The present study evaluates the seal quality in the apex delta of uniradicular teeth filled with light-cured materials (calcium hydroxide, glass ionomer, and Flow-Fill Magic composite). A total of 45 roots prepared by the endo PTC/Dakin technique were used. All sample restorations were light-cured with 488-nm argon laser light. A 200-microm optical fiber introduced into the root canal delivered 100 mW of light power to the filler material. The fiber tip was positioned 5 mm away from the apex. Light was applied for 20 s. After curing, the samples were immersed in a methylene blue solution for 24 h. Then the samples were cut longitudinally and analyzed under a stereoscopic microscope for dye infiltration. For the sake of comparison, an additional group of ten samples submitted to conventional treatment with EndoREZ root canal sealer was also analyzed. The samples sealed with calcium hydroxide or with the glass ionomer presented less dye infiltration, as compared to those sealed with the Flow-Fill Magic composite. All products activated by fiber optic-delivered light showed superior sealing quality when compared with the self-activated EndoREZ sealer.