الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
This in-vitro study was designed to evaluate the microshear bond strength of two different types of resin composite (nanohybrid resin composite and nanohybrid ormocer) as a repair material to polymer-infiltrated-ceramic-network (Vita Enamic) blocks after different surface treatments to the polymer-infiltrated-ceramic-network block surface.
A total of twelve slices were prepared out of VITA ENAMIC CAD/CAM ceramic blocks using diamond discs under continuous water irrigation. The slices were polished in a circular motion using silicon carbide papers. After the polishing procedures, the substrate surfaces were ultrasonically cleaned in distilled water for 30 s and then dried. Then, each disc was mounted in an acrylic mold with the disc surface flushing with the acrylic mold surface.
The 12 VITA ENAMIC slices were randomly assigned into three groups according to surface treatment before repair. where the first group received no surface treatment as a control group, the second group received bur roughening to the surface and the third group received sandblasting to the surface. Each group was divided into two subgroups according to the repair material used where the first subgroup is bonded to Filltek Z250XT (Light-curing nano-hybrid resin composite material) and the second subgroup was bonded to Admira Fusion (Light-curing organically modified ceramic restorative material) after silane application and a universal bond (Single Bond Universal) application.
Each specimen with the bonded composite micro-cylinders was secured with tightening screws to the lower fixed compartment of Universal testing machine. And the microshear bond strength of the repair material to the Polymer-infiltrated-ceramic-network was tested. Data was recorded, tabulated and analyzed. Statistical analysis was performed with
Summary and Conclusions
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IBM® SPSS® Statistics Version 25 for Windows. Data showed parametric distribution so; it was represented by mean and standard deviation (SD) values. Two-way ANOVA followed by Tukey’s post hoc test was used to study the effect of different tested variables and their interaction on microshear bond strength (Mpa). Simple main effects were compared utilizing Bonferroni correction.
The microshear bond strength testing showed that there was no significant difference between samples treated with different surface treatments. And that samples repaired with nanohybrid composite had a significantly higher mean value of microshear bond strength than those which were repaired by ormocer composite.
Conclusions:
Within the limitations of this study, the following conclusions could be withdrawn:
1- Surface treatment of the polymer infiltrated ceramic network materials has no remarkable value on the immediate bond strength of the used repair materials.
2- Nanohybrid resin composite as a repair material highly affects the bond strength values to the sandblasted polymer infiltrated ceramic network materials.
3- Coupling Silane and Universal adhesive has no synergistic effect on the bond strength of PICN to the repair resin composite material.
Summary and Conclusions
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Clinical Recommendations:
Within the limitations of this study, the following recommendations could be withdrawn:
1. It is recommended to use nanohybrid resin composite as a repair material while restoring a defect or a fracture in a polymer-infiltrated-ceramic-network (Vita Enamic) restoration. And it is better to pre-treat the Vita Enamic surface with sandblasting to obtain higher bond strength.
2. Further investigations are required for assessing the μSBS of the repair materials in short and long-term after aging.
3. More in-vivo studies are needed about the repair of indirect restorations regarding the repair protocols and materials as well as the different substrates