الفهرس 
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Abstract
The success of the sandwich technique rely on the intensity of bond between the GICs and the resin composite materials in addition to the strength of the bond between the GICs and dentin. Recently, new generations of HVGICs have been introduced. They have the advantages of conventional glass ionomer. Moreover, they are biocompatible material, resin free and low polymerization shrinkage. These advantages may be useful when combined with nanocomposite in sandwich technique Aim of the study This study aimed to study the influence of different surface treatments on shear bond strength of a highly viscous glass ionomer cement bonded to a nanocomposite filling material using sandwich technique. Materials & Methods Sixty specimens (n=60) were fabricated in acrylic blocks (2.5 cm x 2.5 cm). First, a central hole was created at the top of each acrylic block, presenting with (3mm height x 6 mm diameter). Then, HVGIC was injected into the hole of the acrylic block. Specimens were divided into three groups, according to surface treatment protocols: group I (control group) was surface treated with Total etch adhesive for 15 s, group II was treated with sandblasting with Al2O3 particles for 15 s, group III was treated with sandblasting with Al2O3 particles for 15 s then total etch adhesive for 15 s. Surface roughness test was measured in each group before and after surface treatment. Then, one from each group before and after surface treatment was examined using a Scanning Electron Microscope (SEM). After that, nanofilled composite resin was applied in each group after surface treatment. The shear bond strength was evaluated to thirty specimens (10 specimen from each group) using the Universal Testing Machine at a crosshead speed of 1 mm/min until failure occurs. After the test, the failure modes of each specimen on both surfaces, were evaluated under a stereomicroscope and examined using SEM. Results The results of current study showed that mean surface roughness before surface treatment in total etch group I was (0.803±0.036), while in sandblasting (group II) was (0.810±0.039) and in sandblasting & etching group III showed (0.822±0.045). The mean surface roughness value after surface treatment was higher in group III (2.43±0.25) followed by group II it was (1.89±0.045). On the other hand, lower value was observed in group I (1.54±0.18). One-way ANOVA showed that there was statistically significant difference between the studied groups regarding surface roughness after treatment (p value <0.05). The results of shear bond strength test showed that mean shear bond strength value was higher in group III (6.17±0.303) MPa, followed by group II as it was (4.75±0.15) MPa. On the other hand, the lower value was observed group I (4.07±0.23) MPa. One-way ANOVA showed that there was statistically significant difference observed between the studied groups (p value <0.05). SEM observations showed relative irregularities of the cement surfaces after surface treatments with etching after sandblasting when compared to specimens after surface treated with sandblasting or acid etching and before surface treatment. Predominant failure was cohesive failure of cements in group III that indicated beneficial effects of these surface treatments in increasing the bond strength between GIC and composite-resin.