Dual-cured adhesive system improves adhesive properties of dentin cavities restored with a bulk-fill resin composite

Aim: To evaluate the impact of a dual-cured adhesive system on the in situ degree of conversion (DC), bond strength (BS) and failure mode (FM) of adhesive interfaces in dentin cavities restored with a bulk-fill resin composite. Methods: 4-mm-deep dentin cavities with a 3.1 C-factor were created in 68 bovine incisors (n = 17 per group). The lightcured (Scotchbond™ Universal) or the dual-cured (Adper™ Scotchbond™ Multi-purpose Plus) adhesive system was applied to the cavities, which were then restored with a bulkfill resin composite (Filtek™ Bulk Fill). In situ DC analysis was performed by means of micro Raman spectroscopy at the top and bottom interfaces. Push-out BS was measured in a universal testing machine after 24-h or 6-month water storage. FM was determined with a stereomicroscope. Data of in situ DC and BS were analyzed by two-way analysis of variance (ANOVA) and Tukey test (p<0.05), while the FM was analyzed descriptively. Results: The groups that received the dual-cured adhesive system showed statistically higher in situ DC and BS than those that received the light-cured adhesive system. Cohesive failure mode was the most frequent in all conditions. Conclusion: In situ DC and BS were influenced by the curing strategies of the adhesive systems with better performance of the dual-cured material.

Evaluation of Wear Properties of Four Bulk-Fill Composites: Attrition, Erosion, and Abrasion

Purpose. Wear and increased surface roughness are among the reasons for failure of posterior composite restorations. Considering the widespread use of bulk-fill composites in the posterior region, information about their wear resistance is imperative. The aim of this study was to compare the wear and surface roughness of four bulk-fill composite resins with a conventional composite. Methods. Thirty composite discs ( 4 mm × 10 mm ) were fabricated from EverX Posterior (GC), X-tra fil (Voco), Filtek Bulk-Fill Posterior (3M, USA), SonicFill 2 (Kerr), and Z250 (3M) composites. The baseline weight and surface roughness of specimens were measured. For the assessment of the attrition wear, the specimens were placed in a chewing simulator (Mechatronik). pH cycling was performed to erode the composite discs. They were then placed in a tooth brushing simulator machine (Dorsa) for abrasion wear. Finally, the weight and surface roughness of the specimens were measured. Data were compared using one-way ANOVA ( alpha ≤ 0.05 ). Results. One-way ANOVA showed that the mean weight changes were significant after attrition, abrasion, and erosion ( P = 0.019 ), but changes in surface roughness were not significant ( P ≥ 0.05 ). The results of Tukey’s test showed no significant difference between the bulk-fill composites and Z250 regarding weight loss ( P ≥ 0.05 ), but the weight loss of X-tra fil was significantly greater than that of EverX ( P = 0.007 ) and Filtek Bulk-Fill ( P = 0.005 ). Conclusions. Considering the limitations of this study, it appears that the wear and surface roughness of bulk-fill composites are within the acceptable range and are not different from those of a conventional composite.

HIGH FIDELITY BUILDING BLOCK AND VALIDATION PROTOCOLS FOR NEXTGEN COMPOSITE METHODS

The High Fidelity Building Block and Validation Protocols for NextGen Composite Methods Program (N00014-21-C-1008) seeks to provide industry with the critical experimental data and supporting guidelines by which to evaluate, validate, and demonstrate the predictive capabilities of advanced computational analysis tools. Following from the successful development of a coupon level database (N00014-14-C-0128), the HiFi NextGen program focuses on the subelement and element levels of the design-test-certification building block wherein the greatest expense for design substantiation is incurred. Additionally, data is developed to provide improved understanding of fundamental material behavior for composite material models. Advanced inspection techniques such as digital image correlation and in-situ micro computed tomography are used to capture damage onset, damage propagation, and ultimate failure within representative composite structure test specimens. Where applicable, the test program includes relevant environmental conditions. Validation guidelines focus on the use of emerging progressive damage and failure analysis (PDFA) computational techniques and address modeling considerations such as length scale, material models, numeric implementation, mesh objectivity, modeling strategy, and computational scalability. All test articles are fabricated from IM7/5320-1 tape and fabric as well as FM309-1 structural adhesive to maintain a high degree of relevancy for future aircraft needs.

Qualitative and Quantitative Analysis of Housing Indices at the Neighborhood Level: Case Study of Region 6 of Tehran Municipality

Most of the cities in Iran have experienced very rapid development. The urban population in the last decade has been increased by migration, and cities in Iran are faced with many problems. Housing is becoming one of the major problems, and standard housing indices have taken an important place in urban planning to provide good conditions for better urban planning. Region 6 of Tehran municipality is home to a large portion of upper-middle social class people for whom owning a house is more than merely a place to live. The aim of the research was to analyze qualitative and quantitative indices for Region 6 of Tehran municipality. The study is based on analytical and descriptive methods. The secondary data collected from the latest Iran census report in 2016 and composite methods used to measure the special effects of changes in population size, growth rate, and indices of quantitative and qualitative assessment are wide-ranging housing which was analyzed based on the t-test, correlation test and regression with SPSS and GIS software. GIS software is used as an effective tool for generating maps to better understanding the behaviors of residents in a neighborhood. The result shows that Region 6 of Tehran is among the areas of serious urban decline and neighborhoods in the neighboring regions are influenced by the activities of other bordering neighborhoods.

SVECV-f12: benchmark of a composite scheme for accurate and cost effective evaluation of reaction barriers.

A simple composite scheme is presented, based on a combination of density functional geometry and frequencies evaluation, valence energies obtained using the CCSD(T)-f12 method extrapolated to the complete basis set limit, and core-valence correlation corrections employing the MP2 method. The procedure was applied to the 38 reactions in Truhlar’s HTBH38/08 and NHTBH38/08 databases and the errors in the barriers with respect to their best values are presented. Mean unsigned deviation (MUD) for the complete set of 68 independent barriers is 0.40 kcal mol-1 , compared to 1.31 kcal/mol for G4 and 1.62 kcal/mol for the dispersion-corrected M06- 2X method. The accuracy of the procedure is also better that that of other calculations using composite methods of similar cost. The MUD of the new scheme on the barriers in the DBH24/08 subset (12 out of the 38 reactions in the other two sets) is 0.27 kcal mol-1 , better than that obtained at the expensive CCSD(T,full)/aug-cc-pCV(T+d)Z level (0.46 kcal mol-1 ) and comparable to the 2 most exact (and costly) Wn calculations (MUD=0.14 kcal mol-1 ). The maximum unsigned deviation (MaxUD) for all the reactions studied is 0.99 kcal/mol. G4 and M06-2X, on the other side, exhibit MaxUDs of 6.7 and 8.0 kcal/mol respectively. The method was further tested against a subset of the reactions in the databases, for which the geometry and energies of all species were determined at the much more demanding CCSD(T)-F12//pVQZ-F12 level. These results showed that Truhlar’s calculations in this subset are off the best values by a considerable amount, with an rmse of 0.56 kcal/mol. As a consequence, a new dataset of barrier heights, SV20, is presented. The SVECV-F12 procedure on this SV20 database results in rmse and MUD values of only 0.21 and 0.16 kcal/mol. The possible residual errors introduced by the approximations used for each component of the method are tested against more sophisticated calculations and shown to be accurate enough to obtain barriers well under the chemical precision limit at a reasonable cost for molecules of interest in atmospheric chemistry.

Benchmark calculations for bond dissociation energies and enthalpy of formation of chlorinated and brominated polycyclic aromatic hydrocarbons

Benchmark calculations using state-of-the-art DFT functionals and composite methods for bond dissociation energy and enthalpy of formation of halogenated polycyclic aromatic hydrocarbons are performed.

Flexural Properties of Steel-Bamboo Composite Slabs in Different Connection Methods

This paper presents a study aimed to estimate the flexural performance of profiled steel sheet-bamboo plywood composite slabs as a first step to evaluate its potential application as structural components. Nine specimens were tested to investigate the stability of steel-bamboo composite structure. According to different connection methods, three types of composite slabs were discussed, including pure bonding slabs (PBSs), composite bonding slabs (CBSs), and reinforced composite bonding slabs (RCBS). The result showed that specimens employed multiple composite methods (RCBS) exhibited excellent flexural bearing capacity and stiffness compared with PBS. The increase of bamboo plywood thickness could improve bearing capacity and flexural stiffness of composite slabs, while the reduction of screw spacing could enhance the bearing capacity and ductility of composite slabs. The RCBS, which can provide higher bearing capacity and stiffness and possess excellent deformation capability, are well worth of research and practical application.