الفهرس 
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Abstract
Sixty anterior bovine teeth were extracted from sacrificed bovine jaws. The sixty prepared samples have been divided randomly into sex groups (10 each) according to the type of abrasive fineness.Gr2 (60 grit). Gr3 (120 grit). Gr4 (320 grit). Gr5 (600 grit). Gr6 (1000 grit).The remaining 10 samples have been assigned as a control group (G1) where no abrasive-silicon carbide paper were used. each group has been wet ground with silicon carbide paper. thoroughly washed under running water, air dried, bonded with mild self-etch adhesive (single bond universal) for 10 s followed by 5 seconds of gentle air drying and then light activation for 20 seconds using LED light curing unit. The resin composite material (filtek TM Z250 XT) was packed inside the hole of a specially constructed circular split Teflon mold with metallic ring holder and central hole using plastic instrument. over the cured adhesive then covered with polyester strip and cured for 30 second . after cur the resin composite material the Teflon mold was carefully removed using bard parker blade no.11.The specimens were stored for 24 hours in distilled water. Prior shear loading by universal testing machine. Load was applied until failure at a cross head speed 0.5mm/min. The maximum load recorded (in Newton) was divided over the surface area (in square) and shear bond strength was calculated in mega pascal. ANOVA and Tucky tests were used to compare the means of the data. The statistical analysis significant as (p<0.05).
The statistical analysis revealed that Group1 with no silicon carbide paper abrasion showed highest value of the shear bond strength followed by Group6 with grit 1000 followed by Gruop4 with grit 320 followed by Group3 with grit 120 and Group5 with grit 600.The lowest mean value was found in Group2 with grit 60.
There is significant difference between groups. ANOVA was flowed by Tukey post hock test which showed that there is sig difference between G1 and G6.The significance level was set at P≤ 0.05.Statistical
Under the limitations of the present study, the following could be concluded.
1- The fineness of the preparation tool used could affect the bond strength of mild self etch adhesive to dentin.
2- For ultra mild one-step self etch adhesive, bonding effectiveness can be significantly improved by finishing cavity preparation with finer grit size.