Gender trends in dentistry: Dental faculty and academic leadership.

OBJECTIVES: Gender equality in the healthcare workforce has been a topic of discourse for many decades. In dental academia, women's representation of enrolled students and faculty has risen consistently since the 1980s. However, women in faculty leadership positions may still be lagging when compared to men. The purpose of this study was to evaluate the number of women who occupy the upper echelons of academic rank and title by analyzing cross-referenced data from the American Dental Association and the American Dental Education Association on women dental school graduates in relation to academic appointments. METHODS: Gender distribution in rank, title, and appointments in the decade from 2011 to 2019, as well as percentage of women graduates over the same period, were collected for descriptive statistics. Multiple linear regression analysis, Cochran Armitage, and chi-square tests were conducted to examine trends over the years and to determine significant differences in overall percentages (p < 0.05). RESULTS: The total women faculty percentages ranged from 36% to 40%. While the lower-level rank of instructor retained a higher representation of women (56%-65%), the higher rank of professor had disproportionately lower women percentages (18%-26%). Graduates, full-time faculty, lower-level academic ranks, and higher-level academic ranks for women followed similar upward trends that were statistically significant (p < 0.05). When comparing the different groups against each other, the annual increase in women DMD/DDS graduate percentage was higher than women full-time faculty (0.28%), instructor rank (0.92%), professor rank (0.50%), and department chair appointments (0.49%). CONCLUSIONS: Our data show that women are still underrepresented at higher academic ranks. However, the upward trends for professors, assistant deans, and program chairs suggest that in recent years, more women faculty may have been encouraged, mentored, or offered higher administrative positions in academic institutions.

Surface species in direct liquid phase synthesis of dimethyl carbonate from methanol and CO2: an MCR-ALS augmented ATR-IR study.

The reaction mechanism of dimethyl carbonate (DMC) production over ZrO2 from CO2 and CH3OH is well-known, but the level of understanding has not improved in the last decade. Most commonly, the reaction mechanism has been explored in the gas phase, whilst DMC production occurs in the liquid phase. To overcome this contradiction, we exploited in situ ATR-IR spectroscopy to study DMC formation over ZrO2 in the liquid phase. A multiple curve resolution-alternate least square (MCR-ALS) approach was applied to spectra collected during the CO2/CH3OH interaction with the catalyst surface, leading to the identification of five pure components with their respective concentration profiles. CO2 and CH3OH activation to carbonates and methoxide species was found to strongly depend on the reaction temperature. Low temperature prevents methanol dissociation leaving a catalyst covered with stable carbonates, whilst higher temperature decreases the stability of the carbonates and enhances the formation of methoxides. A reaction path involving the methoxide/carbonate interaction at the surface was observed at low temperature (≤50 °C). We propose that a different reaction path, independent of carbonate formation and involving the direct CO2/methoxide interplay, occurs at 70 °C.

From gaseous HCN to nucleobases at the cosmic silicate dust surface: an experimental insight into the onset of prebiotic chemistry in space.

HCN in the gas form is considered as a primary nitrogen source for the synthesis of prebiotic molecules in extraterrestrial environments. Nevertheless, the research mainly focused on the reactivity of HCN and its derivatives in aqueous systems, often using external high-energy supply in the form of cosmic rays or high energy photons. Very few studies have been devoted to the chemistry of HCN in the gas phase or at the gas/solid interphase, although they represent the more common scenarios in the outer space. In this paper we report about the reactivity of highly pure HCN in the 150-300 K range at the surface of amorphous and crystalline Mg2SiO4 (forsterite olivine), i.e. of solids among the constituents of the core of cosmic dust particles, comets, and meteorites. Amorphous silica and MgO were also studied as model representatives of Mg2SiO4 structural building blocks. IR spectroscopic results and the HR-MS analysis of the reaction products revealed Mg2+O2- acid/base pairs at the surface of Mg2SiO4 and MgO to be key in promoting the formation of HCN oligomers along with imidazole and purine compounds, already under very mild temperature and HCN pressure conditions, i.e. in the absence of external energetic triggers. Products include adenine nucleobase, a result which supports the hypothesis that prebiotic molecular building blocks can be easily formed through surface catalytic processes in the absence of high-energy supply.

Insights on a Hierarchical MFI Zeolite: A Combined Spectroscopic and Catalytic Approach for Exploring the Multilevel Porous System Down to the Active Sites.

The hierarchization of zeolites to overcome the major drawbacks related to molecular diffusion limitation in micropores is a popular concept in heterogeneous catalysis. Despite the constant increase of new synthesis strategies to produce such hierarchical systems, the deep knowledge of their structural arrangement and how the zeolitic lattice is organized in a multilevel porous system is often missing. This information is essential to design a structure, tuning the porosity and the distribution of easily accessible active sites, and successively controlling the catalytic properties. In the present work, the synthesis of one of the most sophisticated forms of the hierarchical ZSM-5 zeolite has been reproduced, obtaining two multilevel porous materials with different crystallinity degrees, with the final aim of investigating and clarifying the finest features of their active sites. For this purpose, an extended characterization step by means of a unique multitechnique approach has been performed, thus revealing the active site nature, abundance, and distribution. IR spectroscopy with different molecular probes and a targeted catalytic test based on the hydroconversion reaction of n-decane were the toolbox for disclosing how the MFI lattice takes part in the hierarchical structure and how it, working in synergy with the mesoporous system, confers to this material a totally new shape-size selectivity. Merging the information obtained for the synthesized hierarchical zeolite with the characterization results of two reference materials (a mesoporous aluminum-containing MCM-41 and a microporous commercial ZSM-5), it was possible to define an internal and external map of the pore network of this complex and unique molecular sieve, where strong Brønsted acidic sites are located at the mouth of the MFI micropores and, at the same time, exposed at the surface of the mesoporous channels. Hence, the possibility of easily releasing bulky products is ensured and the application possibilities of the MFI lattice are expanded beyond cracking reactions.

Influence of Photon-Induced Photoacoustic Streaming (PIPS) on Root Canal Disinfection and Post-Operative Pain: A Randomized Clinical Trial.

The aim of this study was to evaluate the ability of a PIPS (photon-induced photoacoustic streaming) Er:YAG laser to reduce the root canal system bacterial count in vivo in comparison to the traditional irrigation technique. The post-operative patients' quality of life (QoL) after endodontic therapy was evaluated through a questionnaire. Fifty-four patients affected by pulp necrosis with or without apical periodontitis biofilm disease were selected for endodontic treatment and randomly assigned to Group A (n = 27) with traditional irrigation and Group B (n = 27), with PIPS irrigation applied according to the protocol. Shaping was performed with ProGlider and ProTaper Next, and irrigation was performed with 5% NaOCl and 10% EDTA. Intracanal samples for culture tests were collected before and after irrigation. The microbiological analysis was evaluated by the Kolmogorov-Smirnov normality and Mann-Whitney tests (p < 0.05). A self-assessment questionnaire was used to evaluate the QoL during the 7 days after treatment; differences were analysed with Student's t-test. Irrigation with the PIPS device was significantly effective in reducing bacterial counts, which were higher for facultative than obligate anaerobic strains, particularly for Gram-negative bacteria, without statistical significance (p > 0.05). There were no significant differences among the QoL indicators, except for the maximum pain (p = 0.02), eating difficulty (p = 0.03) and difficulty performing daily functions (p = 0.02) in the first few days post-treatment. PIPS may represent an aid to root canal disinfection not affecting the patients' QoL, particularly for the first day after treatment.

Unravelling the water adsorption in a robust iron carboxylate metal-organic framework.

A Fe-MOF was obtained from aqueous solution in high yield under reflux. The water sorption properties were studied by powder X-ray diffraction, volumetric and gravimetric sorption experiments and molecular simulations. The subsequent filling of hydrophobic and hydrophilic pores as well as the stability of the material are demonstrated.

Titanium Defective Sites in TS-1: Structural Insights by Combining Spectroscopy and Simulation.

Ti silicates, and in particular, titanium silicalite-1 (TS-1), are nowadays important catalysts for several partial oxidation reactions in the presence of aqueous H2 O2 as an oxidant. Despite the numerous studies dealing with this material, some fundamental aspects are still unclear. In particular, the structure and the catalytic role of defective Ti sites, other than perfect tetrahedral sites recognized as the main active species, has not been quantitatively discussed in the literature. We assess the structural features of defective Ti sites on the basis of outcomes of electronic spectroscopies, as interpreted through quantum mechanical simulation. Strong evidence is disclosed to support the fact that the most common defective Ti sites, often reported in the TS-1 literature, are monomeric Ti centers that are embedded in the zeolite framework, and which have a distorted octahedral local symmetry.

Monitoring the Reactivity of Formamide on Amorphous SiO2 by In-Situ UV-Raman Spectroscopy and DFT Modeling.

Formamide has been recognized in the literature as a key species in the formation of the complex molecules of life, such as nucleobases. Furthermore, several studies reported the impact of mineral phases as catalysts for its decomposition/polymerization processes, increasing the conversion and also favoring the formation of specific products. Despite the progresses in the field, in situ studies on these mineral-catalyzed processes are missing. In this work, we present an in situ UV-Raman characterization of the chemical evolution of formamide over amorphous SiO2 samples, selected as a prototype of silicate minerals. The experiments were carried out after reaction of formamide at 160 °C on amorphous SiO2 (Aerosil OX50) either pristine or pre-calcined at 450 °C, to remove a large fraction of surface silanol groups. Our measurements, interpreted on the basis of density functional B3LYP-D3 calculations, allow to assign the spectra bands in terms of specific complex organic molecules, namely, diaminomaleonitrile (DAMN), 5-aminoimidazole (AI), and purine, showing the role of the mineral surface on the formation of relevant prebiotic molecules.

A quantum mechanical study of dehydration vs. decarbonylation of formamide catalysed by amorphous silica surfaces.

Formamide is abundant in the interstellar medium and was also present during the formation of the Solar system through the accretion process of interstellar dust. Under the physicochemical conditions of primordial Earth, formamide could have undergone decomposition, either via dehydration (HCN + H2O) or via decarbonylation (CO + NH3). The first reactive channel provides HCN, which is an essential molecular building block for the formation of RNA/DNA bases, crucial for the emergence of life on Earth. In this work, we studied, at the CCSD(T)/cc-pVTZ level, the two competitive routes of formamide decomposition, i.e. dehydration and decarbonylation, either in liquid formamide (by using the polarization continuum model technique) or at the interface between liquid formamide and amorphous silica. Amorphous silica was adopted as a convenient model of the crystalline silica phases ubiquitously present in the primordial (and actual) Earth's crust, and also due to its relevance in catalysis, adsorption and chromatography. Results show that: (i) silica surface sites catalyse both decomposition channels by reducing the activation barriers by about 100 kJ mol-1 with respect to the reactions in homogeneous medium, and (ii) the dehydration channel, giving rise to HCN, is strongly favoured from a kinetic standpoint over decarbonylation, the latter being, instead, slightly favoured from a thermodynamic point of view.

Bimetallic hexanuclear clusters in Ce/Zr-UiO-66 MOFs: in situ FTIR spectroscopy and modelling insights.

In situ FTIR spectroscopy in combination with results from DFT calculations was used to determine the composition of mixed-metal clusters {CexZr6-x(µ3-O)4(µ3-OH)4} in Ce/Zr-UiO-66 compounds. Detailed, quantitative evaluation of vibrational bands ν(OH) of (µ3-OH)CexZr3-x groups allowed us to distinguish between two possible models: a solid solution or the presence of distinct clusters. This relatively straightfoward method should be also transferable to other mixed-metal metal-organic frameworks (MOFs).

A spectroscopic and computational study of a tough MOF with a fragile linker: Ce-UiO-66-ADC.

The thermolabile acetylene dicarboxylic acid has been introduced as linker in UiO-66 topology, synthetizing the compound with formula [Ce6O4(OH)4(ADC)6] and denoted as Ce-UiO-66-ADC MOF. The characterization by multi-technique approach coupled with computational modelling revealed a peculiar intrinsic defective nature related to the nature of the linker.

Exact Stoichiometry of Ce xZr6- x Cornerstones in Mixed-Metal UiO-66 Metal-Organic Frameworks Revealed by Extended X-ray Absorption Fine Structure Spectroscopy.

Bimetallic Ce/Zr-UiO-66 metal-organic frameworks (MOFs) proved to be promising materials for various catalytic redox applications, representing, together with other bimetallic MOFs, a new generation of porous structures. However, no direct proof for the presence of both metals in a single cornerstone of UiO-type MOFs was reported so far. Employing element-selective X-ray absorption spectroscopy techniques herein, we demonstrate, for the first time, that our synthesis route allows obtaining Ce/Zr-UiO-66 MOFs with desired Ce content and bimetallic CeZr5 cornerstones. Performing multiple-edge extended X-ray absorption fine structure analysis, we determine the exact stoichiometry of the cornerstones, which explains the dependence of thermal and chemical stability of the materials on Ce content.

Topology-dependent hydrocarbon transformations in the methanol-to-hydrocarbons reaction studied by operando UV-Raman spectroscopy.

The methanol-to-hydrocarbons (MTH) reaction represents a versatile, industrially viable alternative to crude-oil based processes for the production of chemicals and fuels. In the MTH reaction, the shape selectivity of acidic zeolites is exploited to direct the synthesis towards the desired product. However, due to unavoidable side reactions occurring under processing conditions, all MTH catalysts suffer deactivation due to coke formation. Though it is likely that some common characteristics for carbon formation exist for all zeolite topologies, it has been proposed that the differences in shape selectivity among the different catalysts will also influence the individual deactivation mechanisms. As deactivating species are mostly aromatic compounds, highly methylated benzenes and/or polycyclic aromatic hydrocarbons (PAHs) have been discussed. In some cases, these can further grow to extended carbon structures. Here, we have investigated the hydrocarbon reactivities and carbon formation for five topologically different zeolite catalysts through an operando UV-Raman approach, taking advantage of the high sensitivity of this technique towards aromatic and other carbonaceous species. The combination of the spectroscopic tool with activity measurements allowed us to obtain valuable details and some general trends on the deactivation paths during MTH. This approach made accessible unique insight on the complex chemistry of MTH by allowing the real-time observation of hydrocarbon transformations typical for the peculiar topology of each catalyst, usually inaccessible by ex situ techniques.

Formamide Adsorption at the Amorphous Silica Surface: A Combined Experimental and Computational Approach.

Mineral surfaces have been demonstrated to play a central role in prebiotic reactions, which are understood to be at the basis of the origin of life. Among the various molecules proposed as precursors for these reactions, one of the most interesting is formamide. Formamide has been shown to be a pluripotent molecule, generating a wide distribution of relevant prebiotic products. In particular, the outcomes of its reactivity are strongly related to the presence of mineral phases acting as catalysts toward specific reaction pathways. While the mineral⁻products relationship has been deeply studied for a large pool of materials, the fundamental description of formamide reactivity over mineral surfaces at a microscopic level is missing in the literature. In particular, a key step of formamide chemistry at surfaces is adsorption on available interaction sites. This report aims to investigate the adsorption of formamide over a well-defined amorphous silica, chosen as a model mineral surface. An experimental IR investigation of formamide adsorption was carried out and its outcomes were interpreted on the basis of first principles simulation of the process, adopting a realistic model of amorphous silica.

Prospective study of the impact of peri-implant soft tissue properties on patient-reported and clinically assessed outcomes.

BACKGROUND: It has been proposed that the presence of a zone of keratinized mucosa (KM) around implants is associated with less discomfort during brushing and improved esthetic outcomes. Therefore, mucogingival procedures have been recommended for patients with discomfort during brushing, and to enhance esthetic results around implants without KM. However, no study has systematically assessed and compared discomfort during brushing, patient soft tissue esthetic satisfaction, and other clinical parameters between implants with and without KM. METHODS: Group 1 included patients with implants surrounded by KM, whereas patients in Group 2 had no KM around implants. Patient discomfort during brushing and esthetic satisfaction were measured with a visual analog scale and compared between the 2 groups using a mixed model. Clinical width of KM, probing depth, peri-implant recession, plaque index, and bleeding on probing were compared within and between groups 3 and 6 months following implant restoration. RESULTS: Twenty-four patients (12 in each group) were evaluated at the 3- and 6-month follow-up visits. Patients without peri-implant KM were less satisfied with the esthetics of the soft tissue around their implants (P < 0.01). However, lack of KM was not associated with discomfort during brushing. In Group 1, width of KM was significantly increased after 6 months (P < 0.01). There was greater recession around implants without KM after 3 months (P < 0.01), but not after 6 months. CONCLUSIONS: Patients reported that presence or absence of keratinized mucosa did not affect discomfort associated with brushing. Yet, esthetically, patients preferred implants with a zone of keratinized mucosa.

Effect of Molecular Guest Binding on the d-d Transitions of Ni2+ of CPO-27-Ni: A Combined UV-Vis, Resonant-Valence-to-Core X-ray Emission Spectroscopy, and Theoretical Study.

We used Ni K-edge resonant-valence-to-core X-ray emission spectroscopy (RVtC-XES, also referred to as direct RIXS), an element-selective bulk-sensitive synchrotron-based technique, to investigate the electronic structure of the CPO-27-Ni metal-organic framework (MOF) upon molecular adsorption of significant molecular probes: H2O, CO, H2S, and NO. We compare RVtC-XES with UV-vis spectroscopy, and we show that the element selectivity of RVtC-XES is of strategic significance to observe the full set of d-d excitations in Ni2+, which are partially overshadowed by the low-energy π-π* transitions of the Ni ligands in standard diffuse-reflectance UV-vis experiments. Our combined RVtC-XES/UV-vis approach provides access to the whole set of d-d excitations, allowing us a complete discussion of the changes undergone by the electronic configuration of the Ni2+ sites hosted within the MOF upon molecular adsorption. The experimental data have been interpreted by multiplet ligand-field theory calculations based on Wannier orbitals. This study represents a step further in understanding the ability of the CPO-27-Ni MOFs in molecular sorption and separation applications.

Tailoring adsorption induced phase transitions in the pillared-layer type metal-organic framework DUT-8(Ni).

Tailoring the characteristics of gating transitions in the porous network, Ni2(ndc)2dabco (ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane), also termed DUT-8(Ni) (DUT = Dresden University of Technology), was achieved by systematically adjusting the critical synthesis parameters. The impact of the starting composition and solvent mixtures in the synthesis was found to critically affect the guest-response properties of the obtained materials. A comprehensive set of physical characterization methods, namely thermal analysis, 1H NMR of digested crystals, solid state 13C NMR, PXRD, SEM, IR and Raman spectroscopy shows that the crystallite size is a crucial factor, determining the differing characteristics such as "gate pressure" and adsorption capacity in the guest-responsive switching behaviour of DUT-8. Crystallites smaller than 500 nm in size retain the open form after removal of the guest molecules resulting in typical "Type Ia" isotherm, whereas crystallites larger than 1 µm transform into the "closed pore" form and therefore can show a characteristic "gate opening" behaviour during gas adsorption. The particle size distribution of DUT-8(Ni) can be tailored by changing the synthesis conditions and consequently the slope of the isotherm at the "gating step" is affected. The in depth analysis of synthesis conditions and switching behaviour is an important step towards a better understanding of the fundamental principles responsible for guest responsive porosity switching in the solid state.

The role of dispersive forces determining the energetics of adsorption in Ti zeolites.

Ti-zeolites are interesting materials because of their key role in partial oxidation reactions, as well as under a fundamental point of view being regarded as single site catalysts. Both experimental and computational approaches have been widely applied to the characterization of their active sites, reaching a level of knowledge unmatchable by most other important catalysts. However, several questions are still open, being a proper energetic simulation of the adsorption process of simple molecules, fitting with the experimental outcomes, still missing. The present work wants to underline the role of dispersive forces in correctly determining the adsorption energies of H2 O and NH3 in Ti chabazite: first dispersive contributions have been included through an ONIOM scheme, comparing the results from semiempirical Grimme scheme and fully ab initio MP2. Being the key contribution of dispersion proved, a fully periodic, Grimme dispersions inclusive approach has been applied, coming to results close to the experimental values. © 2016 Wiley Periodicals, Inc.

Solvent-Driven Gate Opening in MOF-76-Ce: Effect on CO2 Adsorption.

A cerium-based metal-organic framework with MOF-76 topology has been synthesized by a very simple and fast solvothermal method that has been tested for a one gram yield. Variable-temperature powder XRD and X-ray absorption data, analyzed by Rietveld and multiple-scattering extended X-ray absorption fine-structure methods, revealed high thermal stability and the presence of three different stable structures. X-ray absorption near-edge structure and FTIR spectroscopy probed the presence of cerium(III), which was characterized by coordinatively unsaturated sites that, however, played no major role in carbon dioxide adsorption. The material revealed excellent carbon dioxide adsorption properties: the highest gravimetric capacity of 15 wt% was observed at 1.1 bar in the case of the sample activated at 250 °C in vacuum, whereas the strongest interaction energy of 35 kJ mol(-1) was observed for the sample activated at 150 °C. Negligible nitrogen uptake of the sample activated at 150 °C indicates that this material is a promising candidate for nitrogen/carbon dioxide separation purposes.

New insights into UTSA-16.

Among the metal organic framework materials proposed for CO2 separation, UTSA-16 possesses the highest CO2 volumetric density explained on the basis of favourable interactions between CO2 and structural water molecules in the material, as revealed by neutron diffraction. In this study, UTSA-16 was synthesised and extensively characterised by XRD, TEM combined with EDX analysis and DR-UV-Vis, Raman and FTIR spectroscopies, as well as by TGA measurements. The synthesised material shows XRD patterns, surface area, CO2 capacity and isosteric heat coincident to the ones reported for UTSA-16 in the original papers but a higher thermal stability and a complete removal of water upon activation under mild conditions (363 K). On the basis of EDX and IR measurements, the formula of UTSA-16 used in the present study is proposed to be K2Co3(cit)2. Infrared spectroscopy clearly shows that UTSA-16 described in this work reversibly interacts with water vapor, CO and CO2. The interaction is attributed to K(+) species, which are present as counterions in the pores. At 1 bar and 298 K a fraction of K(+) sites adsorbs 2 CO2 molecules.