Physical properties of glass ionomer cement containing pre-reacted spherical glass fillers

Abstract The aim of this study was to assess the effect of different commercial liquid phases (Ketac, Riva, and Fuji IX) and the use of spherical pre-reacted glass (SPG) fillers on cement maturation, fluoride release, compressive (CS) and biaxial flexural strength (BFS) of experimental glass ionomer cements (GICs). The experimental GICs (Ketac_M, Riva_M, FujiIX_M) were prepared by mixing SPG fillers with commercial liquid phases using the powder to liquid mass ratio of 2.5:1. FTIR-ATR was used to assess the maturation of GICs. Diffusion coefficient of fluoride (DF) and cumulative fluoride release (CF) in deionized water was determined using the fluoride ion specific electrode (n=3). CS and BFS at 24 h were also tested (n=6). Commercial GICs were used as comparisons. Riva and Riva_M exhibited rapid polyacrylate salt formation. The highest DF and CF were observed with Riva_M (1.65x10-9 cm2/s) and Riva (77 ppm) respectively. Using SPG fillers enhanced DF of GICs on average from ~2.5x10-9 cm2/s to ~3.0x10-9 cm2/s but reduced CF of the materials on average from ~51 ppm to ~42 ppm. The CS and BFS of Ketac_M (144 and 22 MPa) and Fuji IX_M (123 and 30 MPa) were comparable to commercial materials. Using SPG with Riva significantly reduced CS and BFS from 123 MPa to 55 MPa and 42 MPa to 28 MPa respectively. The use of SPG fillers enhanced DF but reduced CF of GICs. Using SPG with Ketac or Fuji IX liquids provided comparable strength to the commercial materials.

Resumo O objetivo deste estudo foi avaliar o efeito de diferentes fases líquidas comerciais (Ketac, Riva e Fuji IX) e o uso de partículas esféricas de vidro pré-reagido (SPG) na maturação do cimento, liberação de flúor, força de compressão (CS) e resistência biaxial à flexão (BFS) de cimentos de ionômero de vidro (GICs) experimentais. Os GICs experimentais (Ketac_M, Riva_M, FujiIX_M) foram preparados pela mistura de partículas SPG com fases líquidas comerciais usando a proporção de pó para massa líquida de 2,5: 1. O FTIR-ATR foi usado para avaliar a maturação dos GICs. O coeficiente de difusão do flúor (DF) e a liberação cumulativa de flúor (CF) em água deionizada foram determinados usando o eletrodo específico do íon fluoreto (n = 3). CS e BFS em 24 h também foram testados (n = 6). GICs comerciais foram usados como comparações. Riva e Riva_M exibiram rápida formação de sal de poliacrilato. Os maiores DF e CF foram observados com Riva_M (1,65x10-9 cm2/s) e Riva (77 ppm), respectivamente. O uso de partículas SPG melhorou o DF de GICs em média de ~ 2,5x10-9 cm2/s a ~ 3,0x10-9 cm2/s, mas reduziu o CF dos materiais em média de ~ 51 ppm a ~ 42 ppm. O CS e BFS de Ketac_M (144 e 22 MPa) e Fuji IX_M (123 e 30 MPa) foram comparáveis aos materiais comerciais. Usar SPG com Riva reduziu significativamente CS e BFS de 123 MPa para 55 MPa e 42 MPa para 28 MPa, respectivamente. O uso de SPG partículas melhorou o DF, mas reduziu o CF dos GICs. O uso de partículas SPG com líquidos Ketac ou Fuji IX proporcionou resistência comparável aos materiais comerciais.

The effects of surface grinding and polishing on the phase transformation and flexural strength of zirconia

PURPOSE: The purpose of this in vitro study was to evaluate the effect of surface grinding and polishing procedures using high speed zirconia diamond burs with different grit sizes on the phase transformation and flexural strength of zirconia.

Mechanical Properties and Microstructure of the Leucite-Reinforced Glass-Ceramics for Dental CAD/CAM / 치위생과학회지

The computer-aided design/computer-aided manufacturing (CAD/CAM) system was introduced to shorten the production time of all-ceramic restorations and the number of patient visits. Among these types of ceramic for dental CAD/CAM, they have been processed into inlay, onlay, and crown shapes using leucite-reinforced glass-ceramics to improve strength. The purpose of this study was to observe the mechanical properties and microstructure of leucite-reinforced glass-ceramics for dental CAD/CAM. Two types of leucite-reinforced glass-ceramic blocks (IPS Empress CAD, Rosetta BM) were prepared with diameter of 13 mm and thickness of 1 mm. Biaxial flexural testing was conducted using a piston-on-three-ball method at a crosshead speed of 0.5 mm/min. Weibull statistics were used for the analysis of biaxial flexural strength. Fracture toughness was obtained using an indentation fracture method. Specimens were observed by field emission scanning electron microscopy to examine the microstructure of the leucite crystalline phase after acid etching with 0.5% hydrofluoric acid aqueous solution for 1 minute. The results of strength testing showed that IPS Empress CAD had a mean value of 158.1±8.6 MPa and Rosetta BM of 172.3±8.3 MPa. The fracture toughness results showed that IPS Empress CAD had a mean value of 1.28±0.19 MPa·m(1/2) and Rosetta BM of 1.38±0.12 MPa·m(1/2). The Rosetta BM sample exhibited higher strength and fracture toughness. Moreover, the crystalline phase size and ratio were increased in the Rosetta BM sample. The above results are expected to elucidate the basic mechanical properties and crystal structure characteristics of IPS Empress CAD and Rosetta BM. Additionally, they will help develop leucite-reinforced glass-ceramic materials for CAD/CAM.

Effect of different grinding burs on the physical properties of zirconia

PURPOSE: Grinding with less stress on 3Y-TZP through proper selection of methods and instruments can lead to a long-term success of prosthesis. The purpose of this study was to compare the phase transformation and physical properties after zirconia surface grinding with 3 different grinding burs. MATERIALS AND METHODS: Forty disc-shaped zirconia specimens were fabricated. Each Ten specimens were ground with AllCeramic SuperMax (NTI, Kahla, Germany), Dura-Green DIA (Shofu Inc., Kyoto, Japan), and Dura-Green (Shofu Inc., Kyoto, Japan). Ten specimens were not ground and used as a control group. After the specimen grinding, XRD analysis, surface roughness test, FE-SEM imaging, and biaxial flexural strength test were performed. RESULTS: After surface grinding, small amount of monoclinic phase in all experimental groups was observed. The phase change was higher in specimens, which were ground with Dura-Green DIA and AllCeramic SuperMax burs. The roughness of surfaces increased in specimens, which were ground with Dura-Green DIA and AllCeramic SuperMax burs than control groups and ground with Dura-Green. All experimental groups showed lower flexural strength than control group, but there was no statistically significant difference between control group and ground with Dura-Green DIA and AllCeramic SuperMax burs. The specimens, which were ground with Dura- Green showed the lowest strength. CONCLUSION: The use of dedicated zirconia-specific grinding burs such as Dura-Green DIA and AllCeramic SuperMax burs decreases the grinding time and did not significantly affect the flexural strength of zirconia, and therefore, they may be recommended. However, a fine polishing process should be accompanied to reduce the surface roughness after grinding.

Evaluación in vitro del efecto de la concentración y el tiempo de aplicación del ácido fluorhídrico sobre la resistencia a la flexión biaxial y la rugosidad del disilicato de litio de última generación / In vitro evaluation of the effect of concentration and time of application of hydrofluoric acid on the biaxial flexural strength and roughness of lithium disilicate

El objetivo fue evaluar in vitro el efecto de la concentración y del tiempo de aplicación del ácido fluorhídrico sobre la rugosidad de la superficie y la resistencia a la fractura de la cerámica de Disilicato de litio de última generación. Se fabricaron 90 discos de cerámica IPS e.max press (14 mm diámetro, 1,2 mm espesor), mediante la técnica de inyección y posterior pulido. Se utilizaron 60 discos para evaluar la resistencia a la flexión biaxial mediante la prueba del pistón y las 3 esferas; se realizó un acondicionamiento con ácido fluorhídrico al 4,6% y al 9,5% durante 20, 40 y 60 segundos (10 discos por cada tiempo y concentración). Los 30 discos restantes se utilizaron para medir los valores de rugosidad superficial (Ra) con ácido fluorhídrico al 4,6% y al 9,5% durante 20, 40 y 60 segundos (5 discos por grupo) mediante microscopia óptica 3D, la cual permitió medir los valores de Rugosidad (Ra). Los datos fueron analizados mediante una prueba de ANOVA y Post- Hoc para determinar las diferencias significativas entre los grupos de estudio. Los valores promedio de la resistencia a la flexión biaxial en los grupos 1, 2 y 3 con la aplicación del ácido fluorhídrico al 4,6% y tiempos de 20, 40 y 60 fueron de 448,45±68,1 Mpa, 357,23±59,5 Mpa y 317,69±45,97 Mpa, respectivamente. Los valores en los grupos al 9,6% fueron de 365,40±46,93 Mpa, 334,38±40,75 Mpa y 348,83±79,39 Mpa. La resistencia a la flexión biaxial de la cerámica de disilicato de litio de última generación se ve afectada por la concentración y el tiempo de aplicación del ácido fluorhídrico. A mayor tiempo de aplicación y concentración del ácido fluorhídrico, menor la resistencia del material. El efecto de la concentración del ácido fluorhídrico y el tiempo de aplicación sobre la cerámica de disilicato de litio no altera significativamente su rugosidad superficial. Según los valores de resistencia a la flexión biaxial encontrados en el presente estudio se recomienda el uso del ácido fluorhídrico a una concentración 4,6% por 20 segundos tal como lo indica el fabricante.

The purpose of this study was to evaluate in vitro the effect of concentration and time of application of hydrofluoric acid on the surface roughness and fracture resistance of lithium disilicate ceramic generation. 90 IPS e.max press ceramic discs (14 mm diameter, 1.2 mm thick) were fabricated by the press technique and then polished. 60 discs to evaluate the biaxial flexural strength test by the piston and the three spheres were used; under 4.6% hydrofluoric acid and 9.6% conditioned treatment was carried out for 20, 40 and 60 seconds (10 disks per each time and concentration). The remaining 30 discs were used to measure the surface roughness values (Ra) with 4.6% and 9.6% hydrofluoric acid for 20, 40 and 60 seconds (5 discs per group) using 3D optical microscopy, which it possible to measure the values of roughness (Ra). Data were analyzed by ANOVA and Post Hoc to determine significant differences between the study groups. Average values of the biaxial flexural strength in groups 1, 2 and 3 with the application of 4.6% HFL and times of 20, 40 and 60 seconds were 448.45±68.1 MPa, 357.23±59.5 MPa and 317.69±45.97 MPa respectively. The values in groups of 9.6% were 365.40±46.93 MPa, 334.38±40.75 and 348.83±79.39 Mpa. The biaxial flexural strength of the ceramic lithium disilicate generation is affected by the concentration and time of application of hydrofluoric acid. A longer time of application and concentration of hydrofluoric acid, less material strength. The effect of the concentration of hydrofluoric acid and application time on the ceramic lithium disilicate did not significantly alter the roughness of the ceramic surface. According to the values of biaxial flexural strength found in the present study the use of hydrofluoric acid is recommended at a concentration 4.6% for 20 seconds as indicated by the manufacturer.

A comparative study on biaxial flexural strength and Vicker`smicrohardness of different zirconia materials: Effect of glazingand thermal cycling / Estudo comparativo da resistência à flexão biaxial e microdureza Vickers` em diferentes materiais à base de zircônia: Efeito doglazeamento e da ciclagem térmica

Objetivo: Este estudo avaliou o efeito do glazeamento e da ciclagem térmica na resistência à flexão biaxial e na dureza Vicker’s de diferentes materiais à base de zircônia. Material e Métodos: Espécimes de disco (15 mm x 1,15 mm) de zircônia foram confeccionados usando 3 sistemas (ZirkonZahn, Cercon, Ceramill) de acordo com a recomendação de cada fabricante. Os espécimes de cada sistema cerâmico foram randomicamente divididos em 2 grupos. Enquanto metade dos espécimes foram glazeados, a outra metade permaneceu não glazeado. Adicionalmente, cada grupo foi divido em 4 subgrupos submetidos a diferentes ciclagens térmicas (0-control, 1000, 3000, 5000 ciclos, 5-55 ºC). A resistência à flexão biaxial foi realizada em uma máquina de teste universal (1 mm/min). As amostras não glazeadas foram submetidas a microdureza Vicker’s antes e após a ciclagem térmica (0-control, 1000, 3000, 5000 cycles, 5-55 ºC). Os dados foram estatisticamente analisados usando ANOVA 1-fator, ANOVA 2-fatores e teste de Tukey’s (p < 0,05). Resultados: Nas amostras não cicladas (1104-1388 MPa), o glazeamento reduziu significativamente a resistência à flexão biaxial de todos os sistemas cerâmicos (845.65-897.35 MPa) (p = 0,000). Enquanto nos grupos não glazeados todas as modalidades de ciclagem térmica reduziram significantemente a resistência à flexão biaxial (864- 1156 MPa) (p = 0,000), nos grupos glazeados a ciclagem térmica não afetou os resultados (829.4- 854.9 MPa) (p = 0,405). Comparados aos grupos não envelhecidos (1414.1 VHN), a ciclagem térmica reduziu significantemente a dureza Vickers apenas para o Cercon (1365.9 VHN) (p = 0,005). Conclusão: O glazeamento reduz a resistência à flexão biaxial dos sistemas à base de zircônia testados. As amostras não glazeadas foram mais afetadas pela ciclagem que as amostras glazeadas. Estas informações podem ter relevância clínica na durabilidade de reconstruções em zircônia monolítica.

Objective: This study evaluated the effect of glazing and thermal cycling on biaxial flexural strength and Vickers hardness of different zirconia framework materials. Material and Methods: Disc shaped zirconia specimens (15 mm x 1.15 mm) were fabricated using three systems (ZirkonZahn, Cercon, Ceramill) according to each manufacturer`s instructions. The specimens of each system were randomly divided into 2 groups. While half of the specimens were glazed, the other half was left unglazed. Each group was further divided into 4 subgroups to be subjected to thermal cycling (0-control, 1000, 3000, 5000 cycles, 5-55 ºC). Biaxial flexural strength was tested in a universal testing machine (1 mm/min). Unglazed zirconia specimens were subjected to Vickers microhardness with and without thermal cycling (0-control, 1000, 3000, 5000 cycles, 5-55 ºC). Data were statistically analyzed using one-way ANOVA, twoway ANOVA and Tukey’s test (p < 0.05). Results: In non-aged conditions (1104-1388 MPa), glazing significantly decreased the biaxial flexural strength of all zirconia ceramics (845.65-897.35 MPa) (p = 0.000). While in the non-glazed groups, all thermal cycling regimens significantly decreased the biaxial flexural strength (864 -1156 MPa) (p = 0.000), in glazed groups thermal cycling did not affect the results (829.4-854.9 MPa) (p = 0.405). Compared to the non-aged group (1414.1 VHN), thermal cycling decreased the Vickers hardness significantly only for Cercon (1365.9 VHN) (p = 0.005). Conclusion: Glazing decreased the biaxial flexural strength of the zirconia ceramics tested. Unglazed zirconia ceramics were weaker against thermal cycling compared to glazed ones. For the long-term durability of monolithic zirconia reconstructions, this information may have clinical significance.

Flexural strength and microstructure of two lithium disilicate glass ceramics for CAD/CAM restoration in the dental clinic

OBJECTIVES: There has been a growing interest in glass ceramic systems with good esthetics, high fracture resistance and bonding durability, and simplified fabrication techniques using CAD/CAM. The aim of this study is to compare flexural strength before and after heat treatment of two lithium disilicate CAD/CAM blocks, IPS e.max CAD (Ivoclar Vivadent) and Rosetta SM (Hass), and to observe their crystalline structures. MATERIALS AND METHODS: Biaxial flexural strength was tested according to ISO 6872 with 20 disc form specimens sliced from each block before and after heat treatment. Also, the crystalline structures were observed using field-emission scanning microscopy (FE-SEM, Hitachi) and x-ray diffraction (XRD, Rigaku) analysis. The mean values of the biaxial flexural strength were analyzed by the Mann-Whitney U test at a significance level of p = 0.05. RESULTS: There were no statistically significant differences in flexural strength between IPS e.max CAD and Rosetta SM either before heat treatment or after heat treatment. For both ceramics, the initial flexural strength greatly increased after heat treatment, with significant differences (p < 0.05). The FE-SEM images presented similar patterns of crystalline structure in the two ceramics. In the XRD analysis, they also had similar patterns, presenting high peak positions corresponding to the standard lithium metasilicate and lithium disilicate at each stage of heat treatment. CONCLUSIONS: IPS e.max CAD and Rosetta SM showed no significant differences in flexural strength. They had a similar crystalline pattern and molecular composition.

Effects of the color components of light-cured composite resin before and after polymerization on degree of conversion and flexural strength / 대한치과보존학회지

OBJECTIVES: This study investigated the effects of the color components of light-cured composite resin before and after polymerization on degree of conversion (DC) and biaxial flexural strength (FS). MATERIALS AND METHODS: Four enamel shades (A1, A2, A3, A4) and two dentin shades (A2O, A3O) of Premisa (Kerr Co.) and Denfil (Vericom Co.) were evaluated on their CIE L*, a*, b* color components using the spectrophotometer before curing, after curing and at 7 day. The DC of same specimens were measured with Near-infrared spectrometer (Nexus, Thermo Nicolet Co.) at 2 hr after cure and at 7 day. Finally, the FS was obtained after all the other measurements were completed at 7 day. The correlations between each color component and DC and FS were evaluated. RESULTS: The light-curing of composite resin resulted in color changes of Premisa in red-blue direction and Denfil in green-blue direction. The DC and FS were affected by product, time and shade (3-way ANOVA, p < 0.05) and product and shade (2-way ANOVA, p < 0.05), respectively. Premisa only showed a significant correlation between the DC and CIE a* component - before and after polymerization (Pearson product moment correlation, p < 0.05). The FS of Premisa showed significant negative correlations with CIE a* and CIE b* components. CONCLUSIONS: The DC and FS of the light-curing composite resin were affected by the color components of the material before and after polymerization.