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Objectives: The aim of the present study was to examine the influence of different cleaning methods on the bond strength of resin cement to saliva-contaminated lithium disilicate ceramic. Materials and methods: Lithium disilicate ceramic specimens (n = 8/group) were etched with 5% hydrofluoric acid (HF) to comprise the control group. After or before saliva contamination, specimens were cleaned with one of five methods: rinsing with water-spray (WS), K etchant GEL (PA), Ivoclean (IC), AD Gel (ADG), or application of a silane coupling agent before immersion in saliva (SCA). Stainless steel rods were bonded to the ceramic with resin cement. The tensile bond strength was measured after 24 h (TC0) and after thermal cycling at 4-60 °C (TC20000). Specimen surfaces were also evaluated using X-ray photoelectron spectroscopy. Data were statistically analyzed using two-way ANOVA and Tukey tests (α = 0.05). Results: Both the cleaning method (p = 0.0001) and storage condition (p = 0.0001) significantly affected the bond strength results. Before or after TCs, no significant differences in bond strength were observed between the control group and the other cleaning groups except for the WS group, which had a significantly lower bond strength than did the PA, IC, ADG, or SCA groups (p < 0.05). The level of nitrogen in the ADG group was almost equal to that in the control group. Conclusions: WS cleaning did not restore the bond strength of resin cement to saliva-contaminated lithium disilicate ceramic etched with HF, while PA, IC, ADG, and SCA all benefited. Clinical relevance: Lithium disilicate ceramic restorations etched with HF should to be cleaned with ADG after saliva contamination.

Purpose: To compare the shear bond strength of composite cement to lithium-disilicate glass-ceramic coated zirconia vs to alumina air-abraded zirconia and to analyze the residual stresses on both of lithium-disilicate glass-ceramic coated zirconia vs alumina air-abraded zirconia specimens. Materials and methods: One hundred eighty zirconia disks (diameters 10 mm and 5 mm, 4.5 mm thick) were divided into two groups: lithium-disilicate glass-ceramic coating followed by hydrofluoric acid etching and Monobond N Primer (LiDi) or alumina air-abrasion (AA). For each group, two different sizes of identically pre-treated zirconia specimens were bonded with Multilink Speed Cement. A total of 90 specimens were stored in distilled water at 37°C for 24 h and then assigned to three subgroups (n = 15/test group): 1. short-term test; 2. thermocycling for 5000 cycles; 3. thermocycling for 10,000 cycles. Bond strength was tested in shear mode and results were analyzed using two-way ANOVA, followed by one-way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical and scanning electron microscopy. X-ray diffraction was used to analyze t-m phase transformation and residual stresses on mechanically pre-treated LiDi and AA surfaces. Results: The LiDi groups recorded higher mean bond strength than AA groups after thermocycling (p < 0.05). Thermocycling did not affect the bond strength of either LiDi or AA groups (p > 0.05). Most of specimens in AA groups exhibited mixed failure. Alumina air-abraded surfaces exhibited higher residual compressive stresses than did surfaces with a lithium-disilicate glass-ceramic coating. Conclusion: Following thermocycling, composite-zirconia bond strength of specimens with a lithium-disilicate glass-ceramic coating was greater than that of alumina air-abraded specimens.

Aim: This study evaluated the influence of a silane-coupling agent on the bond strength of a self-adhesive cement and a conventional resin cement to a lithium disilicate glass ceramic. Materials and methods: A total of eight ceramic blocks were fabricated and divided into four groups (n = 2). In groups 1 and 3, ceramic surfaces were etched with hydrofluoric acid 10% for 20 seconds, rinsed for 30 seconds, and air-dried. One layer of a silane agent was applied onto all ceramic specimens and air-dried for 30 seconds. In groups 2 and 4, ceramic surfaces were etched with hydrofluoric acid, rinsed, and air-dried without application of the silane-coupling agent. The ceramic blocks were bonded to a block of composite with a self-adhesive resin cement or with a conventional resin cement, according to the manufacturer's instructions. After 24 hours in distilled water at 37°C, the specimens were sectioned perpendicular to the bonding interface area to obtain beams with a bonding area of 0.8 mm(2) and submitted to a microtensile bond strength test at a crosshead speed of 0.5 mm/min. Data were statistically analyzed with one-way analysis of variance and the Games-Howell post hoc test (p = 0.05). Fractured specimens were examined under optical microscopy at 40x magnification. Results: Silanization resulted in higher microtensile bond strength compared to groups without silane. No significant differences were found between the conventional resin cement and the self-adhesive resin cement with silane agent (p = 0.983), and without silane agent (p = 0.877). Conclusion: Silanization appears to be crucial for resin bonding to a lithium disilicate-based ceramic, regardless of the resin cement used. The self-adhesive resin cement performed as well as the conventional resin cement. Clinical significance: Applying one layer of a silane-coupling agent after etching the ceramic surface with hydrofluoric acid 10% enhanced the bond strength between resin cements and a glass ceramic.