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/cm 2 ). 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.

Effect of prolonged application of single‐step self‐etching primer and hydrofluoric acid on the surface roughness and shear bond strength of CAD/CAM materials

“…However, there was no statistical difference between 5%, 7.5%, and 10% HF acid etching groups. Another study by VERISSIMO et al (23) presented results showing that 60 s of HF etching of lithium disilicate glass-ceramic sections did not result in statistically different SBS values than observed for samples etched for 20 s. This result complies with the study by MOKHTARPOUR et al (4). Given the hazardous nature of HF (40), it is essential to determine the ideal concentration and duration of HF that can provide acceptable SBS values.…”

“…Calculation of the number of specimens needed in each group was based on previous studies, in which power analysis was performed for a 95% confidence level (2,23). Two hundred eighty ceramic samples were prepared from four CAD/CAM material blocks (n = 70 per CAD/CAM restorative material) using a low-speed diamond saw (Iso-Met 1000; Buehler, Lake Bluff, IL, USA) under watercooling.…”

<p>Lithium Disilicate Crown, Zirconia Hybrid Abutment and Platform Switching to Improve the Esthetics in Anterior Region: A Case Report</p>

“…14 Adequate acid etching in the restoration is also important for the glass matrix to be dissolved and to ensure adequate and durable adhesive bond strength between the restoration and resin cement. 15…”

Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

“…Two blocks from each group were examined at 1500x magnification with SEM (Hitachi TM 3000, Tokyo, Japan) to analyze the effect of different HF concentrations and exposure time on the ceramic surface topography. 19,21…”

“…A longer etching time, besides increasing roughness and favoring adhesion, can also weaken the biaxial flexural strength, especially in feldspar ceramics. 13,21 The kinetics between HF and ceramic depends on chemical reactions on the surface, which are affected not only by time and acid concentration, but also by the physical structure of the ceramic. 10,28 Feldspar ceramics have an amorphous glass matrix consisting of a random network of cross-linked silica tetrahedrons, which have varying amounts of undissolved feldspar.…”