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.

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.

[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.

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.

Estudio de movimientos de dientes soportes en función de la localización de los apoyos oclusales de las prótesis parciales removibles de extremo libre, a través de métodos de elementos finitos tridimensionales (trad) / A study of support teeth movements according to the occlusal rests of the distal extension removable partial dentures, by three-dimensional finite elements methods

En las prótesis parciales removibles inferiores de extremidades libres, los apoyos oclusales además de ejercer funciones propias, actúan como fulcrum de fuerzas cuando se mueve la prótesis en el plano horizontal. Su localización en los dientes pilares reviste especial importancia, influyendo en la formación del sistema de palanca y consecuentemente en el dislocamiento que el diente soporte sufre cuando hay incidencia de fuerzas masticatorias. Este estudio fue hecho a través de un programa computarizado para analizar funciones denominado "Método de elementos finitos tridimensional" en que fueron construídos dos modelos, cuyas variables utilizadas fueron la localización de retenedores y apoyos sobre el diente pilar

On the size of Hassall's corpuscles in human fetuses.

The areas of prevailingly solid (SHC) and prevailingly cystic (CHC) Hassall's corpuscles in the thymuses of both male and female fetuses 16-39 weeks old were established. The results show that the mean areas of the Hassall's corpuscles increase with fetal age, with the greatest difference between the 16-19 week and 20-23 week age groups. The data indicate that the thymus represent an organ showing a developmental pattern similar to other organs like the spleen's relative growth in human fetus, whose functions are different during the fetal period, being necessary to study its growth in distinct short periods to determinate differentials growth coefficients.

[Stress in teeth restored with gold and copper-aluminum alloys under distributed force. Finite element method]. / Contribuição para o estudo das tensões que ocorrem em dentes restaurados, utilizando ligas de ouro e de cobre-alumínio, sob ação de força distribuída. Método dos elementos finitos.

The author studied the stress distribution which occurs in casted metalic restoration a gold alloy type II and a copper-aluminum, with cavity preparation of both types: intracoronal or extracoronal cavity using the finite elements method in a first right inferior molar. The conclusion was that the mechanical performance of both are very similar. Stress occurred in a dental structure which alloy cast restoration are smaller than that occurred in a tooth without cavity preparation. The cavity preparation with intracoronal shows a better stress distribution in the dentine than that with extracoronal. In the region near the buccopulpal line angle occurs a stress concentration in despite of the type of the cavity metallic alloy used.

[Dimensional changes in die stones with an additive and sodium chloride]. / Contribuição para o estudo da alteração dimensional dos gessos para troquel, com a presença de aditivo e cloreto de sodio.

The obtention of a working model and the preparation of the die must be developed with great care and attention to detail. Based on these principles, a study was conducted referring to the different kinds of special plasters or die plasters available on the market, with respect to dimensional alterations, as well as an investigation of the dimensional behavior of special plasters in the presence of two additives. The results shows that Vel-mix had the greatest difference. All the special plasters brands showed alterations when the Gypsum Hardener were used. These alterations did not occur with sodium chloride.