Abstract: Objective: To evaluate the marginal microleakage of SiO2/Poss and the other three kinds of composites. Methods: 32 healthy maxillary premolars were collected and were divided into four groups, and Class V cavity was prepared on each tooth. The cavities were restored by SiO₂/Poss, Z350, Z250 and Beautiful Ⅱ composite resin. Then the teeth were cut into half through the middle of the restoration after thermal cycling and dying. The depths of the fuchsin solution penetration on the gingival and occlusal wall of the cavity were observed under the stereomicroscope and then measured. Results: The teeth restored by SiO₂/Poss composite showed the least marginal microleakage, while the others showed no difference. Conclusion: SiO₂/Poss composite could be a potential material for clinic use.

Key words: SiO₂/Poss, Inlays, Microleakage