RESUMO Objetivo: Avaliar a de resistência de união da interface adesiva associada a uma camada hidrofóbica extra de selamento, e comparar após três e seis meses de armazenamento em água destilada. Métodos: Foram utilizados 12 terceiros molares humanos extraídos hígidos (n=6), que foram divididos em dois grupos, sendo grupo SB - controle - autocondicionante; e grupo SBHidrof - autocondicionante associado à camada hidrofóbica (Adhesive layer, 3m ESPE). Após restauração incremental com resina composta (Opalis, FGM), os dentes foram fatiados para obtenção de espécimes (1mm2) e em seguida, submetidos à máquina de ensaio universal (INSTRON 1mm/min.) imediato e após três e seis meses. Os dados obtidos foram submetidos à normalidade (Shapiro Wilk), e análise comparativa ANOVA (dois fatores: técnica e tempo) e Tukey (p<0,05). Resultados: Nos valores imediatos não houve diferença estatisticamente significante (p>0,05), porém após três e seis meses de imersão dos espécimes, em água destilada, foi observado manutenção dos valores de resistência de união no grupo que recebeu a camada hidrofóbica (p<0,05). Conclusão: Ao incorporar uma camada hidrofóbica sobre um sistema adesivo universal, foi possível preservar a longevidade da adesão dentinária.

ABSTRACT Objective: evaluate bond strength of a universal adhesive, associated to an extra hydrophobic sealing layer, and compare after three and six months immersed in distilled water. Methods: After ethical approval of the CEP / HUUFMA, 12 human third molars (n = 6) were extracted, which were divided into two groups: SB - control group - selfetching; and SBHidrof - selfetching group associated to the hydrophobic layer (Adhesive layer, 3m ESPE). After incremental restoration with composite resin (Opalis, FGM), the teeth were sliced to obtain specimens (1mm2) and then submitted to the universal test machine (INSTRON 1mm / min.), immediate and after three and six months. The data were submitted to normality (Shapiro Wilk), and comparative Analysis of variance (two ways: technique and time) and Tukey (p <0.05). Results Immediate values showed no statistically significant difference (p> 0.05), but after three and six months of immersion of the specimens, in distilled water, bond strength values were maintained in the group that received the hydrophobic layer (p<0.05). Conclusion: It was observed that, by incorporating a hydrophobic layer on a universal adhesive system, it was possible to preserve dentin adhesion.

Abstract This study evaluated microtensile bond strength (µTBS), degree of conversion, modulus of elasticity and ultramicrohardness of three etch-and-rinse adhesives systems. The materials evaluated were: Ambar (FGM), Optibond (Kerr) and Magic Bond (Vigodent). The degree of conversion was analyzed by FTIR/ATR. To evaluate bond strength (μTBS) in dentin, 15 teeth (n = 5) were restored and sliced to obtain the specimens (0.8mm2). The dynamic ultra microhardness tester was used to evaluate the hardness and modulus of elasticity. The Magic Bond adhesive system showed lower µTBS than Ambar and Optibond (p <0.001). For degree of conversion, comparisons between groups of adhesive systems evaluated showed statistically significant difference (p<0.001), with higher values for Ambar and Optibond when compared a Magic Bond. For modulus of elasticity and ultramicrohardness, Ambar and Magic Bond showed lower values than Optibond. The best results in all properties evaluated were obtained by the Optibond adhesive system.

Abstract To evaluate the influence of rewetting solutions on bond strength to root dentin of conventional gutta-percha (GP) or niobium phosphate glass-based gutta-percha (GNb) associated with a bioceramic sealer. The root canals of 80 human mandibular premolars were prepared using nickel-titanium instruments and irrigation with sodium hypochlorite and EDTA. The teeth were randomly divided into four groups according to the gutta-percha used: GNb or GP associated with EndoSequence BC Sealer (BC) and the solution for rewetting dentin before filling (distilled water; phosphate buffer saline solution - PBS; simulated body fluid – SBF; or no solution). The root canals were filled with a single cone using warm vertical condensation. Micropush-out bond strengths associated with the filling materials in slices from middle root thirds was determined 30 days after root filling. The failure mode was analyzed with stereoscopic lens. The data were statistically analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). There was significant difference in the types of gutta-percha (p < 0.001) and in the different rewetting solutions (p = 0.003). The interaction between gutta-percha and rewetting solutions was not significant (p = 0.53). The SBF solution provided an increase in bond strength for both gutta-percha solutions. The GNb+BC (3.42 MPa) association increased bond strength when compared with GP+BC (2.0 MPa). The use of SBF as a dentin rewetting solution increased bond strength in the groups studied. Association of GNb with bioceramic sealer was beneficial, increasing the bond strength to dentin when compared with the association with GP.

Resumo Avaliar o efeito da incorporação de vidro niobofosfato bioativo (NbG, 40% em peso) em dois sistemas adesivos simplificados convencionais (One Step [OS] e Prime & Bond {PB}) com e sem silano, no grau de conversão (%) e resistência de união (RU) após 6 meses. Os seguintes grupos foram testados: Controle OS: sem adição de partículas; OS e adição de NbG sem silano (OSNbG); OS e adição de partículas silanizadas NbG (OSNbGS); Controle PB: sem adição de partículas; PB e adição de partículas de NbG sem silano (PBNbG); PB e adição de partículas silanizadas NbG (PBNbGS). O grau de conversão (GC) foi determinado utilizando espectroscopia de Fourier (FTIR/ATR). Para RU, 48 terceiros molares humanos (n=8) foram restaurados e cortados para obter corpos-de-prova (0,8 mm2) e, em seguida, testados em dois momentos: imediato e após seis meses. O padrão de fratura foi avaliado com lupa estereoscópica (40×) e microscópio eletrônico de varredura (MEV). Os dados foram submetidos à análise de variância e Tukey (a=0,05). NbG não comprometeu valores de GC dos sistemas adesivos (p>0,05). Além disso, a adição de NbG aos sistemas adesivos não afetou os valores de RU (p>0,05). O padrão de fratura ocorreu predominantemente na interface dentina-adesivo. NbG não afetou os resultados de GC e RU.

Abstract To evaluate the effect of incorporating niobium phosphate bioactive glass (NbG) into commercial etch-and-rinse adhesive systems, with and without silane, on their degree of conversion (DC) (%) and microtensile bond strength (μTBS). The NbG micro-filler was added to two etch-and-rinse adhesive systems: One Step (OS) and Prime & Bond (PB) at 40% concentration. The following groups were formed: control without glass addition OS; addition of unsilanized NbG (OSNbG); addition of silanized NbG (OSNbGS); control without glass PB; addition of unsilanized NbG (PBNbG); addition of silanized NbG (PBNbGS). The DC was determined using total Fourier spectroscopy reflection (FTIR/ATR). For μTBS testing, 48 human third molars (n=8) were restored and sliced to obtain specimens (0.8 mm2) and they were tested at two different time intervals: immediately and after 6 months. The fracture mode was evaluated with a stereoscopic loupe (40×) and by scanning electron microscopy (SEM). The data were subjected to ANOVA and Tukey tests (a=0.05). NbG addition did not compromise the adhesive system DC values (p>0.05). Furthermore, the NbG added to the adhesive systems did not affect μTBS values (p>0.05). Fracture occurred predominantly at the dentin-adhesive interface. NbG bioactive glass did not affect the DC or microtensile bond strength results.

Resumo Este estudo avaliou o pH e a liberação de íons cálcio, sódio e fosfato de diferentes medicamentos em dentina humana. Cinquenta pré-molares foram preparados e divididos aleatoriamente em grupos: (CHX) - clorexidina gel 2%; (CHX + CH) - CHX + hidróxido de cálcio PA; (CH) - CH + propilenoglicol 600; (NPBG) - vidro experimental nióbio fosfato bioativo + água destilada; (BG) - vidro bioativo (Bio-Gran) + água destilada. Os espécimes foram submersos em água deionizada e as variações de pH foram mensuradas. A quantificação dos íons nas soluções foi feita por espectrometria de emissão atômica com plasma indutivamente acoplado (ICP - AES) nos tempos de 10 min, 24 h, 7, 14, 21 e 30 dias. Os resultados foram analisados por ANOVA e teste Tukey, com um nível de significância de 5%. Verificou-se que CH a teve a maior liberação íons de cálcio ao final de 30 dias, enquanto CHX e BG liberaram mais íons de sódio. BG, NPBG e CHX apresentaram a maior liberação de íons fosfato. O pH de CH foi significativamente maior em comparação com os outros grupos testados. O grupo CH aumentou o pH e a liberação de íons cálcio. Os vidros bioativos obtiveram uma maior liberação de íons sódio e fosfato e apresentaram pH alcalino imediato e ao final de 30 dias.

Abstract This study evaluated pH and release of calcium, sodium and phosphate ions from different medications in human dentin. Fifty premolars were prepared and randomly divided into groups: (CHX) - 2% chlorhexidine gel; (CHX + CH) - CHX + calcium hydroxide PA; (CH) - CH + propylene glycol 600; (NPBG) - experimental niobium phosphate bioactive glass + distilled water; (BG) - bioactive glass (Bio-Gran) + distilled water. The specimens were immersed in deionized water and the pH variations were measured. The quantification of ions in the solutions was made by inductively coupled plasma - atomic emission spectroscopy (ICP/AES) at 10 min, 24 h, 7, 14, 21 and 30 days. The results were analyzed by ANOVA and Tukey`s test, with a significance level of 5%. CH had the highest level of calcium ions release at 30 days, while CHX and BG released more sodium ions. BG, NPBG and CHX released a higher amount of phosphate ions. The pH of CH was significantly higher compared with the other groups. CH favored the greatest increase of pH and calcium ions release. The bioactive glasses released more sodium and phosphate ions and presented an alkaline pH immediately and after 30 days.

The purpose of this study was to evaluate the effects of long-term storage on the microtensile bond strength (µTBS) to dentin of two self-adhesive and three multi-step resin cements. Two self-adhesive cements RelyX U100 (U100) and seT PP (SET), and 3 multi-step resin cements, one using 2-step etch-and-rinse adhesive AllCem (ALC), and two conventional resin cements with self-etching primer Panavia F (PAN) and Multilink (MULT) were used. Human molars were restored (n=5), sectioned and subjected to the μTBS test after 24 h and 6 months. Fractured specimens were examined by stereomicroscope and SEM. The µTBS were analyzed by one-way ANOVA and Tukey test (α=0.05). ANOVA revealed a difference between groups (p<0.0001). All multi-step resin cements ALC, MULT and PAN showed statistically similar bond strength values that were higher than those of the U100 and SET groups. The bond strength value of ALC, MULT and PAN decreases significantly after 6 months. The majority of the failures were adhesive for all the groups. The µTBS produced by the self-adhesive cements were significantly lower than those observed for multi-step luting agents. Regardless of the numbers of steps of resin cements, the storage time reduces µTBS values to dentin only to multi-step luting agents.

<p>O objetivo deste estudo foi avaliar a influência dos sistemas adesivos simplificados (condicionamento ácido total e auto-condicionante) e fluorfosfato acidulado a 1,23% (FFA) na resistência de união ao microcisalhamento (μ-RUC) de resinas compostas em molares e incisivos decíduos. O esmalte vestibular de quarenta molares e quarenta incisivos decíduos foi tratado com Clearfil SE Bond (CSE, Kuraray) ou Adper Single Bond 2 (SB2, 3M/ESPE). Cada grupo foi subdividido com base no tratamento prévio do esmalte com ou sem aplicação tópica de FFA a 1,23%. Em seguida, matrizes foram posicionadas e preenchidas com resina composta e posterior fotopolimerização. Depois da armazenagem em água destilada a 37±1 °C por 24 h, os espécimes foram submetidos ao μ-RUC em uma máquina de ensaio universal. Teste Kruskal-Wallis e Mann-Whitney (p<0,05) mostraram que a aplicação prévia de FFA a 1,23% levou a uma redução significativa na resistência de união. O tipo de adesivo não exerceu influência significativa na resistência de união. Na análise intergrupos, entretanto, redução significativa na resistência de união foi encontrada para os incisivos quando CSE foi empregado sem FFA. Falha adesiva foi o tipo de fratura mais comum. A resistência de união foi afetada pela aplicação de FFA a 1,23% e tipo de dente.</p>

<p>The aim of this study was evaluate in vitro the influence of simplified adhesive systems (etch-and-rinse and self-etching) and 1.23% acidulated phosphate fluoride (APF) on the microshear bond strength (μ-SBS) of composite resins on primary molars and incisors. Forty primary molars and forty incisors vestibular enamel was treated with either the self-etching Clearfil SE Bond (CSE, Kuraray) or etch-and-rinse Adper Single Bond 2 (SB2, 3M/ESPE) adhesive system. Each group was subdivided based on the prior treatment of the enamel with or without the topical application of 1.23% APF. Thereafter, matrices were positioned and filled with composite resin and light cured. After storage in distilled water at 37±1°C for 24 h, the specimens were submitted to μ-SBS in a universal testing machine. Kruskal-Wallis and Mann-Whitney tests (p<0.05) showed that the prior application of 1.23% APF led to a significant reduction in bond strength. The type of adhesive exerted no significant influence bond strength. In the inter-group analysis, however, significantly bond strength reduction was found for the incisors when CSE was employed with APF. Adhesive failure was the most common type of fracture. The bond strength was affected by the prior application of 1.23% APF and type of tooth.</p>

The aim of this study was to evaluate the pH, ultimate tensile strength (UTS), and micro-shear bond strength (µSBS) of two self-adhesive resin cements to enamel and dentin. Sound bovine incisors (n = 10) and two self-adhesive resin cements (i.e., RelyX U-100 and seT PP) were used. The pH of the resin cements was measured using a pH-indicator paper (n = 3). Specimens for UTS were obtained from an hourglass-shaped mold. For µSBS, cylinders with internal diameter of 0.75 mm and height of 0.5 mm were bonded to the flat enamel and dentin surfaces. Bonded cylinders were tested in the shear mode using a loop wire. The fracture mode was also evaluated. The cement seT PP showed a low pH; U-100 showed significantly higher UTS (49.9 ± 2.0) than seT PP (40.0 ± 2.1) (p < 0.05) and high µSBS to enamel (10.7 ± 3.7). The lowest µSBS was found for seT PP to dentin (0.7 ± 0.6); seT PP to enamel (4.8 ± 1.7), and for U-100 to dentin (7.2 ± 1.9), showing an intermediate µSBS value (p < 0.05). Adhesive failure was the most frequently observed failure mode. The resin cement that presented the lowest pH and UTS also presented the lowest micro-shear bond strength to enamel and dentin.

O objetivo deste estudo foi avaliar a influência da microestrutura e da composição de ligas básicas quanto à resistência de união (RU) a um agente cimentante resinoso. Foram usadas as seguintes ligas: Supreme Cast-V (SC), Tilite Star (TS), Wiron 99 (W9), VeraBond II (VBII), VeraBond (VB), Remanium (RM) and IPS d.SIGN 30 (IPS). Cinco padrões em cera (13 mm de diâmetro e 4 mm de altura) para cada uma das ligas básicas foram incluídos e fundidos em uma máquina de fundição. As amostras foram então embutidas em resina, polidas com lixas e jateadas. Após a limpeza das superfícies, seis cilindros de tygon tube (0,5 mm de altura e 0,75 mm de diâmetro) foram colocados sobre a superficie da liga e preenchida com cimento resinoso (Panavia F), o excesso foi removido antes da fotoativação. Após armazenagem (24 h/37ºC), cada amostra foi ensaiada por microcisalhamento a 0,5 mm/min. Os dados foram tratados por análise de variância para e medidas repetidas e teste Tukey (α=0,05). Para avaliar a microesturutura, as mesmas amostras foram polidas e condicionadas com solução específica. Os valores mais altos da RU (média/desvio padrão em MPa) foram encontrados para as ligas com estrutura dendrítica, formação eutética e precipitados: VB (30,6/1,7), TS (29,8/0,9), SC (30,6/1,7), com exceção da IPS (31,1/0,9) que apresentou alto valor de RU, mas sem formação eutética. As ligas W9 (28,1/1,5), VBII (25,9/2,0) and RM (25,9/0,9) apresentaram os menores valores de RU e ausência de formação eutética. Pode-se inferir que os valores mais elevados de resistência de união ao cimento resinoso fotoativado ocorre com as ligas que apresentam formação de eutético.

The aim of this study was to evaluate the influence of microstructure and composition of basic alloys on their microshear bond strength (µSBS) to resin luting cement. The alloys used were: Supreme Cast-V (SC), Tilite Star (TS), Wiron 99 (W9), VeraBond II (VBII), VeraBond (VB), Remanium (RM) and IPS d.SIGN 30 (IPS). Five wax patterns (13mm in diameter and 4mm height) were invested, and cast in a centrifugal casting machine for each basic alloy. The specimens were embedded in resin, polished with a SiC paper and sandblasted. After cleaning the metal surfaces, six tygon tubes (0.5 mm height and 0.75 mm in diameter) were placed on each alloy surface, the resin cement (Panavia F) was inserted, and the excess was removed before light-curing. After storage (24 h/37°C), the specimens were subjected to µSBS testing (0.5 mm/min). The data were subjected to a one-way repeated measures analysis of variance and Turkey's test (α=0.05). After polishing, their microstructures were revealed with specific conditioners. The highest µSBS (mean/standard deviation in MPa) were observed in the alloys with dendritic structure, eutectic formation or precipitation: VB (30.6/1.7), TS (29.8/0.9), SC (30.6/1.7), with the exception of IPS (31.1/0.9) which showed high µSBS but no eutectic formation. The W9 (28.1/1.5), VBII (25.9/2.0) and RM (25.9/0.9) showed the lowest µSBS and no eutectic formation. It seems that alloys with eutectic formation provide the highest µSBS values when bonded to a light-cured resin luting cement.

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.

Antibiotic resistance is an emerging problem worldwide present in many bacteria, specially in Escherichia coli, which has high percentages of resistance to ampicilline, thrimethoprim-sulfamethoxazole, tetracycline, chloramphenicol and nalidixic acid, which implies important complications in antibiotic treatment when required. The increasing antibiotic resistance is due to the acquisition of different molecular mechanisms of resistance through point chromosomal mutations and /or horizontal transfer of genetic material between related or different species facilitated by some genetic elements such as integrons. This review discusses the effects of the most common molecular mechanisms of antibiotic resistance in E. coli: enzymatic inactivation, changes in the target site and permeability disturbances. Getting to know the mechanisms of resistance which are involved, as the World Health Organization recommends, will allow us to improve the surveillance of the antibiotic resistance, the control policies and the antibiotic utilization at a national level.

La resistencia antibiótica es un problema emergente a nivel mundial presente en diversas bacterias, en especial en la Escherichia coli, que tiene altos porcentajes de resistencia hacia ampicilina, trimetoprim-sulfametoxazol, tetraciclina, cloramfenicol y ácido nalidíxico, lo que supone grandes complicaciones en el tratamiento antibiótico cuando este es requerido. Este aumento de resistencia antibiótica se debe a la adquisición de diferentes mecanismos moleculares de resistencia mediante mutaciones puntuales a nivel cromosómico o transferencia horizontal de material genético entre especies relacionadas o diferentes, facilitada por algunos elementos genéticos tales como los integrones. Esta revisión discute los efectos de los mecanismos moleculares de resistencia más comunes en E.coli: inactivación enzimática, alteraciones en el sitio blanco y alteraciones de la permeabilidad. El conocer los mecanismos de resistencia implicados, como lo recomienda la Organización Mundial de la Salud, permitirá optimizar la vigilancia de resistencia y las políticas de control y uso de antibióticos a nivel nacional.

OBJECTIVE: To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. MATERIAL AND METHODS: A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled) and three brands of silver nitrate salt (Merck, Synth or Cennabras) at 0, 1, 2, 24, 48, 72, 96 and 168 h after preparation, and storage in transparent or dark bottles. Ionic silver was assayed according to the post-preparation times (2, 24, 48, 72, 96, 168 h) and concentrations (1, 5, 25, 50%) of solutions by atomic emission spectrometry. For each sample of each condition, three readings were obtained for calculating the mean value. Class V cavities were prepared with enamel margins on primary and permanent teeth and restored with the adhesive systems OptiBond FL or OptiBond SOLO Plus SE and the composite resin Filtek Z-250. After nail polish coverage, the permanent teeth were immersed in 25% or 50% AgNO3 solution and the primary teeth in 5% or 50% AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5%). RESULTS: The mean pH of the solutions ranged from neutral to alkaline (7.9±2.2 to 11.8±0.9). Mean ionic silver content differed depending on the concentration of the solution (4.75±0.5 to 293±15.3 ppm). In the microleakage test, significant difference was only observed for the adhesive system factor (p=0.000). CONCLUSIONS: Under the tested experimental conditions and based on the obtained results, it may be concluded that the aqueous AgNO3 solutions: have neutral/alkaline pH and service life of up to 168 h; the level of ionic silver is proportional to the concentration of the solution; even at 5% concentration, the solutions were capable of indicating loss of marginal seal in the composite restorations; the 3-step conventional adhesive system had better performance regarding microleakage in enamel on primary and permanent teeth.

O presente estudo analisou a resistência à flexão de três compósitos recomendados para restaurações estéticas diretas: um compósito poliácido-modificado (Dyract AP), uma resina composta unimodal (Filtek Z250) e uma resina composta híbrida (Point 4). Os fatores de variação, além do tipo de compósito, foram o método de fotoativação e o período de armazenagem em água. Os materiais foram fotoativados continuamente por 40 s (500 mW/cm²) ou com intensidade de luz crescente (0-800 mW/cm² por 10 s seguidos de 30 s a 800 mW/cm²). Os períodos de armazenagem foram de 24 horas ou 30 dias em água destilada a 37°C. Os dados foram submetidos à análise de variância e ao teste de Tukey para comparações múltiplas (alfa = 0,05). A resina composta Z250 apresentou a maior média de resistência à flexão (166,74 MPa) e a Dyract AP, a menor (129,76 MPa). A armazenagem por 30 dias diminuiu a resistência à flexão para o método de fotoativação crescente (24 h: 156,64 MPa; 30 dias: 135,58 MPa). O método de fotoativação isoladamente não conduziu a diferentes valores de resistência à flexão.

The present study evaluated the flexural strength of three composite resins recommended for direct esthetic restorations: a polyacid modified composite (Dyract AP), a unimodal composite resin (Filtek Z250) and a hybrid composite resin (Point 4). The variation factors, apart from the type of composite resin, were the light activation method and the water storage period. The composite resins were light-cured in continuous mode (40 s, 500 mW/cm²) or in ramp mode (0-800 mW/cm² for 10 s followed by 30 s at 800 mW/cm²) and stored for 24 hours or 30 days in distilled water at 37°C. The data were analyzed by ANOVA and Tukey test for multiple comparisons (alpha = 0.05). The composite resin Z250 presented the highest mean flexural strength (166.74 MPa) and Dyract AP presented the lowest one (129.76 MPa). The storage for 30 days decreased the flexural strength in ramp mode (24 h: 156.64 MPa; 30 days: 135.58 MPa). The light activation method alone did not lead to different flexural strength values.

Este estudo avaliou a microdureza de ligas de Ni-Cr usadas em prótese fixa fundidas sob diferentes condições. As condições de fundição foram: (1-maçarico) chama composta por uma mistura de gás/oxigênio e centrífuga sem o controle do ambiente de fundição; (2-indução/argônio) indução eletromagnética com o ambiente controlado com argônio; (3-indução/vácuo) indução eletromagnética com o ambiente sob vácuo; (4-indução/ar) indução eletromagnética sem o controle da atmosfera. Foram utilizadas três ligas: Ni-Cr-Mo-Ti, Ni-Cr-Mo-Be e Ni-Cr-Mo-Nb. Foram realizadas 4 fundições com 5 espécimes cilíndricos de 15 mm de comprimento (diâmetro de 1,6 mm). Depois das fundições os espécimes foram embutidos e polidos para as mensurações de microdureza Vickers (VH) em um Shimadzu HMV-2 (1.000 g por 10 s). Um total de 5 indentações foram feitas por anel, uma em cada espécime. Os dados de VH foram avaliados pelos testes de ANOVA e Tukey (alfa = 0,05) para contraste de média. A microdureza das ligas apresentou a seguinte ordem: Ni-Cr-Mo-Ti (422 ± 7,8) > Ni-Cr-Mo-Nb (415 ± 7,6) > Ni-Cr-Mo-Be (359 ± 10,7), sendo diferentes entre si. Os valores obtidos nas condições indução/argônio e indução/vácuo foram semelhantes entre si (p > 0,05) e menores que os obtidos nas condições indução/ar e maçarico, estes últimos semelhantes entre si (p > 0,05). A microdureza das ligas é dependente da composição da liga e do método de fundição. A dureza das ligas de Ni-Cr foi maior quando fundidas nas condições indução/ar e maçarico.

This study evaluated the microhardness of Ni-Cr alloys used in fixed prosthodontics after casting under different conditions. The casting conditions were: (1-flame/air torch) flame made of a gas/oxygen mixture and centrifugal casting machine in a non-controlled casting environment; (2-induction/argon) electromagnetic induction in an environment controlled with argon; (3-induction/vacuum) electromagnetic induction in a vacuum environment; (4-induction/air) electromagnetic induction in a non-controlled casting environment. The 3 alloys used were Ni-Cr-Mo-Ti, Ni-Cr-Mo-Be, and Ni-Cr-Mo-Nb. Four castings with 5 cylindrical, 15 mm-long specimens (diameter: 1.6 mm) in each casting ring were prepared. After casting, the specimens were embedded in resin and polished for Vickers microhardness (VH) measurements in a Shimadzu HMV-2 (1,000 g for 10 s). A total of 5 indentations were done for each ring, one in each specimen. The data was subjected to two-way ANOVA and Tukey's multiple comparison tests (alpha = 0.05). The VH values of Ni-Cr-Mo-Ti (422 ± 7.8) were statistically higher (p < 0.05) than those of Ni-Cr-Mo-Nb (415 ± 7.6). The lowest VH values were found for Ni-Cr-Mo-Be (359 ± 10.7). The VH values obtained in the conditions induction/argon and induction/vacuum were similar (p > 0.05) and lower than the values obtained in the conditions induction/air and flame/air torch (p < 0.05). The VH values in the conditions induction/air and flame/air were similar (p > 0.05). The microhardness of the alloys is influenced by their composition and casting method. The hardness of the Ni-Cr alloys was higher when they were cast with the induction/air and flame/air torch methods.

Este estudo avaliou os efeitos de métodos para envelhecimento na microinfiltração de um sistema adesivo usado para selar superfícies oclusais. Após o condicionamento com ácido, as superfícies de 60 dentes permanentes foram contaminadas com 1 mL de plasma e seladas com OptiBond dual cure, ativado pelo Optilux 501, no modo rampa. A amostra foi dividida em oito grupos experimentais e um grupo controle ou imediato O envelhecimento dos espécimes foi realizado por 20 dias a 5, 37, 55 e 5-55°C (200 ciclos/dia) em contato com a água ou não. Após submeter os espécimes à técnica de infiltração com AgNO3, eles foram secionados duas vezes e os valores médios da penetração do corante foram tratados por análise de variância. Nenhum grupo apresentou vedamento hermético na interface, nem mesmo o grupo sem envelhecimento (imediato ou controle). O grupo que permaneceu a 5°C sem contato com a água mostrou o menor grau de penetração (p=0,015) e a interação envelhecimento x água foi significante (p=0,033). Os resultados levam às seguintes conclusões: 1) todos os grupos mostram microinfiltração, inclusive o controle; 2) o grupo mantido a 5ºC sem contato com a água mostrou os menores valores de microinfiltração; 3) em contato com a água, as variações térmicas parecem não afetar o grau de penetração do corante.

This study evaluated the effects of aging methods on the microleakage of an adhesive system used for sealing pit and fissure surfaces. After acid etching, the occlusal surfaces of 60 permanent teeth were contaminated with 1mL of human plasma and then sealed with OptiBond dual cure, activated in the ramp mode (Optilux 501). The sample was then divided into eight experimental and a control groups. Aging was performed for 20 days in 5, 37, 55 and 5-55ºC (200 cycles/day) under water contact or not. After subjecting the specimens to the AgNO3 technique, they were sectioned twice. Dye penetration was measured and the mean values were subjected to ANOVA. No group provided hermetic seal against dye penetration, even the control group (without treatment). Significant aging x water interaction effect (p=0.033) was observed. The group without water contact at 5ºC (p=0.015) showed the least dye penetration value. The results led to the main conclusions: 1) all groups showed dye penetration, even the control group; 2) storage teeth at 5ºC on dry condition provided the lowest degree of dye penetration; 3) in the presence of water, the temperature variations seem not to affect the microleakage values.