Nitric oxide activation facilitated by cooperative multimetallic electron transfer within an iron-functionalized polyoxovanadate-alkoxide cluster.

A series of NO-bound, iron-functionalized polyoxovanadate-alkoxide (FePOV-alkoxide) clusters have been synthesized, providing insight into the role of multimetallic constructs in the coordination and activation of a substrate. Upon exposure of the heterometallic cluster to NO, the vanadium-oxide metalloligand is oxidized by a single electron, shuttling the reducing equivalent to the {FeNO} subunit to form a {FeNO}7 species. Four NO-bound clusters with electronic distributions ranging from [VV3VIV2]{FeNO}7 to [VIV5]{FeNO}7 have been synthesized, and characterized via 1H NMR, infrared, and electronic absorption spectroscopies. The ability of the FePOV-alkoxide cluster to store reducing equivalents in the metalloligand for substrate coordination and activation highlights the ultility of the metal-oxide scaffold as a redox reservoir.

Site-selectivity in the halogenation of titanium-functionalized polyoxovanadate-alkoxide clusters.

Herein, we report the synthesis and characterization of a dititanium-functionalized polyoxovanadate-alkoxide cluster. The incorporation of a second heterometal within the cluster core results in striking differences in reactivity of the multimetallic complex. Chlorination of the metal oxide cluster is reported, revealing the directing role of titanium in M-O bond cleavage.

Polyoxovanadate-alkoxide clusters as multi-electron charge carriers for symmetric non-aqueous redox flow batteries.

Non-aqueous redox flow batteries have emerged as promising systems for large-capacity, reversible energy storage, capable of meeting the variable demands of the electrical grid. Here, we investigate the potential for a series of Lindqvist polyoxovanadate-alkoxide (POV-alkoxide) clusters, [V6O7(OR)12] (R = CH3, C2H5), to serve as the electroactive species for a symmetric, non-aqueous redox flow battery. We demonstrate that the physical and electrochemical properties of these POV-alkoxides make them suitable for applications in redox flow batteries, as well as the ability for ligand modification at the bridging alkoxide moieties to yield significant improvements in cluster stability during charge-discharge cycling. Indeed, the metal-oxide core remains intact upon deep charge-discharge cycling, enabling extremely high coulombic efficiencies (∼97%) with minimal overpotential losses (∼0.3 V). Furthermore, the bulky POV-alkoxide demonstrates significant resistance to deleterious crossover, which will lead to improved lifetime and efficiency in a redox flow battery.

Tuning the redox profiles of polyoxovanadate-alkoxide clusters via heterometal installation: toward designer redox Reagents.

Herein, we describe a rational synthetic approach for tuning the electrochemical profiles of a series of Lindqvist polyoxovanadate-alkoxide clusters through heterometal functionalization. Synthetic procedures for group(IV) functionalization of the mixed-valent POV-alkoxide cluster, [V6O7(OCH3)12], are established, resulting in the heterometallic species, [NBu4][V5O6(OCH3)12MOCH3] (M = Ti, Zr, Hf). We demonstrate that these d0, heterometallic dopants anodically shift the potential of the electrochemical processes associated with the cluster, making the molecule more resistant to oxidation. Conversely, incorporation of electron rich heterometals yields a more readily oxidized molecule, with redox processes shifted cathodically. The predictable tuning and remarkable electrochemical profiles of this family of heterometal-functionalized polyoxometalates highlights their potential use as designer redox agents.

An assessment of an environmental gradient using coral geochemical records, Whitsunday Islands, Great Barrier Reef, Australia.

Coral cores were collected along an environmental and water quality gradient through the Whitsunday Island group, Great Barrier Reef (Australia), for trace element and stable isotope analysis. The primary aim of the study was to examine if this gradient could be detected in coral records and, if so, whether the gradient has changed over time with changing land use in the adjacent river catchments. Y/Ca was the trace element ratio which varied spatially across the gradient, with concentrations progressively decreasing away from the river mouths. The Ba/Ca and Y/Ca ratios were the only indicators of change in the gradient through time, increasing shortly after European settlement. The Mn/Ca ratio responded to local disturbance related to the construction of tourism infrastructure. Nitrogen isotope ratios showed no apparent trend over time. This study highlights the importance of site selection when using coral records to record regional environmental signals.

Effect of diode laser and fluoride varnish on initial surface demineralization of primary dentition enamel: an in vitro study.

INTRODUCTION: Previous investigations have demonstrated improved enamel caries resistance after laser irradiation. The purpose of this in vitro study was to assess the caries-preventive potential of 809 nm diode laser treatment of the enamel of primary teeth compared to topical fluoride application. METHODS: Eighty samples of sound primary teeth were embedded in plastic and stored in saline solution. The enamel surface of 80 samples was polished in an area of 2 x 2 mm. These tooth specimens were randomly assigned to one control and three test groups: (1) no treatment/control; (2) application of 0.1 mg of fluoride varnish (Duraphat) for 6 h; (3) diode laser application (809 nm, 140 mJ, 50 Hz, Ø 600 micro m fibre, contact mode, absorber, 1 min; ORA-LASER01 I.S.T.); and (4) combined application - laser/fluoride varnish. Caries-like lesions were created by pH-cycling. After lesion formation, longitudinal sections were taken and examined by polarized light microscopy. RESULTS: In the control group, all samples showed lesions up to 30 micro m in depth. After laser application, lesions could be identified in 15 out of 20 samples. Topical fluoride treatment in groups 2 (varnish) and 4 (laser/varnish) completely inhibited the development of caries-like lesions in all samples. CONCLUSION: In this in vitro investigation, topical fluoride treatment enhances the resistance of sound enamel of primary teeth more effectively than diode laser application.

Reattachment of fractured teeth: a review of literature regarding techniques and materials.

Anterior crown fractures are a common form of injury that mainly affects children and adolescents. The position of maxillary incisors and their eruptive pattern carries a significant risk for trauma. In the pre-adhesive era, fractured teeth needed to be restored either with pin-retained inlays or cast restorations that sacrificed healthy tooth structure and were a challenge for clinicians to match with adjacent teeth. The development of adhesive dentistry has allowed dentists to use the patient's own fragment to restore the fractured tooth. Since then, several successful case reports that use a variety of techniques and materials to reattach fractured teeth have been published. This article presents a comprehensive literature review on techniques and materials used to restore uncomplicated dental trauma.

[Microleakage in class V cavities restored with esthetic materials, using different restorative techniques]. / Infiltração marginal em cavidades de classe V restauradas com materiais estéticos, utilizando diferentes técnicas restauradoras.

The purpose of this study was to compare the microleakage of class V cavities restored with composite resin (CR), resin-modified glass ionomer cement (RMGIC) and polyacid-modified resin composite (PAMRC), using different clinical procedures. Thirty-six noncarious human molars were used in this study. A class V cavity, measuring approximately 3 mm x 4 mm x 2 mm, was prepared in each tooth in both buccal and lingual aspects, with a diamond bur (number 1,093) at high speed, with coolant water spray. The occlusal margin was located on enamel and the gingival margin was located on dentin. The teeth were divided into 9 groups with 8 specimens each. The cavities were restored according to different techniques. The specimens from groups 1, 2, 4 and 5 did not receive acid etching. The samples were stored in water at 37 degrees C for 24 hours, subjected to occlusal load, thermocycled and immersed in rhodamine B. The restorations were then washed and sectioned in buccolingual direction. The depth of dye penetration was scored from zero (no leakage) to 3 (maximum leakage). The Kruskal-Wallis test revealed statistically significant differences between the materials (p < 0.05). PAMRC used without acid etching showed the greatest score of leakage in both margins. In the gingival margin, CR showed scores of leakage lower than those of PAMRC and RMGIC. Additional retentions and acid etching were able to decrease microleakage in PAMRC restorations in both gingival and occlusal margins.

[Bond strength to dentin of resin composites associated with filled and unfilled adhesive systems]. / Resistência de união à dentina de resinas compostas associadas a sistemas adesivos com e sem carga.

This study analyzed in vitro two brands of one-step adhesive systems of fourth generation (Optisolo--Kerr, filled; and Single Bond--3M, unfilled) and two composite resins (Prodigy--Kerr and Z100--3M), aiming at evaluating their bond strength to dentin. Eighty human extracted molars were embedded in acrylic resin and grounded until dentin was exposed in longitudinal direction. The specimens were divided in 4 groups. Composite resin cones were bonded to the specimens using the mentioned adhesive systems, following the instructions of the manufacturers. The test-specimens were submitted to tensile tests using a 4442 Universal Mini-Instron Machine with the speed of 0.5 mm/min. The results were converted into MPa, according to the area of adhesion, and submitted to statistical analysis with ANOVA. There was significant statistical difference (p < 0.01) between the adhesive systems (F = 7.24). Optisolo (m = 11.03 +/- 4.23) showed better bond strength than Single Bond (m = 8.37 +/- 4.54). There was no significant statistical difference (p > 0.05) between the composites (F = 0.43).

[Assessment of superficial roughness of 3 composite resins treated with different polishing techniques]. / Avaliação da rugosidade superficial de três resinas compostas submetidas a diferentes técnicas de polimento.

In this study, the superficial roughness of two composite resins classified as condensable and of a traditional hybrid composite resin was analyzed after different polishing techniques. Test specimens were confected, immersed in distilled water for 24 hours and submitted to two different techniques of superficial treatment, in which disc systems (Sof-Lex and Super Snap) and silicon tips (Enhance) were utilized. The results revealed the greater superficial roughness of Alert, when compared with Solitaire and Degufill Mineral--no statistically significant differences were observed between the last two materials. The superficial roughness of the specimens polished with Enhance tips was greater than that of the specimens polished with discs and there were no statistically significant differences between both disc systems.

The influence of the surface treatment and saliva on the color of two porcelains.

The color of an object is a psychophysical phenomenon. Regarding its physical aspect, the amount of light reflected from the surface of an object is taken into consideration many times. Two brands of porcelain were used to make 10 specimens that were submitted to the following treatments: glaze, grinding, polishing and overglaze. All samples were analyzed with or without saliva. The final color differences of the ceramic were evaluated using a spectrophotometer, and reflectance curves were obtained. Results showed that there were no differences between the brands of porcelain. Saliva did not interfere with the color of the porcelain, but re-established the original one, after the grinding process had altered it. The polishing also contributed to re-established the original color. The overglaze altered the original color, with or without saliva.

Brachyspira (Serpulina) hyodysenteriae gyrB mutants and interstrain transfer of coumermycin A(1) resistance.

To further develop genetic techniques for the enteropathogen Brachyspira hyodysenteriae, the gyrB gene of this spirochete was isolated from a lambdaZAPII library of strain B204 genomic DNA and sequenced. The putative protein encoded by this gene exhibited up to 55% amino acid sequence identity with GyrB proteins of various bacterial species, including other spirochetes. B. hyodysenteriae coumermycin A(1)-resistant (Cn(r)) mutant strains, both spontaneous and UV induced, were isolated by plating B204 cells onto Trypticase soy blood agar plates containing 0.5 microg of coumermycin A(1)/ml. The coumermycin A(1) MICs were 25 to 100 microg/ml for the resistant strains and 0.1 to 0.25 microg/ml for strain B204. Four Cn(r) strains had single nucleotide changes in their gyrB genes, corresponding to GyrB amino acid changes of Gly(78) to Ser (two strains), Gly(78) to Cys, and Thr(166) to Ala. When Cn(r) strain 435A (Gly(78) to Ser) and Cm(r) Km(r) strain SH (DeltaflaA1::cat Deltanox::kan) were cultured together in brain heart infusion broth containing 10% (vol/vol) heat-treated (56 degrees C, 30 min) calf serum, cells resistant to chloramphenicol, coumermycin A(1), and kanamycin could be isolated from the cocultures after overnight incubation, but such cells could not be isolated from monocultures of either strain. Seven Cn(r) Km(r) Cm(r) strains were tested and were determined to have resistance genotypes of both strain 435A and strain SH. Cn(r) Km(r) Cm(r) cells could not be isolated when antiserum to the bacteriophage-like agent VSH-1 was added to cocultures, and the numbers of resistant cells increased fivefold when mitomycin C, an inducer of VSH-1 production, was added. These results indicate that coumermycin resistance associated with a gyrB mutation is a useful selection marker for monitoring gene exchange between B. hyodysenteriae cells. Gene transfer readily occurs between B. hyodysenteriae cells in broth culture, a finding with practical importance. VSH-1 is the likely mechanism for gene transfer.

Microhardness of Nd:YAG laser irradiated enamel surfaces.

Several studies have been conducted in order to verify effects of laser irradiation on dental structures. However, different settings and methods employed have led to inconclusive results. The aim of this study was to evaluate the effects of several settings of Nd:YAG laser irradiation on enamel microhardness. Fifteen groups of 10 human third molars each were submitted to Vickers microhardness indentations prior to and after laser irradiation. The data were submitted to the t-test for dependent samples (P < 0.05) for statistical evaluation. Lower total delivered energy (under 30 J) resulted in no statistically significant difference of microhardness between irradiated and non-irradiated samples, whereas higher energy settings decreased enamel surface microhardness significantly. This can be due to the significant temperature rise during irradiation. Thus, we conclude that laser irradiation, under the conditions of this study, is not suitable for improving enamel properties, because of decreased microhardness of irradiated samples.

Pulp response and cytotoxicity evaluation of 2 dentin bonding agents.

OBJECTIVE: This study evaluated the biocompatibility of two dentin bonding agents (Clearfil Liner Bond 2 and Scotchbond Multi-Purpose) applied in human dental pulps and cell cultures. METHOD AND MATERIALS: In vivo: Twenty human third molars that were scheduled for extraction were used. After cavity preparation, pulp exposure was achieved with a carbide bur. Hemorrhage control was obtained with saline solution. In 16 teeth, adhesive pulp capping was performed and the cavities were sealed with resin composite. In the control group (n = 4), pulps were capped with Ca(OH)2 and the cavities were sealed with IRM. Teeth were extracted 30 or 90 days following treatment and prepared for histological examination and bacterial detection. In vitro: materials were applied in Petri dishes, where NIH-3T3 cells were plated. The cells were counted 2, 4, and 6 days after plating to obtain the growth curves and to determine cell viability. All data were submitted to statistical analysis. RESULTS: In vivo: Dentin bridge formation was seen in all teeth capped with Ca(OH)2, without an inflammatory response. Mild inflammatory responses and dentin bridge formation after 90 days were observed in 50% of specimens treated with Liner Bond 2. Pulps treated with Scotchbond Multi-Purpose presented mild to severe inflammatory response, and no mineralized tissue formation was detected. Bacteria were not disclosed in any specimen. In vitro: The cytotoxicity was similar between the two bonding agents, and both had statistically higher cytotoxic effects (P < 0.002) than Ca(OH)2. CONCLUSION: Ca(OH)2 produced pulp healing in all teeth and exhibited lower cytotoxic effects than both adhesive systems; however, pulp healing was also observed under Liner Bond 2.

[In vitro study of marginal microleakage in dental caries treated with Er:YAG laser and restored with esthetic materials]. / Estudo in vitro da microinfiltração marginal em cavidades submetidas ao tratamento com laser de Er:YAG e restauradas com materiais estéticos.

The aim of this in vitro study was to evaluate marginal microleakage in class V preparations submitted to treatment with Er:YAG laser and restored with aesthetic materials. Sixty human molars were selected and class V cavities were prepared on the buccal and lingual aspects of their cervical thirds. The restorative technique followed the instructions of the manufacturers. The samples were divided in 3 groups of 20 teeth each: Group 1--control; Group 2--Er:YAG laser was applied on the enamel margin before the restoration was placed; Group 3--a thin layer of calcium hydroxide was applied on the axial wall before the restoration was placed. Each group was divided in 4 sub-groups and the teeth were restored with different aesthetic materials. All samples were submitted to thermocycling and stained with 50% silver nitrate. Based on the obtained results, we could conclude that there are statistically significant differences between the 12 experimental conditions tested. The samples which presented the greatest microleakage were those treated with Er:YAG laser and restored with light-cured glass ionomer cement, followed by those that received Er:YAG laser and the sandwich technique, the cavities restored with light-cured glass ionomer cement and those restored by means of the sandwich technique, in this order.

Nd:YAG laser effects on the microleakage of composite resin restorations.

OBJECTIVE: This study evaluated microleakage of composite restorations submitted to marginal treatment with Nd:YAG laser and surface sealant. BACKGROUND DATA: Previous studies have demonstrated that Nd:YAG-lased enamel melted and became recrystallized with a morphologic appearance similar to lava, and has been used clinically in the sealing of enamel pits and fissures. METHODS: Class V cavities in enamel of human premolars were restored with composite resin (Z100, 3M) and randomly divided in six groups: G1, control; G2, surface sealant marginal treatment; G3 to G6, were treated with pulsed Nd:YAG laser (1.064 microm) marginal treatment, contact fiberoptic (300 microm), air cooling, for 30 seconds, powers of 1.2-2 W, repetition rates of 20-30 Hz, energies of 40-100 mJ. Teeth were impermeabilized, immersed in a rhodamine dye, sectioned, and evaluated under stereomicroscope microscopy with scores. RESULTS: There were significant differences between marginal treatments; there were no differences between groups 1, 2, and 4, and 3,5, and 6; lower values of microleakage were at groups 3, 5, and 6 (Kruskal-Wallis,p = 0.05). CONCLUSION: Nd:YAG laser showed improved marginal sealing and decreased microleakage of composite resins restorations.

The bactericidal effect of Ho:YAG laser irradiation within contaminated root dentinal samples.

OBJECTIVE: This in vitro study investigates the bactericidal effect of pulsed Ho:YAG laser irradiation in the depth of contaminated dentin specimens. BACKGROUND DATA: Previous studies have shown the effectiveness of laser irradiation in bacterial reduction of infected root canal. METHODS: Root dentin of bovine teeth were sliced longitudinally in 180 samples of 100 microm, 300 microm, and 500 microm thickness, sterilized, dried, and inoculated on one side, with 1 microL of Enterococcus faecalis suspension. The opposite side's were irradiated four times for 5 seconds each with Ho:YAG laser irradiation, a wavelength of 2.10 microm, using four different energy settings: 1 W/5 Hz; 1 W/10 Hz; 1.5 W/5 Hz, and 2.0 W/5 Hz through a 320-microm quartz fiber at an angle of approximately 5 degrees. In addition, two control groups were investigated, the first was inoculated and not submitted to any treatment, the second was inoculated and treated with NaOCl and H2O2. The remaining bacteria from each dentin sample in a transport media were removed by vibration, serially diluted, and plated out on culture dishes selective for Enterococcus faecalis. RESULTS: When compared with the untreated control group or even with the group treated with NaOCl plus H2O2, counting of colonies forming units (CFU) from the laser-treated samples revealed a high significant bacterial elimination with a maximum of 98.46% and a minimum of 83.65%. CONCLUSIONS: Our findings demonstrate a significant decrease of the bacterial population in depth, suggesting that the Ho:YAG laser irradiation could be effective to eliminate the microorganisms harbored within dentin or contaminated canals.

Nd:YAG laser influence on tensile bond strength of self-etching adhesive systems.

OBJECTIVE: We evaluated the tensile bond strength of composite resin on enamel and dentine, treated with Nd:YAG laser before and after bonding procedures. BACKGROUND DATA: The use of laser radiation in dentistry is being developed day by day. One of the possible applications of dental lasers includes increasing the quality of self-etching bonding systems. METHODS: Forty-eight human teeth were used and separated into six groups: Group 1 (enamel control), Clearfil Liner Bond 2V (CLB 2V); group 2 (enamel), Nd:YAG + CLB 2V; group 3 (enamel), CLB 2V + Nd:YAG; group 4 (dentine control), CLB 2V; group 5 (dentine), Nd:YAG + CLB 2V; group 6 (dentine), CLB 2V + Nd:YAG. Tensile bond strength was performed. RESULTS: Enamel means (15,54) were lower than dentine means (20,38). Bond strength of laser before (15,73) was lower than laser after (20,65). Interaction results G1 x G3; G2 x G3; G4 x G1; G2 x G5 were statistically significant. CONCLUSIONS: Tensile bond strength of composites reached with self-etching adhesive systems were greater in dentine than in enamel. The best moment for application of Nd:YAG laser is after the use of adhesive system. Self-etching adhesive systems tested in this study can be used together with Nd:YAG laser without compromising to adhesion to dentine.

Microleakage of resin-based composite restorations with ceramic inserts.

PURPOSE: To evaluate dye penetration of proximal vertical slot resin-based composite (RBC) restorations as a function of cavity size and restorative material employed (RBC, ceramic inserts with low-viscosity resin, and RBC with low-viscosity resin liner). Microleakage was measured using rank scoring and linear measurement of dye penetration and ANOVA and non-parametric tests were used to evaluate the statistical significance of the results. MATERIALS AND METHODS: Ninety erupted crack- and caries-free mandibular third molars, extracted for orthodontic reasons, were used. Proximal vertical slots were prepared on the mesial surfaces of the teeth using diamond instruments at high speed under distilled water coolant. Teeth were placed randomly into nine groups. Three sizes of diamond burs of an ultrasonic cavity preparation system were used under low energy in order to standardize cavity size and shape, each tip size being used in 30 different teeth. The gingival margins were prepared 1 mm above the cemento-enamel junction. Specimens were etched, prepared with bonding agent, restored using three different materials, and immersed in a 50% AgNO3 solution for 8 hrs and sectioned to evaluate the dye penetration. RESULTS: Statistical analysis revealed no statistically significant differences among the nine groups.

Nd:YAG laser influence on sound dentin bond strength.

OBJECTIVE: In the present study, the authors evaluated tensile bond strength of composite resin to dentin treated with Nd:YAG laser before and after bonding procedures. SUMMARY BACKGROUND DATA: Lasers have been widely used in dentistry and have contributed to the development of new technologies. Adhesive systems have been indicated for most dental procedures and have produced good results. Studies concerned with the combined use of this adhesive system was the subject of this study. METHODS: Thirty noncarious human anterior teeth, freshly extracted, for periodontal reasons, were used. After grinding the buccal dentinal surface until its exposition, specimens were separated into three groups and received the following treatments: (group 1) control--acid etching plus primer plus bond; (group 2) laser plus acid etching plus primer plus bond; (group 3) acid etching plus primer plus bond plus laser. Specimens of composite resin (Z100, 3M, Saint Paul, MN) were constructed on an inverted truncated 3-mm diameter cone mold. Tensile bond strength was performed using Inströn Universal machine, at 0.5 mm/min speed. RESULTS: Analysis of variance (ANOVA) (p < 0.05) determined that the type of dentinal treatments used had an influence on tensile bond strength. Tukey's test, however, showed that group 1 (15.46) and 3 (15.67) had similar results both of which were higher than group 2 (4.57). CONCLUSIONS: Based on the results obtained, one can conclude that group 1 (without laser) and group 3 (laser after bonding) had similar results, both higher than those observed for group 2 (laser before bonding). These results indicate that more research is needed about how a hybrid layer is formed when laser radiation is used.