The Effect of Hydrofluoric Acid Concentration on the Bond Strength and Morphology of the Surface and Interface of Glass Ceramics to a Resin Cement

Abstract

The purpose of this study was to evaluate the influence of various concentrations of hydrofluoric acid (HF) on the surface/interface morphology and μ-shear bond strength (μSBS) between IPS Empress Esthetic (EST) (Ivoclar Vivadent) and IPS e.max Press (EMX) (Ivoclar Vivadent) ceramics and resin cement. Ceramic blocks were divided into 12 groups for each kind of ceramic. Six different HF concentrations were evaluated: 1%, 2.5%, 5%, 7.5%, 10%, and 15%. All groups were silanated after etching, and half of the specimens within each group received a thin layer of unfilled resin (UR). Three resin cement cylinders were prepared on each ceramic block for μSBS testing. The specimens were stored in distilled water at 37°C for 24 hours. The μSBS test was carried out in a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. The data were submitted to three-way analysis of variance and multiple comparisons were performed using the Tukey post hoc test (p<0.05). The etched surfaces and bonded interfaces were evaluated using scanning electron microscopy. μSBS means (MPa) for 1%, 2.5%, 5%, 7.5%, 10%, and 15% HF concentrations were, respectively, 25.2, 27.2, 30.1, 31.4, 33.3, and 31.8. μSBS means with or without UR application measured 32.24 and 27.4, respectively; EST and EMX measured 29.8 and 29.9, respectively. For the HF concentrations, 10% and 15% showed higher μSBS means than did 1% and 2.5% (p<0.05); 7.5% was higher than 1% (p<0.05); and no statistical differences were found among the other concentrations (p>0.05). When evaluating UR, μSBS mean was significantly higher and better infiltration was observed on the etched surfaces. No statistical difference was found between the ceramics. The HF concentration and UR influenced the bond strength and surface/interface morphology.

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

“…By containing half of the ionized HF, the 5% HF did not remove enough glass matrix to produce a suitable micromechanical bond between the ceramic and the resin cement, 30 which may explain the results of our study. Sundfeld Neto et al 31 also investigated different HF concentrations and observed that higher concentrations provided higher bond strengths between disilicate ceramic and resin cement, but for leucite-reinforced ceramics the variation did not yield significant differences, corroborating our findings. In our study, for leucite-reinforced and lithium disilicate (CAD / CAM) ceramics, the variation of HF concentration and exposure time did not significantly interfere in the bond strength, similar to previous similar studies.…”

Influence of hydrofluoric acid etching time and concentration on shear bond strength of metal brackets to ceramic surfaces

“…This leads to change in its morphology by creating irregularities that will help the wetting proposed by saline, and consequently, a more effective bond 4,5,9 , intensifying the bond strength 10 . Criticism of the use of hydrofluoric acid arises from its caustic power, capable of promoting soft tissue lesions, in addition to the possibility of weakening the ceramic 6,9 . Commercially, it is found in various concentrations, therefore it is necessary to conduct studies to establish an adequate application protocol, so that the intended retention will be obtained without weakening the ceramic part [11][12][13] .…”

Influence of different treatments of the ceramic surface and thermal cycling on the bond strength of brackets to ceramic

“…A study showed that CCP silane could be used without previous acid etching of the ceramic 2 . On the other hand, it is questionable if the resin cement and silane are effective in wetting the ceramic surface and filling up irregularities when HF acid is not used 9 . Previous study showed that the use of adhesive improves adaptation and bond strength of substrates along the resin cement/ceramic interface 9 .…”

“…HF acid is an efficient surface modification agent that is capable of dissolving the glassy ceramic matrix, increased the roughness 6 , contact surface and wettability 7,8 , promoting higher bond between bonding materials and ceramics [9][10][11] . The application of hydrofluoric acid followed by a silane solution have been used prior to bonding glass ceramic to increase the bond strength and durability between brackets and ceramic surface 3,12,13 or luting glass ceramic restorations 12 .…”

“…Besides that, previous study showed that the effectiveness of bond when only silane is used depends on the ability of bonding materials to fill irregularities and promoted contact between the ceramic and bonding materials 9 . In this study, when an unfilled resin was used after RCP silane group 4, it infiltrated the etched surface irregularities; however, the bond strength was significantly lower than group 2 where after etching CCP silane was used before bonding materials, without unfilled resin.…”