Calcium Pre-Rinse: Effect on permeability of dentin tubules by fluoride rinse.

BACKGROUND: The aim of this study was to evaluate whether calcium (CaL) solution would enhance the capacity of sodium fluoride (NaF) solution in reducing the permeability of hypersensitive dentin. MATERIAL AND METHODS: Thirty-two Wistar rats ingested for 45 days acidic isotonic drink (Gatorade, pH 2.7) ad libitum to induce dental erosion. Then, molar teeth received a cold stimulus to confirm the presence and score the intensity of dentin hypersensitivity based on body contraction and noise. Animals were allocated to four groups (n=8), according to the solution(s) applied in the oral cavity: NaF (12 mmol/L, 1 min); CaL (150 mmol/L, 1 min); CaL followed by NaF (CaF+NaF, 1 min each); distilled water (DW, 1 min, as negative control). The animals were euthanized and the mandibles dissected into hemimandibles, which were sealed with sticky wax, except for the occlusal surface of the molar teeth. The samples were immersed in 10% copper sulphate solution and in 1% dithioxamide alcoholic solution (25 min each). The samples were sectioned longitudinally and imaged under optical microscope. Then, dentin permeability was measured as the area of copper ion penetration, using ImageJ software. Photomicrographs were obtained by scanning electron microscopy. RESULTS: 68.7% of animals had body contraction associated or not with noise. One-way ANOVA followed by Tukey´s test indicated that groups treated with NaF solution, whether or not preceded by CaL solution, presented lower permeability than the remaining groups [CaL+NaF: 3405.7 µm2 (±1796.4); NaF: 4111.7 µm2 (±2450.6); CaL: 42254.6 µm2 (±30399.2); DW: 37064.6 µm2 (±21994.4)]. Photomicrographs showed that CaL+NaF group presented an increased proportion of occluded dentin tubules in comparison to the NaF-only group. CONCLUSIONS: Although qualitatively there seems to be a benefit in using CaL pre-rinse, this solution did not quantitatively enhance the capacity of NaF in reducing permeability of hypersensitive dentin. Key words:Dentin hypersensitivity, Fluoride, Calcium lactate, Animal model.

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.

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.

In vitro evaluation of proximal carious lesions using digital radiographic systems.

The study aimed to compare the sensitivity and specificity of digital radiographic systems for the diagnosis of proximal carious lesions. Extracted human teeth (3 canines, 3 premolars, and 3 molars) were submitted to one of three types of proximal lesions (demineralized area, cavity affecting the enamel alone, and cavity affecting enamel and dentin). Bitewing radiographs were obtained from each system (Sirona, Kodak, and Schick) and evaluated by 12 raters (4 dental students, 4 radiology specialists, and 4 dentists). The chi-squared test was used to determine the frequency of correct diagnoses among the different systems, raters, teeth, and types of lesion. Sensitivity and specificity regarding demineralized areas were calculated for each system. The frequencies of correct diagnoses were found: Schick (70.8%), Kodak (63.9%), Sirona (59.0%), specialists (69.4%), students (62.5%), dentists (61.8%), premolars (70.1%), canines (65.3%), and molars (58.3%). No significant differences were found among the different systems, raters, or teeth (P > 0.05). Sensitivity and specificity were 0.64 and 0.47 (Schick), 0.56 and 0.50 (Sirona), and 0.48 and 0.58 (Kodak). The most correct diagnoses were achieved using the Schick digital system on premolars and evaluated by specialists in radiology. The systems demonstrated low sensitivity and specificity for the diagnosis of demineralized areas.

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.

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.

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.

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.

Characterization of aqueous silver nitrate solutions for leakage tests.

OBJECTIVES: 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.

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.

Can the durability of one-step self-etch adhesives be improved by double application or by an extra layer of hydrophobic resin?

OBJECTIVES: This study evaluated the immediate and 6-month resin-dentin micro-bond strength (microTBS) of one-step self-etch systems (Adper Prompt L-Pop [AD] 3M ESPE; Xeno III [XE] Dentsply De Trey; iBond [iB] Heraeus Kulzer) under different application modes. MATERIALS AND METHODS: Dentin oclusal surfaces were exposed by grinding with 600-grit SiC paper. The adhesives were applied according to the manufacturer's directions [MD], or with double application of the adhesive layer [DA] or following the manufacturer's directions plus a hydrophobic resin layer coating [HL]. After applying the adhesive resins, composite crowns were built up incrementally. After 24-h water storage, the specimens were serially sectioned in "x" and "y" directions to obtain bonded sticks of about 0.8mm2 to be tested immediately [IM] or after 6 months of water storage [6M] at a crosshead speed of 0.5mm/min. The data from each adhesive was analyzed by a two-way repeated measures ANOVA (mode of application vs. storage time) and Tukey's test (alpha=0.05). RESULTS: The adhesives performed differently according to the application mode. The DA and HL either improved the immediate performance of the adhesive or did not differ from the MD. The resin-dentin bond strength values observed after 6 months were higher when a hydrophobic resin coat was used than compared to those values observed under the manufacturer's directions. CONCLUSIONS: The double application of one-step self-etch system can be safety performed however the application of an additional hydrophobic resin layer can improve the immediate resin-dentin bonds and reduce the degradation of resin bonds over time.

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.

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 degrees 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.

Microhardness of Ni-Cr alloys under different casting conditions.

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.

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.

Resistência à tração e alongamento de ligas de Ni-Cr fundidas sob diferentes condições / Tensile strength and elongation of Ni-Cr alloys under different casting conditions

Este trabalho avaliou a resistência à tração e alongamento de ligas a base de Ni-Cr fundidas sob diferentes condições (CF). Foram utilizadas três ligas: Ni-Cr-Mo-Ti, Ni-Cr-Mo-Be e Ni-Cr-Mo-Nb, fundidas em 4 CF: indução/argônio (IA), indução/vácuo (IV), indução/controle (IATM) e maçarico (gás/O2). As composições das ligas foram analisadas por meio de um espectrômetro de florescência de raios X. Foram preparados 4 anéis de fundição, sendo que cada anel apresentava 5 espécimes na forma de cilindros (45m x 1,6m). O teste de resistência à tração (RT) e alongamento (AL) foi conduzido em uma máquina Riehle (0,5 mm/min). Os dados de RT e AL foram avaliados pela análise de variância e teste de Tukey (a=0,05) para contraste de média. Quanto à RT, somente os fatores principais (liga e condições de fundições) foram significantes (p<0,05). A liga Ni-Cr-Mo-Ti teve a maior média (1.012 ± 59 MPa), seguida da liga Ni-Cr-Mo-Be (870 ± 86 MPa) e da liga de Ni-Cr-Mo-Nb (629 ± 84 MPa), todas diferentes entre si (p<0,05). Já para as condições de fundição, apenas o maçarico (889 ± 188 MPa) teve valores significantemente maiores do que as outras condições (p<0,05). As condições IV (818 ± 184 MPa), IATM (817 ± 198 MPa) e IA (800 ± 165 MPa)obtiveram valores semelhantes entre si (p>0,05). Para o AL, apenas o fator principal liga apresentou diferenças (p<0,05). A liga Ni-Cr-Mo-Be (1,63 ± 0,4) apresentou o maior valor; Ni-Cr-Mo-Nb, o menor (0,51 ± 0,1) e a Ni-Cr-Mo-Ti, valores intermediários (1,19 ± 0,3), sendo todas diferentes entre si (p<0,05). Tanto a composição quanto as condições de fundição influíram na resistência à tração, mas apenas as ligas influenciaram o alongamento.

Influência da aplicação de primers metálicos na resistência adesiva entre cimentos resinosos e duas ligas à base de Ni-Cr / Influence of adhesive metal primers on bond strength between resin cements and nickel-chromium alloys

O objetivo deste trabalho foi estudar a adesão entre cimentos resinosos e ligas de níquel-cromo em função da aplicação de condicionadores (primers) de superfícies. Foram realizados testes de resistência à tração após a ciclagem térmica de discos metálicos cimentados entre si. Discos de níquel-cromo (Durabond) e níquel-cromo-berílio (Verabond) foram cimentados com os cimentos Panavia F (Kurakay Co.) e Bistite II DC (Tokuyama Corp.) e com os primers Alloy Primer (Kurakay Co.), Metaltite (Tokuyama Corp.) e Cesead Opaco Primer (Kurakay Co.). Discos cimentados sem primers serviram como grupo controle. Os resultados mostraram que houve diferença estatisticamente significante entre as duas ligas (Ni-Cr - 22,32 ± 7,9 MPa e Ni-Cr-Be - 24,82 ± 7,6 MPa). Quanto ao cimento, o Panavia F (27,49 ± 4,8 MPa) apresentou os maiores valores de resistência de união quando comparado com o Bistite II (19,63 ± 8,4 MPa). Os primers não apresentaram influência positiva sobre o Panavia F já que o grupo sem primer não apresentou diferença estatística em relação aos demais grupos. Entretanto, para o cimento Bistite II, os primers Alloy Primer e Metaltite obtiveram as menores médias, 12,7 ± 7,6 MPa e 15,71 ± 4,8 MPa, respectivamente, enquanto que sem primer ou com o Cesead Opaque Primer, as médias foram 24,47 ± 6,0 MPa e 25,70 ± 6,8 MPa, respectivamente. Concluiu-se que os primers adesivos metálicos não potencializaram a adesão dos cimentos testados sobre as ligas de Ni-Cr.

Effects of aging methods on microleakage of an adhesive system used as a sealant on contaminated surfaces%Efeitos de métodos para envelhecimento na microinfiltração de um sistema adesivo usado como selante em superfícies contaminadas

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 5-55ºC (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 5ºC 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