Abstract: Abstract：　Objective　To evaluata the effect of the application sequence of CPP-ACP pretreatment on bond strength of deciduous dentin and tubule occlusion . Methods　56 fresh and not crack primary molars were randomly selected and the enamel of tooth surface was grinded to form the dentin plane．48 primary molars were randomly divided into 3 group(n=16).Group A was etched with 35% phosphoric acid for 15 s.Group B wree treated with CPP-ACP. Afterward,these groups were etched with 35% phosphoric acid for 15 s.Group C were initially etched and then treated with CPP-ACP.In each group, samples were equally distributed into two subgroups (n = 8)to bond with either Adper Single Bond 2 (SB) or Prime&Bond NT(PB).The shear bond strengths (SBS) were tested .Remaining 8 primary molars were prepared to evaluate tubule occlusion prior to bonding using SEM. Results The shear bond strengths (SBS) shows there was no significant difference among the three groups of AN,BN,C（P>0.05). And there was also no significant difference among the three groups of AS,BS,CS（P>0.05).Group AN＞group AS，group BN＞group BS，group CN＞group CS，the difference was statistically significant( P＜0.05).However, the effective dentine tubule occlusion was observed in the CPP-ACP group after acid etching.Conclusions　CPP-ACP treatment of deciduous dentin after acid etching did not affect the bond strength of NT and SB2,and the effective closure of dentin tubules can be realized.The adhesive strength of Prime&Bond NT (NT) is higher than that of Single bond 2 (SB2).

Key words: CPP-ACP, dentine dentin, shear bond strength