الفهرس 
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Abstract
This study was conducted to evaluate the effect of curing mode of dual-cure core build-up material and aging using universal adhesives with different pH values on the micro-shear bond strength to dentin.
A total of 80 bovine dentin specimens were equally assigned to 4 main groups according to universal adhesive used: Tokuyama universal bond (TUB), One coat 7 universal (OCU), One coat 7 universal + One coat 7.0 Activator (OCU+DCA) and All-bond universal (ABU). Bonding procedure was performed according to manufacturers’ instructions, polyethylene tubes were placed on dentin specimens into which the resin core material was injected and either light activated (DC mode) or left to cure chemically (CC mode) without light activation. Micro-shear bond strength testing was performed after 24 hours or after 1 year of water storage.
Three-way ANOVA showed that there was significant difference for the adhesive type, curing protocol, aging as well as their interactions. One-way ANOVA followed by post-hoc test showed that within the DC mode, OCU and OCU+DCA groups showed no significant difference from each other, while were significantly higher than TUB and ABU groups. While in CC mode, OCU+DCA and ABU groups showed statistically higher bond strength values than the other tested groups.
As for the effect of mode of curing, OCU and OCU+DCA showed significant higher bond strength values in the DC mode than their respective in the CC mode. While TUB and ABU groups showed no significant difference in the bond strength values between curing modes.
Aging negatively affected the bond strength values and SEM evaluation showed deterioration of the adhesive interface. However, TUB in DC mode and OCU in CC mode showed enhancement of the bond strength.
Curing mode of dual-cure core material, aging as well as adhesive pH had a significant effect on micro-shear bond strength.
Conclusions:
Within the limitations of this study, it could be concluded that:
1. The effect of curing mode of resin core material on the bond strength was dependent on the type of adhesive system used.
2. Chemical composition as well as the pH level of the adhesive system had direct effect on the bond strength of dual-cure resin core material to dentin.
3. Aging had significant effect of the bond strength of resin core material to dentin within different curing modes but is shown to be material dependent.
Recommendations:
1. Photo-activation of dual-cure core build-up material is recommended, in order to guarantee a long-term stability of the bonded interface.
2. Using materials from same manufacturer is highly recommended, to avoid any unpredictable results.
3. Studying the effect of chemical and mechanical cycling on the bonding outcomes is advocated, for simulating natural oral conditions.