Introduction & Objective: Light curing and composite placement is effective on microleakage prevention. The aim of the present study was to compare the effect of two incremental com-posite placement and two light curing methods on microleakage of composite class one resto-rations. Materials & Methods: In this experimental study 60 maxillary premolars after class one prepa-ration were assigned to 4 different groups according to light curing method (soft or full power) and two incremental methods (horizontal or oblique) 1. Horizontal incremental placement with full power cure 2. Horizontal incremental placement with soft star cure 3. Oblique incremental placement with full power cure and 4. Oblique incremental placement with soft start cure. After etching and bonding, teeth were restored with Tetric Ceram HB composite. Samples were thermocycled and immersed in 0.2% fuchsin solution for 48 hours. Samples were sectioned buccolingually and evaluated under stereomicroscope (40×). Micro-leakage was scored as follow 0: No microleakage, 1: Microleakage till enamel edge, 2: Microleakage between dentin edge and floor of the cavity and 3:Microleakage extended to the floor of cavity or pulp. Data was analyzed by SPSS software version 16 using Kruscal Wallis and Mann Whitney U test at the significant level of 0.05.

Results: There was a significant difference between four experimental groups, micro leakage (P=0.000). The mean micro leakage of group 1 was significantly different from groups 2, 3 and 4 (P<0.001) and between groups 3 and 4 (P<0.05). Additional, the mean micro leakage of group 2 had no significant difference with the mean scores of groups 3 and 4 (P>0.05).

Conclusion: Restorative material placement technique and curing mode was effective on the microleakage of class 1 composite restoration, however, curing mode was more effective on reduced composite microleakage compared to the placement technique.