Comparison of Root Coverage by the Subepithelial Connective Tissue Graft With and Without Root Biomodification: A Comprehensive Clinical Study.

BACKGROUND: Being an autologous graft, a subepithelial connective tissue (SECT) graft shows more predictable root coverage better than other techniques. Hence, it is most likely to be widely used for recession treatment. During root planing, a smear layer forms on the root surface that cannot be removed by water or saline rinsing. To remove this smear layer, root biomodification agents are widely used. The present study was conducted to assess the efficacy of an SECT graft for root coverage with and without root biomodification. METHODS: This study included 20 patients with no gender predilection, with an age range of 24-36 years and a mean age of 27.6 ± 4.24 years. The chosen range facilitated the acquisition of data in a relatively homogeneous population, minimizing the confounding effects of factors such as aging-related tissue changes or early-onset periodontal issues. All 40 sites were treated with the SECT and coronally advanced flap. Root conditioning in controls was done with distilled saline and tested using 24% ethylenediaminetetraacetic acid (EDTA) gel (Maquira; STM Meditech, Kerala). At baseline and at one, three, and six months postoperatively, pocket depth (PD) and clinical attachment levels (CALs) were assessed at four sites using a UNC-15 probe, and from the gingival margin to the cementoenamel junction (CEJ), the vertical recession was assessed. RESULTS: For the buccal surface, CALs were reduced significantly (p < 0.001). Following root conditioning with 24% EDTA, no difference was seen in the CAL in the control and test group either buccally or interproximally with a p-value of greater than 0.05. For PD, following a SECT graft or root conditioning, no significant change was observed in the buccal or interproximal region (p > 0.05). The vertical recession was significantly reduced with a p-value of less than 0.001 and depth coverage of 97.5%. The difference between the two groups was statistically non-significant (p > 0.05). The root surface coverage decreased significantly from 16.6 ± 2.8 to 0.45 ± 0.4 from baseline to six months, which was statistically significant (p < 0.001). This intergroup difference was non-statistical (p > 0.05). CONCLUSION: The present study concludes that the use of an SECT graft in root coverage can significantly improve the CAL, root surface area, and vertical recession both with and without root biomodification. We conclude that there is a significant decrease in the probing depth following SECT grafting and with root biomodification.

Recent Advancements in Polyurethane-based Tissue Engineering.

In tissue engineering, polyurethane-based implants have gained significant traction because of their high compatibility and inertness. The implants therefore show fewer side effects and lasts longer. Also, the mechanical properties can be tuned and morphed into a particular shape, owing to which polyurethanes show immense versatility. In the last 3 years, scientists have devised methods to enhance the strength of and induce dynamic properties in polyurethanes, and these developments offer an immense opportunity to use them in tissue engineering. The focus of this review is on applications of polyurethane implants for biomedical application with detailed analysis of hard tissue implants like bone tissues and soft tissues like cartilage, muscles, skeletal tissues, and blood vessels. The synthetic routes for the preparation of scaffolds have been discussed to gain a better understanding of the issues that arise regarding toxicity. The focus here is also on concerns regarding the biocompatibility of the implants, given that the precursors and byproducts are poisonous.

Outcomes Following Hydraulic Pressure Indirect Sinus Lift in Cases of Simultaneous Implant Placement With Platelet-Rich Fibrin.

Background To achieve a better long-term prognosis in the posterior maxilla with poor quality of bone, the sinus lift must ensure bone regeneration till the apex of the dental implant for osseointegration. An indirect sinus lift is a minimally invasive procedure where simultaneous bone condensation is achieved. During the sinus lift procedures, different graft materials are used to gain the height of the bone in the sinus. The present study aimed to evaluate the outcomes of indirect sinus lift with hydraulic pressure and the simultaneous placement of implant using platelet-rich fibrin (PRF). Methodology In total, 24 subjects aged 18-74 years with missing maxillary premolars and first and second molars who opted for dental implants placed with indirect sinus lift with hydraulic pressure and had low sinus with less residual ridge height, bone density, and bone height were assessed at one day, one week, one month, three months, and six months. Results The average mean height preoperatively was 5.573 ± 0.66 mm which showed a significant increase postoperatively to 9.603 ± 0.78 mm (p < 0.001). Mean sinus membrane lift was 4.8 ± 2.2 mm at six months. The implant stability quotient increased significantly at six months postoperatively from 69.07 ± 3.39 at the immediate postoperative time to 72.92 ± 2.714 at six months postoperatively (p < 0.001). Conclusions The current study suggests that minimally invasive indirect sinus lift with bone augmentation utilizing PRF increased residual alveolar ridge height and implant stability with fewer problems than previous sinus lift procedures in the posterior maxillary area.

Breaking the trade-off between selectivity and adsorption capacity for gas separation.

The trade-off between selectivity and adsorption capacity with porous materials is a major roadblock to reducing the energy footprint of gas separation technologies. To address this matter, we report herein a systematic crystal engineering study of C2H2 removal from CO2 in a family of hybrid ultramicroporous materials (HUMs). The HUMs are composed of the same organic linker ligand, 4-(3,5-dimethyl-1H-pyrazol-4-yl)pyridine, pypz, three inorganic pillar ligands, and two metal cations, thereby affording six isostructural pcu topology HUMs. All six HUMs exhibited strong binding sites for C2H2 and weaker affinity for CO2. The tuning of pore size and chemistry enabled by crystal engineering resulted in benchmark C2H2/CO2 separation performance. Fixed-bed dynamic column breakthrough experiments for an equimolar (v/v = 1:1) C2H2/CO2 binary gas mixture revealed that one sorbent, SIFSIX-21-Ni, was the first C2H2 selective sorbent that combines exceptional separation selectivity (27.7) with high adsorption capacity (4 mmol·g-1).

Refractive index of graphene AA and AB stacked bilayers under the influence of relative planar twisting.

The optical properties of graphene in monolayer and bilayer structure is essential for the development of optical devices viz surface plasmon resonance (SPR) based bio-sensors. The band structure of the twisted bilayer graphene (BLG) is remarkably different than the normal AA or AB stacking. This provides an opportunity to control the optical and electrical properties of BLG by applying an in-plane twist to one of the layer relative to other in a BLG system. Here, we calculated the refractive index (RI) of AA and AB stacking of BLG system using density functional theory. Though the spectrum for AA stacking shows some similarity with that of monolayer graphene, the spectrum for AB stacking was found to be remarkably different. The spectrum of AB stacked layer is red-shifted and the absorption peaks in low energy regime increases nearly by three-folds. A large dependency of the twist angle on RI of twisted BLG were found. Based on the calculation, a schematic of phase diagram showing material behavior of such twisted BLG systems as a function of twist angle and photon energy was constructed. The twisted AA stacked BLG shows largely dielectric behavior whereas the twisted AB stacked BLG shows predominately semimetallic and semiconducting behavior. This study presents a RI landscape of twisted BLG dependent on important parameters viz photon energy and inplane relative twist angle. Our studies will be very useful for the design and development of optical devices employing BLG systems particularly SPR based bio-sensors which essentially measures change in RI due to adsorption of analytes.

Mixed-metal hybrid ultramicroporous material (HUM) precursor to graphene-supported tetrataenite as a highly active and durable NPG catalyst for the OER.

Current interest in investigating non-precious group (NPG) metals for catalyzing the oxygen evolution reaction (OER) has revealed that doping of Ni hydroxides with Fe results in the dramatic enhancement of catalytic activity. Herein, a facile pathway to construct tetrataenite, an NiFe alloy of extraterrestrial origin and to address the limited electrical conductivity of metal oxides/hydroxides by directly constructing them atop graphene sheets is described. In this approach, a one-pot, bottom-up assembly of hybrid ultramicroporous materials (HUMs) was carried out, in the presence of suspended graphene (G), to homogeneously deposit the HUMs on unmodified graphene sheets, affording HUMs@G. Single metal (SIFSIX-3-Ni@G) and mixed metal (SIFSIX-3-NiFe@G) HUMs can be readily synthesized from their respective metal salts to afford a well-designed catalyst for the OER. The pyrolysis of SIFSIX-3-NiFe@G resulted in the deposition of the nanoalloy tetrataenite on G, demonstrating an exceptionally low OER onset potential of 1.44 V vs. RHE and reduced overpotential at 10 mA cm-2 (η10 = 266 mV). The synergy between the composition of the active catalyst and the electronically conductive support was attained by designing a reaction system encoding the self-assembly of a crystalline pre-catalyst on G sheets.

Crystal engineering of a rectangular sql coordination network to enable xylenes selectivity over ethylbenzene.

Separation of the C8 aromatic isomers, p-xylene (PX), m-xylene (MX), o-xylene (OX) and ethylbenzene (EB), is relevant thanks to their widespread application as chemical feedstocks but challenging because of their similar boiling points and close molecular dimensions. Physisorptive separation could offer an energy-efficient solution to this challenge but sorbents which exhibit strong selectivity for one of the isomers remain a largely unmet challenge despite recent reports of OX or PX selective sorbents with high uptake capacity. For example, the square lattice, sql, topology coordination network [Co(bipy)2(NCS)2] n (sql-1-Co-NCS) exhibits the rare combination of high OX selectivity and high uptake capacity. Herein we report that a crystal engineering approach enabled isolation of the mixed-linker sql coordination network [Co(bipy)(bptz)(NCS)2] n (sql-1,3-Co-NCS, bipy = 4,4'-bipyridine, bptz = 4,4'-bis(4-pyridyl)tetrazine) and study of its C8 vapour and liquid sorption properties. sql-1,3-Co-NCS was found to exhibit high adsorption capacity from liquid xylenes (∼37 wt%) and is to our knowledge the first sorbent to exhibit high selectivity for each of xylene isomer over EB (S OX/EB, S MX/EB, S PX/EB > 5). Insights into the performance of sql-1,3-Co-NCS are gained from structural studies which reveal stacking interactions between electron-deficient bptz linkers and the respective xylenes. sql-1,3-Co-NCS is the first N-donor mixed-linker sql coordination network studied for its gas/vapour sorption properties and represents a large and diverse class of understudied coordination networks.

Ultramicropore Engineering by Dehydration to Enable Molecular Sieving of H2 by Calcium Trimesate.

The high energy footprint of commodity gas purification and increasing demand for gases require new approaches to gas separation. Kinetic separation of gas mixtures through molecular sieving can enable separation by molecular size or shape exclusion. Physisorbents must exhibit the right pore diameter to enable separation, but the 0.3-0.4 nm range relevant to small gas molecules is hard to control. Herein, dehydration of the ultramicroporous metal-organic framework Ca-trimesate, Ca(HBTC)⋅H2 O (H3 BTC=trimesic acid), bnn-1-Ca-H2 O, affords a narrow pore variant, Ca(HBTC), bnn-1-Ca. Whereas bnn-1-Ca-H2 O (pore diameter 0.34 nm) exhibits ultra-high CO2 /N2 , CO2 /CH4 , and C2 H2 /C2 H4 binary selectivity, bnn-1-Ca (pore diameter 0.31 nm) offers ideal selectivity for H2 /CO2 and H2 /N2 under cryogenic conditions. Ca-trimesate, the first physisorbent to exhibit H2 sieving under cryogenic conditions, could be a prototype for a general approach to exert precise control over pore diameter in physisorbents.

Reversible Switching between Nonporous and Porous Phases of a New SIFSIX Coordination Network Induced by a Flexible Linker Ligand.

Closed-to-open structural transformations in flexible coordination networks are of potential utility in gas storage and separation. Herein, we report the first example of a flexible SiF62--pillared square grid material, [Cu(SiF6)(L)2]n (L = 1,4-bis(1-imidazolyl)benzene), SIFSIX-23-Cu. SIFSIX-23-Cu exhibits reversible switching between nonporous (ß1) and several porous (α, γ1, γ2, and γ3) phases triggered by exposure to N2, CO2, or H2O. In addition, heating ß1 to 433 K resulted in irreversible transformation to a closed polymorph, ß2. Single-crystal X-ray diffraction studies revealed that the phase transformations are enabled by rotation and geometrical contortion of L. Density functional theory calculations indicated that L exhibits a low barrier to rotation (as low as 8 kJmol-1) and a rather flat energy surface. In situ neutron powder diffraction studies provided further insight into these sorbate-induced phase changes. SIFSIX-23-Cu combines stability in water for over a year, high CO2 uptake (ca. 216 cm3/g at 195 K), and good thermal stability.

An overview on trace CO2 removal by advanced physisorbent materials.

This review paper focuses on various gas processing technologies and materials that efficiently capture trace levels of carbon dioxide (CO2). Fundamental separation mechanisms such as absorption, adsorption, and distillation technology are presented. Liquid amine-based carbon capture (C-capture) technologies have been in existence for over half a century, however, liquid amine capture relies upon chemical reactions and is energy-intensive. Liquid amines are thus not economically viable for broad deployment and offer little room for innovation. Innovative C-capture technologies must improve both the environmental footprint and cost-effectiveness. As a promising alternative, physisorbents have many advantages including considerably lower regeneration energy. Generally, existing classes of physisorbent materials, such as metal-organic frameworks (MOFs) and zeolites are selective toward C-capture. However, their selectivity is currently not high enough to remove trace levels (e.g., ~1%) of CO2 from various natural gas process streams. This review summarizes the current advancements in physisorbent materials for CO2 capture. Here, key performance parameters needed to select the most suitable candidate are highlighted. Furthermore, this review discusses the scope for the development of better performing CO2 selective physisorbents from both environmental and economic perspectives. In addition, hybrid ultra microporous materials (HUMs), characterized mainly by ultra-micro pores (<0.7 nm), are discussed in reference to C-capture. Various characteristics of HUMs result in high selectivity and applicability in difficult separations such as the gas sweetening and C-capture from complex humid mixed gas streams.

Trace CO2 capture by an ultramicroporous physisorbent with low water affinity.

CO2 accumulation in confined spaces represents an increasing environmental and health problem. Trace CO2 capture remains an unmet challenge because human health risks can occur at 1000 parts per million (ppm), a level that challenges current generations of chemisorbents (high energy footprint and slow kinetics) and physisorbents (poor selectivity for CO2, especially versus water vapor, and/or poor hydrolytic stability). Here, dynamic breakthrough gas experiments conducted upon the ultramicroporous material SIFSIX-18-Ni-ß reveal trace (1000 to 10,000 ppm) CO2 removal from humid air. We attribute the performance of SIFSIX-18-Ni-ß to two factors that are usually mutually exclusive: a new type of strong CO2 binding site and hydrophobicity similar to ZIF-8. SIFSIX-18-Ni-ß also offers fast sorption kinetics to enable selective capture of CO2 over both N2 (S CN) and H2O (S CW), making it prototypal for a previously unknown class of physisorbents that exhibit effective trace CO2 capture under both dry and humid conditions.

Synergistic sorbent separation for one-step ethylene purification from a four-component mixture.

Purification of ethylene (C2H4), the largest-volume product of the chemical industry, currently involves energy-intensive processes such as chemisorption (CO2 removal), catalytic hydrogenation (C2H2 conversion), and cryogenic distillation (C2H6 separation). Although advanced physisorbent or membrane separation could lower the energy input, one-step removal of multiple impurities, especially trace impurities, has not been feasible. We introduce a synergistic sorbent separation method for the one-step production of polymer-grade C2H4 from ternary (C2H2/C2H6/C2H4) or quaternary (CO2/C2H2/C2H6/C2H4) gas mixtures with a series of physisorbents in a packed-bed geometry. We synthesized ultraselective microporous metal-organic materials that were readily regenerated, including one that was selective for C2H6 over CO2, C2H2, and C2H4.

Tuning the Gate-Opening Pressure in a Switching pcu Coordination Network, X-pcu-5-Zn, by Pillar-Ligand Substitution.

Coordination networks that reversibly switch between closed and open phases are of topical interest since their stepped isotherms can offer higher working capacities for gas-storage applications than the related rigid porous coordination networks. To be of practical utility, the pressures at which switching occurs, the gate-opening and gate-closing pressures, must lie between the storage and delivery pressures. Here we study the effect of linker substitution to fine-tune gate-opening and gate-closing pressure. Specifically, three variants of a previously reported pcu-topology MOF, X-pcu-5-Zn, have been prepared: X-pcu-6-Zn, 6=1,2-bis(4-pyridyl)ethane (bpe), X-pcu-7-Zn, 7=1,2-bis(4-pyridyl)acetylene (bpa), and X-pcu-8-Zn, 8=4,4'-azopyridine (apy). Each exhibited switching isotherms but at different gate-opening pressures. The N2 , CO2 , C2 H2 , and C2 H4 adsorption isotherms consistently indicated that the most flexible dipyridyl organic linker, 6, afforded lower gate-opening and gate-closing pressures. This simple design principle enables a rational control of the switching behavior in adsorbent materials.

Highly selective CO2 removal for one-step liquefied natural gas processing by physisorbents.

Industrial specifications require CO2 concentrations in natural gas below 50 ppm during liquefaction because of corrosion and CO2 freezing. Herein, we report a physisorbent (TIFSIX-3-Ni) that exhibits new benchmark CO2/CH4 selectivity and fast kinetics, thereby enabling one-step LNG processing to CO2 levels of 25 ppm.

Coordination Network That Reversibly Switches between Two Nonporous Polymorphs and a High Surface Area Porous Phase.

We report a 2-fold interpenetrated primitive cubic (pcu) network X-pcu-5-Zn, [Zn2(DMTDC)2(dpe)] (H2DMTDC = 3,4-dimethylthieno[2,3- b]thiophene-2,5-dicarboxylic acid, dpe = 1,2-di(4-pyridyl)ethylene), that exhibits reversible switching between an as-synthesized "open" phase, X-pcu-5-Zn-α, and two nonporous or "closed" polymorphs, X-pcu-5-Zn-ß and X-pcu-5-Zn-γ. There are two unusual features of X-pcu-5-Zn. The first relates to its sorption properties, which reveal that the α form exhibits high CO2 uptake (ca. 255 cm3/g at 195 K) via reversible closed-to-open switching (type F-IV isotherm) of the type desirable for gas and vapor storage; there are only three other reports of porous materials that combine these two features. Second, we could only isolate the ß form by activation of the CO2 loaded α form and it persists through multiple CO2 adsorption/desorption cycles. We are unaware of a new polymorph having been isolated in such a manner. That the observed phase changes of X-pcu-5-Zn-α occur in single-crystal-to-single-crystal fashion enabled structural characterization of the three forms; γ is a coordination isomer of α and ß, both of which are based upon "paddlewheel" clusters.

Impact of partial interpenetration in a hybrid ultramicroporous material on C2H2/C2H4 separation performance.

Phases of a 2-fold pcu hybrid ultramicroporous material (HUM), SIFSIX-14-Cu-i, exhibiting 99%, 93%, 89%, and 70% partial interpenetration have been obtained. 1 : 99 C2H2/C2H4 gas separation studies reveal that as the proportion of interpenetrated component decreases, so does the separation performance.

Efficient CO2 Removal for Ultra-Pure CO Production by Two Hybrid Ultramicroporous Materials.

Removal of CO2 from CO gas mixtures is a necessary but challenging step during production of ultra-pure CO as processed from either steam reforming of hydrocarbons or CO2 reduction. Herein, two hybrid ultramicroporous materials (HUMs), SIFSIX-3-Ni and TIFSIX-2-Cu-i, which are known to exhibit strong affinity for CO2 , were examined with respect to their performance for this separation. The single-gas CO sorption isotherms of these HUMs were measured for the first time and are indicative of weak affinity for CO and benchmark CO2 /CO selectivity (>4000 for SIFSIX-3-Ni). This prompted us to conduct dynamic breakthrough experiments and compare performance with other porous materials. Ultra-pure CO (99.99 %) was thereby obtained from CO gas mixtures containing both trace (1 %) and bulk (50 %) levels of CO2 in a one-step physisorption-based separation process.

Controlling the Uptake and Regulating the Release of Nitric Oxide in Microporous Solids.

Representative compounds from three classes of microporous solids, namely, metal-organic frameworks (MOFs), hybrid ultra-microporous materials (HUMs), and porous-organic polymers (POPs), were investigated for their nitric oxide gas uptake and release behavior. Low-pressure sorption studies indicated strong chemisorption of NO on the free amine groups decorating the MOF UiO-66-NH2 when compared to its non-amine-functionalized parent. The HUMs demonstrated reversible physisorption within the low-pressure regime, but interestingly in one case there was evidence for chemisorption following pressurization with NO at 10 bar. Significant release of chemisorbed NO from the UiO-66-NH2 and one of the HUMs was triggered by addition of acid to the medium, a pH change from 7.4 to 5.4 being sufficient to trigger NO release. An imidazole-based POP exhibited chemisorption of NO at high pressure wherein the ring basicity facilitated both NO uptake and spontaneous release upon contact with the aqueous release medium.

The effect of centred versus offset interpenetration on C2H2 sorption in hybrid ultramicroporous materials.

Fine-tuning of hybrid ultramicroporous materials (HUMs) can significantly impact their gas sorption performance. This study reveals that offset interpenetration can be antagonistic with respect to C2H2 separation from C2H2/C2H4 gas mixtures.

Water Vapor Sorption in Hybrid Pillared Square Grid Materials.

We report water vapor sorption studies on four primitive cubic, pcu, pillared square grid materials: SIFSIX-1-Cu, SIFSIX-2-Cu-i, SIFSIX-3-Ni, and SIFSIX-14-Cu-i. SIFSIX-1-Cu, SIFSIX-3-Ni, and SIFSIX-14-Cu-i were observed to exhibit negative water vapor adsorption at ca. 40-50% relative humidity (RH). The negative adsorption is attributed to a water-induced phase transformation from a porous pcu topology to nonporous sql and sql-c* topologies. Whereas the phase transformation of SIFSIX-1-Cu was found to be irreversible, SIFSIX-3-Ni could be regenerated by heating and can therefore be recycled. In contrast, SIFSIX-2-Cu-i, which is isostructural with SIFSIX-14-Cu-i, exhibited a type V isotherm and no phase change. SIFSIX-2-Cu-i was observed to retain both structure and gas sorption properties after prolonged exposure to heat and humidity. The hydrolytic stability of SIFSIX-2-Cu-i in comparison to its structural counterparts is attributed to structural features and therefore offers insight into the design of hydrolytically stable porous materials.