Objective To evaluate the effect of furcal perforation treated with cobalt-chrome alloy inlays, including both morphologic and microleakage study. Methods 42 newly extracted human maxillary and mandibular molars were collected. 38 of them, perforations were made in the center of the pulp chamber floor by using the 8 high speed round bur, divided randomly into two experimental groups. The other intact 4 sample were used as the negative controls. In the experimental groups, group A were repaired by cobalt -chrome alloy inlays, group B were repaired by indirect composite inlay. Resin reinforced glass ionomer was used in all samples as cement. 4 of each group were evaluated under scanning electron microscope（SEM）, and microleakage of others was measured by the concentration of leaked glucose with the oxidase-peroxidase method. Results Microleakage of group A was higher than group B, but no statistical difference（P>0.05）. The two groups had reached a good furcation shape. The gap width of group A was less than B group by SEM. Conclusion For repairing furcal perforation, the method of cobalt-chrome alloy inlay is as good as that of indirect composite inlay.
