الفهرس 
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Abstract
The present study was conducted to compare shear bond strength in-vitro between HEMA-containing and HEMA-free self-etch adhesives on superficial surface and deep surface of dentin.
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 and level of dentin used.
Group A: 10 Teeth bonded with (Clearfil S3) on superficial dentin.
Group B: 10 teeth bonded with (Clearfil S3) on deep dentin.
Group C: 10 teeth bonded with (G-ænial bond) on superficial dentin.
Group D: 10 teeth bonded with (G-ænial bond) on deep dentin.
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.
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)
The fractured specimens were evaluated for the mode of bond failure using a stereomicroscope at 20 original magnification.
Comparison between studied groups showed that there was no significant difference between HEMA-containing and HEMA-free self-etch adhesives when they were used on superficial dentin (group A and C) and also no significant difference between the two adhesives on deep dentin (group B and D).
Shear bond strength of HEMA-containing self-etch adhesive on superficial dentin (group A) was significantly higher than that of the same adhesive on deep dentin (group B). Also, it was significantly higher than that of HEMA-free self-etch adhesive on deep dentin (group D).
Shear bond strength of HEMA-free self-etch adhesive on superficial dentin (group C) was significantly higher than that of the same adhesive on deep dentin (group D), and also significantly higher than HEMA-containing self-etch adhesive on deep dentin (group B).
Stereomicroscopic images for the fractured specimens showed that the mixed mode of failure was the most common type. While for superficial dentin, cohesive failure mode was higher than the adhesive mode of failure which had the higher values in deep dentin.