This study evaluated the influence of a desensitizer(MS coat) on microtensile bond strength of different adhesives: a three-step adhesive(All-Bond 2), a two-step adhesive(Single Bond), a one-step adhesive(One-up Bond F).

Non-caries extracted human molars were used. Dentin surface was obtained by horizontal section on midportion of crown using a water-cooled low speed diamond saw. Teeth were randomly divided into 6 group. AMO(MS coat + All Bond)-, SMO(MS coat + Single Bond)- and OMO(MS coat + One-up Bond F)-dentin surface were treated with 17% EDTA before bonded adhesive. AMX-, SMX- and OMX-dentin surface were bonded with All-Bond 2, Single Bond and One-up Bond F, respectively, with no previous treatment with MS coat and 17% EDTA. About 1cm high resin composite(Z-250™) were incrementally build-up on the treated surface. The specimens for the microtensile test were serially sectioned perpendicular to the adhesive layer to obtain 0.7×0.7 mm sticks. 30 sticks were prepared from each group.

After that, tensile bond strength for each stick was measured with Microtensile Tester at a 1mm/min crosshead speed. Fractured dentin surfaces were observed under the SEM. The results were statistically analysed by using a One-way ANOVA and Tukey's test(p<0.05).

Value in MPa were: AMO-44.35±13.21; SMO-39.35±13.32; OMO-31.07±10.25; AMX-49.22±16.38; SMX-56.02±13.35; OMX-72.93±16.19. Application of MS coat reduced microtensile bond strengths of both Single Bond and One-up Bond F, whereas microtensile bond strengths of All-Bond 2 were not affected significantly.