الفهرس 
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Abstract
The present study was conducted to compare in vitro between shear bond strength of new self-etching adhesives and shear bond strength of etch-and-rinse adhesive systems. A total of forty caries free extracted human permanent molar teeth prepared in forty acrylic molds were used in this study. The teeth were divided to four groups ten for each according to the adhesive system used. Group A: used Single bond universal self-etch adhesive. Group B: used Single bond universal in an etch-and-rinse procedure. Group C: used Adper easy one self-etch adhesive. Group D: used Adper single bond 2 etch-and-rinse adhesive. After application of composite over the different adhesives used in this study, all specimens were shear tested to failure at a crosshead speed of 1mm/min until fracture occurred using a universal testing machine and the load was recorded in newton.
The shear bond strength values (MPa) were calculated from the peak load at failure divided by the specimen surface area using the following equation:
Shear bond strength = F/A
F=breaking load (in Newton)
A=area of composite dentin interface
Area= π r² (π = 3.14 , r = radius of the plastic mold)
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The fractured specimens were evaluated for the mode of bond failure using stereomicroscope at 30 original magnification. The results of the shear bond strength study showed that there was no significant difference between the two self-etch adhesive groups (group A and C) and also no significant difference between the two etch-and-rinse groups (group B and D).
The shear bond strength of the single bond universal adhesive when used in an etch-and-rinse procedure (group B) was significantly higher than the shear bond strength of the single bond universal when used in a self-etch procedure (group A) and also significantly higher than that of the Adper easy one self etch adhesive (group C).
Shear bond strength of Adper single bond 2 etch-and-rinse adhesive (group D) was significantly higher than that of the two self-etch adhesive groups (group A and C).
Stereomicroscopic images for the fractured specimens showed that:
1- The predominant mode of bond failure for group A was adhesive failure
2- The predominant mode of bond failure for group B was cohesive failure
3- The predominant mode of bond failure for group C was adhesive failure
4- The predominant mode of bond failure for group D was mixed failure