Effect of an hydrophobic layer on a universal adhesive / Efeito de uma camada hidrofóbica sobre um adesivo universal

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.

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.

Effect of rewetting solutions on micropush-out dentin bond strength of new bioceramic endodontic material

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.

Adhesives Doped with Bioactive Niobophosphate Micro-Filler: Degree of Conversion and Microtensile Bond Strength

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 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.

Ions Release and pH of Calcium Hydroxide-, Chlorhexidine- and Bioactive Glass-Based Endodontic Medicaments

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.

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.

Effect of Fluoride and Simplified Adhesive Systems on the Bond Strength of Primary Molars and Incisors

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.

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.

Effectiveness of nano-calcium phosphate paste on sensitivity during and after bleaching: a randomized clinical trial

The study aimed to evaluate the effectiveness of in-office bleaching and associated tooth sensitivity on application of nano-calcium phosphate paste as desensitizing agent. Bleaching was performed with 35% hydrogen peroxide gel in 40 patients who were randomly divided into placebo and nano-calcium phosphate paste groups. Bleaching efficacy (BE) was evaluated using a value-oriented Vita shade guide. Tooth sensitivity was recorded using a numeric rating scale (0–4) during bleaching and up to 48 h after each session. The primary outcome of absolute risk of tooth sensitivity was compared using the Fisher’s exact test (α = 0.05). The intensity of tooth sensitivity and the efficacy of in-office bleaching were also statistically evaluated. No significant differences in absolute risk and intensity of tooth sensitivity were detected between the groups (p = 1.0 and p = 0.53, respectively). BE was also found to be similar between the groups (p = 0.67). Although the use of a nano-calcium phosphate paste associated with fluoride and potassium nitrate did not influence the whitening outcome, but it also did not reduce bleaching-induced tooth sensitivity.

Properties of Composite Materials Used for Bracket Bonding

The purpose of this study was to evaluate in vitro the shear bond strength to enamel, flexural strength, flexural modulus, and contraction stress of one orthodontic composite and two flowable composites. Orthodontic brackets were bonded to 45 human maxillary premolars with the composites Transbond XT, Filtek Z-350 flow and Opallis flow and tested for shear bond strength. For measurement of flexural strength and flexural modulus, specimens were fabricated and tested under flexion. For the contraction stress test, cylindrical specimens were tested and an extensometer determined the height of the specimens. The data were subjected to one-way ANOVA and Tukey's test (α=0.05). The shear bond strength values were significantly lower (p<0.05) for the flowable composites compared with the orthodontic composite. For the flexural strength, no statistically significant difference was found among the composites (p>0.05) while the flexural modulus was significantly higher (p<0.05) for Transbond XT than for Filtek Z-350 flow and Opallis flow. The orthodontic composite presented significantly lower contraction stress values than the flowable composites (p<0.05). The light-activated orthodontic composite material presented higher flexural modulus and shear bond strength and lower contraction stress than both flowable composites.

O objetivo desse estudo foi avaliar a resistência ao cisalhamento no esmalte, resistência flexural, módulo flexural, tensão de contração de polimerização de duas resinas flow e uma resina ortodôntica. Os bráquetes ortodônticos foram colados em 45 pré-molares humanos e divididos: Transbond XT, Filtek Z-350 flow, Opallis flow e testado para resistência ao cisalhamento (n=15). Para a resistência e módulo flexural espécimes foram confeccionados e testados sob flexão. Para o teste de tensão de contração de polimerização, espécimes cilíndricos foram confeccionados e monitorados com um extensômetro (Instron). Os dados foram submetidos aos testes ANOVA a um critério e Tukey (α=0,05) para contraste de média. (n=15). A resistência de união das resinas flow foram significantemente menos que o da resina ortodôntica (p>0,05). A resistência flexural não demonstrou diferença significante entre os grupos testados (p>0,05). O módulo flexural da resina ortodôntica foi significantemente maior que o grupo das resinas flow (p<0,05). A tensão de contração de polimerização da resina ortodôntica foi significantemente menor (p<0,05). A resina ortodôntica obteve os maiores valores de resistência de união ao cisalhamento, resistência flexural e a menor tensão de contração de polimerização quando comparada as resinas flow testadas.

Adhesion of four endodontic sealers to root dentin conditioned with different chemical solutions / Adesão de quatro cimentos endodônticos em dentina condicionada com diferentes soluções químicas

Objective - To evaluate in vitro adhesion of endodontic sealers Rickert, AH Plus, Sealapex and Epiphany to dentin previously conditioned with one of two different chemical solutions. Methods - A total of 80 specimens were made up with bovine incisive teeth that were prepared by cutting predetermined sections and wearing them, producing standard experimental samples. Forty samples were treated with 2.5% sodium hypochlorite and divided into four groups with 10 specimens each, to be coated with the different sealers. Dentin of other forty samples was treated with 17% EDTA, and these samples were also divided into four groups. Prepared specimens were hydrated uniformly, dried, bonded and kept at 37°C and 100% relative humidity. After 72 hours, specimens were analyzed using an Instron universal testing machine in traction mode. Data were analyzed by Kruskal-Wallis test (?=0.05). Results - EDTA treatment led to the greatest adhesiveness in all experimentalgroups. Conclusion - It was concluded that conditioning of the surface with chelating agents increase adhesiveness of the tested sealers and similar behavior was observed in the adhesion of epoxy-based and methacrylate-based sealers.

Objetivo - Avaliar in vitro a adesão dos cimentos endodônticos Rickert, AH Plus, Sealapex e Epiphany à dentina previamente tratada por duas soluções irrigadoras. Métodos - Foram empregados 80 corpos de prova obtidos a partir de dentes incisivos bovinos que foram preparados por cortes e desgastes pré-estabelecidos, resultando em modelos experimentais padronizados. Quarenta dessas amostras foram tratadas com hipoclorito de sódio 2,5% e subdivididas em quatro grupos de 10 espécimes para cada cimento. As demais 40 amostras tiveram a dentina tratada com EDTA a 17% e foram divididos igualmente em 4 grupos. Os espécimes preparados foram uniformemente hidratados, secos, receberam os cimentos, e foram mantidos sob umidade relativa a 37ºC. Após 72 horas os espécimes foram submetidos a testes de tração com auxilio da máquina de ensaio universal Instron, sendo os dados analisados pelo teste de Kruskal-Wallis (?=0.05). Resultados - O tratamento com EDTA proporcionou maiores índices de adesão para todos os grupos experimentais (p<0.05). Conclusão - Pode-se concluir que o tratamento da superfície com agente quelante, aumenta a capacidade de adesão dos cimentos testados. Não houve diferença na adesão dos cimentos a base de resina epóxica e a base de metacrilatos.

Influence of alloy microstructure on the microshear bond strength of basic alloys to a resin luting cement

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.

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.

Evaluation of radiographic waste management in dental offices and radiology clinics of São Luís (MA)

Introduction: Lack of information continues to lead the professionals of various areas to contribute to environment degradation, and Dentistry is a potential source of contamination through chemical residues resulting from radiographic procedures. Objective:To evaluate the management of residues resulting from radiographic processing in dental radiology clinics and dental offices in São Luís - MA, Brazil. Material and methods: A semi-structured questionnaire was prepared with the aim of characterizing the behavior of professionals and their procedures for discarding the processing solutions (developer, fixer, and water) and radiographic packing materials. A sample of 100 individuals represented 7.8% of the total number of 1,281 dentists in the city of São Luís.Results: A total of 92% of the participants believed that radiographic effluents could cause damage to the environment. Concerning to the fixer discarding, 43% affirmed that they threw the solution directly through the sink, 36% diluted the fixer in water and threw it into the sink, 14% used a specialized company to discard it and 7% used other means. The developer was discarded as follows: 42% threw it down the sink, 36% diluted it in water before throwing it into the sink, 13% used a specialized company to discard it and 9% used other ways. Considering to the discarding of the packing of the radiographic films, 51% threw them into the trash and 49% used a specialized disposal company. Conclusion: Large portions of dentists do not discard radiographic processing residues and films correctly.

Efeito da clorexidina a 2% no mecanismo de adesão do cimento de ionômero de vidro: resistência ao cisalhamento / Chlorhexidine's effect at 2% in the mechanism of adhesion of glass ionomer: shear bond strength

Objetivo: O objetivo deste estudo foi verificar a influência da clorexidina gel a 2% na resistência de união ao cisalhamento do cimento de ionômero de vidro (CIV). Material e Métodos: Foram confeccionados 45 blocos de 10x10mm de dentes bovinos, incluídos em resina acrílica, lixados até obter uma superfície plana em dentina e divididos em 3 grupos (n=15): I - Controle: superfície limpa com spray, seca e restaurada com CIV-Vitro Molar; II - superfície limpa com spray, seca, seguida de aplicação de clorexidina gel a 2%, deixada em repouso por 2 minutos, limpa com "bola" de algodão e restaurada; III - lavagem, aplicação de clorexidina gel a 2%, deixada em repouso por 2 minutos, limpeza com spray, seca e restaurada. Os corpos de prova foram submetidos ao teste de cisalhamento em uma máquina TIRATest 2420. Resultados: Os resultados foram avaliados pelo teste Kruskal-Wallis (p<0,05). Verificou-se diferença significante em função do tratamento aplicado p=0,049. Conclusão: A aplicação da clorexidina por 2 minutos e lavagem posterior comportou-se semelhante ao grupo-controle.

Objective: The goal of this study was to investigate the interference of chlorhexidine gel at 2% by shear tests the adhesion of Glass Ionomer Cement. Material and Methods: The 45 bovine teeth were used and made of blocks of 10x10 mm, including acrylic resin and polished until a flat dentin surface. Then randomly divided into 3 groups (n = 15): I - Control: the surface was cleaned with spray (water/air), dried and restored with glass ionomer Vitro Molar (DFL) II - the surface washed with spray (water/air), dried, followed by the application of chlorhexidine gel at 2%, left to stand for 2 minutes, cleaned with a "ball" of cotton and restored; III - the washing was done with an application of chlorhexidine gel at 2%, left rest to for 2 minutes, then cleaned with spray (water/air), dried and restored. The specimens were subjected to shear stress by the machine TIRATest 2420. Results: The results were analyzed by Kruskal-Wallis (p < 0,05). From the graphical analysis, we found the shear stresses with p = 0,049. It showed a significant difference between the tensions according the treatment applied. Conclusion: The application of chlorhexidine for 2 minutes and posterior rinsing behaved similar to the control group.

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.

Evaluation of shear bond strength of orthodontic resin and resin modified glass ionomer cement on bonding of metal and ceramic brackets

Objective:The aim of this study was to evaluate the shear bond strength of orthodontic resin and resin-modified glass ionomer cement on bonding of metal and ceramic brackets. Material and methods: Forty bovine teeth were sectioned and embedded into PVC with chemically-cured acrylic resin. The labial surfaces were flattened and received prophylaxis with pumice and water. Then they were divided into four groups, according to the bonding material and the type of bracket. Group 1: metallic bracket + Transbond XT; Group 2: metallic bracket + Vitremer; Group 3: ceramic bracket + Transbond XT; Group 4: ceramic bracket + Vitremer. The bonding was performed according to the manufacturers’ recommendations. The shear bond strength test was conducted in a universal testing machine (TIRAtest 2420) at a crosshead speed of 0.5 mm/min. Then, the fractured surfaces were evaluated using a stereomicroscope (x15 magnification) to check the adhesive remnant index. Data was subjected to two-way ANOVA and Tukey’s test for pairwise comparisons (a = 0.05).Results: The results suggested a non-significant effect of the interaction (p > 0.97), and only main factors were significant (p = 0.0001). The bond strength of Transbond XT was statistically higher than Vitremer. Ceramic brackets obtained the highest values of resistance when compared with metal brackets. Conclusion: The ceramic brackets bonded with Transbond XT orthodontic resin have excellent bond strength results.

Microinfiltração em restaurações classe V: análise da forma geométrica da cavidade e do tipo de adesivo / Microleakage of class V restorations: analyses of the cavity's geometric shape and type of adhesive

Introdução: o desenvolvimento de materiais e técnicas na Odontologia Restauradora tem como finalidade a obtenção de um confiável vedamento marginal, pois a microinfiltração ainda é um dos principais motivos de insucesso das restaurações. Objetivo: analisar "in vitro" o efeito da configuração cavitária e do tipo de sistema adesivo na microinfiltração em restaurações classe V, em esmalte, com resina composta. Material e método: foram selecionados 60 dentes bovinos, confeccionadas 30 cavidades na face vestibular de forma retangular e 30 de forma circular, sendo então divididos aleatoriamente em seis grupos, conforme a forma geométrica e o sistema adesivo utilizado: Magic Bond, Adper Single Bond 2 e Clearfil SE BOND. Os dentes foram restaurados com resina composta Z-350, utilizando um incremento, fotopolimerizado por 40 segundos, e feito o acabamento/polimento com disco Sof-Lex. Posteriormente, os dentes foram armazenados em água destilada à temperatura ambiente por sete dias e impermeabilizados com esmalte cosmético, deixando uma margem de 1 mm ao redor da restauração. Foram imersos, então, em solução aquosa de nitrato de prata a 50% por um período de duas horas no escuro, lavados com água corrente, colocados em solução reveladora por seis horas, lavados, seccionados no centro da restauração e as fatias foram analisadas na lupa estereoscópica de 25× de aumento. Os dados foram submetidos à análise estatística não paramétrica de Kruskal-Wallis (p < 0,05). Resultado: não houve diferença estatisticamente significante para ambos os fatores analisados (p = 0,233 e p = 0,158). Conclusão: a forma da cavidade não influenciou na microinfiltração; todos os adesivos comportaram-se de maneiras semelhantes quanto à microinfiltração.

Introduction: the development of materials and techniques in restorative dentistry aims to achieve a good marginal sealing because microleakage is still one of the main reasons for failure of restorations. Objective: To analyze "in vitro" the effect of cavity configuration and the type of adhesive system on microleakage of class V resin composite, in enamel. Material and method: 60 bovine teeth were selected, and 60 cavities were prepared on the buccal surface, 30 rectangular and 30 rounded shaped. They were randomly divided in 6 groups according to the geometric form and the bonding system used: Magic Bond, Adper Single Bond 2 and Clearfil SE BOND. The teeth were restored with Z-350 composite resin, using one increment, lightcured for 40 seconds and polished with a Sof-Lex disc. After that the teeth were stored in distilled water at room temperature for seven days and further sealed with nail varnish, leaving a 1 mm window around the restoration margin. They were then immersed in 50% aqueous silver nitrate solution for 2 hours in the dark, rinsed under tap water, placed in revealing solution for 6 hours under fluorescent light, washed, sectioned in the center of the restoration and the slices were viewed under stereoscopic glasses at 25× magnification. The data were submitted to Kruskal-Wallis non-parametric test (p < 0.05). Result: no statistically significant difference for either factor analyzed (p = 0.233 and p = 0.158) was observed. Conclusion: the cavity shape did not influence in microleakage; all the adhesives behaved in similar manners as to microleakage.

Mecanismos moleculares de resistencia antibiótica en Escherichia coli asociadas a diarrea / Molecular mechanisms of antibiotic resistance in Escherichia coli- associated diarrhea

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.

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.

Characterization of aqueous silver nitrate solutions for leakage tests

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 percent) 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 percent or 50 percent AgNO3 solution and the primary teeth in 5 percent or 50 percent AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5 percent). 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 percent 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.

Propriedades mecânicas do titânio comercialmente puro e da liga Ti-6Al-4V fundidos em diferentes ambientes / Mechanical properties of commercially pure titanium and Ti-6Al-4V alloys casting in different environments

Problema: O emprego do titânio e ligas de titânio para aplicações médicas e odontológicas tem aumentado nas últimas décadas, porém, o alto custo do material desestimula o seu uso rotineiro. Objetivos: Avaliar o efeito da pureza do argônio nas propriedades mecânicas, microestrutura e modo de fratura do titânio comercialmente puro (Grau I) e da liga Ti-6Al-4V. Material e Métodos: As fundições para cada liga foram realizadas em uma máquina de indução eletromagnética com um argônio de alta pureza (99,999%) e um argônio conhecido como industrial (99,98%). Os testes de resistência à tração, limite de proporcionalidade e alongamento foram realizados em máquina de ensaio universal sob velocidade de 1 mm/min. Os espécimes fraturados foram embutidos em resina fenólica (baquelite) e polidas para a realização da microdureza Vickers (100g/15s), a 25, 50, 100, 200 e 500μm da borda do corpo-de-prova. A microestrutura das ligas também foi analisada em alguns espécimes, com o objetivo de avaliar a superfície fraturada dos espécimes alguns foram submetidos à microscopia eletrônica de varredura. Análise estatística: Os dados provenientes de cada teste mecânico foram submetidos a uma análise de variância (tipo de titânio vs. pureza do argônio) e teste de Tukey (α = 0,05). Os dados de microdureza Vickers foram submetidos a uma análise de variância de medidas repetidas (fatores principais: liga e argônio) e medida repetida: distância e teste de Tukey para o contraste entre médias (α = 0,05). Resultados: O grau de...

Background: Although CP titanium and titanium alloys have been used for medical and dental applications, their high cost has not stimulated their current use. Objective: The purpose of this study was to evaluate the effect of argon purity on the mechanical properties, microstructure and fractography of CP Ti (Grade I) and Ti-6Al-4V cast alloys. Material and Methods: The castings for each alloy were made in a centrifugal casting machine using either a high-purity (99.999%) and or an industrial argon gas (99.98%). The ultimate tensile strength (UTS), proportional limit (PL) and elongation (EL) were evaluated in a universal testing machine at a crosshead speed of 1 mm/min. The fractured specimens were embedded in phenolic resin and polished down for Vicker’s microhardness (VHN) measurement (100g, 15s) from 25μm below the cast surface, then at 50μm, 100μm, 200μm and 500μm. The microstructures of the alloys were also revealed. Scanning electron microscopy fractography was undertaken for the fractured surfaces after tensile testing. The datafrom the mechanical tests and hardness were subjected to a two-way ANOVA and Tukey’s test (α = 0.05). Results: The mean values of UTS, PL, EL and VHN were not affected by the argon gas purity. Higher UTS, PL and VHN and lower EL was observed for Ti-6Al-4V. The microhardness values of both alloys were higher at the surface layers and it was not influenced by the argon gas purity. Conclusions: It was...

Effect of light-activation methods and water storage on the flexural strength of two composite resins and a compomer

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 (a = 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.

Microhardness of Ni-Cr alloys under different casting conditions

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 (a = 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.