Effect of photopolymerization time on the microhardness of resin cement beneath feldspathic ceramic.

During ceramic veneer luting, resin cement polymerization is performed with interposition of the dental ceramic. Aim: To evaluate how and how much the photoactivation time affects the Vickers hardness of resin-based cements with interposed ceramic. Materials and Method: A total 24 specimens H mm in diameter and 1 mm thick were made from Paracore White Coltene (PC), Densell Resin Duo Cement (DC), 3MRelyX Veneer (RX) and Coltene Fill Up! (FU), interposing VitablockMarkII (Vita Zahnfabrik) feldspathic ceramic 0.6 mm thick during photoactivation. The materials were polymerized using 100% and 25% of the times indicated by the manufacturers with a Coltolux LED ((Coltene) light with intensity 1200 mW/cm2. Each polymerization time group consisted of three specimens of each material, which were stored dry in darkness at 37 °C for 7 days. Three Vickers microhardness measurements were made on the top and bottom surfaces of each specimen using a Vickers Future Tech FM300 microhardness tester (300 g, 5 s). The values were averaged, and the bottom/top ratios calculated. Results were analyzed by ANOVA. (p<0.05) complemented with multiple comparisons using Tukey's test (p<0.05). Results: Different photoactivation times were found to have a significant effect on hardness values of the cements evaluated, with significant differences between some of the cements. No statistically significant difference was found for the effect of photoactivation time on bottom/top microhardness ratio in those materials. Conclusions: Under the experimental conditions employed, it can be concluded that photopolymerization for shorter times and the interposition of restorative material significantly affectpolymerization quality as evaluated by microhardness, but the bottom/top ratio was unaffected by differences in polymerization time.

Durante la fijación de una carilla cerámica, la polimerización del cemento a base de resinas se realiza con la interposición de la cerámica dental. Objetivo: evaluar en qué forma y magnitud afecta el tiempo de fotoactivación en la dureza Vickers de los cementos a base de resinas con la cerámica interpuesta. Materiales y Método: se confeccionaron 24 probetas de 11 mm de diámetro y 1 mm de espesor con: Paracore White Coltene (PC), Resin Duo Cement de Densell (DC), RelyX Veneer de 3M (RX) y Fill Up! De Coltene (FU) interponiendo 0,6 mm de espesor de cerámica feldespática Vitablock Mark II (Vita Zahnfabrik) durante la fotoactivación. Se polimerizó utilizando el 100% y el 25% del tiempo indicado por el fabricante con lámpara Coltolux LED ((Coltene) con 1200 mW/cm2 de intensidad. Cada grupo quedó conformado con tres probetas de cada material que se almacenaron a oscuras y en seco a 37 °C durante 7 días. Se registraron tres mediciones de microdureza Vickers de las superficies top y bottom de cada probeta con un microdurómetro Vickers Future Tech FM300 (300 g, 5 s) y se calculó su promedio, así como la relación entre los valores registrados en cada una de sus caras. Los resultados fueron analizados por medio de la prueba de ANOVA. (p<0.05). complementada con comparaciones múltiples por medio de la prueba de Tukey (p<0.05). Resultados: se encontró un efecto significativo de la modificación del tiempo de fotoactivación en los valores de dureza de los cementos evaluados con diferencias significativas entre algunos de ellos. Simultáneamente no se encontró significación estadística en el efecto de ese factor sobre la relación microdureza bottom/top registrada en esos materiales. Conclusiones: en las condiciones experimentales empleadas puede concluirse que la fotopolimerización en menor tiempo e interposición de material restaurador afecta significativamente la calidad de polimerización evaluada mediante los valores de microdureza, pero la proporción bottom/ top no fue afectada en la variación en el tiempo de polimerización.

Effect of photopolymerization time on the microhardness of resin cement beneath feldspathic ceramic / Efecto del tiempo de fotopolimerización en la dureza de cementos de resina debajo de una cerámica feldespática

ABSTRACT During ceramic veneer luting, resin cement polymerization is performed with interposition of the dental ceramic. Aim: To evaluate how and how much the photoactivation time affects the Vickers hardness of resin-based cements with interposed ceramic. Materials and Method: A total 24 specimens H mm in diameter and 1 mm thick were made from Paracore White Coltene (PC), Densell Resin Duo Cement (DC), 3MRelyX Veneer (RX) and Coltene Fill Up! (FU), interposing VitablockMarkII (Vita Zahnfabrik) feldspathic ceramic 0.6 mm thick during photoactivation. The materials were polymerized using 100% and 25% of the times indicated by the manufacturers with a Coltolux LED ((Coltene) light with intensity 1200 mW/cm2. Each polymerization time group consisted of three specimens of each material, which were stored dry in darkness at 37 °C for 7 days. Three Vickers microhardness measurements were made on the top and bottom surfaces of each specimen using a Vickers Future Tech FM300 microhardness tester (300 g, 5 s). The values were averaged, and the bottom/top ratios calculated. Results were analyzed by ANOVA. (p<0.05) complemented with multiple comparisons using Tukey's test (p<0.05). Results: Different photoactivation times were found to have a significant effect on hardness values of the cements evaluated, with significant differences between some of the cements. No statistically significant difference was found for the effect of photoactivation time on bottom/top microhardness ratio in those materials. Conclusions: Under the experimental conditions employed, it can be concluded that photopolymerization for shorter times and the interposition of restorative material significantly affectpolymerization quality as evaluated by microhardness, but the bottom/top ratio was unaffected by differences in polymerization time.

RESUMEN Durante la fijación de una carilla cerámica, la polimerización del cemento a base de resinas se realiza con la interposición de la cerámica dental. Objetivo: evaluar en qué forma y magnitud afecta el tiempo de fotoactivación en la dureza Vickers de los cementos a base de resinas con la cerámica interpuesta. Materiales y Método: se confeccionaron 24 probetas de 11 mm de diámetro y 1 mm de espesor con: Paracore White Coltene (PC), Resin Duo Cement de Densell (DC), RelyX Veneer de 3M (RX) y Fill Up! De Coltene (FU) interponiendo 0,6 mm de espesor de cerámica feldespática Vitablock Mark II (Vita Zahnfabrik) durante la fotoactivación. Se polimerizó utilizando el 100% y el 25% del tiempo indicado por el fabricante con lámpara Coltolux LED ((Coltene) con 1200 mW/cm2 de intensidad. Cada grupo quedó conformado con tres probetas de cada material que se almacenaron a oscuras y en seco a 37 °C durante 7 días. Se registraron tres mediciones de microdureza Vickers de las superficies top y bottom de cada probeta con un microdurómetro Vickers Future Tech FM300 (300 g, 5 s) y se calculó su promedio, así como la relación entre los valores registrados en cada una de sus caras. Los resultados fueron analizados por medio de la prueba de ANOVA. (p<0.05). complementada con comparaciones múltiples por medio de la prueba de Tukey (p<0.05). Resultados: se encontró un efecto significativo de la modificación del tiempo de fotoactivación en los valores de dureza de los cementos evaluados con diferencias significativas entre algunos de ellos. Simultáneamente no se encontró significación estadística en el efecto de ese factor sobre la relación microdureza bottom/top registrada en esos materiales. Conclusiones: en las condiciones experimentales empleadas puede concluirse que la fotopolimerización en menor tiempo e interposición de material restaurador afecta significativamente la calidad de polimerización evaluada mediante los valores de microdureza, pero la proporción bottom/ top no fue afectada en la variación en el tiempo de polimerización.

Centric relation registration with intraoral central bearing on curved vs. flat plates with rim trays in edentulous patients.

The aim of this study was to compare jaw relation record in the completely edentulous patient using acrylic rim trays with curved or flat registration plates or using the manual guidance technique. The study included 17 patients - 11 female and 6 male, average age 70 years. Three jaw relation records were taken during one session, in the same vertical dimension, using acrylic rim trays: (1) with manual guidance (IM), (2) with self-guided recording system with acrylic rim tray and central support using a curved plate (BYC) and (3) with self-guided recording system with acrylic rim tray and central support using a flat plate (BYR). The models were mounted on a Whip Mix 2240 articulator to which a condyle position device (Orthodent) was added to register, at the level of the condyle box and incisal table, the differences among the positions recorded with the different setups (IM, BYC and BYR). The distances were measured on millimeter paper provided by the recording system manufacturer. For statistical analysis, confidence intervals (95%) were calculated for the mean differences and Student's t-test for paired data (significance level: alpha<0.05). On both the mesiodistal plane and the vertical plane at the level of each condyle box and the incisal table, there were statistically significant differences among the three systems (p<0.001). At the level of incisal table, BYC and BYR provided more retrusive records than IM [arithmetic means (standard deviations) in millimeters: 3.82 (2.10) and 4.53 (2.18), respectively). The records obtained with BYR were significantly more retrusive with BYC [arithmetic mean (standard deviation) in millimeters: 1.41 (1.00)]. We reject the null hypothesis that proposes that all three registration systems described are clinically equivalent for establishing a jaw relation record in completely edentulous patients.

El objetivo de este estudio fue comparar el registro de la posición intermaxilar en el paciente desdentado total obtenido con el uso de cubetas rodete de acrílico y platinas de registro curva o recta y con la técnica de inducción manual. Se incluyeron en el estudio 17 pacientes, 11 mujeres y 6 varones con edad promedio de 70 años. En cada uno de ellos se obtuvieron en la misma sesión y en la misma dimensión vertical tres registros intermaxilares con cubetas rodete de acrílico: uno con inducción manual (IM), otro autoinducido con el sistema de cubeta rodete de acrílico y apoyo central único utilizando una superficie palatina de registro curva (BYC) y un tercero con este mismo sistema pero con la superficie palatina recta (BYR). Los modelos correspondientes fueron montados en un articulador Whip Mix modelo 2240 al que se le adicionó un dispositivo de posición condilar (Orthodent) para registrar, a nivel de la caja condílea y la platina incisiva, las diferencias existentes entre las posiciones obtenidas con cada una de las variantes de las platinas en las cubetas rodete acrílicas y la posición registrada con inducción manual. Las distancias fueron medidas sobre papel milimetrado provisto por el fabricante del sistema de registro. El análisis estadístico se llevó a cabo mediante el cálculo de intervalos de confianza (95%) para las diferencias medias y prueba de t de student para datos apareados (nivel de significancia: alfa<0,05). Tanto en el plano mesiodistal como en el vertical a nivel de cada caja condilea como en la platina incisiva, se encontró diferencia estadísticamente significativa entre las tres variables de registro (p<0,001). A nivel de las platinas incisivas tanto BYC como BYR proporcionaron registros más retrusivos que IM [medias aritméticas (desviaciones estándar) en milímetros: 3,82 (2,1º) y 4,53 (2,18), respectivamente). Los obtenidos con BYR fueron significativamente más retrusivos que en el grupo BYC [media aritmética (desviación estándar) en milímetros: 1,41 (1,00)]. Rechazamos la hipótesis nula que propone que los tres sistemas de registro expuestos son clínicamente equivalentes para establecer una posición de registro intermaxilar en desdentados totales.

Centric relation registration with intraoral central bearing on curved vs. flat plates with rim trays in edentulous patients / Registro de relación céntrica con apoyo central intraoral en platinas curvas vs. rectas con cubetas rodete en edéntulos

ABSTRACT The aim of this study was to compare jaw relation record in the completely edentulous patient using acrylic rim trays with curved or flat registration plates or using the manual guidance technique. The study included 17 patients - 11 female and 6 male, average age 70 years. Three jaw relation records were taken during one session, in the same vertical dimension, using acrylic rim trays: (1) with manual guidance (IM), (2) with self-guided recording system with acrylic rim tray and central support using a curved plate (BYC) and (3) with self-guided recording system with acrylic rim tray and central support using a flat plate (BYR). The models were mounted on a Whip Mix 2240 articulator to which a condyle position device (Orthodent) was added to register, at the level of the condyle box and incisal table, the differences among the positions recorded with the different setups (IM, BYC and BYR). The distances were measured on millimeter paper provided by the recording system manufacturer. For statistical analysis, confidence intervals (95%) were calculated for the mean differences and Student's t-test for paired data (significance level: alpha<0.05). On both the mesiodistal plane and the vertical plane at the level of each condyle box and the incisal table, there were statistically significant differences among the three systems (p<0.001). At the level of incisal table, BYC and BYR provided more retrusive records than IM [arithmetic means (standard deviations) in millimeters: 3.82 (2.10) and 4.53 (2.18), respectively). The records obtained with BYR were significantly more retrusive with BYC [arithmetic mean (standard deviation) in millimeters: 1.41 (1.00)]. We reject the null hypothesis that proposes that all three registration systems described are clinically equivalent for establishing a jaw relation record in completely edentulous patients.

RESUMEN El objetivo de este estudio fue comparar el registro de la posición intermaxilar en el paciente desdentado total obtenido con el uso de cubetas rodete de acrílico y platinas de registro curva o recta y con la técnica de inducción manual. Se incluyeron en el estudio 17 pacientes, 11 mujeres y 6 varones con edad promedio de 70 años. En cada uno de ellos se obtuvieron en la misma sesión y en la misma dimensión vertical tres registros intermaxilares con cubetas rodete de acrílico: uno con inducción manual (IM), otro autoinducido con el sistema de cubeta rodete de acrílico y apoyo central único utilizando una superficie palatina de registro curva (BYC) y un tercero con este mismo sistema pero con la superficie palatina recta (BYR). Los modelos correspondientes fueron montados en un articula-dor Whip Mix modelo 2240 al que se le adicionó un dispositivo de posición condilar (Orthodent) para registrar, a nivel de la caja condílea y la platina incisiva, las diferencias existentes entre las posiciones obtenidas con cada una de las variantes de las platinas en las cubetas rodete acrílicas y la posición registrada con inducción manual. Las distancias fueron medidas sobre papel milimetrado provisto por el fabricante del sistema de registro. El análisis estadístico se llevó a cabo mediante el cálculo de intervalos de confianza (95%) para las diferencias medias y prueba de t de student para datos apareados (nivel de significancia: alfa<0,05). Tanto en el plano mesiodistal como en el vertical a nivel de cada caja condilea como en la platina incisiva, se encontró diferencia estadísticamente significativa entre las tres variables de registro (p<0,001). A nivel de las platinas incisivas tanto BYC como BYR proporcionaron registros más retrusivos que IM [medias aritméticas (desviaciones estándar) en milímetros: 3,82 (2,1°) y 4,53 (2,18), respectivamente). Los obtenidos con BYR fueron significativamente más retrusivos que en el grupo BYC [media aritmética (desviación estándar) en milímetros: 1,41 (1,00)]. Rechazamos la hipótesis nula que propone que los tres sistemas de registro expuestos son clínicamente equivalentes para establecer una posición de registro intermaxilar en desdentados totales.

Post preparation: cleanness achieved by different irrigating protocols.

The aim of this study was to evaluate the ability of different irrigation protocols to remove from the walls of the root canal and entrance to dentinal tubules the smear layer produced during preparation for a fiber post. Fifty decoronated human lower premolars were treated endodontically and the apical third of the canal was filled with a single gutta-percha point using warm vertical compaction. Ten millimeters were left free for post preparation, which was done by sequential use of a Largo #1 drill and Exacto #3 pilot drill (Angelus, Brazil), with irrigation with distilled water upon each instrument change. Samples were distributed randomly into 5 groups (n=10). G 1: No irrigation after post preparation. G 2: Distilled water activated for 60 s + distilled water. G 3: 5.25% NaOCl 15 s+ distilled water. G 4: 17% EDTA (Farmadental, Argentina) 60 s + 5.25% NaOCl 15 s + distilled water. G 5: 10% polyacrylic acid (Densell) 15 s + distilled water. Irrigant was activated mechanically with a low-speed conical brush. Roots were then split longitudinally in vestibular-lingual direction. Each surface was observed under SEM in its different thirds. Microphotographs were taken at 150X and 600X magnification and results analyzed statistically using Kruskall Wallis and Friedman tests (p<0.05). The results [mean (standard deviation)] were: for 150X: G1 11.00 (1.33), G2 7.50 (3.13), G3 6.30 (2.58), G4 2.20 (2.80), G5 4.30 (1.50), and for 600X G1 11.40 (0.84), G2 10.00 (1.94), G3 7.70 (3.33), G4 5.80 (3.70), G5 7.20 (2.65). The statistical analysis showed significant differences between irrigants (p<0.05) but not between root thirds (p>0.05). The EDTA+NaOCl combination and polyacrylic acid showed greater capacity to remove the smear layer created during post preparation.

El objetivo del presente trabajo fue evaluar la capacidad de diferentes protocolos de irrigación para remover el barro dentinario de las paredes del conducto y entrada de los túbulos dentinarios, producido durante la preparación para anclaje intarradicular. Se utilizaron 50 premolares inferiores humanos a los cuales se les cortó la corona clínica. Luego se les realizó tratamiento endodóntico y obturación del tercio apical con cono único de conicidad aumentada y compactación vertical caliente. Se dejaron libres 10 mm para la preparación para poste que se realizó utilizando secuencialmente fresa de Largo # 1y fresa piloto Exacto #1(Angelus, Brasil), irrigando a cada cambio de instrumento con agua destilada. Las muestras fueron distribuidas aleatoriamente en 5 grupos (n=10). G 1: No se efectuó ningún lavaje. Los irrigantes fueron activados con cepillo mecánico cónico a baja velocidad. G 2: Agua destilada activada 60 s+ agua destilada G 3: NaOCl al 5,25%, 15 s+ agua destilada. G 4: EDTA al 17% (Farmadental, Argentina) 60 s +NaOCl al 5,25% 15 s , + agua destilada. G 5 : Ácido poliacrílico al 10% ( Densell) 15 s + agua destilada. Posteriormente, las raíces fueron seccionadas longitudinalmente en sentido vestíbulo lingual. Cada superficie fue observada al MEB en sus diferentes tercios. Las micrografías se realizaron a 150 y 600 X y los resultados analizados estadísticamente mediante test de Kruskall Wallis y Friedman (p<0,05), Los resultados [Medias (desviaciones estándar)] fueron: para 150X G1 11,00(1,33), G2 7,50 (3,13), G3 6,30 (2,58), G4 2,20 (2,80), G5 4,30 (1,50) y para 600X G1 11,40 (0,84), G2 10,00 (1,94), G3 7,70 (3,33), G4 5,80 (3,70), G5 7,20 (2,65). El análisis estadístico mostró diferencia significativa entre irrigantes (p<0,05) pero no entre tercios radiculares (p>0,05). La combinación de EDTA+NaOCl y el ácido poliacrílico tendrían mayor capacidad de remoción del barro dentinario creado durante la preparación para poste.

Post preparation: cleanness achieved by different irrigating protocols / Preparación para poste: limpieza lograda por diferentes protocolos de irrigación

ABSTRACT The aim of this study was to evaluate the ability of different irrigation protocols to remove from the walls of the root canal and entrance to dentinal tubules the smear layer produced during preparation for a fiber post. Fifty decoronated human lower premolars were treated endodontically and the apical third of the canal was filled with a single gutta-percha point using warm vertical compaction. Ten millimeters were left free for post preparation, which was done by sequential use of a Largo #1 drill and Exacto #3 pilot drill (Angelus, Brazil), with irrigation with distilled water upon each instrument change. Samples were distributed randomly into 5 groups (n=10). G 1: No irrigation after post preparation. G 2: Distilled water activated for 60 s + distilled water. G 3: 5.25% NaOCl 15 s+ distilled water. G 4: 17% EDTA (Farmadental, Argentina) 60 s + 5.25% NaOCl 15 s + distilled water. G 5: 10% polyacrylic acid (Densell) 15 s + distilled water. Irrigant was activated mechanically with a low-speed conical brush. Roots were then split longitudinally in vestibular-lingual direction. Each surface was observed under SEM in its different thirds. Microphotographs were taken at 150X and 600X magnification and results analyzed statistically using Kruskall Wallis and Friedman tests (p<0.05). The results [mean (standard deviation)] were: for 150X: G1 11.00 (1.33), G2 7.50 (3.13), G3 6.30 (2.58), G4 2.20 (2.80), G5 4.30 (1.50), and for 600X G1 11.40 (0.84), G2 10.00 (1.94), G3 7.70 (3.33), G4 5.80 (3.70), G5 7.20 (2.65). The statistical analysis showed significant differences between irrigants (p<0.05) but not between root thirds (p>>0.05). The EDTA+NaOCl combination and polyacrylic acid showed greater capacity to remove the smear layer created during post preparation.

RESUMEN El objetivo del presente trabajo fue evaluar la capacidad de diferentes protocolos de irrigación para remover el barro dentinario de las paredes del conducto y entrada de los túbulos dentinarios, producido durante la preparación para anclaje intarradicular. Se utilizaron 50 premolares inferiores humanos a los cuales se les cortó la corona clínica. Luego se les realizó tratamiento endodóntico y obturación del tercio apical con cono único de conicidad aumentada y compactación vertical caliente. Se dejaron libres 10 mm para la preparación para poste que se realizó utilizando secuencialmente fresa de Largo # 1y fresa piloto Exacto #1(Angelus, Brasil), irrigando a cada cambio de instrumento con agua destilada. Las muestras fueron distribuidas aleatoriamente en 5 grupos (n=10). G 1: No se efectuó ningún lavaje. Los irrigantes fueron activados con cepillo mecánico cónico a baja velocidad. G 2: Agua destilada activada 60 s+ agua destilada G 3: NaOCl al 5,25%, 15 s+ agua destilada. G 4: EDTA al 17% (Farmadental, Argentina) 60 s +NaOCl al 5,25% 15 s , + agua destilada. G 5 : Ácido poliacrílico al 10% ( Densell) 15 s + agua destilada. Posteriormente, las raíces fueron seccionadas longitudinalmente en sentido vestíbulo lingual. Cada superficie fue observada al MEB en sus diferentes tercios. Las micrografías se realizaron a 150 y 600 X y los resultados analizados estadísticamente mediante test de Kruskall Wallis y Friedman (p<0,05), Los resultados [Medias (desviaciones estándar)] fueron: para 150X G1 11,00(1,33), G2 7,50 (3,13), G3 6,30 (2,58), G4 2,20 (2,80), G5 4,30 (1,50) y para 600X G1 11,40 (0,84), G2 10,00 (1,94), G3 7,70 (3,33), G4 5,80 (3,70), G5 7,20 (2,65). El análisis estadístico mostró diferencia significativa entre irrigantes (p<0,05) pero no entre tercios radiculares (p>0,05). La combinación de EDTA+NaOCl y el ácido poliacrílico tendrían mayor capacidad de remoción del barro dentinario creado durante la preparación para poste.

Effect of post-curing treatment on mechanical properties of composite resins.

The aim of this study is to assess the effect of additional curing procedures on the flexural strength and modulus of elasticity of indirect and direct composite materials. Twenty-four rectangular prism-shaped 2 mm x 2 mm x 25 mm samples of Belleglass, Premisa (Kerr), Adoro and Heliomolar (Ivoclar Vivadent) were prepared. Each composite was packed in an ad-hoc stainless steel device with a TeflonR instrument. A mylar strip and a glass slab were placed on top to obtain a flat surface. Polymerization was activated for 20 seconds with a halogen unit (Astralis 10, Ivoclar - Vivadent) with soft start regime and an output with a 350 to 1200 mw/cm2 range at four different points according to the diameter of the end of the guide. The specimens obtained were then randomly divided into two different groups: with and without additional treatment. In the group with additional treatment, the samples adorro were submitted to 25 minutes in Lumamat 100 (Ivoclar Vivadent) and the rest to 20 minutes in BelleGlass HP (Kerr). After the curing procedures, all samples were treated with sandpapers of decreasing grain size under water flow, and stored in distilled water for 24 h. Flexural strength was measured according to the ISO 404920 recommendations and elastic modulus was determined following the procedures of ANSI/ADA standard No. 27. Statistical differences were found among the different materials and curing procedures employed (P<0.01). The elastic modulus was significantly higher after the additional curing treatment for all materials except Premisa. Further work is needed to determine the association between the actual monomers present in the matrix and the effect of additional curing processes on the mechanical properties of both direct and indirect composites, and its clinical relevance.

Effect of post-curing treatment on mechanical properties of composite resins. / Effect of post-curing treatment on mechanical properties of composite resins.

The aim of this study is to assess the effect of additional curing procedures on the flexural strength and modulus of elasticity of indirect and direct composite materials. Twenty-four rectangular prism-shaped 2 mm x 2 mm x 25 mm samples of Belleglass, Premisa (Kerr), Adoro and Heliomolar (Ivoclar Vivadent) were prepared. Each composite was packed in an ad-hoc stainless steel device with a TeflonR instrument. A mylar strip and a glass slab were placed on top to obtain a flat surface. Polymerization was activated for 20 seconds with a halogen unit (Astralis 10, Ivoclar - Vivadent) with soft start regime and an output with a 350 to 1200 mw/cm2 range at four different points according to the diameter of the end of the guide. The specimens obtained were then randomly divided into two different groups: with and without additional treatment. In the group with additional treatment, the samples adorro were submitted to 25 minutes in Lumamat 100 (Ivoclar Vivadent) and the rest to 20 minutes in BelleGlass HP (Kerr). After the curing procedures, all samples were treated with sandpapers of decreasing grain size under water flow, and stored in distilled water for 24 h. Flexural strength was measured according to the ISO 404920 recommendations and elastic modulus was determined following the procedures of ANSI/ADA standard No. 27. Statistical differences were found among the different materials and curing procedures employed (P<0.01). The elastic modulus was significantly higher after the additional curing treatment for all materials except Premisa. Further work is needed to determine the association between the actual monomers present in the matrix and the effect of additional curing processes on the mechanical properties of both direct and indirect composites, and its clinical relevance.

Powder-liquid ratio and properties of two restorative glass ionomer cements.

Changes in the powder-liquid ratio of glass ionomer cements may affect some of its physical properties and acid erosion. The aim of this study was to evaluate the physical properties and acid erosion of two conventional restorative glass ionomer cements against ISO 9917-1:2007 standards after changing the powder-liquid ratio to an adequate consistency for luting indirect restorations. The methodology of ISO Specification 9917-1:2007 was applied to the powder-liquid ratio indicated by the manufacturer and to a modified ratio. Two restorative glass ionomer cements, ChemFil (Ch) (Dentsply) and lonofil Plus (IP) (Voco), were used to evaluate film thickness, compressive strength, net setting time and acid erosion. Thickness was measured three times with a digital micrometer (Digimatic Mitutoyo Corporation). Sample size was five for each cement or condition. Compressive strength (Instron 1011, crosshead speed of 1 mm/min) was evaluated after 24 h immersion in water at 37 degreesC. Sample size was five for each cement or condition. Setting time was evaluated for Ch and IP at 37 degreesC. Sample size was three for each cement or condition. Specimen moulds (30 x 30 x 5 mm) with a central perforation of 5 mm in diameter and 2 mm depth were usedfor acid erosion tests. Erosion depth was measured with a micrometer gauge with a precision of 0. 001 mm, before and after 24-hour immersion in a lactic acid-sodium lactate solution with pH 2.74 at 370C. Sample size wasfivefor each condition. Student's t test was performed with a level of significance ofp< O.05 for each material and condition tested. Arithmetic mean (Standard Deviation). Powder-liquid ratio according to manufacturers: film thickness (in pm): Ch 220 (40), IP: 382 (5); compressive strength (in MPa) at 24 hs: Ch 166.3 (16,6), IP: 100 (10); net setting time (in min.) at 370C: Ch 3.44 (0.3), IP: 5.26 (0.1) ; depth of acid erosion (in mm): Ch 0.15 (0.02), IP: 0.17 (0.02). Modified powder-liquid ratio: film thickness (in pm): Ch 23(1), IP:24(1); compressive strength at 24 hs (in MPa): Ch: 69.3 (14.6), IP: 46.5 (7.4); net setting time (in min.) at 370C: Ch 5.72 (0.1) and IP 9.38 (0.1); depth of acid erosion (in mm): Ch 0.22 (0.02). Data were not recorded for IP because the sample disintegrated in the solution. Student's t test was performed for both materials and conditions with a level of significance of p< 0.05. The difference between each condition tested was statistically significant (p<0.01). While changes in the powder-liquid ratio of a restorative glass ionomer cement can result in some of its properties having values that are not far from those required for luting cements according to ISO specifications, it did not meet the requirements for acid erosion.

Effect of energy density on color stability in dental resin composites under accelerated aging.

The effects of the energy density that is used for polymerization on properties of dental resin composites are well known. However, few studies relate color stability to this factor. The aim of this study was to assess color changes (deltaE*), in vitro, in terms of accelerated aging under UV exposure of specimens prepared with different energy densities. Four commercial dental resin composites were included in the study. Thirty six specimens were prepared for each one of them, following the procedure established by ISO 4049 Standard, and assigned to three groups: A (3.75 J/cm2), B (9 J/cm2), C (24 J/cm2). Each group was further subdivided into four subgroups: 1 (no aging), 2 (500 hours aging), 3 (1000 hours aging) and 4 (1500 hours aging). The results were analyzed by means of ANOVA and Tukey's test (alpha = 0.05) to determine the effect of the factors. Correlation was performed in order to determine the possible relationship among variables. Energy density is not a significant factor in color stability. However aging is directly proportional to color changes. deltaE* depends on filler size; hybrid material presented deltaE* of 2.1(0.5), 2.4(0.6) and 3.3(0.3) at 500, 1000 and 1500 hours of accelerated aging respectively, and nanofilled material showed deltaE* of 3.0(0.6), 4.5(1.2) and 5.9(0.6) at the same times respectively. It can be concluded that deltaE* does not depend on energy density; however other factors are involved in color change. Further studies in this area are warranted.

Film thickness of resin cements used with adhesive systems.

The final film thickness of a resin adhesive and a resin cement could be affected by previous polymerization of the adhesive systems on dentin surfaces. The aim of this work was to evaluate changes in the film thickness of dual resin based cements with their adhesives as a function of polymerization of the latter on dentin surfaces. The materials used were: RelyX ARC (R) + Single Bond (SB) and Variolink base (VB) and high (HV) or low (LV) viscosity catalyst + Syntac Classic (S) or Excite DSC (E); 56 human dentin discs and 56 composite resin discs (Z250). Dentin disc surfaces were treated with 35% phosphoric acid (except for S) and the adhesive system was either polymerized or not polymerized. A 0.05 ml increment of cement mixture was placed on the dentin disc and covered with the resin disc. A 25 N load was applied for ten minutes and then, the combined thickness was measured with a digital micrometer. Sample size (n) was 4 for each cement or condition. A two-way analysis of variance was performed with a level of significance of p < 0.05. The mean film thickness (and standard deviations) in microm, with and without previous polymerization of the adhesive layer, were: R+SB: 16.50 (2.64) and 17.00 (1.41); VB+S: 21.75 (5.37) and 62.25 (0.95); VB LV+S: 24.50 (3.87) and 72.75 (1.89); VB HV+S: 28.75 (8.46) and 93.00 (53.63); VB+E: 31.75 (8.38) and 42.75 (4.34); VB LV+E: 47.75 (2.50) and 45.75 (3.20); VB HV+E: 49.25 (25.50) and 45.75 (2.75). Significant differences (p < 0.01) were found for the cements and polymerization condition as well as for the interaction between them. Instructions regarding polymerization of the adhesive layer must be followed when adhesive systems are used in combination with dual polymerized resin based cements. Otherwise, final film thickness of the adhesive and the resin cement could be affected.

Significance of moist root canal dentin with the use of methacrylate-based endodontic sealers: an in vitro coronal dye leakage study.

This in vitro study compared the effect of different levels of moisture of root canals, from none to wet, on the coronal seal after filling with resin-coated gutta-percha cones/EndoRez [RGPC/ER (groups 1-4)], Resilon/Epiphany [RE/EP (groups 5-8)], and gutta-percha/Grossman's cement [GP/G (groups 9-12)]. The length of 76 single-rooted extracted human teeth was standardized to approximately 17 mm. After instrumentation with size 10 K-Files, #2 and #3 Gates Glidden burs, and preparation to the working length with K-Type files, the smear layer was removed with 17% ethylenediaminetetraacetic acid followed by flooding with distilled water. On the basis of similarities of canal shape determined by x-rays, roots were assigned to the groups (n = 5 per group) and treated according to one of the following protocols. (I) ETOH: excess distilled water was removed with paper points followed by dehydration with 95% ethanol; (II) PAPER POINTS: the canals were blot-dried with paper points with the last one appearing dry; (III) MOIST: the canals were dried with low vacuum by using a luer adapter for 5 seconds followed by 1 paper point for 1 second; and (IV) WET: the canals remained totally flooded. The roots were then filled with one of the obturation systems outlined above. The teeth were coated with 2 layers of nail varnish and 1 layer of sticky wax, except for the coronal access. In addition, positive and negative controls were added. After immersion in 2% methylene blue dye for 7 days, the samples were embedded in clear orthodontic resin and cross-sectioned at 0.5-mm intervals along the length of the roots. Dye penetration was evaluated by an independent investigator with a stereomicroscope at 40x magnification. The results indicated that dye leakage was affected by the degree of moisture. All materials evaluated showed some evidence of dye penetration, however, root canals filled with resin-coated gutta-percha/EndoRez and Resilon/Epiphany demonstrated significantly less leakage (P < .05) when moist conditions II and III were present.

Immediate polymerization shrinkage in light cured restorative resins.

The purpose of this study was to evaluate the immediate polymerization shrinkage of restorative resins following activation with different amounts of light energy. The composites used were: Z-100 (3M-ESPE), Z-250 (3M-ESPE), Ariston pHc (Ivoclar-Vivadent), Filtek P-60 (3M-ESPE), SureFil (Dentsply), Tetric Flow (Ivoclar-Vivadent), Silux Plus (3M-ESPE) and F-2000 (3M-ESPE). The percentage shrinkage after an 80-second activation was determined by means of a capillary mercury dilatometer The power of the light beam that reached the unpolymerized material was regulated at 350 mW/cm2 (Group I) or 275 mW/cm2 (Group II) positioning the end of the light source (XL-3000, 3M-ESPE) either in contact with or 5 mm from the dilatometer stopper. Four measurements were taken for each material and experimental condition, reading the dilatometer scale one minute after light activation. Data were recorded as percentage volumetric shrinkage as a function of the material volume calculated from the specimen mass and density. Analysis of variance and Tukey's test were used for statistical evaluation. Shrinkage was found to be significantly greater in Group I - 1.43% (0.43) - than in Group II -1.04 % (0.38). Some significant differences were found among some of the products. A reduction in polymerization shrinkage occurred concomitantly with the reduction in light activation energy and varied according to the organic content and the physical and chemical characteristics of each material.

Espesor de película de cementos resinosos bajo la aplicación de diferentes cargas / Film thickness of resin cements under application of different forces

El objetivo de este trabajo fue evaluar la variación del espesor de película de los cementos resinosos duales en función de la carga aplicada sobre la superficie del sustrato a fijar. Los cementos seleccionados fueron Relyx ARC (3M-ESPE) y Variolink II (Ivoclar-Vivadent. De este último se utilizó la pasta base, la mezcla de la pasta base y la catalizadora de baja viscosidad y la pasata base con la catalizadora de alta viscosidad. Se utilizaron dos superficies de vidrio liso; sobre una de ellas se aplicó en su parte central un volumen de 0,05 ml de material, para luego posicionar otro vidrio idéntico sobre él. La manipulación de los materiales se realizó según las indicaciones de cada fabricante. Se aplicaron diferentes cargas compresivas de 5, 25 y 50N durante 1 minuto. Transcurrido dicho lapso, cada probeta fue sometida a lectura de espesor de película (diferencia entre el espesor de los vidrios con y y sin el cemento interpuesto) utilizando un micrómetro digital. El tamaño de la muestras fue n=5. Se encontraron diferencias estadísticamente significativas (P < 0.01) entre los materiales utilizados, las diferentes cargas y su interacción. Para todos los cementos, cuanto mayor fue la carga aplicada, menor fue el espesor de película registrado. Puede concluirse que el espesor de película de los cementos resinosos se ve influenciado por la tensión que se aplica cuando se intenta cementar una restauración. Se sugiere utilizar cargas entre 25 y 50 N para obtener un espesor adecuado. Esta última es la más favorable cuando se seleccionan cementos resinosos de alta viscosidad

Espesor de película de cementos resinosos bajo la aplicación de diferentes cargas / Film thickness of resin cements under application of different forces

El objetivo de este trabajo fue evaluar la variación del espesor de película de los cementos resinosos duales en función de la carga aplicada sobre la superficie del sustrato a fijar. Los cementos seleccionados fueron Relyx ARC (3M-ESPE) y Variolink II (Ivoclar-Vivadent. De este último se utilizó la pasta base, la mezcla de la pasta base y la catalizadora de baja viscosidad y la pasata base con la catalizadora de alta viscosidad. Se utilizaron dos superficies de vidrio liso; sobre una de ellas se aplicó en su parte central un volumen de 0,05 ml de material, para luego posicionar otro vidrio idéntico sobre él. La manipulación de los materiales se realizó según las indicaciones de cada fabricante. Se aplicaron diferentes cargas compresivas de 5, 25 y 50N durante 1 minuto. Transcurrido dicho lapso, cada probeta fue sometida a lectura de espesor de película (diferencia entre el espesor de los vidrios con y y sin el cemento interpuesto) utilizando un micrómetro digital. El tamaño de la muestras fue n=5. Se encontraron diferencias estadísticamente significativas (P < 0.01) entre los materiales utilizados, las diferentes cargas y su interacción. Para todos los cementos, cuanto mayor fue la carga aplicada, menor fue el espesor de película registrado. Puede concluirse que el espesor de película de los cementos resinosos se ve influenciado por la tensión que se aplica cuando se intenta cementar una restauración. Se sugiere utilizar cargas entre 25 y 50 N para obtener un espesor adecuado. Esta última es la más favorable cuando se seleccionan cementos resinosos de alta viscosidad (AU)

Espesor de película de cementos resinosos bajo la aplicación de diferentes cargas / Film thickness of resin cements under application of different forces

El objetivo de este trabajo fue evaluar la variación del espesor de película de los cementos resinosos duales en función de la carga aplicada sobre la superficie del sustrato a fijar. Los cementos seleccionados fueron Relyx ARC (3M-ESPE) y Variolink II (Ivoclar-Vivadent. De este último se utilizó la pasta base, la mezcla de la pasta base y la catalizadora de baja viscosidad y la pasata base con la catalizadora de alta viscosidad. Se utilizaron dos superficies de vidrio liso; sobre una de ellas se aplicó en su parte central un volumen de 0,05 ml de material, para luego posicionar otro vidrio idéntico sobre él. La manipulación de los materiales se realizó según las indicaciones de cada fabricante. Se aplicaron diferentes cargas compresivas de 5, 25 y 50N durante 1 minuto. Transcurrido dicho lapso, cada probeta fue sometida a lectura de espesor de película (diferencia entre el espesor de los vidrios con y y sin el cemento interpuesto) utilizando un micrómetro digital. El tamaño de la muestras fue n=5. Se encontraron diferencias estadísticamente significativas (P < 0.01) entre los materiales utilizados, las diferentes cargas y su interacción. Para todos los cementos, cuanto mayor fue la carga aplicada, menor fue el espesor de película registrado. Puede concluirse que el espesor de película de los cementos resinosos se ve influenciado por la tensión que se aplica cuando se intenta cementar una restauración. Se sugiere utilizar cargas entre 25 y 50 N para obtener un espesor adecuado. Esta última es la más favorable cuando se seleccionan cementos resinosos de alta viscosidad (AU)

Evaluación de las preparaciones realizados con diferentes técnicas de conformación de conductos utilizando instrumental rotatorio de Niti / Assessement of preparation with different shaping techniques throught the use of Niti instruments

Se evaluó la modificación de la morfología inicial producida en conductos radiculares simulados como consecuencia de lapreparación manual y rotatoria. Se diseñaron 8 grupos en función de la técnica de preparación utilizada. En uno de los grupos setrabajó con limas manuales de acero flexibles (Flexofile Maillefer Instruments SA, Baillegues, Switzerland), el resto de losmismos se trabajaron con instrumental rotatorio de Niti (Orifice Shaper, Profile, GT Rotary (Maillefer instruments SA, Baillegues,Switzerland) y Quantec LX (SybronEndo) a las velocidades de rotación indicadas por los fabricantes. Para las técnicas II, III, IVy V se utilizaron instrumentos Profile, en la VI Quantec y en las VII y VIII GT Rotary. Sobre la imagen de cada conductosimulado se valoró la diferencia producida en el contorno de las preparaciones a distancias de 1, 3, 5, 7, 9, 11 y 13 mm delextremo apical y se calculó el trasporte producido sobre el eje original del conducto. Se utilizó análisis de variancia y comparaciónmúltiple por prueba de Duncan para la evaluación de los resultados. La diferencia estadísticamente significativa entre elvalor de transporte de la técnica I con respecto al generado por las restantes, mostró el efecto de la mayor rigidez del instrumentode acero utilizado en ella. Las diferencias a favor de las técnicas rotatorias con instrumentos de níquel titanio fueron menosmanifiestas en las longitudes 3 y 5. Los valores medios obtenidos con el instrumento de acero no difirieron significativamente delos registrados con las técnicas V y VIII. En la longitud 7 con la técnica con instrumental de acero se registraron valores negativosmayores y sólo no fue significativa la diferencia con la técnica VIII. En función de estas observaciones se concluyó que tanto laflexibilidad del instrumento como la forma en que es utilizado influyen en el grado de deformación producida en la forma originaldel conducto radicular.

It assessed the initial morphology produced in resin simulated blocks as a consequence of hand and rotary cleaning and shaping.Eight groups were formed according to the preparation technique. One of them was treated with stainless steel hand files (FlexofileMaillefer Instruments, Baillegues, Switzerland). For the rest, rotary instrumentation was utilized (Orifice Shaper, Profile, GTRotary (Maillefer instruments SA, Baillegues, Switzerland) and Quantec (SybronEndo). For techniques II, III, IV and V, Profileinstruments were used (Maillefer Instruments, Baillegues, Switzerland), in technique VI Quantec LX (SybronEndo), and GTRotary (Maillefer Instruments, Baillegues, Switzerland) in Techniques VII and VIII. Using a photographic image of each resinroot canal we assessed the difference caused in their contour by the preparation procedure at 1, 3, 5, 7, 9, 11, and 13 mm from ofthe apical end and transportation over the axis was calculated. Analysis of variance and Duncan´s multiple comparison test wasused to evaluate the results. The statistically significant difference between the transportation produced by technique I over theone observed with the other procedures showed the effect of the greater stiffness of the instrumented that had been used in it. Thedifferences in favor of rotary techniques with NiTi instruments were not so evident at 3 and 5 mm. The mean values obtained withstainless steel instrumentation did not differ considerably from those recorded with techniques V and VIII. At 7 the stainless steelinstruments produced greater negative values and the difference was not significant only with technique VIII. These observationsallow us to conclude that both the flexibility of the instrument and the way in which it is used, influence the degree of deformationcaused in the original shape of the root canal.