Effect of delayed light polymerization of dual-cured composites on the microleakage of class ii restorations: a stereomicroscopic study

Aims: This in vitro study was carried out to determine the effect of delayed start of light polymerization of a dual-cured composite base on the microleakage of Class II open-sandwich composite restorations. Settings and Design: Teeth were randomly divided into 5 groups according to the method of polymerization of the dual-cured composite base: (A) self-cured, (B) light-cured immediately, (C) light-cured 30 seconds after placement, (D) light-cured 60 seconds after placement, and (E) light-cured 120 seconds after placement. A top layer of light-cured composite was placed and cured. Restorations were stored for 1 week at 37°C and 100% relative humidity, subjected to 500 thermocycles between 50C and 550C with 15 seconds of dwell time and immersed in a 1% aqueous solution of methylene blue for 24 hours. Samples were sectioned mesiodistally, dye penetration was done and finally evaluated under a stereomicroscope. Statistical analysis used: Kruskal Wallis Test Conclusions: Within the limitations of this in-vitro study it can be concluded that delayed, rather than immediate, light polymerization of the dual-cured composites base reduced microleakage in Class II open-sandwich restorations.