الفهرس 
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Abstract
This study was conducted to evaluate the effect of (1) exposure of dentin to astringent, (2) adhesive type whether two-step or one-step self-etching adhesive and (3) different surface treatment protocols on shear bond strength to dentin. One hundred and twenty dentin samples were made by sectioning of sixty non-carious sound molars mesiodistally. They were divided into two main groups, 60 each, according to exposure of dentin surface to astringent into non-exposed or exposed groups. Each was further classified into 2 subgroups, 30 each according to the adhesive applied to bond the nano-hybrid composite into either two-step or one-step self-etching adhesive. Each subgroup was further classified into 3 classes according to dentin’s surface treatment protocol (normal application of the adhesive- conditioning before the adhesive application- double application of the self-etching primer). All samples were subjected to shear bond strength testing using universal testing machine and data were recorded in MPa and subjected to statistical analysis.
Results showed that astringent exposure (7.714± 2.57) non-significantly (p > 0.05) lowered shear bond strength than that of non-exposed (7.921± 2.41), non-significant (p > 0.05) higher shear bond strength of two steps self-etch adhesive (8.198 ± 2.35) than one step self-etch adhesive (7.379 ± 2.58) and that there was significant difference (p<0.05) between the double application time subgroup (7.085± 2.002) and the other two subgroups; acid conditioned subgroup (8.287± 1.844) and normal application subgroup (8.08± 2.254) where the double application subgroup recorded the lowest bond strength while the conditioned subgroup recorded the highest bond strength.
Conclusions:
Under the limitation of this research, the following conclusions could be detected:
1) Exposure of dentin to astringent affected the shear bond strength of self-etching adhesives negatively.
2) In case of astringent exposure, AdheSE (two-step self-etching adhesive) performed better than AdheSE One F (one-step self-etching adhesive) regarding shear bond strength to dentin.
3) In case of astringent exposure, conditioning of dentin for 5 seconds with phosphoric acid gel improved the bond strength than normal application or double application time of self-etching adhesives did.
Recommendations
Under the limitation of this research, the following recommendations could be detected:
1) In case of astringent exposure, two-step self-etching adhesive may be preferred than one-step self-etching adhesive.
2) In case of astringent exposure, conditioning of dentin for 5 seconds with phosphoric acid gel may be preferred before application of the self-etching adhesive.