الفهرس 
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Abstract
Enamel demineralization and white spot lesions are some of the greatest challenges faced by clinicians not only for esthetic reasons but also because this subsurface demineralization represents the first stage of caries formation. In recent years, a group of remineralizing materials has been introduced like casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride-containing casein-phosphopeptide–amorphous calcium-phosphate (CPP–ACPF). Tooth pre-treatments with these agents on the enamel can therefore interfere with the bonding mechanism and the bond strength of brackets, especially with bleached teeth. So, the present study was carried out to evaluate and compare the effect of CPP-ACP and fluoridated CPP-ACP on the shear bond strength of two different types of composites on bleached teeth.
Materials and methods:
Seventy-two teeth will be arranged in six equal groups as follow:
group 1: Bleached teeth bonded with conventional composite (Transbond XT, light-cure adhesive, 3M Unitek).
group 2: Bleached teeth bonded with low viscosity light cure adhesive with nanofillers (Transbond Supreme LV,3M).
group 3: Bleached teeth treated with a paste containing CPP-ACP (GC Tooth Mousse RECALDENT) then bonded with conventional composite (Transbond XT light-cure adhesive, 3M Unitek).
group 4: Bleached teeth treated with a paste containing CPP-ACP(GC Tooth Mousse RECALDENT) then bonded with low viscosity light cure adhesive with nanofillers (Transbond Supreme LV,3M).
group 5: Bleached teeth treated with a paste containing fluoridated CPP-ACP (GC Tooth Mousse RECALDENT) then bonded with conventional composite (Transbond XT light-cure adhesive, 3M Unitek).
group 6: Bleached teeth treated with a paste containing fluoridated CPP-ACP (GC Tooth Mousse RECALDENT) then bonded with low viscosity light cure adhesive with nanofiller (Transbond Supreme LV,3M).
Another three teeth will be checked under SEM one after bleaching and two after remineralization.
All treated specimens were used to assess the shear bond strength using the Instron Universal testing machine (model 3345).
Results:
It was found that the highest mean value of shear bond strength was in group 3. While the lowest mean value of shear bond strength was found in group 2. For groups 3 and 4, The application of CPP-ACP increased the mean value of shear bond strength of adhesives after their application in comparison with groups 1 and 2. For groups 5 and 6, The application of fluoridated CPP-ACP increased the mean value of shear bond strength of adhesives after their application in comparison with groups 1 and 2 and lower than groups 3 and 4.
Conclusion:
from the results of the present study, the following conclusion could be drawn:
1- Orthodontic bonding should be delayed for 2–3 weeks if patients have a history of in-office bleaching with 40% hydrogen peroxide.
2- The application of CPP-ACP cream after bleaching increased the mean value of shear bond strength of orthodontic adhesives.
3-The application of fluoride-containing CPP-ACP cream after bleaching increased the mean value of shear bond strength of orthodontic adhesives.