Abstract
The aim of the current study was to evaluate the influence of hydrofluoric (HF) acid concentration and conditioning time on the shear bond strength (SBS) of dual cure resin cement to pressed lithium disilicate ceramic compared to treatment with an Etch and Prime self-etching glass-ceramic primer (EP). A total of 100 samples of pressed lithium disilicate (IPS e.max Press, Ivoclar Vivadent) were randomly divided into five groups (n = 20) according to surface treatment: two different concentrations of HF (5% or 9%), for different durations (20 or 90 s), or treatment with EP. Adhesion of light-cured resin cement to the treated surface was tested by the SBS test. The substrate surfaces of the specimen after failures were examined by SEM. Data were analyzed using Weibull distribution. The highest cumulative failure probability of 63.2% of the shear bond strength (η parameter) values was in the 9% HF −90 s group (17.71 MPa), while the lowest values were observed in the 5% HF −20 s group (7.94 MPa). SBS values were not affected significantly by the conditioning time (20 s or 90 s). However, compared to treatment with 5% HF, surface treatment with 9% HF showed a significantly higher η (MPa) as well as β (reliability parameter). Moreover, while compared to 9% HF for 20 s, EP treatment did not differ significantly in SBS values. Examination of the failure mode revealed a mixed mode of failure in all the groups. Within the limits of this study, it is possible to assume that IPS e.max Press surface treatment with 9% HF acid for only 20 s will provide a better bonding strength with resin cement than using 5% HF acid.
Highlights
All-ceramic systems can be categorized into two main groups: those based on oxide ceramics, such as zirconia, which have high mechanical strength, and those based on silica ceramics, such as lithium disilicate, which have reduced mechanical properties but better translucency and aesthetic results, even compared to modern cubic/tetragonal high translucency zirconia [2,3]
According to the manufacturer’s directions of use, etching the lithium disilicate surface is recommended with 5% HF acid for 20 s [16]
The results of the shear bond strength test according to the Weibull distribution (Weibull parameters) are presented in Table 2 and Figure 2
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Restoring teeth with full-coverage metal-ceramic crowns has been the gold standard for more than five decades, compared to natural teeth; they often present a compromised aesthetic appearance [1]. A search for an ideal dental material that transmits and refracts light like a natural tooth has led to the development of allceramic restorations. All-ceramic systems can be categorized into two main groups: those based on oxide ceramics, such as zirconia, which have high mechanical strength, and those based on silica ceramics, such as lithium disilicate, which have reduced mechanical properties but better translucency and aesthetic results, even compared to modern cubic/tetragonal high translucency zirconia [2,3]
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