The purpose of the present study were to evaluate microleakage of a fourth generation dentin-bonding agent following a walking bleaching treatment, to determine the effect of temporary postbleaching dressing with calcium hydroxide on microleakage and to investigate the effect of delayed intracoronal restoration on microleakage.

The results of this study were as follows:

1. Bleached groups showed more microleakage than unbleached group.

2. Immediately restored group following bleaching procedure showed the highest microleakage score.

3. One-week delayed restorations showed less microleakage but there were no statistically significant difference between group II and III.

4. Provisional dressing with calcium hydroxide had no influence on microleakage.

It is necessary to know the time that has elapsed from the bleaching treatment to the restoration procedure to achieve optimal seal, as well as to reduce the risk of microleakage in adhesive restoration.