Influência da manipulação na elasticidade de siliconas de adição em consistência de massa

The handling of vinyl polysiloxane (addition silicone) impression putties with latex gloves is said to interfere with the setting of these impression materials. The aim of this study is to evaluate the effect of handling techniques on the setting of vinyl polysiloxane impression putties using several types of gloves. The setting of these materials was evaluated by means of an elasticimeter. Four vinyl polysiloxane putty impression materials and five brands of gloves (one made of vinyl, one of synthetic rubber, and three of natural rubber) were studied. Based on the type of glove, they were previously washed or not, and a spatula was used or not for initial mixing (before handmixing). The vinyl, the synthetic and one of the natural rubber gloves did not require the previous washing procedure and/or the use of a spatula for initial mixing. Two other natural rubber gloves - depending on the silicone -, showed satisfactory results only when the initial mixing was performed with a spatula. It was concluded that setting inhibition depends on the kind of vinyl polysiloxane impression material and the kind of gloves used, but when the initial mixing was performed with the spatula this setting inhibition was overcome. The results of this study also showed that it is possible to associate cross-contamination control and satisfactory performance of addition silicone putty materials. When doubts arise from the compatibility between vinyl polysiloxane impression putties and gloves, the initial mixing should be performed with a spatula.A finalidade da presente pesquisa foi avaliar a influência na elasticidade da manipulação de silicones de adição em consistência de massa, por meio de várias técnicas, empregando-se luvas. A polimerização dos materiais foi avaliada por meio de um elasticímetro. Ensaiaram-se quatro silicones, empregando cinco marcas de luvas (uma de vinil, uma de borracha sintética e três de borracha natural). Dependendo do tipo de luva, ela foi lavada ou não e ainda foi utilizada ou não uma espátula para a mistura inicial dos silicones. Os resultados demonstraram que no emprego das luvas de vinil, uma das de borracha sintética e uma das de borracha natural não precisaram ser lavadas, nem a utilização de espátula para a mistura inicial foi necessária. Duas luvas de borracha natural não conduziram a resultados satisfatórios com todos os silicones sem que a mistura inicial fosse feita com a espátula mas, com essa prática, todas as luvas foram compatíveis com todos os silicones. Pode-se concluir que, em caso de dúvida sobre a compatibilidade entre tipo de luva e marca de silicone, o emprego de espátula na mistura inicial contorna o problema

Bond strength of four adhesive systems to dentin

O objetivo do presente estudo foi avaliar a resistência adesiva de quatro sistemas adesivos, composicionalmente diferentes, aplicados à dentina humana. Doze dentes terceiros molares humanos tiveram o esmalte oclusal removido para exposição de uma superfície plana de dentina, na qual foram realizados os procedimentos de adesão. Os dentes foram aleatoriamente divididos em quatro grupos, considerando-se o sistema adesivo e a resina composta a serem empregados: Grupo 1 - Single Bond + P60 (SB); Grupo 2 - Bond 1 + Surefil (B1); Grupo 3 - Prime & Bond NT + Alert (NT) e Grupo 4 - Prime & Bond 2.1 + TPH (2.1). Após 24 h de armazenagem em água destilada a 37ºC, os dentes foram seccionados, longitudinalmente, em cortes perpendiculares entre si, para que fossem obtidos espécimes em formato de um paralelogramo com secção transversal retangular de 0,8 mm² de área e 10 mm de comprimento, em média. Os espécimes foram submetidos ao teste de microtração. A análise de variância (alfa = 0,05) demonstrou não haver diferença significante entre os valores médios de resistência obtidos pelos quatro adesivos, embora a análise dos espécimes que sofreram fratura precoce tenha evidenciado menor sensibilidade para o sistema SB.The purpose of the present study was to evaluate the bond strength of four adhesive systems to dentin. Twelve human third molars had their occlusal enamel removed in order to expose a flat dentinal surface, on which the adhesive procedures were carried out. The teeth were divided into four groups, according to the employed adhesive system and composite resin: Group 1 - Single Bond + P60 (SB); Group 2 - Bond 1 + Surefil (B1); Group 3 - Prime & Bond NT + Alert (NT); and Group 4 - Prime & Bond 2.1 + TPH (2.1). After 24 h in distilled water at 37ºC, the teeth were longitudinally sectioned in two perpendicular directions in order to obtain parallelogram-shaped specimens with a cross-sectional area of 0.8 mm² and 10 mm of length, on the average. The test specimens were submitted to microtensile test. The data were submitted to ANOVA (alpha = 0.05), which revealed no differences between the groups, although the analysis of the specimens that presented early fracture evidenced the lower sensitivity of the SB system

Does the casting mode influence microstructure, fracture and properties of different metal ceramic alloys?

The aim of the present study was to evaluate the tensile strength, elongation, microhardness, microstructure and fracture pattern of various metal ceramic alloys cast under different casting conditions. Two Ni-Cr alloys, Co-Cr and Pd-Ag were used. The casting conditions were as follows: electromagnetic induction under argon atmosphere, vacuum, using blowtorch without atmosphere control. For each condition, 16 specimens, each measuring 25 mm long and 2.5 mm in diameter, were obtained. Ultimate tensile strength (UTS) and elongation (EL) tests were performed using a Kratos machine. Vickers Microhardness (VM), fracture mode and microstructure were analyzed by SEM. UTS, EL and VM data were statistically analyzed using ANOVA. For UTS, alloy composition had a direct influence on casting condition of alloys (Wiron 99 and Remanium CD), with higher values shown when cast with Flame/Air (p < 0.05). The factors "alloy" and "casting condition" influenced the EL and VM results, generally presenting opposite results, i.e., alloy with high elongation value had lower hardness (Wiron 99), and casting condition with the lowest EL values had the highest VM values (blowtorch). Both factors had significant influence on the properties evaluated, and prosthetic laboratories should select the appropriate casting method for each alloy composition to obtain the desired property.CNPqCNPq [479369/2009-7]FAPEMAFAPEMA [01164/09, 617/2011

AVALIAÇÃO CLÍNICA DE RESTAURAÇÕES INLAYS/ONLAYS EM RESINA COMPOSTA DIRETA TRATADA TERMICAMENTE: ACOMPANHAMENTO DE 1 ANO / CLINICAL EVALUATION OF INLAYS/ONLAYS RESTORATIONS MADE IN DIRECT COMPOSITE RESIN HEAT-TREATED: 1 YEAR MONITORING

Introdução: O tratamento térmico de resinas compostas resulta em melhorias em suas propriedades mecânicas. Objetivo: Avaliar o desempenho clínico de restaurações indiretas do tipo inlays/onlays usando duas resinas compostas para uso direto, submetidas a tratamento térmico. Método: Foi realizado um estudo clínico longitudinal, duplo-cego, prospectivo e randomizado. A amostra foi composta de quatorze pacientes atendidos no Sistema Único de Saúde (SUS) que foram alocados em dois grupos-teste (G1 e G2) para avaliação da eficácia de duas resinas compostas. As restaurações inlays/onlays, após fotopolimerizadas, foram tratadas termicamente usando calor seco, a 170°C, durante 10 min. A avaliação do desempenho clínico foi realizada nos tempos baseline, 6 e 12 meses usando o critério de avaliação USPHS (United States Public Health Service) modificado. Os Testes estatísticos de Mann-Whitney e Exato de Fisher avaliaram as diferenças entre as resinas nos parâmetros clínicos nos diferentes tempos e a ANOVA avaliou as diferenças entre os grupos e entre os tempos. Resultados: As 33 restaurações confeccionadas apresentaram excelente desempenho (Alfa) em 100% dos casos para todos os parâmetros clínicos avaliados no baseline, sem diferença entre os grupos. Observou-se, no entanto, aumento da proporção de desempenho Bravo e Delta na forma anatômica (P<0,001), adaptação marginal (P<0,001), descoloração (P=0,007), cor (P<0,001) e rugosidade superficial (P=0,027) com o passar do tempo. Cárie secundária e perda de restauração não diferiram entre os grupos e permaneceram estáveis após 6 e 12 meses. Conclusão: As restaurações indiretas feitas com as resinas tratadas termicamente apresentaram desempenhos clínicos semelhantes e satisfatórios quanto aos parâmetros avaliados.Palavras-chave: Odontologia. Resinas compostas. Tratamento térmico.AbstractIntroduction: The heat treatment of composite resins results in improvements in their mechanical properties. Objective: toevaluate the clinical performance of indirect inlays/onlays restorations using two composite resins for direct use submitted tothermal treatment. Method: A longitudinal, double-blind, prospective and randomized clinical study was carried out. The sampleconsisted of fourteen patients treated at the Brazilian Unified Health System (SUS) who were allocated to two test groups (G1and G2) to evaluate the effectiveness of two composite resins. The inlays/onlays were, after light curing, heat treated using dryheat at 170°C for 10 min. The evaluation of the clinical performance was performed at baseline times, 6 and 12 months usingthe modified USPHS (United States Public Health Service) evaluation criteria. Statistical analysis included Mann-Whitney test andFisher's exact test to assess differences between resins in clinical parameters at different times and ANOVA to assess differencesbetween groups and between times. Results: 33 inlays/onlays were made. The restorations showed excellent performance(Alpha) in 100% of the cases for all clinical parameters evaluated in the baseline, with no difference between groups. However,there was an increase in the proportion of Bravo and Delta performance in anatomical form (P<0.001), marginal adaptation(P<0.001), discoloration (P =0.007), color (P<0.001) and surface roughness (P=0.027) over time. Secondary caries and loss ofrestoration did not differ between groups and remained stable after 6 and 12 months. Conclusion: The indirect restorationsmade with the heat-treated resins showed similar clinical performance and satisfactory regarding the evaluated parameters.Keywords: Dentistry. Composite resins. Heat treatment

Chemical and Mechanical Properties of Experimental Dental Composites as a Function of Formulation and Postcuring Thermal Treatment

This study evaluated the influence of formulation and thermal treatment on the degree of conversion, fracture toughness, flexural strength, and elastic modulus of experimental composites. Six composites were analyzed at BisGMA : TEGDMA molar ratios of 1 : 1 and 7 : 3 with filler at 30, 50, and 70 wt%. The degree of conversion was analyzed by Fourier transform infrared spectroscopy, fracture toughness was measured using the single-edge notched beam, and flexural strength and elastic modulus were measured with the 3-point bend test. For all tests, one-half of the specimens received thermal treatment at 170°C for 10 min. Data were analyzed by the Kruskal-Wallis or ANOVA/Tukey’s test (α = 5%). The 1 : 1 BisGMA : TEGDMA ratio showed higher properties than the 7 : 3 ratio. Although the material with 70% filler had a conversion lower than the one with 50%, it showed higher mechanical properties. The thermal treatment improved all properties in all materials. Therefore, the use of an equimolar ratio of BisGMA : TEGDMA can be paired with 70 wt% filler to design dental composites that possess increased advantageous physical and chemical properties. Furthermore, the simple and low-cost method of thermal treatment proposed for use in clinical dentistry has been shown to effectively improve the properties of all evaluated materials

Artificial methods of dentine caries induction: A hardness and morphological comparative study

Objective: To assess the ability of two chemical and a microbiological methods to produce dentine caries lesions resembling naturally developed dentine caries lesions.Design: Forty sound second primary molars were divided into four experimental groups according to the method to produce artificial caries lesions: (1) sound (negative control); (2) acidified gel; (3) pH-cycling; and (4) microbiological, all for 14 days. Ten second primary molars presenting natural dentine caries lesions comprised the (5) positive control group. After the artificial caries induction, all samples were longitudinally sectioned and polished in order to obtain Knoop microhardness values from 10 to 500 mu m depth from the bottom of the cavities. Morphological analysis of the surfaces was carried out by SEM. Hardness data were compared among the five experimental groups using One-Way ANOVA and post hoc SNK's test.Results: The hardness values of chemically created caries-like lesions did not differ from that of natural caries lesions on shallower depths. The results indicated that chemical caries induction methods promote a superficial demineralization and that pH-cycling is more effective than acidified gel. The former, produced a thicker layer of demineralization, with similar hardness values than natural lesions. Despite the microbiological method provided an excessive softness of the primary dentine, this method presented morphology more comparable to natural lesions.Conclusions: pH-cycling is more appropriated to simulate a substrate that resembles affected caries dentine layer, after caries removal. The microbiological method seems more indicated to simulate a dentine caries lesion with an infected layer, previously to caries removal. (C) 2009 Elsevier Ltd. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq