The effect of hydrofluoric acid and resin cement formulation on the bond strength to lithium disilicate ceramic

Abstract

To investigate how the hydrofluoric acid (HF) concentrations applied to a lithium disilicate glass-ceramic (EMX) affects the surface morphology and microtensile bond strength (μTBS) of ceramics to dentin, using light-cured resin cements with or without UDMA. Sixty-three EMX square ceramic blocks were etched for 20 seconds using different HF concentrations (1%, 5% and 10%) and luted to dentin using two types of resin cement combinations: BisGMA/TEGDMA and BisGMA/TEGDMA/UDMA (n = 10). Each bonded EMX-dentin block was sectioned to obtain 1 mm2 sticks for μTBS evaluation. Half of the sticks were tested after 24 hours and the other half was assessed after 6 months of water storage. Data were statistically assessed using split-plot three-way ANOVA and multiple comparisons were performed using the Tukey's post hoc test (α = 0.05). One EMX sample from each HF concentration was analyzed using field-emission scanning electron microscope (FE-SEM) to characterize the etching pattern. According to the FE-SEM images, increasing the concentration of HF from 1 to 5 and then to 10% led to increased removal of glassy matrix and greater exposure of lithium disilicate crystals. The 10% HF concentration yielded higher μTBS when compared to 1% for BisGMA/TEGDMA formulation (p < 0.05); whereas HF 1% and 5% showed similar μTBS values when compared to 10% HF for BisGMA/TEGDMA/UDMA resin matrix (p > 0.05) at both storage times. Water aging decreased the μTBS values (p < 0.05), except when 10% HF was associated with BisGMA/TEGDMA resin cement. Resin cement formulation and hydrofluoric acid concentrations can interfere with the immediate and long-term glass-ceramic bond strength to dentin.

Current status on lithium disilicate and zirconia: a narrative review

“…For LS 2 , 20 s HF etching (at 5% concentration) is suggested, that is a shorter time than requested for feldspathic and leucite-based ceramics (generally 60 s). Higher HF concentrations (9-10%) and longer etching times have been shown to be too aggressive and can introduce relevant damages, not only to the surface but also to the internal microstructure of the material, negatively influencing mechanical performance (reduction of flexure strength), adhesion potential and long-term success of ceramic restorations, particularly when thickness is low [38][39][40][41]. Another system to create surface microirregularities is sandblasting LS 2 with aluminum oxide particles.…”

Influence of Shear Bonding Strength of Lithium Disilicate to Enamel under Different Surface Treatments

“…In bonding interfaces, adhesive systems tend to water sorption, which might absorb water from the ceramic structure, resulting in mechanical properties reduction and polymer plasticization, but might further offer water for the cleavage of siloxane bond. 10 A significant reduction of bond strength at the interface is occurred over a time period, when a silanized interface is exposed to water due to the presence of hydrolytic cleavage of siloxane bonds in the siloxane. 3 Therefore, all of the aforementioned concerns might contribute to a minimized bond strength investigated in all the groups of this study.…”

“…9 This monobond Etch & Prime (MEP) and one bottle system combine silane and ammonium polyfluoride on the basis of trimethoxy propyl methacrylate to show a thin chemically bonded layer. 10 The introduction of this primer was to simplify the bonding procedure by priming glass and etching ceramics using a one-step process. In particular, a milder acidity is observed in ammonium polyfluoride as compared to hydrofluoric acid, resulting in weaker etching pattern.…”

“…11 Despite of the advantages of the HF acid etching followed by silane application, the protocol of etching ceramics is still not clear. 10 In this regard, the study aims to evaluate the changes in surface treatment protocols on the tensile bonding strength between enamel and ceramic restorations (lithium disilicate). Following hypotheses have been proposed based on the aforementioned objective.…”

Tratamento de Superfície em Cerâmicas de Dissilicato de Lítio: uma Revisão de Literatura

“…O mecanismo de condicionamento da AF na cerâmica vítrea de dissilicato de lítio consiste na remoção da matriz vítrea em função da maior afinidade do flúor (presente no AF) que reage com o silício, o que permite ao AF ionizado dissolver o silício-oxigênio, ligações (silanol) presentes nas vitrocerâmicas. Consequentemente, há uma exposição de cristais de dissilicato de lítio que serão locais futuros para intertravamento micromecânico dos cimentos resinosos, criando fortes ligações formadas entre os cimentos resinosos e as cerâmicas vítreas condicionadas com AF (SUNDFELD et al, 2018).…”