The effects of pretreatment with an experimental ‹Phytic acid-SnF
2› primer, which requires a 2-step treatment with 7% phytic acid solution and then with 3% SnF
2 solution, on the bonding durability of Clearfil Photo Bond to bovine dentin were evaluated by thermal cycling test (4-60°C, each for lmin.). The result was compared with those of pretreatment with 10-3 solution, which contained 10% citric acid and 3% FeCl
3, and K-etchant. In addition, the effect of additional treatment with 35% HEMA aqueous solution was also examined.
The shear bond strength after 20, 000 thermocycles was about 9 and 6 MPa for experimental primer and 10-3 solution, respectively. These values were almost equal to the initial bond strength. However, the bond strength for K-etchant decreased to about 4 MPa even after 5, 000 thermocycles. When the additional HEMA treatment was performed, the bond strength after 20, 000 thermocycles increased to about 14, 10 and 8 MPa for experimental primer, 10-3 solution and K-etchant, respectively. SEM observation of resin-dentin interfaces revealed that the width of hybrid layer expanded in all cases by the second HEMA treatment after each pretreatment. This suggests that the monomer permeability of demineralized dentin was improved by the additional HEMA treatment.
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