Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique

This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 mu g) and human (2.27 +/- 0.41 mu g) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.

Barrier penetration for supersymmetric shape-invariant potentials

Exact reflection and transmission coefficients for supersymmetric shape-invariant potentials barriers are calculated by an analytical continuation of the asymptotic wavefunctions obtained via the introduction of new generalized ladder operators. The general form of the wavefunction is obtained by the use of the F(-infinity, +infinity)-matrix formalism of Froman and Froman which is related to the evolution of asymptotic wavefunction coefficients.

Energy efficiency for standard penetration tests

The need for standardization of the measured blow count number N-spt into a normalized reference energy value is now fully recognized. The present paper extends the existing theoretical approach using the wave propagation theory as framework and introduces an analysis for large displacements enabling the influence of rod length in the measured N-spt values to be quantified. The study is based on both calibration chamber and field tests. Energy measurements are monitored in two different positions: below the anvil and above the sampler. Both experimental and numerical results demonstrate that whereas the energy delivered into the rod stem is expressed as a ratio of the theoretical free-fall energy of the hammer, the effective sampler energy is a function of the hammer height of fall, sampler permanent penetration, and weight of both hammer and rods. Influence of rod length is twofold and produces opposite effects: wave energy losses increase with increasing rod length and in a long rod composition the gain in potential energy from rod weight is significant and may partially compensate measured energy losses. Based on this revised approach, an analytical solution is proposed to calculate the energy delivered to the sampler and efficiency coefficients are suggested to account for energy losses during the energy transference process.

Penetration of a light-cured glass ionomer and a resin sealant into occlusal fissures and etched enamel.

PURPOSE: To evaluate the penetration of a light-cured glass ionomer and a resin sealant into occlusal fissures and etched enamel. MATERIALS AND METHODS: Forty-eight maxillary and mandibular caries-free premolars scheduled for extraction for orthodontic reasons were isolated, the occlusal surfaces subjected to prophylaxis and acid-etched with orthophosphoric acid prior to the application of the VariGlass VLC glass ionomer and Concise resin sealants. The teeth were extracted, two longitudinal median sectiors from each tooth were ground to a thickness of 80-100 microns, and the sealant penetration into the fissures evaluated. The sections were placed in nitric acid to dissolve the enamel so the lengths of the tags which had penetrated into the etched enamel could be measured at different sites on the walls of the fissures. RESULTS: Both sealants adapted well to the fissures but penetrated deeper into shallow, open fissures than into deep, constricted fissures. The VariGlass VLC tags into etched enamel were generally longer than the Concise projections.

Effect of capacitation of stallion sperm with polyvinylalcohol or bovine serum albumin on penetration of bovine zona-free or partially zona-removed equine oocytes

Experiments were conducted to study effects of macromolecules on stallion sperm capacitation and fertilization as determined by penetration of bovine zona-free and equine partially zona-removed oocytes. Stallion sperm were capacitated in TYH medium (modified Krebs-Ringer bicarbonate) supplemented with either 1 mg/mL of polyvinylalcohol (PVA) or 4 mg/ mL of BSA. Capacitation was induced with 8 bromoadenosine cyclic monophosphate (8BrcAMP; 0.5 mM) alone or in combination with 0.1 μM of ionomycin. Intraspecies gametes were co-incubated in TYH/PVA or TYH/ BSA for 18 to 20 h. For zona-free bovine oocytes, penetration rate (35%) with the combination of 8BrcAMP and ionomycin in PVA-containing medium was higher (P < 0.05) than any treatment in BSA-containing medium (5 to 6%). A similar study was conducted using equine oocytes with partially removed zonae. Sperm capacitated and used for in vitro fertilization (IVF) in PVA-containing medium had higher penetration rates (P < 0.01) than sperm in BSA-containing medium (54 vs. 11%). The effect of equine preovulatory follicular fluid on bovine oocyte penetration was assessed. Bovine oocytes were matured in tissue culture medium-199 with 0, 20, 50, or 100% equine preovulatory follicular fluid, and 1 IU/mL of equine chorionic gonadotropin. Stallion sperm were treated with 8BrcAMP + ionomycin in PVA- or BSA-containing media. The penetration rates of bovine zona-free oocytes by stallion sperm were again higher with PVA (47%) than BSA (18%; P < 0.01). Penetration rates of oocytes matured in 100% follicular fluid were higher (P < 0.05) than for oocytes matured with 0% follicular fluid. The effects of equine follicular fluid and PVA/BSA during sperm capacitation on standard bovine IVF were examined. Culture of bovine oocytes with equine follicular fluid did not affect oocyte maturation or penetration rates after IVF. Bovine sperm capacitated with heparin in PVA-containing medium yielded lower (P < 0.05) fertilization rates than those capacitated in BSA-containing medium when incubated with both zona-intact and zona-free bovine oocytes. In summary, PVA was superior to BSA for ionophore-induced capacitation of equine sperm for penetration of zona-free bovine oocytes or partially zona-removed equine oocytes, but not for standard bovine IVF with bovine sperm. Zona-free bovine oocytes may be useful for assaying in vitro capacitation and fertilization of stallion sperm. © 2003 American Society of Animal Science. All rights reserved.

Comparative study of the cuticular hydrocarbon composition of Melipona bicolor Lepeletier, 1836 (Hymenoptera, Meliponini) workers and queens

In social insects, cuticular hydrocarbons are involved in species, kin, caste and nestmate recognition. Gas chromatography and mass spectrometry were used to compare the cuticular hydrocarbon composition of workers, males and queens of Melipona bicolor. The cuticular hydrocarbon composition of this species was found to consist mainly of C23, C25:1, C25, C27:1, C27, C29:1 and C29, which are already present in imagoes that have not yet abandoned the brood cell. This composition varied quantitatively and qualitatively between and within the castes and sexes. The newly emerged workers and young queens (virgins) had similar cuticular hydrocarbon profiles, which were different from those of the males. When the females start executing their tasks in the colony, the cuticular hydrocarbon profile differences appear. The workers have less variety, while the queens conserve or increase the number of cuticular hydrocarbon compounds. The queens have more abdominal tegumentary glands than the workers, which apparently are the source of the new cuticular compounds.

Cuticular Hydrocarbons of Heterotermes tenuis (Isoptera: Rhinotermitidae): Analyses and Electrophysiological Studies

Termites have become an important pest of Eucalyptus and Pinus reforestations, sugarcane and other cultures. An alternative for the control of this pest would be the use of attractive traps that take in account the social behavior of these insects. Diverse factors are important for the insects in the localization of the habitat and the choice of the food and specific odors can facilitate this. Studies referring to Heterotermes tenuis (Isoptera: Rhinotermitidae) are scarce. The objective of this work was to analyze the tergal cuticular extract of H. tenuis and determine the selectivity and sensitivity of its antennae to the components of this extract by electroantennography (EAG). The composition of the cuticular extract was determined by GC-MS analysis. The hydrocarbons found were restricted to linear alkanes, being most abundant C24 to C27 that comprises ca. 65% of the total. Olefins were not detected. EAG and behavioral test responses to the cuticular hydrocarbons were greater and significantly different from the control and the high selectivity of the antennae to the extract indicates its potential as chemical messenger. Cuticular hydrocarbons mixture is species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers or imagoes. Difference in the composition appears to relate with the type of habitat of specie.

In vitro penetration of bleaching agents into the pulp chamber

Aim: To investigate pulp chamber penetration of bleaching agents in teeth following restorative procedures. Methodology: Bovine lateral incisors were sectioned 3 mm apical to the cemento-enamel junction and the coronal pulpal tissue was removed. Teeth were divided into six groups (n = 10): G1, G2 and G3 were not submitted to any restorative procedure, while G4, G5 and G6 were submitted to Class V preparations and restored with composite resin. Acetate buffer was placed in the pulp chamber and treatment agents were applied for 60 min at 37°C as follows: G1 and G4, immersion into distilled water; G2 and G5, 10% carbamide peroxide (CP) exposure; G3 and G6, 35% CP bleaching. The buffer solution was removed and transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm. A standard curve made with known amounts of hydrogen peroxide was used to convert the optical density values of the coloured samples into microgram equivalents of hydrogen peroxide. Data were submitted to ANOVA and Tukey's test (5%). Results: Amounts of hydrogen peroxide found in the pulp chamber of G2 and G5 specimens (0.1833 ± 0.2003 μg) were significantly lower (P = 0.001) when compared to G3 and G6 specimens (0.4604 ± 0.3981 μg). Restored teeth held significantly higher (P = 0.001) hydrogen peroxide concentrations in the pulp chamber than intact teeth. Conclusion: Higher concentrations of the bleaching agent produced higher levels of hydrogen peroxide in the pulp chamber, especially in restored teeth.

Diagnosis of a compacted area for mining through the mechanical resistance to the penetration using geostatistical methods in the Amazon Forest

The mining process promotes land modification and complete landscape alteration. Those alterations in the surface are shown more obviously in the aesthetical aspect as the visual elements of form, texture, climbs, complexity and color which composes the landscape. As a consequence, mining has impacts on the topography, in the soil, in the vegetation and in the area's drainage, with a direct influence on the enterprise. A quite common problem in the recovery of degraded areas in mineral exploration is the compaction of the soil due to the intense traffic of machines and earth movement. The most common problem of the compaction of a degraded surface is an increase of the mechanical resistance to the penetration of plant roots, a reduction of the aeration, an alteration of the flow of water and heat, also in the availability of water and nutrients. Thus, the present work had the basic objective of diagnosing the compaction of an area degraded by mining in a spacial way, through the mechanical resistance and the penetration, to guide the future subsoiling in the area requiring recovery. Through the studies, it was concluded that the krigagem method in agreement with the space variation allows the division of the area under study into sub areas facilitating a future work to reduce costs and unnecessary interference to the atmosphere. The method was shown to be quite appropriate and it can be used in the diagnosis of compaction in a degraded area by mining, foreseeing the subsoiling requirement.