A method for calculating the compliance of bonded-interfaces under shrinkage: validation for Class I cavities.

OBJECTIVE: The compliance for tooth cavity preparations is not yet fully described in the literature. Thus, the objectives were to present a finite element (FE) method for calculating compliance and to apply this to peak shrinkage stress regions in model cavities restored with resin-composite. METHODS: Three groups of FE-models were created, with all materials considered linear, homogeneous, elastic and isotropic: (a) a pair of butt-joint bonded cubic prisms (dentin/resin-composite), with dentin of known compliance (0.0666 µm/N). Free ends were fixed in the Z-axis direction. A 1% volumetric shrinkage was simulated for the resin-composite. Mean displacements in the Z direction at each node at the dentin-resin interface were calculated and divided by the sum of normal contact forces in Z for each node. (b) A series of more complex restored cavity configurations for which their compliances were calculated. (c) A set of 3D-FE beam models, of 4 mm × 2 mm cross-section with lengths from 2 to 10mm, were also analyzed under both tensile and bending modes. RESULTS: The compliance calculated by FEM for the butt-joint prisms was 0.0652 µm/N and corresponded well to the analytical value (0.0666 µm/N). For more accurate representations of the phenomenon, such as the compliance of a cavity or any other complex structure, the use of the displacement-magnitude was recommended, as loading by isotropic contraction also produces transversal deformations. For the beam models, the compliance was strongly dependent upon the loading direction and was greater under bending than in tension. SIGNIFICANCE: The method was validated for the compliance calculation of complex structures subjected to shrinkage stress such as Class I 'cavities'. The same FEM parameters could be applied to calculate the real compliance of any interface of complex structures. The compliance concept is improved by considering specific load directions.

Effect of light irradiation on tooth whitening: enamel microhardness and color change.

The aim of this study was to evaluate the influence of light exposure associated with 35% hydrogen peroxide (Pola Office, SDI, Melbourne, Vic., Australia) or 15% hydrogen peroxide (BriteSmile, Discus, Culver City, CA, USA) on the microhardness and color changes of bovine enamel. Experimental groups were Britesmile + Light (BL) (15% hydrogen peroxide + plasm arc; 4 x 20 minutes), Britesmile + No Light (BN) (BL, no light), Pola office + Light (PL) (35% hydrogen peroxide + LED; 4 x 8 minutes), and Pola office + No light (PN) (PL, no light). Color changes (DeltaE) and the CIELAB (Commission Internationale de l' Eclairage, L* a* b* color system) parameters (L*, a*, and b*) were assessed with a spectrophotometer before (B), immediately (A), 1 day and 7 days after bleaching. The microhardness was measured before (B) and after (A), the obtained data were submitted to a two-way analysis of variance, and DeltaE were submitted to t-test for each period. Only Pola Office, in which the peroxide is associated with the light, improved DeltaE when evaluated immediately after bleaching (p < 0.001). Light exposure did not influence DeltaE after 1 day or 7 days for either bleaching system. The enamel microhardness was not altered after bleaching for BriteSmile. However, enamel microhardness was reduced after bleaching for Pola Office, 283 MPa (+/-21) and 265 MPa (+/-27), respectively. It was concluded that these two bleaching systems were efficient regardless of the light systems used. However, the 35% hydrogen peroxide altered the enamel microhardness. CLINICAL SIGNIFICANCE Enamel microhardness was affected by a 35% hydrogen peroxide in-office bleaching therapy. Moreover, the in-office bleaching outcome was not improved by using the light associated with systems tested in this study. (J Esthet Restor Dent 21:387-396, 2009).

Chemical versus conventional caries removal techniques in primary teeth: a microhardness study.

The aim of this in vitro study was to assess the remaining dentinal surface after carious tooth tissue removal with a low speed conventional bur and two chemomechanical methods, (Papacárie and Carisolv), using the microhardness test. It was concluded that the hardness of the remaining dentin after carious tissue removal was lower than that obtained on healthy dentin, without significance between the different means of carious tissue removal (p<0.05).

Microtensile bond strength of photoactivated and autopolymerized adhesive systems to root dentin using translucent and opaque fiber-reinforced composite posts.

STATEMENT OF PROBLEM: The use of fiber-reinforced composite resin posts in endodontically treated teeth has increased. However, selecting an adhesive system that provides reliable and long-lasting bonding to root canal dentin remains difficult. PURPOSE: This study evaluated the microtensile bond strength of 2 adhesive systems to root dentin and 2 different fiber-reinforced composite resin posts. MATERIAL AND METHODS: Forty single-rooted teeth were instrumented, and root canals were prepared for translucent (Light Post [LP]) or opaque (Aestheti Post [AP]) quartz fiber-reinforced composite resin posts. Two adhesive systems were used: Scotchbond Multi-Purpose Plus (SBMP) (autopolymerized) as a control group, and Single Bond (SB) (photoactivated). Teeth were assigned to 4 groups (n=10): SBMP+LP, SBMP+AP, SB+LP, SB+AP. After post cementation, roots were perpendicularly sectioned into 1-mm-thick slices, which were trimmed to obtain dumbbell-shaped specimens. The specimens were divided into 3 regions: cervical (C), middle (M), and apical (A). To determine the bond strength, the bonding area of each specimen was calculated, and specimens were attached to a device to test microtensile strength at a crosshead speed of 1 mm/min. Data were analyzed using 3-way analysis of variance and the Tukey test (alpha=.05). Fractured specimens were examined under a x 25 stereomicroscope to determine the mode of fracture. RESULTS: There were significant differences only among root dentin regions (P<.001). The cervical third (9.16 +/- 1.18 MPa) presented higher mean bond strength values, especially for SBMP. Middle and apical regions demonstrated lower values (7.08 +/- 0.92 and 7.31 +/- 0.60 MPa, respectively). Adhesive and post main factors did not demonstrate significance. Also, no interaction was significant. No cohesive fractures within resin cement, fiber-reinforced composite resin post, or root dentin were identified. CONCLUSIONS: Both adhesive systems tested demonstrated reliable bonding when used with translucent and opaque fiber-reinforced composite posts.

Composite depth of cure obtained with QTH and LED units assessed by microhardness and micro-Raman spectroscopy.

This study analyzed the depth of cure of a composite assessed by microhardness and the degree of conversion as a function of the light cure unit (LCU) used. Two light cure units, one LED (Ultraled-Dabi Atlante) and one quartz-tungsten-halogen (QTH, Optilux 401-Demetron) unit were used to cure 4.0 x 4.0 mm and 5.0 mm deep composite specimens (Filtek Z250, 3M ESPE). After 24 hours storage at 37 degrees C, Knoop microhardness and degree of conversion were measured on the irradiated surface and at each millimeter of the sample's depth. The degree of conversion was determined by using micro-Raman spectroscopy. The specimens cured with the QTH unit presented uniform decay in microhardness up to 4 mm in depth. Beyond 4 mm, the drop was abrupt. With LED photoactivation, uniform decay was observed only up to 2 mm. At higher depths, the decay in microhardness increased rapidly, especially beyond 3 mm. Depth of cure assessed by micro-Raman revealed that the degree of conversion behaved similarly to microhardness for both LCUs. A strong linear regression between microhardness and the degree of conversion, including both LCUs, was established with R2 = 0.980.

Shear versus micro-shear bond strength test: a finite element stress analysis.

OBJECTIVES: This study aimed at comparing the stress distribution in shear and micro-shear test set-ups using finite element analysis, and suggesting some parameter standardization that might have important influence on the results. METHODS: Two-dimensional plane strain finite element analysis was performed using MSCPatran and MSCMarc softwares. Model configurations were based on published experimental shear and micro-shear test set-ups and material properties were assumed to be isotropic, homogeneous and linear-elastic. Typical values of elastic modulus and Poisson's ratios were assigned to composite, dentin and adhesive. Loading conditions considered a single-node concentrated load at different distances from the dentin-adhesive interface, and proportional geometry (1:5 scale, but fixed adhesive layer thickness in 50microm) with similar calculated nominal strength. The maximum tensile and shear stresses, and stress distribution along dentin-adhesive interfacial nodes were analyzed. RESULTS: Stress distribution was always non-uniform and greatly differed between shear and micro-shear models. A pronounced stress concentration was observed at the interfacial edges due to the geometric change: stress values farther exceeded the nominal strength and tensile stresses were much higher than shear stresses. For micro-shear test, the relatively thicker adhesive layer and use of low modulus composites may lead to relevant stress intensification. An appropriate loading distance was established for each test (1mm for shear and 0.1mm for micro-shear) in which stress concentration would be minimal, and should be standardized for experimental assays. SIGNIFICANCE: The elastic modulus of bonded composites, relative adhesive layer thickness and load application distance are important parameters to be standardized, once they influence stress concentration.

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.

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.

Influence of rubber dam isolation on human pulp responses after capping with calcium hydroxide and an adhesive system.

OBJECTIVE: The objective was to evaluate the influence of rubber dam isolation on the response of human pulps capped with calcium hydroxide and an adhesive system. METHODS AND MATERIALS: Direct pulp capping was performed in 40 caries-free human premolars scheduled for extraction as part of orthodontic treatment. The teeth were randomly divided into 8 groups (n = 5) according to the combination of treatment factors: capping agent (adhesive resin or calcium hydroxide), isolation (rubber dam or cotton pellets only), and period of evaluation (30 or 60 days). Class 2 cavities were prepared, and pulp exposures were created on the occlusal floor. After capping, all teeth were restored with Z-100 placed incrementally. After 30 or 60 days, patients were asked about their symptoms, teeth were extracted, and serial sections were evaluated. The data were subjected to a nonparametric test. RESULTS: Overall, the histologic features showed that the pulp response was worse for groups capped with adhesive. For adhesive-capped groups, the pulp response varied from pulp necrosis to acute inflammatory cell infiltrate, and most of the pulps capped without rubber dam isolation showed severe inflammatory cell infiltrate involving the coronal pulp with chronic abscesses. For the calcium hydroxide groups, all specimens showed dentin bridge formation, regardless of the type of isolation used. CONCLUSION: Calcium hydroxide should be used as the material of choice for pulp capping with or without rubber dam isolation. The use of adhesive systems in vital pulp capping is contraindicated, especially if rubber dam isolation is not implemented.

A novel method to obtain microtensile specimens minimizing cut flaws.

Cutting procedures conventionally used for microtensile specimens' preparation induce mechanical stress and attrition, leading to cracks in dental structure. Enamel is mainly affected due to its high module of elasticity and brittleness. As an alternative to the conventional diamond saw, a diamond wire was used for cutting. The two techniques were compared in efficacy in the preparation of two different sample shapes. Forty human molars, flattened in dentin or enamel, were used for sample preparation. After bonding procedures, resin block was built incrementally. Half of the teeth were cut using a diamond disc and the other half using a diamond wire, obtaining slabs and stick-shaped specimens. Slabs were then shaped to obtain hourglass samples. Five samples from each subgroup were randomly selected for Scanning electron microscopy (SEM) analysis. Remaining samples underwent microtensile test and the results were analyzed, including/excluding premature failures (pf), with three-way ANOVA and Tukey test, performed separately, by substrate. On dentin, only the exclusion of pf showed a significant higher bond strength values than when pf were included (p < 0.05); however, on enamel, all factors (equipment, shape and including/excluding pf) had a significant effect on bond strength (p<0.05). The most remarkable finding from SEM was the incidence of specimens' cracks and defects when diamond blade was used. Scratches and cracks in the hourglass-shaped specimens were also detected. In both cases, enamel was more affected than dentin.

Microtensile bond strength of light- and self-cured adhesive systems to intraradicular dentin using a translucent fiber post.

This study evaluated the bond strength of a light- and self-cured adhesive system to different intraradicular dentin areas (cervical, middle and apical thirds). Twenty single-rooted teeth were instrumented and their roots were prepared to receive a #2 translucent fiber post (Light Post). The root canals were irrigated with 0.5% sodium hypochlorite for one minute, rinsed with water and dried using paper tips. The teeth were divided into two groups (n=10): Single Bond [SB] (light-cured) and Scotchbond Multi-Purpose Plus [SBMP] (self-cured). To avoid polymerization of the materials through the root lateral walls, the teeth were placed in a silicone mold and the adhesives applied with a thin microbrush according to manufacturer's instructions. The resin cement, Rely X ARC, was inserted into the root canals using Lentulo burs. The post was then placed and the light-curing procedure was carried out for 40 seconds (+/-500 mW/cm2). The roots were kept in a 100% relative moisture environment for 24 hours and stored in distilled water for an additional 24 hours. Each root was perpendicularly sectioned into 1-mm thick sections, resulting in approximately four slices per region. Dumbbell-shaped slices were obtained by trimming the proximal surfaces of each slice using a diamond bur until it touched the post. The bonded area was calculated, slices were attached to a special device and submitted to microtensile testing at 1 mm/minute crosshead speed. Data were analyzed using ANOVA and Tukey's test. The mean bond strength values (MPa) were: SBMP: cervical=10.8a, middle=7.9b%, apical=7.1bc; SB: cervical=8.1b, middle=6.0c, apical=6.9b. Significant differences were found between adhesive systems only for the cervical third. The cervical region showed higher mean bond strength values than the middle and apical regions (p<0.0001).

The effect of specimen dimensions on the flexural strength of a composite resin

OBJETIVO: A finalidade da presente investigacão foi avaliar a influência das dimensões dos corpos-de-prova (cp) e da superfície de irradiacão na resistência à flexão de uma resina composta (Heliomolar RO). MÉTODOS: As diversas dimensões adotadas - comprimento x largura x altura (mm) foram: 25x2x4; 25x2x2 (ISO 4049); 15x2x2; 10x2x2; 10x2x1. A fotoativacão foi realizada por 40 segundos a 600mW/cm2; três vezes ao longo dos cp de 25mm, duas vezes ao longo dos cp de 15mm e uma vez nos cp de 10mm de comprimento. Os corpos-de-prova de todas as dimensões foram ativados em ambas as superfícies, ou apenas em uma; neste caso a carga de ruptura era aplicada na face de irradiacão ou na oposta. RESULTADOS: Foi mostrado que a resistência à flexão não foi afetada pelo comprimento dos cp. Com a fotoativacão em ambas as superfícies, as resistências obtidas eram semelhantes nos diversos comprimentos. Independentemente do número de faces irradiadas, os cp com 1mm de altura apresentaram resistências semelhantes. Contudo, cp com 4mm de altura e irradiados apenas por um lado, alcancaram os menores valores. CONCLUSAO: Com o emprego de cp com dimensões menores são alcancados valores de resistência à flexão semelhante aos obtidos com cp padronizados (ISO 4049), com a vantagem de menor demanda de material e menor consumo de tempo (o menor comprimento dos cp requer apenas uma ativacão por lado).

Adverse effects of human pulps after direct pulp capping with the different components from a total-etch, three-step adhesive system.

OBJECTIVES: The objective was to evaluate the response of human pulps capped with different components from a total-etch three-step adhesive system. METHODS: Direct pulp capping was performed in 25 caries-free human premolars scheduled for extraction due to orthodontic treatment. The teeth were randomly divided in five groups, and capped with the following materials: Group 1-acid+primer+adhesive were used as recommended; Group 2-only primer was applied; Group 3-only bonding resin (light-cured for 10s); Group 4-only composite resin (light-cured for 40s); Group 5-calcium hydroxide. After capping, all teeth were restored with ScotchBond Multi Purpose Plus and Z-100 was placed incrementally. After 60 days, the teeth were extracted and processed for light microscopic examination (H/E) according to a histological score system. These were subjected to non-parametric tests (alpha<0.05). RESULTS: Overall, the histological features showed that groups 1-4 were quite similar and inferior to group 5. In groups 1-4 the pulp response varied from acute inflammatory cell infiltrate with varying degrees to necrosis. The groups 3 and 4 showed a trend towards better pulp response, since a normal connective tissue could be observed in more than half of the sample. All teeth from group 5 showed normal connective tissue below an amorphous dentin bridge. SIGNIFICANCE: Adhesive components (primer or adhesive) as well as a composite should be avoided for pulp capping. Ca(OH)(2) should be the first choice for pulp capping.

Response of human pulp capped with a bonding agent after bleeding control with hemostatic agents.

PURPOSE: This study evaluated the response of human pulps capped with a bonding agent after bleeding control with different hemostatic agents. MATERIAL AND METHODS: Twenty-five Class II cavities were prepared in 25 caries-free human premolars scheduled for extraction due to orthodontic treatment. The pulp exposures were performed on the occlusal floor. The teeth were randomly divided into five groups. Groups 1-4 were capped with an adhesive system after hemostasis with different agents: Group 1--saline solution; 2--ferric sulfate; 3--2.5% NaOCl; 4--Ca(OH)2 solution. In Group 5, after hemostasis with saline solution, the pulp was capped with calcium hydroxide (control group). Then, ScotchBond Multi Purpose Plus was applied and the resin composite Z-100 placed incrementally according to the manufacturers' directions. After 60 days, the teeth were extracted and processed for light microscopic examination (HE) and the groups were categorized in a histological score system. The data were subjected to a non-parametric test (alpha=0.05). RESULTS: Overall, the histological features showed that the pulp response from Groups 1 through 4 was inferior to the response from Group 5, where dentin bridging occurred. In all groups, where the adhesive system was used for capping, the pulp response varied from an acute inflammatory, with varying degrees, to necrosis. No dentin bridge was formed after adhesive capping.

The effect of specimen dimensions on the flexural strength of a composite resin.

UNLABELLED: PUORPOSE: The aim of this study was to evaluate the effect of specimen dimensions on the flexural strength of a composite resin (Heliomolar RO). METHODS: The different dimensions tested - length x width x height (mm) were: 25x2x4; 25x2x2 (ISO 4049); 15x2x2; 10x2x2 and 10x2x1. Light-curing was performed at 600 mW/cm² for 40s, three times along the 25mm specimens, twice along 15mm specimen and once for the 10mm specimens. Specimens of all dimensions were light-cured on both surfaces, or only on one side. In the latter, the load was applied on the irradiated side or on the opposite one. RESULTS: It was shown that the flexural strength was not affected by specimen length. When light-curing was performed on both surfaces, similar flexural strength values were obtained for any dimension. Despite the number of irradiated surfaces, specimens with a height of 1mm also obtained similar values. On the contrary, specimens with a height of 4mm, exposed only on one surface, reached the lowest strength. CONCLUSION: The use of specimens with lower dimensions can lead to flexural strength values similar to the ones obtained with standardized specimen (ISO 4049), with the advantage of demanding less amount of material and being less time consuming.

Color unit differences (AE) of acrylic resins related to powder-to-liquid ratio, sample thickness and trade marks / Diferenças de unidades de cor (AE) de resinas acrílicas em função de proporções, espessuras e marcas

O objetivo da pesquisa foi determinar as diferenças de cor de resinas acrílicas, empregando corpos-de-prova em peça única, com as espessuras de 6, 4 e 2mm. As resinas ensaiadas foram: duas de cor rosa médio (Clássico e Vipi) e três de cor 66, Dencor (Clássico), Vipi-cor (Vipi) e Duralay (Reliance). Com um espectrifotômetro foram determinados os parâmetros de cor (L*,a*,b*) e calculados as diferenças entre condições diferentes. As diferenças de cor foram determinadas pelo emprego dos seguintes padrões: 1) Proporção pó/líquido normal (do fabricante), à qual foram comparadas aquelas de (em porcentagem): +10, -10 e -20; 2) espessuras de 4 a 2mm, em relação ao padrão de 6mm; 3)comparação entre duas resinas cor de rosae entre as três de cor 66. Os resultados permitiram concluir que: a variação na proporção pó/líquido em relação à normal influenciou pouco na alteração de cor, do ponto de vista clínico, com o maior valor (diferença de cor = 1.6) não perceptível por um grande número de observadores; a comparação, em relação ao padrão de 6mm de espessura, mostrou que a de 4mm não foi grande (diferença de cor = 1.7 no máximo), entretanto, a de 2mm de espessura em relação ao mesmo padrão, apresentou alterações insatisfatórias, que, dependendo da resina e proporções, chegou a diferença de cor = 8.4 entre as resinas cor de rosa, a semelhança de cor foi boa, contudo entre as resinas de cor 66, as diferenças foram insatisfatórias

Marginal fit of cast titanium copings related to investments and casting techniques

The purpose of this study was to evaluated marginal fit of cast titanium coping according to the following conditions: 1) three investment types, 2) use of a doll made up with the three investments and the ring filling with conventional phosphate investment; 3) use of die relief; 4) surface treatment. Casting was made using appropriate equipment for titanium alloys. The results obtained led us to conclude that it is possible to obtain titanium casts with satisfactory marginal it using adequate techniques; rematitan investment led to good results, although they may not used without die relief, especially when the cover technique is employed; Ticoast S + L was the least critical regarding casting techniques, but requires drilling to obtain good fit

Influência do tempo de armazenamento na resistência de união à dentina de dois tipos de adesivos dentários por ensaio de microtração / Influence of water storage time on microtensile bond strength of two dentinbonding agents

O objetivo da pesquisa foi estudar a influência do tempo de armazenamento (24hs e três meses) na resistência adesiva de dois tipos de adesivo dental, sendo um convencional, Single Bond (SB) e outro com primer autocondicionante, ABF experimental (ABF), e também a influência das variações regionais do abstrato dentário. O esmalte oclusal de 16 terceiros molares foi removido, expondo uma superfície dentinária plana. Nesta, foi criada uma camda de smear através de lixas de papel de granulações decrescentes. Após a aplicação dos sistemas adesivos, blocos de resina Z250 de 5 mm de altura foram construídos sobre a superfície dentinária. Os dentes foram divididos em quatro grupos (n=4) de acordo com o material e o tempo de armazenamento, os dentes foram seccionados, longitudinalmente, em cortes perpendiculares entre si, a fim de se obterem corpos-de-prova (cp) em formato de palito de aproximadamente 0,8 mm quadrados de secção transversal, constituídos por resina-adesivo-dentina. Esses cp foram mapeados, com esmaltes de diferentes cores, conforme suas localizações no dente: mais periférica ou interna, no sentido horizontal. Os espécimes foram submetidos ao teste de microtração. A análise de variância demonstrou não haver diferença significante entre os valores médios de sistência dos dois adesivos com diferentes idades de armazenamento, nem entre as diferentes regiões do dente.

The influence of handling on the elasticity of addition silicone putties

The handling of vinyl polysiloxane (addition silicone) impression putties with latex gloves is said to interfere with the setting of these impression materials. The aim of this study is to evaluate the effect of handling techniques on the setting of vinyl polysiloxane impression putties using several types of gloves. The setting of these materials was evaluated by means of an elasticimeter. Four vinyl polysiloxane putty impression materials and five brands of gloves (one made of vinyl, one of synthetic rubber, and three of natural rubber) were studied. Based on the type of glove, they were previously washed or not, and a spatula was used or not for initial mixing (before handmixing). The vinyl, the synthetic and one of the natural rubber gloves did not require the previous washing procedure and/or the use of a spatula for initial mixing. Two other natural rubber gloves - depending on the silicone -, showed satisfactory results only when the initial mixing was performed with a spatula. It was concluded that setting inhibition depends on the kind of vinyl polysiloxane impression material and the kind of gloves used, but when the initial mixing was performed with the spatula this setting inhibition was overcome. The results of this study also showed that it is possible to associate cross-contamination control and satisfactory performance of addition silicone putty materials. When doubts arise from the compatibility between vinyl polysiloxane impression putties and gloves, the initial mixing should be performed with a spatula

The effect of long-term storage on the microleakage of composite resin restorations: qualitative and quantitative evaluation

The aim of this study was to evaluate the influence of storage periods of 24 hours and 3 months on the microleakage of class II cavities. Two methods of assessing microleakage were also compared. Class II cavities were prepared in sound human molars. MO cavities were restored using ABF experimental (Kuraray Medical Inc.) + Z250 composite resin (3M ESPE), and DO cavities were restored using Single Bond (3M ESPE) + Z250. After different storage periods, specimens were thermocycled, immersed in a dye (0.5 percent methylene blue solution for 4 h) and longitudinally sectioned. Dye penetration was scored according to a 0-4 scale. The extent of microleakage was measured using the ImageLab 2000 program. A statistically significant correlation was verified between both evaluation methods (r = 0.978, p < 0.001). ANOVA revealed a statistically significant difference between the tested adhesive systems regarding microleakage (p < 0.001), although it was not influenced by the different storage periods