Objective       To evaluate the effect of cold-light-activated bleaching on marginal microleakage of composite resin with different adhesive and at different restoration moments

in vitro

.       Methods       Freshly extracted 40 healthy premolars were selected

and Class  Ⅴ cavities were prepared on their buccal surfaces. The teeth were divided into 10 groups according to the random number table

named from A t

o J

with 4 teeth in every group. Group A to group E were applied with total-etching adhesive (Adper

TM

Single Bond2) and restored before bleaching

immediately after bleaching

1 and 2 weeks after bleaching

and without bleaching respectively. While

Group F to group J were applied with self-etching adhesive (Adper

TM

Easy One) and restored at the moments mentioned above respectively. So group E and group J served as the control groups. All teeth were restored with composite resin (Filitek

TM

Z350XT). Then after thermo-cycled and stained

all teeth were sectioned buccolingually

and the depth of staining along the tooth restoration interface was measured and recorded under dental microscopy.       Results       The microleakage of restorations with Adper

TM

Single Bond2 was less than that with Adper

TM

Easy One at the same restoration moments (

P

<

0.05

P

<

0.01). Microleakage of restorations with 2 kinds of adhesive in the groups restored before bleaching

immediately after bleaching and 1-week after bleaching was obviously higher than that in groups without bleaching (

P

<

0.05)

and there was no significant difference in microleakage of restorations with 2 kinds of adhesive between groups restored in 2 weeks after bleaching and the groups without bleaching (

P

>0.05).       Conclusion       Total-etching adhesives have less microleakage of restorations. It is better to restore teeth in 2 weeks after bleaching

and the existing restorations before bleaching should be replaced after bleaching.