The Influence Of Tubule Density And Area Of Solid Dentin On Bond Strength Of Two Adhesive Systems To Dentin

Purpose: To determine the correlation between the tubule density (TD) and the area occupied by solid dentin (ASD) with the bond strength of one conventional and one self-etching adhesive system to dentin. Materials and Methods: The crown of extracted human third molars was transversally sectioned with a diamond saw to expose either superficial, middle, or deep dentin. The three groups of dentin surfaces were randomly divided and bonded with either Clearfil Liner Bond 2V (LB) or Prime & Bond 2.1 (PB) adhesive systems according to manufacturer's directions. Resin composite buildup crowns (10.0 mm high) were incrementally constructed on the bonded surfaces and the teeth stored in water at 37°C. After 24 h of storage, the teeth were vertically, serially sectioned in both x and y directions to obtain several bonded sticks of approximately 0.7 mm2 cross-sectional area. Each stick was tested in tension in a EMIC DL-500 tester at 0.5 mm/min until failure. After testing, the dentin side of the fractured specimen was gently abraded with a 1000-grit SiC paper, etched with 37% phosphoric acid for 15 s and allowed to air dry. SEM micrographs at 1000X and 4000X magnification were taken to permit calculation of the TD (number of tubules/mm2) and ASD (% of total area) at the site of fracture. Correlation between TD and ASD with the bond strength data was performed by linear regression. All statistical analysis was done with a = 0.05. Results: Overall bond strength (MPa) for LB was 26.0 ± 10.2, and 42.6 ± 15.2 for PB. There was a significant direct relationship between bond strength and ASD for both materials (r2 = 0.20, p < 0.05 and r2 = 0.66, p < 0.01, respectively for LB and PB). PB bond strength dropped significantly as the TD increased (r2 = 0.63, p < 0.05), while LB was not sensitive to TD (r2 = 0.05, p > 0.05). Mean bond strength of PB was significantly higher than LB for both superficial and middle dentin (p < 0.05), while there was no significant difference for deep dentin (p > 0.05). Conclusion: Regional variations in TD and ASD may modify bond strength of both conventional and self-etching adhesive systems. Bonding sites with larger ASD seem to yield higher bond strengths regardless of the type of adhesive system used.34315324Burrow, M.F., Takakura, H., Nakajima, M., Inai, N., Tagami, J., Takatsu, T., The influence of age and depth of dentin on bonding (1994) Dent Mater, 10, pp. 241-246Carrigan, P.J., Morse, D.R., Furst, M.L., Sinai, I.H., A scanning electron microscopic evaluation of human dentinal tubules according to age and location (1984) J Endod, 10, pp. 359-363Fernandes, C.A.O., (2000) Estudo Comparativo da Resistência Adesiva À Dentina Superficial e Profunda Testada Simultaneamente, Empregando-se Dois Sistemas Adesivos, , Thesis, Bauru School of Dentistry, USP, Bauru, SP, BrazilFosse, G., Saele, P.K., Eide, R., Numerical density and distributional pattern of dentin tubules (1992) Acta Odont Scand, 50, pp. 201-210Garberoglio, R., Brännström, M., Scanning electron microscopic investigation of human dentinal tubules (1976) Archs Oral Biol, 21, pp. 355-362Gwinnett, A.J., Quantitative contribution of resin infiltration/hybridization to dentin bonding (1993) Am J Dent, 6, pp. 7-9McCabe, J.F., Rusby, S., Dentine bonding agents - Characteristic bond strength as a function of dentine depth (1992) J Dent, 20, pp. 225-230Nakajima, M., Sano, H., Burrow, M.F., Tagami, J., Yoshiyama, M., Ebisu, S., Ciucchi, B., Pashley, D.H., Tensile bond strength and SEM evaluation of caries-effected dentin using adhesives (1995) J Dent Res, 74, pp. 1679-1688Nery, S., McCabe, J.F., Wassell, R.W., A comparative study of three dental adhesives (1995) J Dent, 23, pp. 55-61Pashley, D.H., Carvalho, R.M., Dentine permeability and dentine adhesion (1997) J Dent, 25, pp. 335-372Pashley, D.H., Ciucchi, B., Sano, H., Carvalho, R.M., Russell, C.M., Bond strength versus dentine structure: A modelling approach (1995) Archs Oral Biol, 40, pp. 1109-1118Pashley, D.H., Ciucchi, B., Sano, H., Yoshiyama, M., Carvalho, R.M., Adhesion testing of dentin bonding agents. A review (1995) Dent Mater, 11, pp. 117-125Pashley, D.H., Clinical correlations of dentin structure and function (1991) J Prosth Dent, 66, pp. 777-781Pashley, D.H., Dentin: A dynamic substrate - A review (1989) Scanning Microsc, 3, pp. 161-174Pereira, P.N.R., Okuda, M., Sano, H., Yoshikawa, T., Burrow, M.F., Tagami, J., Effect of intrinsic wetness and regional difference on dentin bond strength (1999) Dent Mater, 15, pp. 46-53Prati, C., Pashley, D.H., Dentin wetness, permeability and thickness and bond strength of adhesive systems (1992) Am J Dent, 5, pp. 33-38Suzuki, T., Finger, W.J., Dentin adhesives: Site of dentin vs. Bonding of composite resins (1988) Dent Mater, 4, pp. 379-383Tagami, J., Tao, L., Pashley, D.H., Correlation among dentin depth, permeability, and bond strength of adhesive resins (1990) Dent Mater, 6, pp. 45-50Tao, L., Pashley, D.H., Shear bond strengths to dentin: Effects of surface treatments, depth and position (1988) Dent Mater, 4, pp. 373-378Tay, F.R., Gwinnett, A.J., Wei, S.H.Y., The overwet phenomenon: A scanning electron microscopic study of surface moisture in the acid-conditioned, resin-dentin interface (1996) Am J Dent, 9, pp. 109-114Tay, F.R., Sano, H., Carvalho, R.M., Pashley, E.L., Pashley, D.H., An ultrastructural study of the influence of acidity of self-etching primers and smear layer thickness on bonding to intact dentin (2000) J Adhesive Dent, 2, pp. 83-98Yoshiyama, M., Carvalho, R.M., Sano, H., Horner, J., Brewer, P.D., Pashley, D.H., Interfacial morphology and strength of bonds made to superficial versus deep dentin (1995) Am J Dent, 8, pp. 297-302Yoshiyama, M., Sano, H., Ebisu, S., Tagami, J., Ciucchi, B., Carvalho, R.M., Johnson, M.H., Pashley, D.H., Regional strengths of bonding agents to cervical sclerotic root dentin (1996) J Dent Res, 75, pp. 1404-141

Genótipos de feijoeiro carioca para tolerância ao escurecimento de grão pelos métodos natural e acelerado

The slow darkening of grains is sought by bean breeders because the consumers consider that darker grains demand more time for cooking. The analysis currently used takes around 90 days to differentiate grain color among genotypes. The objective was to evaluate the color as a function of the value of L* (lightness) of carioca beans, by natural and accelerated methods to verify equivalence between methods, validation of the methodology and identification of genotypes tolerant to the darkening. The grain darkening was compared and evaluated by natural darkening method under shelf conditions, in days storage, and accelerated darkening method under ultraviolet light, in hours. The natural darkening time of 90 days was statistically equal to 24 hours of accelerated darkening, and the difference among the genotypes could be obtained in a shorter time, indicating a correspondence in the methods. The accelerated darkening method can be used to shorten the analysis time in the routine of breeding programs43CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão temnão temnão temO escurecimento lento de grãos é almejado por melhoristas de feijoeiro porque o consumidor considera que grãos mais escuros apresentarão maior tempo para cocção. A análise empregada atualmente leva ao redor de 90 dias para diferenciação da cor do grão entre os genótipos. Objetivou-se avaliar a cor em função do valor de L* (luminosidade) de feijoeiro do tipo carioca pelos métodos natural e acelerado para verificar equivalência entre os métodos, validação da metodologia e identificação de genótipos tolerantes ao escurecimento. O escurecimento de grãos foi comparado e avaliado pelo método de escurecimento natural em condições de prateleira, em dias de armazenamento, e pelo método de escurecimento acelerado, em condições de luz ultravioleta, em horas. O escurecimento natural de 90 dias foi estatisticamente igual a 24 horas de escurecimento acelerado, e a diferença entre os genótipos pôde ser obtida em menor tempo, indicando correspondência entre os métodos. O método de escurecimento acelerado pode ser utilizado para encurtar o tempo de análise na rotina dos programas de melhorament

Resistência de plantas daninhas aos herbicidas inibidores da ALS na cultura da soja (Glycine max)

As plantas daninhas Bidens pilosa/Bidens subalternans (picão-preto) e Amaranthus quitensis (caruru) são controladas na cultura da soja por diversos herbicidas, sendo os inibidores da acetolactato sintase (ALS) os mais utilizados pelos sojicultores. O uso intensivo e repetitivo destes herbicidas em áreas cultivadas com soja no município de São Gabriel do Oeste (MS - Brasil) e nas províncias de Córdoba e Tucumã (Argentina) proporcionou grande pressão de seleção nas populações destas plantas daninhas, resultando em populações resistentes. Com o objetivo de determinar a resistência cruzada aos herbicidas inibidores da ALS, pertencentes aos grupos químicos sulfoniluréia e imidazolinona, foi conduzido um experimento, em condições de casa de vegetação, na Escola Superior de Agricultura "Luiz de Queiroz" (ESALQ), Piracicaba, São Paulo. As plantas daninhas picão-preto e caruru, provenientes de áreas com suspeita de resistência aos herbicidas inibidores da ALS, foram tratadas com os herbicidas chlorimuron-ethyl, imazethapyr e nicosulfuron em diversas doses e comparadas com as plantas provenientes de populações suscetíveis. Os tratamentos foram estabelecidos considerando-se doses que proporcionariam no mínimo 50% do controle das plantas daninhas (GR50), utilizando-se para isso doses abaixo e acima das doses recomendadas de cada herbicida. O herbicida chlorimuron-ethyl foi aplicado nas doses de 1.500, 750, 150, 75, 15, 7,5 e 1,5 g i.a. ha-1; o imazethapyr, nas doses de 8.000, 4.000, 800, 400, 80, 40 e 8 g i.a. ha-1; e o nicosulfuron, nas doses de 1.200, 600, 120, 60, 12, 6 e 1,2 g i.a. ha-1. Os biotipos resistentes apresentaram diferentes níveis de resistência cruzada aos herbicidas utilizados. O biotipo resistente de picão-preto apresentou GR50 para chlorimuron-ethyl, imazethapyr e nicosulfuron de 1,49; 1,27; e 20,08 g i.a. ha-1, respectivamente. Da mesma forma, o GR50 do biotipo resistente de caruru foi de 6,8; 2,45; e 23,54 g i.a. ha-1. As curvas de dose-resposta da porcentagem de controle das plantas daninhas aos 14 dias após o tratamento dos biotipos resistentes apresentaram valores inferiores aos das curvas de dose-resposta dos biotipos suscetíveis, mesmo nas doses extremas utilizadas. As taxas de resistência (GR50(resistente)/GR50(suscetível)) para picão-preto foram de 9,90 para chlorimuron-ethyl, 9,07 para nicosulfuron e 27,03 para imazethapyr, enquanto para caruru elas foram de 45,03 para o chlorimuron-ethyl, 181 para o nicosulfuron e 24,55 para o imazethapyr

EFEITO da COMPOSIÇÃO do SUBSTRATO NA FORMAÇÃO DE MUDAS DE LARANJEIRA `PERA'

O efeito de cinco composições de substratos na produção de mudas de laranjeira `Pêra' (Citrus sinensis, L. Osbeck) foi estudado sobre três porta-enxertos (limoeiro `Cravo', Citrus limonia, L. Osbeck; tangerineira `Cleópatra', Citrus reticulata, Blanco; e citrumeleiro `Swingle', Citrus paradisi x Poncirus trifoliata). O experimento obedeceu ao delineamento estatístico de blocos aleatorizados em esquema fatorial 5 x 3 (substratos x porta-enxertos). As composições de misturas utilizadas como substrato e respectivas combinações volumétricas foram: 1) Terra (100%); 2) Terra (33%) + areia fina (33%) + esterco bovino curtido (33%); 3) Terra (33%) + vermiculita (33%) + esterco bovino curtido (33%); 4) Terra (33%) + raspas de madeira (33%) + esterco bovino curtido (33%); 5) Terra (25%) + raspas de madeira (25%) + areia fina (25%) + esterco bovino curtido (25%). A análise dos resultados revelou que plantas de limoeiro `Cravo' e citrumeleiro `Swingle' apresentaram maior desenvolvimento do que as de tangerineira `Cleópatra'. A mistura de materiais com solo mostrou-se vantajosa e induziu à formação de plantas mais desenvolvidas do que aquelas em substrato constituído de terra exclusivamente. A composição do substrato influenciou diferentemente no desenvolvimento de cada porta-enxerto, mas de uma forma geral, composições contento 1/3 de volume de solo e 1/3 de volume de esterco bovino proporcionaram bons resultados para os três porta-enxertos estudados.To verify the effect of five substrate mixtures on the development of young sweet orange trees (Citrus sinensis cv. `Pera'), this study used the rootstocks Ranpur lime (Citrus limonia L. Osbeck), Cleopatra mandarin (Citrus reticulata, Blanco), and Swingle citrumelo (Citrus paradisi x Poncirus trifoliata). The experimental design was in randomized blocks, 5 x 3 factorial (substrates x rootstocks). The different materials and their proportion studied were, respectively: 1) Soil (100%); 2) Soil (33%) + fine sand (33%) + manure (33%); 3) Soil (33%) + vermiculite (33%) + manure (33%); 4) Soil (33%) + wood chips (33%) + manure (33%); 5) Soil (25%) + wood chips (25%) + fine sand (25%) + manure (25%). Plants of Rangpur lime and Swingle citrumelo presented better growth rate as expresed in plant height and trunk diameter than those of Cleopatra mandarin on most substrates. `Pêra' sweet orange budded on those rootstocks also presented better fresh weight when compared to Cleopatra mandarin. All substrate mixtures were better than the control (100%) in inducing plant development. Different substrate mixtures affected each rootstock differently, but in general, the compositions with 1/3 soil and 1/3 manure in volume were the best to produce young sweet orange trees in containers

Carbon dioxide emissions under different soil tillage systems in mechanically harvested sugarcane

Soil tillage and other methods of soil management may influence CO2 emissions because they accelerate the mineralization of organic carbon in the soil. This study aimed to quantify the CO2 emissions under conventional tillage (CT), minimum tillage (MT) and reduced tillage (RT) during the renovation of sugarcane fields in southern Brazil. The experiment was performed on an Oxisol in the sugarcane-planting area with mechanical harvesting. An undisturbed or no-till (NT) plot was left as a control treatment. The CO2 emissions results indicated a significant interaction (p < 0.001) between tillage method and time after tillage. By quantifying the accumulated emissions over the 44 days after soil tillage, we observed that tillage-induced emissions were higher after the CT system than the RT and MT systems, reaching 350.09 g m−2 of CO2 in CT, and 51.7 and 5.5 g m−2 of CO2 in RT and MT respectively. The amount of C lost in the form of CO2 due to soil tillage practices was significant and comparable to the estimated value of potential annual C accumulation resulting from changes in the harvesting system in Brazil from burning of plant residues to the adoption of green cane harvesting. The CO2 emissions in the CT system could respond to a loss of 80% of the potential soil C accumulated over one year as result of the adoption of mechanized sugarcane harvesting. Meanwhile, soil tillage during the renewal of the sugar plantation using RT and MT methods would result in low impact, with losses of 12% and 2% of the C that could potentially be accumulated during a one year period