sustainability of biocomposite foams, the present study focuses on the recycling of cork processing waste for the production of lightweight, non-structural, fireproof thermal and acoustic insulating panels. Egg white proteins (EWP) were used as a matrix model to introduce an open cell structure via a simple and energy-efficient microwave foaming process. Samples with different compositions (ratio of EWP and cork) and additives (eggshells and inorganic intumescent fillers) were prepared with the aim of correlating composition, cellular structures, flame resistance, and mechanical properties.

Antibacterial Properties of Polyurethane Foams Additivated with Terpenes from a Bio-Based Polyol.

Water-blown polyurethane (PU) foams were prepared by bio-polyols from epoxidized linseed oils and caprylic acid in combination with toluene diisocianate (TDI). A series of terpenes (menthol, geraniol, terpineol, and borneol), natural compounds with recognized antibacterial properties, were included in the starting formulations to confer bactericidal properties to the final material. Foams additivated with Irgasan, a broad-spectrum antimicrobial molecule, were prepared as reference.

Crystallization Behavior of Poly(ε-Caprolactone)-Hollow Glass Microspheres Composites for Rotational Molding Technology.

Composites suitable for rotational molding technology based on poly(ε-caprolactone) (PCL) and filled with hollow glass microspheres (HGM) or functionalized hollow glass microspheres (HGMf) were prepared via melt-compounding. The functionalization of glass microspheres was carried out by a silanization treatment in order to improve the compatibility between the inorganic particles and the polymer matrix and achieve a good dispersion of glass microspheres in the matrix and an enhanced filler-polymer adhesion. The crystallization behavior of materials was studied by DSC under isothermal and non-isothermal conditions and the nucleating effect of the glass microspheres was proven.

Styrene-Free Bio-Based Thermosetting Resins with Tunable Properties Starting from Vegetable Oils and Terpenes.

The substitution of fossil-based monomers in the thermosetting formulations is a fundamental issue to face the environmental concerns related to the use of traditional resins. In this paper, styrene-free thermosetting resins were prepared to start from vegetable oils with different compositions and unsaturation degrees, namely soybean, hempseed, and linseed oils. Using terpenic comonomers such as limonene and β-myrcene allows one to prepare thermosets avoiding the traditional fossil-based diluents such as styrene, thus obtaining an outstanding gain in terms of both environmental and safety concerns.

Flexible Polyurethane Foams from Epoxidized Vegetable Oils and a Bio-Based Diisocyanate.

Bio-polyols from epoxidized soybean and linseed oils and caprylic acid or 3-phenyl butyric acid were prepared using an environmentally friendly, solvent-free method evaluating the presence of triethylamine as catalyst. Side reactions, leading to a cross-linking structure with high density, were reduced, introducing the catalyst and properly tuning the reaction conditions. A medium functionality value of around 3 along with a hydroxyl number up to around 90 mg KOH/g, narrow polydispersity index, and relatively low molecular mass up to 2400 g/mol were the experimental targets.

Polyurethane-Based Coatings with Promising Antibacterial Properties.

In coatings technology, the possibility of introducing specific characteristics at the surface level allows for the manufacture of medical devices with efficient and prolonged antibacterial properties. This efficiency is often achieved by the use of a small amount of antibacterial molecules, which can fulfil their duty while limiting eventual releasing problems. The object of this work was the preparation and characterization of silver, titanium dioxide and chitosan polyurethane-based coatings.

Polyurethane-Based Composites: Effects of Antibacterial Fillers on the Physical-Mechanical Behavior of Thermoplastic Polyurethanes.

The challenge to manufacture medical devices with specific antibacterial functions, and the growing demand for systems able to limit bacterial resistance growth, necessitates the development of new technologies which can be easily produced at an industrial level. The object of this work was the study and the development of silver, titanium dioxide, and chitosan composites for the realization and/or implementation of biomedical devices. Thermoplastic elastomeric polyurethane was selected and used as matrix for the various antibacterial functions introduced during the processing phase (melt compounding).

Homo- and Copolymerization of Ethylene with Norbornene Catalyzed by Vanadium(III) Phosphine Complexes.

Herein, we report the homo- and co-polymerization of ethylene (E) with norbornene (NB) catalyzed by vanadium(III) phosphine complexes of the type VCl(PMePh) [n = 2 (), 1 ()] and VCl(PR) [R = phenyl (Ph, ), cyclohexyl (Cy, ), -butyl (Bu, )]. In the presence of EtAlCl and ClCCOOEt (ETA), - exhibit good activities for the polymerization of ethylene, affording linear, semicrystalline PEs with a melting temperature of approximately 130 °C. Mainly alternating copolymers with high comonomer incorporation were obtained in the E/NB copolymerization.

Lightweight Poly(ε-Caprolactone) Composites with Surface Modified Hollow Glass Microspheres for Use in Rotational Molding: Thermal, Rheological and Mechanical Properties.

In this work, novel composites based on poly(ε-caprolactone) (PCL) were prepared and characterized in terms of morphological, thermal, rheological and mechanical properties. Hollow glass microspheres (HGM), alone or surface modified by treatment with (3-aminopropyl)triethoxysilane (APTES) in order to enhance the compatibility between the inorganic particles and the polymer matrix, were used to obtain lightweight composites with improved properties. The silanization treatment implies a good dispersion of filler particles in the matrix and an enhanced filler⁻polymer adhesion.

Terpolymerization of Substituted Cycloolefin with Ethylene and Norbornene by Transition Metal Catalyst.

Ethylene-norbornene terpolymerization experiments using 5-alkyl-substituted norbornenes (5-pentyl-2-norbornene (C₅N) and 5-octyl-2-norbornene (C₈N)) or dicyclopentadiene (DCPD) were conducted with two -metallocenes, [Zr{(η⁵-C₉H₆)₂C₂H₄}Cl2] (1) and [Zr{(η⁵-2,5-Me₂C₅H₂)₂CHEt}Cl₂] (2), activated by methylaluminoxane (MAO). The terpolymers obtained were investigated in detail by determining the microstructure and termonomer contents by C NMR, molar masses and thermal properties. Results were compared to those of ethylene (E)-norbornene (N) terpolymerizations with 1-octene.

A controlled approach to iron oxide nanoparticles functionalization for magnetic polymer brushes.

In this article, we report a detailed study of surface modification of magnetite nanoparticles by means of three different grafting agents, functional for the preparation of magnetic polymer brushes. 3-Aminopropyltriethoxysilane (APTES), 3-chloropropyltriethoxysilane (CPTES), and 2-(4-chlorosulfonylphenyl)ethyltrichlorosilane (CTCS) were chosen as grafting models through which a wide range of polymer brushes can be obtained. By means of accurate thermogravimetric analysis a good control over the amount of immobilized molecules is achieved, and optimal operating conditions for each grafting agent are consequently determined.

A randomized clinical trial comparing at-home and in-office tooth whitening techniques: A nine-month follow-up.

Background: The aim of this split-mouth, randomized controlled trial was to compare the whitening results of at-home and in-office tooth bleaching techniques and the longevity of their effects at nine months after teeth had been bleached.

Methods: The authors conducted a study involving a 14-day bleaching period, during which the first maxillary premolars of 17 participants, who were 20 to 25 years of age, were bleached by means of either an at-home technique involving 10 percent carbamide peroxide or an in-office technique involving 38 percent hydrogen peroxide. The authors recorded color variables as proposed by the Commission Internationale de l'Eclairage-lightness (L*), redness (a*) and yellowness (b*)-by using a spectrophotometer at baseline and at one week, one month and nine months after bleaching.

Crown-root reattachment of a severe subgingival tooth fracture: a 15-month periodontal evaluation.

Traumatic tooth fractures represent an intriguing challenge for clinicians, particularly when they involve the anterior region of the maxilla. In such situations, esthetic, psychosocial, functional, and therapeutic problems may have a negative effect on the patient's quality of life. In addition, fractures that involve the biologic width of the periodontium are even more difficult to treat.

Nanophase separation in polystyrene-polyfluorene block copolymers thin films prepared through the breath figure procedure.

The amphiphilic block copolymer formed by a hydrophobic body of polystyrene and a hydrophilic head of poly[9,9-di(2-(2-tetrahydropyranyl-oxy)hexyl)fluorene-alt-9,9-dioctylfluorene] was synthesized, and its solution was used to create thin films with ordered pattern of holes, by means of the breath figure technique. These porous films, after a thermal treatment, were found to show ordered aggregates of the pi-conjugated blocks in the place of the cavities. This is probably due to a preorganization of the two different blocks of the copolymer occurring during the breath figure formation, which is driven by the condensation of water microdroplets on the polymer solution, and to a following phase segregation occurring during the thermal annealing.

An 8-year follow-up of a fractured endodontically treated incisor restored with a modified laminate veneer.

This clinical report describes the restoration of a left maxillary first incisor using an all-ceramic one-piece coronal post and a laminate veneer feature. This proposed restoration technique represents an alternative to traditional restoration procedures such as metal-ceramic restorations, all ceramic crowns and porcelain laminate veneers. This restoration preserves the remaining tooth structure, re-establishes function and offers good esthetic results.

Influence of operator skill on microleakege of total-etch and self-etch bonding systems.

Objectives: To evaluate the influence of operator skill on microleakage in class V restorations using simplified bonding systems.

Methods: Two cavities were carried out on the buccal and lingual surfaces of 50 human bicuspid teeth. The teeth were randomly assigned to two groups according to the operator's skill: student group and expert group.

Effect of operator skill in relation to microleakage of total-etch and self-etch bonding systems.

Objectives: To evaluate the influence of operator skill on microleakage in class V restorations using two-step bonding systems.

Methods: Two standardized box cavities were made on the buccal and lingual surfaces of 54 human bicuspid teeth, with the cervical margin in dentin. The teeth were randomly assigned to two groups according to the operator's skill.

Morphological and functional rehabilitation of severely infra-occluded primary molars in the presence of aplasia of the permanent premolar: a clinical report.

This clinical report describes the fixed prosthodontic rehabilitation of an infra-occluded primary molar. Diagnostic considerations included the patient's age, occlusal status, condition of the infra-occluded tooth including the degree of infra-occlusion and root resorption, as well as adjacent alveolar bone levels. Due to the patient's young age, an invasive prosthetic approach was delayed in favor of an onlay restoration, which represented a more rapid and conservative therapeutic choice.

Translucent fiber post cementation using a light-curing adhesive/composite system: SEM analysis and pull-out test.

Objectives: The performance of both light-curing and dual-cured adhesive/luting systems (as control), when used in combination with translucent fibre posts, was evaluated by means of pull-out test and scanning electron microscopy (SEM ) observation.

Methods: Forty root canal treated teeth were randomly divided into two groups of 20 specimens each. Group 1 light-curing system: Excite and Tetric Flow; Group 2 dual cured system: All Bond 2+RelyX ARC.

Investigation into the nature of dentin resin tags: a scanning electron microscopic morphological analysis of demineralized bonded dentin.

Statement Of Problem: While the formation of the dentin/adhesive hybrid layer has been generally established, the infiltration and flow of the adhesive resin inside the acid treated dentinal tubules remains controversial.

Purpose: The aim of the present study was to investigate and review the current interpretation of resin tags by means of scanning electron microscopic (SEM) observation.

Material And Methods: Eight noncarious, human third molars were cut transversally and then longitudinally to obtain 8 middle-to-deep dentinal surfaces.