الفهرس 
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Abstract
The present study was conducted to compare in vitro the shear bond strength of two recent HEMA-free seventh-generation bonding agents and HEMA-rich fifth generation bonding agent containing three different solvent at different storage condition in both enamel and dentin, and to compare the mode of failure of the fractured surfaces using the adhesive remnant index.
A total of 150 sound extracted human permanent molar teeth; 75 molar teeth had their buccal surface ground flat to obtain flat enamel surfaces and embedded into the acrylic resin with their buccal surfaces facing upwards, and 75 molar teeth had their occlusal surface ground flat to remove enamel and expose flat dentinal surfaces and they were embedded immediately into the acrylic resin with their occlusal surface facing upwards. The adhesive resins of each group were bonded to the teeth with their respective composites. Enamel and dentin specimens were randomly divided into 3 groups according to the type of adhesive used.
Enamel specimens:
• group 1: 25 teeth bonded with Xeno V bond system.
• group 2: 25 teeth bonded with G-bond system.
• group 3: 25 teeth bonded with Adper Single Bond 2.
Dentin specimens:
• group 4: 25 teeth bonded with Xeno V Bond system.
• group 5: 25 teeth bonded with G-bond system.
• group 6: 25 teeth bonded with AdperTM Single Bond 2.
Each group is subdivided into 4 subgroups and a control group of 5 teeth each:
• Control subgroup a ( Baseline): The bond strength specimen was performed immediately after opening each vial.
• Subgroup b: bonding agent stored for 6 month at 4 ± 1°C in the refrigerator.
• Subgroup c: bonding agent stored for 9 months at 4 ± 1°C in the refrigerator.
• Subgroup d: bonding agent stored for 6 months at room temperature 23± 1°C.
• Subgroup e: bonding agent stored for 9 months at room temperature 23± 1°C.
1- Shear bond strength test:
Specimens were secured to the universal testing machine by means of their metallic molds. The shear load was applied at a constant cross-head speed of 1mm/min with a parallel knife-edge blade at the junction between the tooth surface and the filling material until bonding failure. The shear bond strength was calculated in MPa.
2- Fracture Mode Analysis:
The surface of substrate was observed with a stereomicroscope for assessment of the Adhesive Remnant Index (ARI). The ARI scale has a range between 0 and 3 which is assigned according to the following criteria;
- 0 = No adhesive left on the tooth.
- 1 = Less than half of the adhesive left on the tooth.
- 2 = More than half of the adhesive left on the tooth.
- 3 = All the adhesive left on the tooth.
The results were recorded, tabulated, and statistically analyzed.
The results showed no significant difference in the mean shear bond strength between refrigerated and room temperature for the same adhesive (P > 0.05). However, a decreased in the bond strength was observed after prolonged storage time. AdperTM Single Bond 2 showed the highest mean shear bond strength (29.17 ± 3.44) and (24.31 ± 2.88) in comparison to Xeno V (12.13± 2.83) and (13.14 ± 4.0) and G-Bond (15.92 ±4.35) and (20.66 ± 4.22), for enamel and dentin specimens respectively. G-bond had bond strength slightly higher than Xeno V which showed the lowest bond strength. Also, no significant difference was found between enamel and dentin specimens among the three adhesives.
For fractographic analysis, Xeno V showed higher percentage of ARI score 1 in both enamel and dentin specimens. While, G-Bond and AdperTM Single Bond 2 showed higher percentage of ARI score 2 in both enamel and dentin specimens.
Thus comparison of the adhesives revealed that HEMA-rich and ethanol/water based total-etch adhesives are “gold standard”.