الفهرس 
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Abstract
Our study aimed to investigate the effect of two concentrations of proanthocyanidin ( with different application techniques on the micro-tensile bond strength of the dental adhesive to dentin in two-time intervals. Also, to investigate the effects of these applications on the color stability of resin composite in two-time intervals.
According to the literature, hydrolytic and enzymatic degradation occurs overtime at the resin dentin interface. These degradations might be the reason for decreased bond durability.
Proanthocyanidin, a natural cross collagen linker, was applied to dentin in a concentration of 6.5%w/v and 10%w/v for 1min (clinically relevant time), then washed or left with no wash. It was applied in the form of PA adhesive pre-conditioner.
Micro-tensile bond strength testing of the dental adhesive in the different pretreatment modalities was measured in comparison with the control group. µTBS bond strength testing was performed using a universal testing machine (Instron, 5848 Microtester, USA). The load was applied with a crosshead speed of 1mm/min until debonding occurred, and then the micro-tensile stress was automatically measured through Bluehill software. After micro-tensile bond strength testing, the mode of failure of the debonded specimens was analyzed using a stereomicroscope (40X).
The ability of PA to preserve resin dentin bond durability was challenged by specimen storage in distilled water for 6 months without changing the storage water.
Results of the micro-tensile bond strength testing showed a significant increase in the bond strength after PA application in the two different techniques. The application of 10% PA without washing showed the significantly highest values. After 6 month of water storage, specimens lacking PA in the bonding procedure showed significant deterioration in the bond strength.
On analyzing the failure mode among different subgroups, the predominant fracture mode among all subgroups was a mixed failure.
The result of the color test for all groups treated with PA showed significant color change. Except for the 10% no-wash group, the rest of the groups’ color change was within the clinically accepted range. Results of color change after 6 months of water storage, all groups showed a significant color change compared to the same groups before aging.
Finally, within the limitations of the present study, it can be concluded that the use of 6.5% and 10% PA in a pretreatment step maintained the bond durability when applied in a clinically relevant time of 1 min. Unacceptable color change in the resin composite was associated with a higher concentration of PA with no wash. Thus, the application of Proanthocyanidin during adhesive restorative procedures promises a new and practical approach to improve dentin bond strength properties in a clinical setting considering its effect on the color change of composite.
Conclusions:
1. The higher concentration of PA (10%)in no washing technique yielded stronger bond.
2. Both techniques, washing and washing, had a positive influence on the resin dentin bond durability in both concentrations.
3. The application of both