Influence of light guide tip used in the photo-activation on degree of conversion and hardness of one nanofilled dental composite

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of chlorhexidine and sodium hypochlorite on the microhardness of root canal dentin

Objective. The purpose of this study was to evaluate the effects of endodontic irrigants on the microhardness of root canal dentin.Study design. Thirty extracted single-rooted human teeth were used. The crowns were sectioned at the cementoenamel junction. Each root was transversely sectioned into cervical, middle, and apical segments, resulting in 90 specimens. The 3 sections of each root were separately mounted in an individual silicon device with acrylic resin. The specimens were randomly divided into the following 3 groups (n = 30), according to the irrigant solution used: (1) group 1, control (saline solution); (2) group 2, 2% chlorhexidine gluconate solution; and (3) group 3, 1% sodium hypochlorite (NaOCl). After 15 minutes of irrigation, dentin microhardness was measured on each section at 500 mu m and 1000 mu m from the pulp-dentin interface with a Vickers diamond microhardness tester in Vickers hardness number (VHN).Results. Data obtained were analyzed using analysis of variance and the Tukey test (5%). Specimens irrigated with 2% chlorhexidine (group 2) or 1% NaOCl (group 3) presented lower values of dentin microhardness, with significant difference in relation to the control group (P < .05).Conclusion. It could be concluded that chlorhexidine and NaOCl solutions significantly reduced the microhardness of root canal dentin at 500 mu m and 1000 mu m from the pulp-dentin interface.

Dentine microhardness after different methods for detection and removal of carious dentine tissue

There are several methods for identifying carious dentinal tissue aiming to avoid removal of healthy dentinal tissue. Objectives: The purpose of this study was to test different methods for the detection of carious dentinal tissue regarding the amount of carious tissue removed and the remaining dentin microhardness after caries removal. Material and methods: The dentin surfaces of 20 bovine teeth were exposed and half of the surface was protected with nail polish. Cariogenic challenge was performed by immersion in a demineralizing solution for 14 days. After transverse cross-section of the crown, the specimens were divided into four groups (n=10), according to the method used to identify and remove the carious tissue: "Papacarie", Caries-detector dye, DIAGNOdent and Tactile method. After caries removal, the cross-sectional surface was included in acrylic resin and polished. In a microhardness tester, the removed dentin thickness and the Vickers microhardness of the following regions were evaluated: remaining dentin after caries removal and superficial and deep healthy dentin. Results: ANOVA and Tukey's test (alpha=0.05) were performed, except for DIAGNOdent, which did not detect the presence of caries. Results for removed dentin thickness were: "Papacarie" (424.7 +/- 105.0; a), Caries-detector dye (370.5 +/- 78.3; ab), Tactile method (322.8 +/- 51.5; bc). Results for the remaining dentin microhardness were: "Papacarie" (42.2 +/- 10.5; bc), Caries-detector dye (44.6 +/- 11.8; bc), Tactile method (24.3 +/- 9.0; d). Conclusions: DIAGNOdent did not detect the presence of carious tissue; Tactile method and "Papacarie" resulted in the least and the most dentinal thickness removal, respectively; Tactile method differed significantly from "Papacarie" and Caries-detector dye in terms of the remaining dentin microhardness, and Tactile method was the one which presented the lowest microhardness values.

Identification of Rhizoctonia solani associated with soybean in Brazil by rDNA-ITS sequences

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

TEOR DE VITAMINA C, ATIVIDADE DE ASCORBATO OXIDASE E PERFIL SENSORIAL DE MANGA (Mangífera índica L.) VAR. HADEN, DURANTE O AMADURECIMENTO

The chemical and biochemical composition of mango, varies according to the cultivation conditions, variety and maturation state, generally containing a high level of ascorbic acid. In order to establish the correlation between the activity of the ascorbate oxidase [E.C.1.10.3.3], and ascorbic acid level in the ripening process of the Haden mango (Mangífera índica L.), sample of the fruits related to hard green stage (zero), 2, 4, 6, 8, 10, 12 and 14 days stored at 20 ± 2oC, were tested. The samples were obtained by cutting small cubes of 8 cm3 from pulps of 8 mangoes with texture without significant difference (p£0.05) at Magness-Taylor pressure tester scale. In each sample the activity of ascorbate oxidase was followed, in order to check its participation in possible substrate losses during the ripening fruits. The ascorbic acid level and sensory profile also was determined periodically during the ripening period. The enzymatic activity was spectrophotometrically determined at 245 nm and 30oC. The ascorbic acid was analyzed according modified AOAC methodology, and sensory analysis by descriptive quantitative analysis. Data were analyzed using correlation analysis, analysis of variance (ANOVA), Tukey's test, principal component analysis and stepwise discriminant analysis. During the ripening, the ascorbate oxidase activity increased (from 0 to 5.0 x 10-1 U/ml) and the ascorbic acid level decreased (from 209.3 mg to 110.0 mg per 100g of pulp), showing a significant (p£0.05) inverse linear correlation (r=-0.98). The descriptors terms for mangoes were: characteristic flavor, characteristic aroma, sourness, astringency, yellow coloration of pulp, sweetness and succulence. The sensory profile presented significant improvement during ripening. All sensory attributes increased significantly (p£0.05) except sourness and astringency, wich decreased during the ripening of mangoes.

Confiabilidade inter e intraexaminadores nas mensurações angulares por fotogrametria digital e goniometria

INTRODUÇÃO: A utilização da fotogrametria computadorizada em prol da goniometria, ou vice-versa, na prática clínica ainda necessita de fundamentações consistentes. OBJETIVOS: Os objetivos deste estudo foram: verificar a confiabilidade inter e intraexaminadores avaliadores na quantificação das medidas angulares obtidas a partir da fotogrametria computadorizada e a goniometria e determinar a confiabilidade paralela entre esses dois diferentes instrumentos de avaliação. MATERIAIS E MÉTODOS: 26 voluntários e 4 examinadores foram utilizados no estudo. A coleta foi realizada em 4 etapas sequenciais: demarcação dos pontos anatômicos de referência, mensuração e registro dos valores goniométricos, captação da imagem do voluntário com os marcadores fixados no corpo e avaliação do registro fotográfico no programa ImageJ. RESULTADOS: O goniômetro é um instrumento confiável na maioria das evidências, porém, a confiabilidade das medições depende principalmente da uniformização dos procedimentos. Considerações metodológicas relativas ao estabelecimento de confiabilidade e padronização da colocação dos marcadores se fazem necessárias, de modo a oferecer opções de avaliação ainda mais confiáveis para a prática clínica. CONCLUSÃO: Ambos os instrumentos são confiáveis e aceitáveis, porém, mais evidências ainda são necessárias para suportar a utilização desses instrumentos, pois poucos pesquisadores têm utilizado o mesmo desenho de estudo, e a comparação dos resultados entre eles muitas vezes são difíceis.

Si3N4 ceramic cutting tool sintered with CeO2 and Al2O3 additives with AlCrN coating

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Performance of low/correct pressure radial ply tires

Extensive field testes were conducted using the UCD single wheel tester employing three large radial ply tractor tires in two different soils, four different soil conditions, two axle load levels, and three levels of tire inflation pressures in order to quantify the benefits of using low/correct inflation pressures. During these tests slip, net traction, gross traction, and dynamic axle load were recorded. Furthermore, soil moisture content, cone index, and dry bulk density data were obtained at test locations. The results of the analysis showed a significant increase in net traction and traction efficiency when low/correct inflation was used. Benefits of using low/correct pressure was higher in tilled soil conditions.

Characterization of Rhizoctonia solani associated with soybean in Brazil

Rhizoctonia solani causes pre- and post-emergence damping-off, root and hypocotyl rot and foliar blight in soybean. Foliar blight has resulted in yield losses of 31-60% in north and northeast Brazil. The aim of this study was to characterize isolates of R. solani associated with soybean in Brazil. Among 73 Rhizoctonia isolates examined, six were binucleate and 67 were multinucleate. The multinucleate isolates were characterized according to hyphal anastomosis reaction, mycelial growth rate, thiamine requirement, sclerotia production, and RAPD molecular markers. Four isolates that caused hypocotyl rot belonged to AG-4 and using RAPD analysis they grouped together with the HGI subgroup. Another isolate that caused root and hypocotyl rots was thiamine auxotrophic, grew at 35 °C, and belonged to AG-2-2 IIIB. All 62 isolates that caused foliar blight belonged to AG-1 IA. RAPD analysis of R. solani AG-1 IA soybean isolates showed high genetic similarity to a tester strain of AG-1 IA, confirming their classification. The teleomorph of R. solani, Thanatephorus cucumeris was produced in vitro by one AG-1 IA isolate from soybean. The AG-4 and AG-2-2 IIIB isolates caused damping-off and root and hypocotyl rots of soybean seedlings cv. 'FT-Cristalina', under greenhouse conditions. The AG-2-2 IIIB isolate caused large lesions on the cortex tissue, that was distinct from the symptoms caused by AG-4 isolates. The AG-1 IA isolates caused foliar blight in adult soybean plants cv. 'Xingu' under the greenhouse and also in a detached-leaf assay.

Influence of the final temperature of investment healting on the tensile strength and Vickers hardness of CP TI and TI-6AL-4V alloy

The aim of the work was to evaluate the influence of the temperature of investment healting on the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy casting. Were obtained for the tensile strength test dumbbell rods that were invested in the Rematitan Plus investment and casting in the Discovery machine cast. Thirty specimens were obtained, fiftten to the CP Titanium and fifteen to the Ti-6Al-4V alloy, five samples to each an of the three temperatures of investment: 430°C (control group), 480°C and 530°C. The tensile test was measured by means of a universal testing machine, MTS model 810, at a strain of 1.0 mm/min. After the tensile strenght test the specimens were secctioned, embedded and polished to hardness measurements, using a Vickers tester, Micromet 2100. The means values to tensile tests to the temperatures 430°C, 480 and 530: CP Ti (486.1 - 501.16 - 498.14 -mean 495.30 MPa) and Ti-6Al-4V alloy (961.33 - 958.26 - 1005.80 - mean 975.13 MPa) while for the Vickers hardness the values were (198.06, 197.85, 202.58 - mean 199.50) and (352.95, 339.36, 344.76 - mean 345.69), respectively. The values were submitted to Analysis of Variance (ANOVA) and Tukey' s Test that indicate differences significant only between the materials, but not between the temperature, for both the materias. It was conclued that increase of the temperature of investment its not chance the tensile strength and the Vickers hardness of the CP Titanium and Ti-6Al-4V alloy.

Thermocycling effect on microhardness of laboratory composite resins

Tha aim of this study was to evaluate the thermocycling effect on microhardness of laboratory composite resins, 30 disks were fabricated, 5mm of diameter and 2mm of width, using 3 laboratory resins: G1 (n=10) - RESILAB MASTER (Wilcos-Brasil), G2 (n=10) - Vita VMLC (VITA Zahnfabrik-Germany), and G3 (n=10) - Vita Zeta (VITA Zahnfabrik-Germany). Vickers microhardness (HV) of all specimens was evaluated using a microhardness tester FM-700 (Future Tech- 50 g/10s). The specimens were measured before and after the thermocycling (3,000 times and 12,000 times - 5°/55°C±1). The microhardness values before cycling were (mean±SD): G1: 55.50±4.6; G2: 35.54±2.5; G3: 27.97±1.6; after 3,000 thermocycles: G1: 55.54±3.9; G2: 29.92±2.73; G3:21.01±1.4 and after 12,000 cycles G1: 54.27±3.2; G2: 30.91±1.6; G3: 23.81±0.9. Variance analysis (ANOVA) and Tukey's test was accomplished (p<0.05), the highest microhardness values were observed in G1: G2 and G3 showed reduction of microhardness values. It was concluded that, after thermocycling, the tested laboratory composites resins are susceptible to the decrease of surface microhardness.

The effect of different light-curing units on tensile strength and microhardness of a composite resin

The aim of this study was to evaluate the influence of different light-curing units on the tensile bond strength and microhardness of a composite resin (Filtek Z250 - 3M/ESPE). Conventional halogen (Curing Light 2500 - 3M/ESPE; CL) and two blue light emitting diode curing units (Ultraled - Dabi/Atlante; UL; Ultrablue IS - DMC; UB3 and UB6) were selected for this study. Different light intensities (670, 130, 300, and 600 mW/cm2, respectively) and different curing times (20s, 40s and 60s) were evaluated. Knoop microhardness test was performed in the area corresponding to the fractured region of the specimen. A total of 12 groups (n=10) were established and the specimens were prepared using a stainless steel mold composed by two similar parts that contained a cone-shaped hole with two diameters (8.0 mm and 5.0 mm) and thickness of 1.0 mm. Next, the specimens were loaded in tensile strength until fracture in a universal testing machine at a crosshead speed of 0.5 mm/min and a 50 kg load cell. For the microhardness test, the same matrix was used to fabricate the specimens (12 groups; n=5). Microhardness was determined on the surfaces that were not exposed to the light source, using a Shimadzu HMV-2 Microhardness Tester at a static load of 50 g for 30 seconds. Data were analyzed statistically by two-way ANOVA and Tukey's test (p<0.05). Regarding the individual performance of the light-curing units, there was similarity in tensile strength with 20-s and 40-s exposure times and higher tensile strength when a 60-s light-activation time was used. Regarding microhardness, the halogen lamp had higher results when compared to the LED units. For all light-curing units, the variation of light-exposure time did not affect composite microhardness. However, lower irradiances needed longer light-activation times to produce similar effect as that obtained with high-irradiance light-curing sources.

Microhardness and fluoride release of restorative materials in different storage media

This study evaluated the surface microhardness and fluoride release of 5 restorative materials - Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom and Fluorofil - in two storage media: distilled/deionized water and a pH-cycling (pH 4.6). Twelve specimens of each material, were fabricated and the initial surface microhardness (ISM) was determined in a Shimadzu HMV-2000 microhardness tester (static load Knoop). The specimens were submitted to 6- or 18-h cycles in the tested media. The solutions were refreshed at the end of each cycle. All solutions were stored for further analysis. After 15-day storage, the final surface microhardness (FSM) and fluoride release were measured. Fluoride dose was measured with a fluoride-specific electrode (Orion 9609-BN) and digital ion analyzer (Orion 720 A). The variables ISM, FSM and fluoride release were analyzed statistically by analysis of variance and Tukey's test (p<0.05). There was significant difference in FSM between the storage media for Vitremer (pH 4.6 = 40.2 ± 1.5; water = 42.6 ± 1.4), Ketac-Fil Plus (pH 4.6 = 73.4 ± 2.7; water = 58.2 ± 1.3) and Fluorofil (pH 4.6 = 44.3 ± 1.8; water = 38.4 ± 1.0). Ketac-Fil Plus (9.9 ± 18.0) and Fluorofil (4.4 ± 1.3) presented higher fluoride release in water, whereas Vitremer (7.4 ± 7.1), Fuji II LC (5.7 ± 4.7) and Freedom (2.1 ± 1.7) had higher fluoride release at pH 4.6. Microhardness and fluoride release of the tested restorative materials varied according to the storage medium.

Effect of light-curing method and indirect veneering materials on the Knoop hardness of a resin cement

This study evaluated the Knoop hardness of a dual-cured resin cement (Rely-X ARC) activated solely by chemical reaction (control group) or by chemical / physical mode, light-cured through a 1.5 mm thick ceramic (HeraCeram) or composite (Artglass) disc. Light curing was carried out using conventional halogen light (XL2500) for 40 s (QTH); light emitting diodes (Ultrablue Is) for 40 s (LED); and Xenon plasma arc (Apollo 95E) for 3 s (PAC). Bovine incisors had their buccal face flattened and hybridized. On this surface a rubber mold (5 mm in diameter and 1 mm in height) was bulk filled with the resin cement. A polyester strip was seated for direct light curing or through the discs of veneering materials. After dry storage in the dark (24 h 37°C), the samples (n = 5) were sectioned for hardness (KHN) measurements, taken in a microhardness tester (50 gF load 15 s). The data were statistically analyzed by ANOVA and Tukey's test (α = 0.05). The cement presented higher Knoop hardness values with Artglass for QTH and LED, compared to HeraCeram. The control group and the PAC/Artglass group showed lower hardness values compared to the groups light-cured with QTH and LED. PAC/HeraCeram resulted in the worst combination for cement hardness values. © 2009 Sociedade Brasileira de Pesquisa Odontológica.

Evaluation of hardness and surface roughness of two maxillofacial silicones following disinfection

The purpose of this study was to evaluate the Shore A hardness and surface roughness of two silicones for maxillofacial prosthetic treatment, under the influence of chemical disinfection and storage. Twenty-eight specimens were obtained, half of which were made of Silastic MDX 4-4210 silicone and, the other half were made of Silastic 732 RTV silicone. The specimens were divided into four groups: Silastic 732 RTV and MDX 4-4210 with disinfection 3 times a week with Efferdent tablets and the same materials without disinfection. The hardness of the materials was analyzed with a Shore A Durometer. The surface roughness was established by a digital portable roughness tester, initially and 2 months after the confection of the specimens. A variance test was applied (2-way ANOVA), followed by Tukey test (the level of significance was set at 1%). The storage time factor statistically influenced (p < 0.01) the materials' properties of hardness and roughness. MDX 4-4210 (28.59 Shore A, 0.789 Ra) presented higher values than Silastic 732 RTV (18.08 Shore A, 0.656 Ra) for both properties. Regarding the disinfection period, there was no significant difference in any of the materials tested. © 2009 Sociedade Brasileira de Pesquisa Odontológica.