Abstract
The aim of this work was to analyze the properties and shear bond strength (SBS) of lithium disilicate to resin cement before and after etching the glass-ceramic surfaces. Lithium-metasilicate samples were heat treated and characterized by Scanning Electron Microscopy, X-ray diffraction and roughness measurement. For the analysis of the shear bonding strength (SBS) of lithium disilicate to dental resin cement, three groups (n = 12) of Li2Si2O5 were prepared: 1°)without treatment (NT); 2°)surface etching with hydrofluoric acid(HF), followed by silane agent and adhesive treatment; 3°) surface treatment with a self-etching ceramic primer (SECP). After the heat-treatment, the samples had Li2Si2O5 crystalline phase dispersed in a residual amorphous phase. Roughness of the NT and SECP samples was smaller that of the HF samples. Samples without surface treatment (NT) had the lowest SBS (5.5MPa). HF(24.2MPa) and SECP(24.8MPa) samples has similar SBS. Weibull statistics showed that HF-samples are more reliable than NT and SECP. The SBS was significantly increased by either HF etching and SECP surface treatment. While the chemical characteristics of the surface submitted to SECP treatment are considered to be responsible for the SBS increase, the main adhesion mechanism after HF etching is the increase in surface roughness.
Highlights
The development of new glass-ceramics with good mechanical properties combined with aesthetics results, allowed the manufacture of metal-free ceramic dental prostheses for the restoration of different tooth elements[1,2,3]
The aim of this study was to evaluate the effect of the use of a self-etching ceramic primer (SECP) in the treatment of the surface of lithium disilicate samples, to determine the shear bond strength to resin cement and to compare the results with the conventional hydrofluoric acid etching (HF) acid etching technique
Lithium metasilicate (Li2SiO3) blocks used in the manufacture of dental prostheses were transformed by a heat treatment (840 °C - 7 min) into lithium disilicate (Li2Si2O5) and, the surface was prepared for a bonding strength test with resin cement
Summary
The development of new glass-ceramics with good mechanical properties combined with aesthetics results, allowed the manufacture of metal-free ceramic dental prostheses for the restoration of different tooth elements[1,2,3]. The ceramic performance of adhesive cementation is influenced by Lithium disilicate glass-ceramic (Li2Si2O5) has excellent optical properties and mechanical resistance, is used in many dental applications, such as veneers, inlays, onlays, single and full crowns[3,14]. This biomaterial has adequate mechanical properties to be used in dental restorations with thicknesses up to 0.5 mm and the results are equivalent to those obtained with zirconia covered with porcelain[6]. A thermal treatment is necessary to promote the phase transformation to of lithium disilicate and a reduction of the volume fraction of amorphous material. After this procedure the flexural strength is about 400 MPa10
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