Abstract： Objective To determine whether operator's skills could influence shear bond strength (SBS) of self-etch adhesive to enamel with or without prior acid-etching.Methods Total 90 bovine incisors were prepared to expose the enamel and randomly assigned to three groups according to the operator's experience:no experienced student group (Group A),four-year experienced expert group (Group B) and ten-year experienced expert group (Group C).Each group was further divided in two subgroups.In one of the subgroups,a self-etching adhesive and composite were applied in accordance with the manufacturer's instructions,and in the other subgroup,prior acid-etching with etchant were applied first,then self-etching adhesive and composite were applied.Shear bond strength of these samples was measured and the results were analyzed with one-way ANOVA.Results Without prior acid-etching,there was statistically significant difference between Group A [(16.32 ± 5.99) MPa] and Group B [(21.36 ± 4.07) MPa] (P =0.006),but no statistically significant difference between Group A and Group C [(18.77 ± 3.78) MPa] (P =0.163) was found.As for the prior acid-etching group,there were statistically significant differences between operators with and without previous experience,i.e.A [(21.34 ± 5.62 MPa) and B[(26.18±3.57) MPa](P=0.007),A and C[(25.35±4.51) MPa](P=0.023).Whether the subgroup with prior acid-etching or not,thcrc was no statistically significant difference between expert groups (Group B and Group C).The shear bond strength of experienced expert groups was higher than that in no experienced student group.Furthermore,there was statistically significant difference between subgroups with and without prior acid-etching,i.e.A (P =0.025),B (P =0.002) and C (P =0.000).The shear bond strength with prior acid-etching was higher than those without prior acid-etching.Conclusions Operator's experience in enamel adhesive appears to play an important role in determining the outcome of shear bond strength.In order to achieve optimal adhesive outcomes,it is important for operators to not only be familiar with adhesives' knowledge,but also have some practical experience and should operate strictly according to the manufacturer's instructions.