Introduction:Discoloration of the resin-based composites is a common problem in restorative dentistry. There are many factors associated with the discoloration of dental materials in the oral environment. The purpose of this study was to evaluate the color changes in a nano-composite cured with a quartz-tungsten-halogen (QTH) and light emitting diode (LED) unit.

Methods:80 disk-shaped specimens were prepared using Filtek Z350 XT.The specimens were cured with two LED units (Valo and BluephaseC5) and QTH ) Astralis7 ( with two different energy density (400 & 750 mW/Cm²). The color of the materials was measured before and after immersing in tea and artificial saliva. Color change value (ΔE) were calculated and analyzed by 2-way ANOVA and Tukey’s test.

Results: In artificial saliva group, the composites cured with Astralis7 and BluephaseC5 showed significantly more color stability. In tea group, the composites cured with BluephaseC5 significantly had the least color change.

Conclusions: The type of light curing unit does not affect the color stability. Exposure time and interaction between light source and photo initiator content in composite may be the most important factors affecting color stability.