الفهرس 
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Abstract
This in vitro study was carried out to investigate the effect of solvent type of three different adhesive systems applied to dry and moist dentin on the microtensile bond strength of resin composite at two time intervals (after 24 hours and 3 months).
A total of 60 teeth were used in the study. The teeth were randomly divided into three groups according to the solvent type, ethanol-water, ethanol and acetone solvents. Each group was subdivided into two subgroups according to wet or dry dentin technique used. Each subgroup was divided into two classes according to the testing period (24 hours and 3 months).
The prepared dentin surfaces were thoroughly rinsed with water to remove debris. In each group, entire dentin surface was etched with 37 % phosphoric acid gel for 15 s and rinsed with distilled water for 15 s. In the dry technique subgroups the etched and rinsed dentin was dried for 5 s seconds with an air syringe and the air nozzle was held at 45°to the dentin surface at a distance of approximately 2 cm, leaving the dentin visibly dry. In the wet technique subgroups the etched and rinsed dentin was partially dried by blotting the excess water with a sponge, leaving a visibly moist surface. Adhesive systems were applied according to the manufacturers’ instructions. In each subgroup the bonding agent was applied in one coat over the prepared dentin surface with a saturated disposable brush. The adhesives were gently air-dried for 5 seconds to evaporate the solvent. Solobond M was light cured for 20 seconds while single bond universal and futurabond M+ adhesives were light cured for 10 seconds using a light curing device (lead light 1,470 mW/cm2 intensity).
A nano-hybrid resin composite (Filtek Z250 XT) was used for buildup. Tofflemire matrix system was used to give the restoration its shape during resin composite packing. Composite buildups were packed in two increments of two millimeters each using gold plated composite applicator. Each increment was light cured for 20 seconds according to manufacturer’s instructions
Mechanical loading that represent two different aging periods was performed using a programmable logic controlled equipment; the newly developed four stations multimodal ROBOTA chewing simulator integrated with thermo-cyclic protocol operated on servo-motor. The test was repeated to subject the first half of specimens (control groups) for 417 cycles to clinically simulate the 24 hours chewing condition (T1). The work was then repeated to subject the second half of specimens for 37500 cycles to clinically simulate the 3 months chewing condition (T2).
Each tooth was sectioned to obtain beams by using an isomet cutting machine to produce stick shaped specimens 1 mm in diameter. Microtensile bond strength test was done; data were recorded using computer software (Bluehill Lite sotware, Instron, MA, USA).Microtensile bond strength values were tabulated and statistically analyzed.