Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics

Abstract: The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the "concentration" factor (p = 0.01) and the interaction "acid concentration X ceramic" (p = 0.009) had a significant effect, however, the "ceramic" (p = 0.897) and "conditioning time" (p = 0.260) factors did not influence the results. The LDHP10%60s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10%20s (6.57 MPa)bA, LCAD5%20s (6,90 ±3,5)aB and LDHP5%60s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.

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.

O ácido fluorídrico na resistência ao cisalhamento entre cerâmica feldspática e resina composta / The hydrofluoric acid in the shear strength between feldspathic ceramic and composite resin

Dentre os materiais restauradores, a porcelana se destaca pelo seu alto potencial em reproduzir o aspecto dental. Desta maneira, a sua utilização vem crescendo cada vez mais, e com ela a possibilidade de fraturas. Entretanto, nem sempre uma falha exige a troca da restauração, pois existe a possibilidade de um reparo utilizando resina composta. Este estudo avaliou a resistência ao cisalhamento entre resina composta e cerâmica feldspática submetida ao condicionamento com ácido fluorídrico (HF) em diferentes concentrações. Foram confeccionadas 36 pastilhas de porcelana feldspática e incluídas em resina acrílica, aplainadas com lixas d’água, asperizadas com pontas diamantadas e divididas em três grupos (n=12) de acordo com os tratamentos de superfície: G1) sem condicionamento (controle); G2) condicionamento com HF a 10% por 120 segundos; G3) condicionamento com HF a 5% por 120 segundos. Em seguida, silano e adesivo foram aplicados sobre a superfície da porcelana, seguido da inserção da resina composta com o auxílio de uma matriz metálica bipartida. Após sete dias de armazenamento em estufa, os corpos de prova foram submetidos ao teste de cisalhamento em uma máquina de ensaios universal (EMIC). As médias de resistência foram: G1 105,3N; G2 182,5N e G3 154,51N. Na análise dos dados quantitativos (T student) houve diferença estatística significante entre todos os grupos (p<0,05). A microscopia óptica revelou aproximadamente 58% de falhas coesivas para o G1, 75% para o G3 e 83% para o G2. Concluiu-se que a adesão com o uso do HF a 10% foi superior a adesão obtida quando utilizado o HF a 5%.

Among the restorative materials the porcelain is distinguished by its high potential in reproducing the dental aspect. In this way, their use has been growing increasingly, and, with it the possibility of fracture. However, not every failure demands the exchange the restoration because the possibility of a repair exists with compounded resin. This study evaluated the shear bond strength between composite resin and feldspathic ceramic subjected to etching surface with hydrofluoric acid (HF) at different concentrations. Thirty-six porcelain specimens were mounted into acrylic resin, polished and divided into 3 groups (n=12), according to the following surface treatments: G1) without treatment (control); G2) etched with 10% HF for 120 seconds; G3) etched with 5% HF for 120 seconds. Then the treatment, silane coupling agent and adhesive were applied to the treated specimens, after being bonded with of composite resin with the aid of a bipartite metal matrix. After a 7 days of storage at 37° C, the specimens were subjected to a shearing force in a universal testing machine at a crosshead speed of 0.5 mm/min. The average shear strength were: G1 105.3 N; G2 182.5 N and G3 154.51 N. In the analysis of quantitative data (T student) was difference statistically significant between all groups (p <0.05). Optical microscopy revealed approximately 58% of cohesive failures in the control group, 75% to G3 and 83% for G2. It was concluded that adherence with HF was 10% greater adhesion with the 5% HF.